Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
63 Cards in this Set
- Front
- Back
|
1. Nervous system: CNS, PNS, somatic, autonomic, sympathetic, parasympathetic ( 3% - total body weight)
|
•Central Nervous System - Brain and SC (brain = 100 billion neurons, SC = 100 million neurons)
•Peripheral Nervous System - neural tissue outside CNS, SC & cranial nerves •Somatic Nervous System -lower motor neurons from anterior gray horns -target: skeletal muscle -NT’s (Ach) ( one neuron, one NT’s, one target system) •Sympathetic Nervous System (ANS) -short preGanglionic neurons from lateral gray horn - long postganglionic neurons - ganglion: sympathetic trunk & prevertebral (celiac, superior mesenteric, inferior mesenteric) - preganglionic: gray lateral horns of T1-L2 - target: cardiac and smooth muscles, glands -NT’s: Ach(preganglionic) or NE (postganglionic) •Parasympathetic Nervous System (ANS) –Long preG neurons from lateral gray horn –Short postG neurons –Ganglion: terminal ganglion –preG: III, VII, IX, X, lateral gray horns of S2-S4 –target: cardiac and smooth muscle, glands –NT’s: Ach(preG and postG) (2 neurons, 2NT’s, multiple target systems) |
|
|
Somatic NerVous System
|
Somatic Nervous System (skeletal muscle)
• considered the voluntary aspect of the PNS – but the muscles of posture and balance are controlled involuntarily by the lower brain centers (brain stem, cerebellum) • cell bodies located in the ventral gray horn of the spinal cord • the axon of a motor neuron extends from the CNS continuously to its skeletal muscle target – ANS usually requires two neurons • terminals release acetylcholine – contraction • can only stimulate its target – whereas the ANS can either stimulate or inhibit its target Somatic Nervous System - somatic/motor commands emerge from the ventral horn and travel through the: – dorsal ramus to target the muscles of the back – ventral ramus to target the muscles of the limps and body wall Somatic Nervous System • motor neurons receive incoming information from many converging presynaptic neurons – both excitatory and inhibitory on these motor neurons – some information are part of reflexes originating in the spinal cord – other information can come in from areas of the brain via the descending white matter tracts • motor areas of the cerebral cortex, the basal nuclei and the cerebellum – synapse with the motor neurons in the ventral horn and regulate their activity • activation – impulse sent to muscles • inhibition – no impulse, no contraction • level of activity of a motor neuron is the balance between the EPSPs/activation and the IPSPs/inhibition of the incoming synapsing neurons • therefore motor neurons are considered the final common pathway – considered the only way any other part of the nervous system can influence muscle activity |
|
|
2. know the function of afferent neurons, efferent neurons, interneurons – what do they do?
|
•Sensory (afferent) neurons
(sensory function) –sensory receptors detect internal and external stimuli –information is sent to CNS via sensory (afferent) neurons within sensory nerves a.transport sensory information from skin, muscles, joints, sense organs & viscera to CNS •Motor (efferent) neurons a.send motor nerve impulses to muscles & glands ( motor function) a.decision usually manifests itself as a motor command – contraction of a muscle, secretion by a gland b.motor commands travel along motor (efferent) neurons within motor nerves c.commands are sent to effectors = muscles and glands •Interneurons (association/integrative) neurons -connect sensory to motor neurons, - 90% of neurons in the body (integrative function) –integrates = processing of information within the CNS –stores info and also makes decisions once info is processed –one important integrative function = perception –processed by interneurons within the CNS –90% of the neurons within the CNS are interneurons •Afferent division of PNS •Deliver sensory information from sensory receptors to CNS –free nerve endings: bare dendrites associated with pain, itching, tickling, heat and some touch sensations –Exteroceptors: located near or at body surface, provide information about external environment –Proprioceptors: located in inner ear, joints, tendons and muscles, provide information about body position, muscle length and tension, position of joints –Interoceptors: located in blood vessels, visceral organs and NS -provide information about internal environment -most impulses are not perceived – those that are, are interpreted as pain or pressure –mechanoreceptors: detect pressure, provide sensations of touch, pressure, vibration, proprioception, blood vessel stretch, hearing and equilibrium –thermoreceptors: detect changes in temperature –nociceptors: respond to stimuli resulting from damage (pain) –photoreceptors: light –osmoreceptors: detect changes in OP in body fluids –chemoreceptors: detect chemicals in mouth (taste), nose (smell), and body fluids –Efferent pathways –Stimulate peripheral structures –Somatic motor neurons –Innervate skeletal muscle –Visceral motor neurons –Innervate all other peripheral effectors –Preganglionic and postganglionic neurons |
|
|
3.Types of neurons by structure – unipolar, bipolar, multipolar
|
Based on number of processes found on cell body
a. multipolar = several dendrites & one axon; most common cell type in the brain and SC b. bipolar neurons = one main dendrite & one axon; found in retina, inner ear & olfactory c. unipolar neurons = one process only, sensory only (touch, stretch) • develops from a bipolar neuron in the embryo - axon and dendrite fuse and then branch into 2 branches near the soma - both have the structure of axons (propagate APs) - the axon that projects toward the periphery = dendrites |
|
|
4.Structure of a neuron and functions of its components: nucleus, Nissl bodies, neurofilaments
|
Neuron
- dendrites, dendritic spines ( stimulated by environmental changes or the activities of other cells) - cell body ( contains the nucleus, and mitochondria and ribosomes) - axon ( conduct nerve impulse (action potential) toward synaptic terminals - synaptic terminals ( has synaptic endbulb) affect another neuron or effector (muscle, glands) Cell Body - single nucleus with prominent nucleolus (high synthetic activity) - location for most protein synthesis e.g. neurotransmitters & repair proteins - Nissl bodies – rough ER & free ribosomes for protein synthesis, protein then replace neuronal cellular components for growth and repair of damaged axons in the PNS Neurofilaments – or neurofibrils give cell shape and support – bundles of intermediate filaments, Microtubules move material inside cell. Lipofuscin – pigment clumps (harmless aging) – yellowish brown, the processes that emerge from the body of the neuron = nerve fibers ( dendrites & axons) Cell Processes = dendrites (little trees) – the receiving or the input portion of the neuron, short, tapering and highly branched. - surfaces specialized for contact with other neurons, cytoplasm contains Nissl bodies & mitochondria Cell Processes = axons – conduct impulses away from cell body – propagates nerve impulses to another Neuron - long, thin, cylindrical process of cell, contains mitochondria, microtubules & neurofibrils – NO ER/ NO protein synthesis Axon hillock – join the soma at a cone-shaped elevation Initial segment – first part of the axon Trigger zone – most impulses arise at the junction of the axon hillock and initial segment Axoplasm – cytoplasm Axolemma – plasma membrane Collaterals – side branches arise from the axon Axon terminals – fine processes where axon and collaterals end Synaptic end bulbs – a swollen tips contains vesicles with NT’s |
|
|
5.Types of neuroglia cells in the CNS and PNS – what do each of these do?
|
Neuroglia – support the neurons that do electrical impulses, provides happy environment for the neurons, about half the volume of cells in the CNS, smaller than neurons, 5 to 50 times more numerous, divide by mitoses, neurons donot divide
CNS: Neuroglia that support neurons a. Astrocytes – maintain blood-brain barrier; provide structural support, regulate ion, nutrient and dissolved gas concentrations, absord and recycle NT’s, from scar tissue after injury - star shaped with many processes projecting from the cell body - two types (protoplasmic- short branches found in gray matter. and fibrous- many long unbranched found in white matter. - Make contact with the capillaries supplying the CNS, neurons of the CNS and the pia matter membrane covering the brain and spinal cord. - Make connection with BV and neuron - Take up excess NT’s like GABA and glutamate b. Ependymal cells – line ventricles (brain) and central canal (spinal cavity); assists in producing, circulating and monitoring of cerebrospinal fluid. - CSF: colourless liquid that protects the brain and SC against chemical & physical injuries, carries O2, glucose and other necessary chemicals from the blood to neurons and neuroglia c. Oligodendrocytes – myelinate CNS axons; provide structural framework (network) around CNS - most common glial cell type, each forms myelin sheath around the axons of neurons in CNS (enables electrical impulse without shorting), analogous to Schwann cells d. Microglia – removes cell debris, wastes, and pathogens by phagocytosis - has phagocytic role (clear away dead cells), protect CNS from disease thru phagocytosis of microbes, migrate to areas of injury where they clear away debris of injure cells, may also kill healthy cells. PSN: Neuroglia a. Satellite Cells – surround neuron cell bodies in ganglia, regulate O2, CO2, nutrient, and neurotransmitter levels around neurons in ganglia b. Schwann Cells – surround all axons in PNS, responsible for myelinations of peripheral axons, participate in repair process after injury. |
|
|
6.Gray and white matter: what are they composed of, where are they found in the CNS?
|
CNS: Gray Matter
Neural Cortex – gray matter on the surface of the brain Centers – collections of neurons cell bodies in the CNS, each center has specific processing functions Nuclei – collections of neuron and cell bodies in the interior of the CNS Higher Centers – most complex center in the brain CNS: White Matter Tracts – bundles of CNS axons that share a common origin and destination Columns – several tracts that form an anatomically distinct mass PNS: Gray Matter Ganglia – collections of neuron cell bodies in the PNS PNS: White Matter Nerves – bundles of axons in the PNS a. definition and location of a nucleus (CNS:gray matter) – collection of neuron cell bodies in the CNS b. definition and location of a ganglion (PNS: gray matter) – collection of neurons cell bodies in the PNS c. definition and location of a tract (CNS:white matter) – bundles of CNS axons that share a common origin and destination d. definition and location of a column (CNS: white matter) – several tracts that form an automatically distinct mass. |
|
|
7.What is a membrane potential? How is the MP in neurons generated? Which channel is primarily involved in the MP?
|
Membrane potential – electrical voltage difference measured across the membrane of a cell
Resting MP – membrane potential of a neuron measured when it is unstimulated - results from the build up of negative ions in the cytosol along the inside of the neuron’s PM - the outside of the PM becomes more positive - this difference in charge can be measured as potential energy - happens when more K ions go outside, Na ions go inside, Cl ions go inside Ligand-gated and voltage-gated – involved in the membrane potential Leakage (non-gated) or resting channels – always open, contribute to the resting potential - nerve cells have more K+ than Na+ leakage channel, as a result, membrane permeability to K+ is higher - K+ leaks out of the cell, inside becomes more negative, so the K+ needs to be pumped back in Gated Channels – opens and close in response to stimuli a) voltage-gated channel – open in response to change in MP or voltage (Na or K or Ca voltage gated channel) b) ligand-gated channel – open and close in response to specific extracellular chemical stimuli (NT’s, hormone, ion) e.g. Na and Cl ligand-gated channel c) mechanically-gated – open with mechanical stimulation (cilia in the nose) |
|
|
8.Action potentials – how are they generated? Ion channels involved? What are they types of ion channels found on neurons? Modes of conduction of the AP? What happens to ion flow and MP during depolarization? Repolarization? Hyperpolarization?
|
Graded potentials – local changes in MP, that occur in varying intensities (grades) – caused by opening of ion channels, usually ligand-gated or gated ion channel for sodium
Excitability – ability of cell membrane to conduct electricity (skeletal muscle fibers and neurons) Action Potential - nerve impulse, takes place in two stages depolarizing (+) [ligand-gated NA] and added by voltage-gated NA to reach threshold and generates more depolarization, and repolarizing[votage-gated K], back toward resting potential (-), followed by hyperpolarizing[voltage-gated K or ligand-gated Cl] or refractory period - no new AP can be generated. - starts when a resting membrane potential is triggered and reaches the threshold (by Na ligand gated channel), if the graded potential change exceeds threshold – generates Action Potential. • Refer to the handout from Dr. Zuk |
|
|
9.what factors affect the rate of AP condution?
|
-changes in resting membrane potential induces AP due to differences in sodium and potassium ion concentration in and out of the neuron. K is higher inside the axon, Na is higher outside in the ECF, this produces concentration gradients and changes the charges inside and outside of the neuron, inside of the cell has a higher concentration of negative phosphate ions and proteins.
- Polarized ( exhibits membrane potential) – membrane has Na/K pumps to maintain specific concentrations of these ions in & out of the neurons and therefore maintain the resting membrane potential (move 3 Na out, and 2 K in), inside of the neuron is slightly negative. Continuous conduction – unmyelinated fibers (gray matter) – an AP spreads (propagates) over the surface of the axolemma Salutatory conduction – depolarization only at nodes of Ranvier, areas along the axon that are unmyelinated and where there is a high density of voltage-gated ion channels. Current carried by ions flows thru ECF from node to node - faster than continuous bec. Neurons have long myelinated axon. • the propagation speed of a nerve impulse is not related to stimulus strength, larger = faster conduction, myelin 5 to 7 times faster, larger myelinated fibers conduct impulses faster due to size & salutatory conduction |
|
|
10.What is a presynaptic neuron? a post-synaptic?
|
Synapse – site of intercellular comm. Between 2 neurons or between a neuron and an effector (e.g. muscle)
- permits comm. Between neurons and other cells presynaptic neuron – initiating neuron postsynaptic neuron – receiving neuron axon terminal swell to form synaptic end bulbs or form swollen bumps called varicoties |
|
|
11.Be able to describe the molecular events that occur during the exocytosis of synaptic vesicles – what ion channels are involved?
|
Synaptic vesicles – can be filled, exocytosed and recycled within a minute. It move into proximity near the plasma membrane (PM) of the end bulb = active zone. Opening of voltage-gated CA2+ (depolarization) channels (upon receipt of AP), influx of calcium promotes the docking of the synaptic vesicles with the PM and the exocytosis of their contents. Then the synaptic vesicles components are recycle for future use.
|
|
|
12.Be able to describe what happens to the membrane at the post-synaptic neuron upon release of a neurotransmitter.
|
Propagation of AP at the target post-synaptic neuron usually involves opening of a ligand-gated Na+ channels on the membrane of the post-synaptic neuron (NT’s binds to a receptor on post-synaptic membrane, this receptor is a ligand-gated channels)
Chemical Synapse – conversion of an electrical signal (presynaptic) into chemical signal back into an electrical signal (postsynaptic) (1. nerve impulses (AP) arrives at presynaptic endbulbs. 2 fusion of synaptic vesicles to PM – role of calcium (voltage-gated Ca2+). 3. release of NT’s. 4. opening of channels in PM of postsynaptic neuron (e.g. Na+ ligand-gated) 5. postsynaptic potential develops – depolarization & triggering of AP in postsynaptic neuron. |
|
|
13.Know the types of synapses. Know the two types of chemical synapses (EPSP, IPSP)
|
2 types of synapse (chemical, electrical)
a) Types of chemical synapse (NT’s will cause either excitatory or inhibitory response) EPSP – excitatory postsynaptic potential – if the NT’s depolarizes the postsynaptic neuron = excitatory -causes to have action potential (depolarization), opening of sodium channels or other channels (inward), ligand-gated sodium IPSP – inhibitory postsynaptic potential = hyperpolarization = some NT’s will inhibitory (will stop talking) - opening of chloride channels (inward) ligand-gated chloride or potassium (outward) Neural activity – depends on summation of all synaptic activity – excitatory and inhibitory b) electrical synapse – direct physical contact bet. Cells is required, conducted through gap junctions (adv. Over chemical synapse: faster comm.. – almost instantaneous, synchronization bet. Neurons or muscle fibers e.g. retina, heart-beat) |
|
|
3 types of NT’s
|
a.small molecules: Acetylcholine (Ach) – muscle contraction; all neuromuscular junctions use Ach. Ach also released at chemical synapses bet. 2 neurons, can be excitatory or inhibitory – depends on location and synapse.
- inactivated by an enzyme acetylcholinesterase – inhibitor – degrade acetylcholine Blockage of the Ach receptors by antibodies = myasthenia gravis (attack acetylcholine receptor) – autoimmune disease that destroys these receptors and progressively destroy the NMJ, anticholinesterase drugs (inhibitor of acetylcholinesterase) prevent the breakdown of Ach and raise the level that can activate the still present receptors b.amino acids: (glutamate & aspartate) - excitatory & GABA (inhibitory) glutamate & aspartate – have powerful excitatory effects, stimulate most excitatory neurons in the CNS GABA (gamma amino-butyric acid) inhibitory NT’s for 1/3 of all brain synapses – ligand-gated chloride (hyperpolarization) – inhibits the generation of an action potential by the target neuron. (e.g. Valium – GABA agonist – enhancing its inhibitory effect c. biogenic amines: modified amino acids (catecholamines: norepinephrine(NE), epinephrine(EP), dopamine, serotonin) - all derived from the amino acid tyrosine - NE: role in arousal, awakening, deep sleep, regulating mood - EP (epinephrine – adrenaline): flight or fight response - dopamine: emotional responses and pleasure, decreases skeletal muscle tone -serotonin: derived from trytophan : happy NT’s = contentment, sensory perception, temp. regulation, mood control, appetite, sleep induction, feeling of well-being d. other types: ATP – released with NE from some neurons, Nitric oxide – formed on demand in the neurons then release (brief lifespan), role in memory and learning, produces vasodilation – Viagra enhances the effect of NO. Removal of NT’s a. Diffusion – move down concentration gradient b. Enzymatic degradation – acetylcholinesterase c. Uptake by neurons or glia cells – NT’s transporters (NE, epinephrine, dopamine, serotonin) Neuropeptides: (painkiller) – widespread in CNS, excitatory and inhibitory, acts as hormones elsewhere in the body. Substance P – enhances our perception of pain; opioid peptides: endorphins – release during stress, exercise; enkephalins – analgesics (200x stronger than morphine), pain relieving effect by blocking the release of substance P; dynorphins – regulates pain and emotions |
|
|
15.What is CSF? Where is it formed? What cells form CSF? Where does it circulate? What is its function?
|
CSF: Cerebrospinal Fluid – provides protection on brain. It completely surrounds the CNS and fills a number of cavities located within the brain and spinal cord. Replaced completed up to three times per day. Glucose, proteins, lactic acid, urea, ions.
- It is made by specialized cells in the lateral ventricles (choroids plexus) – network of capillaries in the walls of the ventricles. Covered by ependymal cells (epithelial cells) that filter the blood plasma and produce CSF by secreting it. These cells are capable of allowing passage of certain substances from the blood thru them into the CSF – inhibit the passage of others. - It continually circulates – ventricles of the brain and central canal to subarachnoid space. Functions: a. chemical protection – provided an optimal chemical environment for neuronal signaling b. mechanical protection – acts as a shock absorber, preventing direct physical contact bet. Brain tissue and the bones of the cranium or vertebral canal c. circulation – allows the exchange of nutrients and waste products bet. The blood and nervous tissue |
|
|
16.What is the blood-brain-barrier? How does it form? What cells are involved in its formation
|
BBB: within the body the capillaries are sites of exchange bet. Materials in the blood and ECF – filtration of the blood plasma by capillary cells helps form the ECF. ( Most locations within the body, this exchange is very free)
- the capillary walls are formed of a single layer of cells = endothelium – blood capillaries - the cells are joined loosely and are connected by numerous gap junctions and pores bet. The cells. This allows for an easy diffusion of many plasma components (except large plasma proteins) between the cells themselves. So even small changes in blood plasma contents can dramatically effect the ECF composition - however, in the brain, the capillary cells are careful as to what is filtered out of the blood. The cells of the endothelium are very tightly linked together. The cells are joined by tight junctions to restrict the flow of materials among them and through them into the ECF surrounding the brain. So materials must directly passage the cells themselves to contribute to the ECF. SO the passage of things like glucose, amino acids, ions are carried thru the cells by carrier proteins. But lipid-soluble materials and gases (O2) can cross easily through the PM of the endothelial cells. So transport bet. The cells is anatomically prevented and transport through the cell is physiologically restricted by BBB Cells involved (astrocytes – (physical and chemical barrier), 1.signal the capillaries to get tight. 2. participate in the transport of some ions like K+; ependymal cells – physical and chemical barrier, blood capillaries |
|
|
17.What are the 3 meninges and what are their functions? What are the meningeal spaces?
|
Meninges – 3 consecutive tissue membranes that separate the soft tissue of the CNS from the surrounding bone.
Dura mater – mater is latin for mother, indicating the protective nature of the meninges. Outermost layer, closest to the bone. Dura is latin for hard, durable and dura mater is a very tough, fibrous tissue. Arachnoid mater – middle layer, arachnoid is greek for spider, which appropriately descrives the arachnoid mater’s weblike structure. Normally no space exist bet. The dura and arachnoid Pia mater – pia is latin for tender, kind, the innermost layer, immediately adjacent to the nervous tissue. The space bet. The arachnoid and pia mater is called subarachnoid space – filled with CSF. Denticulate ligaments – bind pia mater to the arachnoid. 3 meningeal spaces Subarachnoid space – bet. Arachnoid and pia: circulation of CSF Subdural space – bet. Arachnoid and dura Epidural space – bet. Spinal cord, potential space |
|
|
18. What are the 5 components for a reflex arc? What is a monosynaptic reflex arc? How does it differ from a polysynaptic? What is a spinal reflex? A cranial reflex?
Reflex arc |
- Neural “wiring” of reflex
- Requires 5 functional components: 1. sensory receptor (arrival of stimulus & activation of receptor) 2. sensory neuron (activation of a sensory neuron) 3. intergrating center (SC or BS) – information processing 4. motor neuron (activation of motor neuron) 5. effector (response by effector) Monosynaptic reflex – one synapse, simplest reflex arc, sensory neuron synapses directly on motor neuron Polysynaptic reflex – multiple synapses (two to several hundred), at least one interneuron, longer delay Classification of Reflexes -by development (innate – genetically determined, acquired – learned foll. Repeated exposure to stimuli) - where information is processed (spinal – interconnections and processing in the spinal cord, cranial-processed in the brain – papillary reflex, corneal blink reflex, accommodation reflex) - motor response (somatic – muscle contractions, visceral – smooth & cardiac, glands) - complexity of neural circuit (monosynaptic) Spinal reflex a. Stretch reflex is monosynaptic - causes contraction in response to stretch i. Regulates skeletal muscle length and tone ii. all monosynaptic reflexes are ipsilateral reflexes - input and output on same side iii. only one synapse in the CNS - between ad single sensory and motor neuron iv. Sensory receptors are found in muscle spindles 1. e.g. Patellar reflex – muscle spindles in the quadriceps muscles, hit with a mallet stretches the quadriceps and its tendon - results in contraction b. Tendon reflexes - polysynaptic - controls muscle tension by causing muscle relaxation before muscle contraction rips tendons -Generally polysynaptic - more than one CNS synapse involved between more than two different neurons - sensory synapses with 2 interneurons - one inhibitory IN synapses with motor neurons and causes inhibition and relaxation of one set of muscles, the other stimulatory IN synapses with motor neurons and causes contraction of the antagonistic muscle c. Postural reflexes - maintain upright position - e.g flexor (withdrawl) reflex - polysynaptic - sensory input -> interneuron -> motor neuron which contracts muscles and pulls limb away - PLUS synapses with motor neurons in adjacent SC segments -> contracts muscle - known as an intersegmental reflex arc - IN ADDITION - the sensory input can cross to the other side of the SC (via the gray commisure) where it synapses with and interneuron and motor neuron to contract the antagonistic muscle group and maintains balance = Intersegmental and Crossed extensor reflexes involved |
|
|
19.What are the major components of the brain?
|
Thalamus - (Relay & Processing centers for sensory information).
Hypothalamus - (Centers controlling emotions, autonomic functions and hormone production. Cerebrum - Conscious thought processes, intellectual functions, memory storage and processing - conscious and subsconscious regulation of skeletal muscle and contractions Cerebellum - coordinates complex somatic motor pattersns, adjust output of other somatic motor centers in brain and spinal cord Midbrain - processing of visual and auditory data, generation of reflexive somatic motor responses, maintenance of consciousness Pons - relays sensory information to cerebellum and thalamus, subconscious somatic and visceral motor centers Myelencephalon (Medulla Oblongata) - relays sensory information to thalamus, autonomic centers for regulation of visceral functions such as cardiovascular, respiratory and digestive activities. |
|
|
20.What is the role of the cerebral cortex? What are the three kinds of white matter tracts in the cerebrum – what do they do.
|
Cerebral cortex – outer layer of the cerebrum – areas for specific processing of sensation, area of voluntary movement, speech, all through processes.
1. white matter - neurons with long, myelinated axons, -organized into tracts A. Association tracts: conduct impulses between gyri within a hemisphere B. Commisural tracts: connects gyri in one hemisphere to others in the other hemisphere 1. corpus callosum 2. anterior commisure 3. posterior commisure C. Projection tracts: tracts that connect cerebrum to the lower parts of the CNS (e.g. Thalamus, brainstem) |
|
|
21.What is the basal ganglia? What is its role?
|
Basal Ganglia
-nuclei found deep within the cerebrum; - links to the midbrain; - receives input from the cortex & provides output to the motor areas of the cortex via the thalamus; -integrates motor commands; -regulates the initiation & termination of muscle mve.; -also functions to anticipate body movements & controls subconscious contraction of skeletal muscle • comprised of the: • 1. striatum – planning and modulation of movement – also involved in cognitive function – secretes the neurotransmitters ACh and GABA – caudate nucleus: controls mve of arms and legs when walking • activity in this area occurs prior to eye movements • also involved in learning and memory • language comprehension • falling in love • obsessive compulsive behavior – putamen: precedes or anticipates body movements • involved in reinforcement learning • projects neurons to the premotor area of the cortex via the GP and thalamus • also considered part of the lenticular nucleus (putamen + globus pallidus + claustrum) – nucleus accumbens • 2. globus pallidus: regulates muscle tone for movements – prepares the body for walking – once moving – the CN and P provide the pattern for the rhythm of trunk and limbs • 3. claustrum: thin strip of gray matter between the putamen and insula – together with the amygdala – receives visual information – other functions not known • 4. substantia nigra: high concentration of dopanergic neurons • 5. subthalmic nucleus |
|
|
22.What is the RAS? What is its role in sleeping and arousal? What other areas of the brain are involved in sleep cycles? How does the epithalamus participate in sleep?
|
Integrative Functions and the Reticular Activating System
• integrative function of the cerebrum – processing of sensory information (analysis and storage) and making a decision • includes sleep and wakefulness, learning and memory, emotional responses • wakefulness/sleep: role of the RAS – 24 hr cycle called circadian rhythm – established by the hypothalamus and epithalamus – transition between the states of sleep and wakefulness is controlled by the RAS – portion of the cerebral cortex that is activated upon sleep arousal – when active – transmission of signals to many areas of the cortex both directly and via the thalamus = general increase in cortical activity – arousal = awakening from sleep • stimulation of the RAS – by touch, pressure, pain, light • no input by olfactory receptors!! • stimulation of cholinergic neurons that release AcH – sleep = state of altered consciousness from which you can be arouse • exact function is still unknown • two components: NREM and REM • NREM – four stages • REM – 3 to 5 episodes per 7 to 8 hour sleep period (10-20 minutes) • regulated by many areas of the brain – hypothalamus, forebrain, medulla oblongata • sleep inducer – adenosine – binds to receptors and inhibits the RAS (inhibits arousal) • caffeine – binds to adenosine receptors and blocks their action – activity of the RAS is maintained • epithalamus – consists of the pineal gland and habenular nuclei; -pineal gland – part of the endocrine system -secretes the hormone melatonin; -increased secretion in dark ; -promote sleepiness and helps set the circadian; rhythms of the body (awake/sleep period) |
|
|
23.What type of memory do we possess? What areas are involved in each type?
|
Integrative Functions
• learning and memory – learning = the ability to acquire new information • no completely satisfactory explanation – memory = the process by which information that is acquired through learning is stored and retrieved – role for long-term potentiation (LTP) – enhances transmission at the hippocampus after a period of high-frequency stimulation – role for glutamate = binds NMDA glutamate receptors on post-synaptic neurons • different categories of memory – 1. immediate: ability to recall ongoing experiences, provides perspective to the present time so we know where we are and what we are doing – 2. short-term: temporary ability to recall information - seconds to minutes old » e.g. look up a phone number and then dial it a few seconds later » hippocampus, mamillary bodies of the hypothalamus and the anterior and medial nuclei of the thalamus – 3. long-term: transfer of short-term into a more permanent type » last from days to years » e.g. use the telephone number enough – stored permanently » role for the basal ganglia, cerebral cortex and cerebellum |
|
|
24.Where is the primary motor area located? Where is the primary somatosensory area located? Where are areas for speech, vision, & hearing located?
|
Cerebral cortex
Primary Somatosensory area • specific areas of the cerebral cortex receive somatic sensory input from various parts of the body • precise localization of these somatic sensations occurs when they arrive at the primary somatosensory area • some regions provide input to large regions of this area (e.g. cheeks, lips, face and tongue) while others only provide input to smaller areas (trunk and lower limbs) Midbrain – speech, vision and hearing located |
|
|
25.What are the 3 components of the brain stem? What do they each control?
|
Brain Stem
1. Medulla oblongata – continuation of the SC that forms the inferior part of the brain stem – relays sensory information and controls automatic motor functions – where the SC and MO meet - 90% of the axons from the right side of the SC cross over to the left side of the MO and vice versa = decussation – white matter contains sensory/ascending and motor/descending tracts – some of the white matter form bulges called pyramids – white tracts that connect the cerebrum to the SC – contains several nuclei also that regulate autonomic functions - reflex centers for regulating heartbeat and BP (cardiovascular center), respiration (respiratory center), plus vomiting, coughing, sneezing, hiccuping and swallowing – nuclei in the posterior part are associated with sensations of touch, proprioception, pressure and vibration -associated with 5 pairs of cranial nerves, VIII, IX, X, XI, XII, -nuclei: -reflex centers – e.g. cardiovascular & respiratory 1. inferior olivary: part of the olive -relay impulses from proprioceptors to the cerebellum – joint and muscle position 2. gracile: ascending sensory tracts from SC synapse here -relayed to the thalamus by postsynaptic neurons 3. cuneate: ascending sensory tracts from SC synapse here -relayed to the thalamus by postsynaptic neurons -white matter: pyramids -injury to the medulla: hard blow to the back of the head or upper neck can be fatal -damages the medullary rhythmicity area of the respiratory center (disrupts pattern of breathing) -non-fatal injury: paralysis and loss of sensation, irregular breathing and heart rate 2. Pons = “bridge” - e.g. connects brain stem to the cerebrum via bundles of axons - superior to the medulla and anterior to the cerebellum – consists of nuclei (cell bodies in gray matter) and tracts – somatic and visceral motor responses • Pontine nuclei – control voluntary movements that originate in the cerebral cortex and are relayed through the pons into the cerebellum • Pneumotaxic area – controls breathing (with medulla) • Apneustic area – controls breathing (with medulla) 3. Midbrain (Mesencephalon) – relay station between the cerebrum and the spinal cord – extends from the pons to the diencephalon – sends motor tracts to the SC, medulla and pons & conducts sensory tracts to the thalamus – anterior portion contains a pair of white tracts = cerebral peduncles • conduct impulses from the cerebrum to the SC, pons and medulla – posterior portion = tectum • white matter tracts = cerebellar peduncles • four round elevations = colliculi • reflex centers for visual activities (tracking, scanning) pupillary reflex, shape of the lens • reflexes that mediate movements of the eyes, head and neck - the startle reflex • relays impulses from hearing receptors to the thalamus -generates involuntary somatic motor responses • release of dopamine from substantia nigra (nuclei) - loss of these neurons = Parkinsons • red nuclei forms synapses with cerebellum to coordinate muscle movements Midbrain Nuclei • colliculi – superior and inferior • red nuclei • substantia nigra • white matter tracts: cerebral peduncles, cerebellar peduncles |
|
|
26.What are the 2 main components of the diencephalon? What do they each control?
a. how is the thalamus structured? b. what does it do? c. where is the hypothalamus located? d. what is its roles? e. what are the mamillary bodies for? the suproptic and preoptic regions |
• Diencephalon
– includes the hypothalamus, thalamus, epithalamus and subthalamus – thalamus: 80% of the diencephalon • paired oval masses of gray matter organized into nuclei, interspersed with white matter • joined by the intermediate mass (gray matter) in about 70% of brains • major relay station for most sensory impulses from the SC, brain stem • crude perception of pain, heat and pressure (refined in cerebrum) • transmits motor information from cerebellum to the cerebrum • relays nerve impulses to and from different areas of the cerebrum • seven major groups of nuclei !!! Thalmic Nuclei • reticular, pulvinar, geniculate – medial and lateral, anterior, medial, ventral – lateral, posterior and anterior • lateral – posterior and dorsal • hypothalamus -Emotions, autonomic functions, hormone production -mamillary bodies – serve as relay stations for reflexes related to eating -supraoptic(hormone) and preoptic nuclei (temp) that in hormone secretion (ADH) and body temp -major functions: 1. control of the ANS – integrates signals from the ANS (regulated smooth and cardiac muscle contraction) major regulator of visceral activities (heart rate, food movements, contraction of bladder) 2. produces hormones & connects with pituitary to regulate its activity 3. regulates emotional and behavioral patterns – rage, aggression, pain and pleasure + sexual arousal 4. regulates eating & drinking – hypothalamus contains a thirst center which responds to a rise in osmotic pressure in the ECF (dehydration) 5. controls body temperature – monitors temp of blood flowing through the hypothalamus Hypothalmic nuclei • mamillary bodies, supraoptic, preoptic, dorsomedial, ventromedial, anterior hypothalamic, posterior hypothalamic, paraventricular, suprachiasmatic, arcuate • epithalamus – consists of the pineal gland and habenular nuclei, -pineal gland – part of the endocrine system -secretes the hormone melatonin, -increased secretion in dark, -promote sleepiness and helps set the circadian, rhythms of the body (awake/sleep period) • subthalamus – works with the cerebrum and cerebellum to control body movements -majority is made of the subthamic nuclei, -sends efferent connections to the caudate nucleus and putamen, to the medial and lateral nuclei of the thalamus and to the red nucleus and substantia nigra of the midbrain -also receives afferent connections from the substantia nigra |
|
|
27. What is the cerebellum responsible for? What are the peduncles? What do they connect? What are the nuclei called?
|
Cerebellum
– divided into hemisphere with lobes - like the cerebrum • anterior and posterior lobes – involuntary motor activities • evaluates and coordinates motor activities initiated by the cerebrum and corrects problems by sending info back to the cerebrum • regulate posture & balance – has a superficial layer of gray matter called the cerebellar cortex - like the brain – deep to the gray matter are tracts of white matter = arbor vitae – also has nuclei = cerebellar nuclei (origin of neurons that connect the cerebellum to the brain and SC) – connected to the brain stem by three cerebellar peduncles • inferior – sensory information from the inner ear and body proprioceptors • middle – carry commands for voluntary movements that originated into the cortex into the cerebellum for coordination • superior – connects to the red nuclei and the nuclei of the thalamus |
|
|
28.What is the midbrain’s role? What are the cerebral peduncles for? What is the role of the substantia nigra? the red nuclei? What is the role of the colliculi?
|
Midbrain’s role – relay station between the cerebrum and the spinal cord, extends from the pons to the diencephalons, sends motor tracts to the SC, medulla and pons & conducts sensory tracts to the thalamus.
Cerebral peduncles – anterior portion contains a pair of white tracts cerebral peduncles - conduct impulses from the cerebrum to the SC, pons and medulla tectum – is the posterior portion, white matter tracts (cerebellar peduncles) , reflex center for visual activities (tracking, scanning) papillary reflex, shape of the lens, reflexes that mediate movements of the eye, head, and neck – startle reflex, relays impulses from hearing receptors to the thalamus colliculi – gray matter ganglion, four round elevations, generates involuntary somatic motor response substantia nigra – release dopamine, loss of these neurons = Parkinson’s disease red nuclei – forms synapses with cerebellum to coordinate muscle movements |
|
|
29.What is the pons’ role? What are the 3 major nuclei in the pons? What do they control
|
Pons – “bridge”, connects brain stem to the cerebrum via bundles of axons, superior to the medulla and anterior to the cerebellum, consists of nuclei (cell bodies in gray matter) and tracts (white matter), somatic and visceral motor responses
3 nuclei – pontine nuclei – control voluntary (somatic) movements that originate in the cerebral cortex and are relayed thru the pons into the cerebellum, pneumotaxic area – controls breathing (with medulla), apneustic area – controls breathing (with medulla) |
|
|
30.What is the role of the medulla oblongata? What is decussation? What are the nuclei of the MO? What are their roles? What are the pyramids?
|
Medulla oblongata - continuation of the SC that forms the inferior part of the brain stem, relays sensory information and controls automatic motor functions, where the SC and MO meet - 90% of the axons from the right side of the SC cross over to the left side of the MO and vice versa = decussation
- white matter contains sensory/ascending and motor/descending tracts - some of the white matter form bulges called pyramids – white tracts that connect the cerebrum to the SC -contains several nuclei also that regulate autonomic functions - reflex centers for regulating heartbeat and BP (cardiovascular center), respiration (respiratory center), plus vomiting, coughing, sneezing, hiccuping and swallowing -nuclei in the posterior part are associated with sensations of touch, proprioception(the perception of the position of limbs and the body), pressure and vibration -associated with 5 pairs of cranial nerves (VIII, IX, X, XI, XII) -nuclei: -reflex centers – e.g. cardiovascular & respiratory 1. inferior olivary: part of the olive, -relay impulses from proprioceptors to the cerebellum – joint and muscle position 2. gracile: ascending sensory tracts from SC synapse here, -relayed to the thalamus by postsynaptic neurons 3. cuneate: ascending sensory tracts from SC synapse here, -relayed to the thalamus by postsynaptic neurons -white matter: pyramids |
|
|
31.What is the limbic system? What are its components?
|
•called the emotional brain, group of structures that surround the brain stem, involved in olfaction and memory
• emotion – anger, fear, happiness (associated with specific responses – behavioral patterns) • basic behavioral patterns: -preparing for attack, laughing, crying, blushing, -also includes sexual behaviors for the continuation of the species, connects with the hypothalamus to regulate these behaviors • main components: – 1. limbic lobe: rim of cerebral cortex on the medial surface of each hemisphere – includes the hippocampus (parahippocampal gyrus), the cingulate gyrus, the insula and the dentate gyrus • Hippocampus (memory) is located within the dentate gyrus and is surrounded by the parahippocampal gyrus • cingulate gyrus is located above the corpus callosum • insula – located within the lateral sulcus that separates the temporal lobe from the parietal lobe – 2. amygdala: integration center between the limbic system, cerebrum and various sensory systems • stimulation – rage, fear recognition, social interaction, recognition of familiar objects, facial expression, interpretation of facial expressions – 3. olfactory bulbs – 4. septal nuclei – 5. mammillary bodies of the hypothalamus – 6. fornix - tract of white matter that connects the hippocampus to the hypothalamus • fibers end at the mammillary bodies – 7. hypothalmic nuclei - other areas include the anterior nuclear group of the thalamus and the reticular system within the brain stem |
|
|
32.What are the 12 cranial nerves and their specific numbers? Which are mixed? which are sensory? which are motor? what do they innervate?
|
12 pairs of cranial nerves
I – Olfactory (from olfactory receptors) VII – Facial (from taste buds & to facial muscles & glands) II – Optic (from retina of eyes) VIII – Acoustic (from inner ear) III – Oculomotor (to eye muscles) IX – Glossopharyngeal (from pharynx & to pharyngeal muscles) IV – Trochlear (to eye muscles) X – Vagus (from & to internal organs) V – Trigeminal (from mouth & to jaw muscles XI – Accessory (to neck & back muscles) VI – Abducens (to eye muscles) XII – Hypoglossal (to tongue muscles) -cranial nerves – 12 pairs -considered part of the peripheral nervous system (PNS) -olfactory & optic contain only sensory axons = sensory nerves -remaining are motor or mixed nerves (both motor and sensory axons) |
|
|
33.What are the components of a spinal nerve? what is a ramus? what is a horn composed of? what is a rami communicantes? what division of the PNS is it part of? what is a column composed of? what are the 6 major tracts of the SC? what do they control?
|
Spinal nerve – after passing through intervertebral foramina the spinal nerve branches = ramus/rami
Dorsal ramus – sensory/motor innervation to skin and muscles of back Ventral ramus – ventrolateral body surface, body wall structures, muscles of the upper and lower limbs *in addition to these rami, the spinal nerves also give off a meningeal branch- re-enters the vertebral canal and supplies the vertebrae, vertebral ligaments and meninges. Pairs of spinal nerves monitor dermatomes. Damaged region of the spinal cord can be distinguished by patterns of numbness over a dermatome region gray matter of SC – concentrated in butterfly-shaped region in the interior of the cord, contains interneurons, cell bodies, dendrites of efferent neurons and the axon terminals of afferent neurons. Consists of one dorsal horn and ventral horn. Dorsal horn – encompases the dorsal (posterior) half of the gray matter on either side; ventral horn - ventral (anterior) half. Afferent fibers originate in the periphery as sensory receptors and terminate in the dorsal horn, where they synapse on interneurons or efferent neurons. Note that cell bodies of these afferent fibers are not located in the spinal cord itself, they are located outside the spinal cord in clusters called dorsal root ganglia White matter of SC – is in the surrounding outer region Rami communicantes – branches from the spinal nerve, - defined as a connection between a spinal nerve and the sympathetic trunk of the ANS: 2 types. 1) gray rami communicantes – unmyelinated post ganglionic axons, 2. white rami communicantes – myelinated preganglionic axons |
|
|
34.what does the somatic division of the PNS control? where are its neuronal cell bodies located? what neurotransmitter is released by a somatic neuron? does this NT stimulate or inhibit its target? how is motor neuron activity regulated?
|
Somatic division of the PNS – controls skeletal muscle, considered the voluntary aspect of the PNS, (but the muscles
of posture and balance are controlled involuntary by the lower brain centers (brain stem, cerebellum) Cell bodies – located in the (anterior) ventral gray horn of the spinal cord, the axon of a motor neuron extends from the CNS continuously to its skeletal muscle target (ANS usually requires 2 neurons) Acetylcholine – the NT’s released by a somatic neuron, can only stimulate its target (whereas ANS can either stimulate or inhibit its target) Somatic NS – somatic/motor commands emerge from the ventral horn and travel thru: dorsal ramus to target the muscles of the back; s to target the muscles of the limbs and body wall. • - motor neurons receive incoming information from many converging presynaptic neurons – both excitatory and inhibitory on these motor neurons – some information are part of reflexes originating in the spinal cord – other information can come in from areas of the brain via the descending white matter tracts • motor areas of the cerebral cortex, the basal nuclei and the cerebellum – synapse with the motor neurons in the ventral horn and regulate their activity • activation – impulse sent to muscles • inhibition – no impulse, no contraction • level of activity of a motor neuron is the balance between the EPSPs/activation and the IPSPs/inhibition of the incoming synapsing neurons • therefore motor neurons are considered the final common pathway – considered the only way any other part of the nervous system can influence muscle activity |
|
|
35.what is a lower motor neuron? what is the final common pathway? what neurons provide input to lower motor neurons? be able to describe these input neurons and what they do.
|
Lower motor neurons (LMN’s) – all excitatory and inhibitory signals that control movement converge on the motor neurons that extend from the brain stem and SC to innervate the skeletal muscle. (have their cell bodies in the brain stem and SC.), their axons extend thru the cranial and spinal nerves to skeletal muscle
Final common pathway – only LMN provide output from the CNS to skeletal muscle fibers. (damaged to the LMN’s produced flaccid paralysis on the same side as the damage – loss of reflex action, motor tone and voluntary contraction 4 inputs provided by neurons to LMN’s • 1. local circuit – input arrives at LMNs from nearby interneurons called local circuit neurons – receive input from somatic sensory receptors and higher centers of the brain – help coordinate rhythmic activities in muscle groups • 2. UMNs – provide input to the local circuit and LMNs – essential for planning, initiating and directing sequences of voluntary movements – extend from the brain to the LMNs via two types of somatic motor pathways • 1. direct motor pathways: nerve impulses for voluntary movement – about 90% decussate within the medulla oblongata – lateral corticospinal, anterior corticospinal and corticobulabar (brain stem) • 2. indirect motor pathways: or extrapyramidal pathways – nerve impulses follow complicated circuits that involve the cortex, basal ganglia, thalamus and brain stem • 3. Basal ganglia – assist movement by providing input to the UMNs – also suppresses unwanted movements by inhibiting the thalamus activity – the production of dopamine by the substantia nigra also effects muscle tone – caudate nucleus and putamen receive imput from sensory, association and motor areas of the cortex and from the substantia nigra – output from the globus pallidus and SN goes to the motor areas of the cortex via the thalamus • this circuit (cortex – basal ganglia – thalamus – cortex) may function in initiating and terminating movements • e.g. the putamen appears to signal just via to movement • 4. Cerebellar – function involves four activities • 1. monitoring intentions for movement • 2. monitoring actual movement • 3. comparing the command (intention and movement) with sensory information • 4. correction – to UMNs – travels via the thalamus to the UMNs in the cerebral cortex – or can go directly to the UMNs in the brain stem |
|
|
36.what is a neuromuscular junction? be able to describe the molecular events that occur at the NMJ. what NT is released at the NMJ. what does this NT do to the target muscle cell? what is an end-plate potential? how is it generated?
|
Neuromuscular junction – specialized central region where a motor neuron synapses with skeletal muscle fiber.
- end of neuron (synaptic terminal or axon bulb) in very close association with a muscle fiber/cell - distance between the bulb and the folded sarcolemma – synaptic cleft Acetylcholine – NT’s that released in NMJ due to nerve impulse, this release will result in activation of the muscle cell and contraction, therefore the NMJ is always excitatory, the only way inhibition can take place is thru the inhibition of the neuron connecting with the muscle Opening of acetylcholine-gated cation channels leads to muscle contraction 1.action potential reaches synaptic end bulb and causes opening of voltage-gated calcium channels -docking and fusion of the Ach-containing synaptic vesicle, -mechanism of multiple docking proteins + calcium 2. AcH binds to myofibril surface – ligand-gated sodium channels resulting in influx of sodium and depolarization of the muscle cell’s PM = end-plate potential 3. this depolarization opens additional Na channels – voltage-gated, -threshold is reached = Action Potential throughout the muscle cell 4. AP causes the release of calcium by sarcoplasmic recticulum = contraction Motor Units • Each skeletal fiber has only ONE NMJ • MU = Somatic neuron + all the skeletal muscle fibers it innervates • Number and size indicate precision of muscle control • Muscle twitch – Single momentary contraction – Response to a single stimulus • All-or-none theory – Either contracts completely or not at all Motor units in a whole muscle fire asynchronously some fibers are active others are relaxed delays muscle fatigue so contraction can be sustained Muscle fibers of different motor units are intermingled so that net distribution of force applied to the tendon remains constant even when individual muscle groups cycle between contraction and relaxation. |
|
|
37.What are the divisions of the ANS? what are preganglionic and postganglionic neurons? what do they synapse with? what NTs do they release?
|
ANS - involuntary motor commands and sensory information , supplies cardiac and smooth muscle, glands (i.e. viscera)
2 divisions of ANS: • efferent branch regulates “visceral” activities (motor commands, involuntary, organs) • also has an afferent branch that receives sensory information from these areas preganglionic(Ach) and postganglionic (Ach, NE, PE) • preganglionic synapses with the cell body of the postganglionic within the ganglion • the pregang and postgang neurotransmitters can differ • the postganglionic neuron is unmyelinated • glands are innervated by the preganglionic neuron – e.g adrenal gland which then releases epinephrine or norepinephrine in response ANS axons exit the lateral gray horn through the ventral (anterior) root of the thoracic spinal nerve along with somatic motor nerve axons, form part of the spinal nerve and exit through an intervertebral foramina, they then enter a white rami communicantes and pass to the nearest sympathetic trunk ganglion (axons or myelinated) – visceral motor commands |
|
|
38.What do the parasympathetic and sympathetic nervous systems do? What neurotransmitters do they secrete (NE and AcH)? what neurons secrete these NTs?
|
Sympathetic Dominance - fight or flight, protective response, elevated heart rate, blood pressure, respiration rate,
increase blood flow to skeletal muscles, lungs, heart, brain; decrease blood flow to digestive, reproductive and urinary organs Parasympathetic Dominance - “rest and digest” response, dominates in quiet, stress-free situations, resets the system after sympathetic stimulation (e.g. slow the heart rate and lower blood pressure) Symphatetic Division - cell bodies of the preG neurons are located in the gray lateral horns of the 12 thoracic spinal nerves • sympathetic ganglia – site of the synapse between the preG and postG neurons – two groups 1. sympathetic trunk ganglia: or vertebral chain ganglia -vertical row lateral to the vertebral column -extend from the base of the skull to the coccyx -short preG lead into these ganglia -postG from these ganglia innervate the organs above the diaphragm -3 cervical, 11 or 12 thoracic, 4 or 5 lumbar and 4 or 5 sacral 2. prevertebral ganglia: or the collateral ganglia -anterior to the vertebral column and close to the large abdominal arteries -postG neurons innervate the abdominal organs -three major prevertebral ganglia: celiac, superior mesenteric and inferior mesenteric • axons exit the lateral gray horn through the ventral (anterior) root of the thoracic spinal nerve along with somatic motor nerve axons • form part of the spinal nerve and exit through an intervertebral foramina • they then enter a white rami communicantes and pass to the nearest sympathetic trunk ganglion (axons or myelinated) – visceral motor commands *** whether it is sympathetic or parasympathetic – the preG neurons release AcH Parasympathetic Division • cell bodies of the preG neurons are located in the four cranial nerves III, VII, IX and X (brain stem) and in the lateral gray horns of the sacral spinal nerves 2 through 4 • emerge as part of the cranial or spinal neve • parasympathetic ganglia: called terminal ganglia – located close to the wall of a visceral organ – the preG fibers are very long because they must extend from the CNS to an organ – synapse with postG within the terminal ganglia – four major TGs – located close to the organ they innervate |
|
|
38.What do the parasympathetic and sympathetic nervous systems do? What neurotransmitters do they secrete (NE and AcH)? what neurons secrete these NTs?
|
Sympathetic Dominance - fight or flight, protective response, elevated heart rate, blood pressure, respiration rate,
increase blood flow to skeletal muscles, lungs, heart, brain; decrease blood flow to digestive, reproductive and urinary organs Parasympathetic Dominance - “rest and digest” response, dominates in quiet, stress-free situations, resets the system after sympathetic stimulation (e.g. slow the heart rate and lower blood pressure) ANS Neurotransmitter • specific neurons release specific NTs – have distinct names • cholinergic neurons and AcH – include all preG neurons from sympathetic and parasympathetic neurons – sympathetic postG that innervate the sweat glands – all parasympathetic postG neurons – two types of receptors • 1. nicotinic • 2. muscarinic • adrenergic neurons and NE – most sympathetic postG – two types of receptors • 1. alpha – a1 and a2 • 2. beta – b1 and b2 and b3 |
|
|
39.be able to describe the organization of the sympathetic and parasympathetic divisions. know their respective ganglia
|
Symphatetic Division - cell bodies of the preG neurons are located in the gray lateral horns of the 12 thoracic spinal nerves
• sympathetic ganglia – site of the synapse between the preG and postG neurons – two groups 1. sympathetic trunk ganglia: or vertebral chain ganglia -vertical row lateral to the vertebral column -extend from the base of the skull to the coccyx -short preG lead into these ganglia -postG from these ganglia innervate the organs above the diaphragm -3 cervical, 11 or 12 thoracic, 4 or 5 lumbar and 4 or 5 sacral 2. prevertebral ganglia: or the collateral ganglia -anterior to the vertebral column and close to the large abdominal arteries -postG neurons innervate the abdominal organs -three major prevertebral ganglia: celiac, superior mesenteric and inferior mesenteric • axons exit the lateral gray horn through the ventral (anterior) root of the thoracic spinal nerve along with somatic motor nerve axons • form part of the spinal nerve and exit through an intervertebral foramina • they then enter a white rami communicantes and pass to the nearest sympathetic trunk ganglion (axons or myelinated) – visceral motor commands *** whether it is sympathetic or parasympathetic – the preG neurons release AcH Parasympathetic Division • cell bodies of the preG neurons are located in the four cranial nerves III, VII, IX and X (brain stem) and in the lateral gray horns of the sacral spinal nerves 2 through 4 • emerge as part of the cranial or spinal neve • parasympathetic ganglia: called terminal ganglia – located close to the wall of a visceral organ – the preG fibers are very long because they must extend from the CNS to an organ – synapse with postG within the terminal ganglia – four major TGs – located close to the organ they innervate |
|
|
40.what are the types of receptors for AcH, for NE called? where are these receptors found? how do they function?
|
ANS Receptors
• the NTs released by the ANS can either stimulate or inhibit its target – depends on the receptors located in the target 1. Cholinergic receptors – respond to AcH • a. nicotinic – named because they are activated by nicotine – found in the ganglia of the symp. and parasymp. division (all ANS ganglia) – respond to AcH release from symp and parasymp preG fibers – binding opens channels for the movement of Na and K – more Na enters the target neurons within the ganglion – depolarization and initiation of an AP by the postG neurons 2. Adrenergic receptors – respond to NE/Epi • alpha and beta classes – a1, a2, b1, b2 • distributed in a specific pattern and respond to either NE or Epi or both • respond to activation by activating G proteins -> second messangers (cAMP or Ca) • therefore they are called G protein coupled receptors |
|
|
41.Define sensation, define perception?
|
Sensation: response to environment via generation of nerve impulse
-sensation occurs upon arrival of nerve impulse at cerebral cortex -before nerve impulse is generated - sensory receptors integrate or sum up the incoming signals -several types of integration: one type is adaptation - decrease in response to a stimulus a. role of the thalamus?? (gatekeeper??) -nerve impulses sent via ascending tracts in spinal cord to the brain Perception: our conscious interpretation of the external world b. created by the brain based on information it receives from sensory receptors c. interpretation of sensation |
|
|
42.How can you classify a sensory receptor? What are the types based on each classification?
|
-sensory receptors: can either be a
1) specialized ending of an afferent neuron 2) a separate cells closely associated with an afferent neurons -can classify a sensory receptor based on: 1. microscopic features: a. free nerve endings: bare dendrites associated with pain, heat, tickle, itch and some touch b. encapsulated nerve endings: dendrites enclosed in a connective tissue capsule - touch e.g. Pacinian corpuscle c. separate cells: individual receptors that synapse with first-order afferent neurons’ e.g. gustatory cells (taste) 2. receptor location: a. exteroceptors: located at or near the body surface, responds to information coming in from the environment (taste, touch, smell, vision, pressure, heat and pain) b. interoceptors: located in blood vessels, visceral organs and the nervous system; provide information about internal environment c. proprioceptors: located in inner ear, skeletal muscle and joints; provides information about position of limbs and head 3. type of stimulus: 1. Chemoreceptors 2. Mechanoreceptors 3. Nociceptors/pain receptors 4. Thermoreceptors 5. Photoreceptors 6. Osmoreceptors |
|
|
43.What are the two types of sensations
|
each type of sensation = sensory modality
one type of neuron carries only one type of modality modalities can be grouped into two classes a. 1. general senses – includes both the somatic and visceral senses • tactile (touch, pressure), thermal, pain and proprioception b. 2. special senses: sight, sound, hearing, taste |
|
|
44.What are the 4 major steps in sensation?
|
1. stimulation of the sensory receptor (depolarization – threshold)
a. alters the permeability of the neuron’s PM b. usually does this through non-specific opening of small ion channels 2. transduction of the stimulus (Action Potential) a. increased influx of Na ions – depolarization – called a graded receptor potential b. therefore the sensory receptor converts (transduces) the energy of the stimulus into a graded potential 3. generation of the nerve impulse (appropriate to CNS) - increase in graded receptor potential past threshold -> Action Potential - AP propagates toward the CNS 4. integration of the sensory input - receipt of sensory information by a particular region in the CNS - integration of sensation and perception |
|
|
46.What are the three types of neurons in a sensory pathway? Where to they travel/what do they connect?
|
Sensory(Motor) Pathways: these pathways consist of thousands of sets of neurons – grouped into threes
1. first order neurons – conduct sensory information from the receptor into the CNS • scranial nerves conduct information from the face, mouth, eyes, ears and teeth • spinal nerves conduct information from the neck, trunk and limbs 2. second order neurons – conduct information from the brain and SC into the thalamus • these neurons decussate (cross over) within the thalamus; always end in thalamus 3. third order neurons – conduct information from the thalamus to the primary somatosensory areas within the cerebral cortex (thalamus to somewhere to cerebrum) • for integration |
|
|
45.From where does the dorsal ramus receive info? Ventral ramus? Rami communicantes?
|
Dorsal ramus – back (muscular or skin of the back), smaller
Ventral ramus – anywhere else – carry more and physically bigger Rami communicantes – motor commands/ ANS(outgoing), visceral sensory input (guts) Lateral gray horn (ANS), somatic motor. Posterior gray horn – synapse via little motors into white column,– sensory - posterioir or lateral (2 columns) Motor - Lateral or anterior column, short trip to the gray horn |
|
|
46.what are the three major sensory pathways? Where are the first, second and third order neurons in these pathways? What kinds of information are carried in these paths?
|
sensory pathways enter the SC and ascend to the cerebral cortex via:
1. the posterior column-medial lemniscus path • for conscious proprioception and most tactile sensations • two tracts of white matter: posterior column and the medial lemniscus • first order neurons from sensory receptors in the trunk and limbs form the posterior columns in the spinal cord • synapse with second order neurons in the medulla oblongata goes to thalamus • these then cross to the opposite side of the medulla and enter the medial lemniscus in the thalamus – synapse with the third order neurons that travel to the cortex (primary somatosensory area) 1. fine touch 2. stereostegnosis – ability to recognize shapes, sizes and textures by feeling 3. proprioception 4. vibratory sensations 2. the anterolateral/spinothalmic path • first order neurons receive impulses from receptors in the neck, trunk or limbs • cell bodies of these neurons are located in the dorsal root ganglion • sensory receptors end in dorsal root ganglion • these receptors synapse with the 1st oder neuron located in the dorsal root ganglion • synapse with second order neurons in the posterior gray horn • second order neurons than cross to the opposite side of the SC and pass upward to the brain stem in either the: 1. lateral spinothalmic tract: pain and temperature 2. anterior spinothalmic tract: information for tickle, itch, crude touch and pressure 3. spinocerebellar two tracts: posterior spinocerebellar and anterior spinocerebellar major routes for proprioceptive impulses that reach the cerebellum, not consciously perceived, critical for posture, balance and coordination, posterior spinocerebellar routes are degraded upon advanced syphillis – severe uncoordination 1st order neuron – muscle spindles & tendon organs 2nd order neuro – cell bodies in dorsal gray horn via thalamus to the cuneate nucleus of basal ganglia 3rd order neurons – thalamus to cerebellum (no dessucation) right leg to right cerebellum, left leg to left cerebellum |
|
|
47.where is the primary somatosensory area? What areas of the body take up the most “room” in this area?
|
Priamary Somatosensory Area - specific areas of the cerebral cortex receive somatic sensory input from various parts
of the body, precise localization of these somatic sensations occurs when they arrive at the primary somatosensory area, some regions provide input to large regions of this area (e.g. cheeks, lips, face and tongue) while others only provide input to smaller areas (trunk and lower limbs) (sensory info – pain, heat, itch) |
|
|
48.what are the kinds of proprioceptors located in your muscles? How are they constructed? How do they work?
|
Proprioceptors (mechanoreceptors) tendon-tension
-located in muscles, joints and tendons -position of limbs and degree of muscle relaxation -located in the inner ear – position of head: -”hair cells” – position relative to the ground and movement -allow us to estimate weight and to determine how much muscular effort is needed for task -high concentration in postural muscles (body position), tendons (muscle contraction) -Patellar reflex: muscle stretch, proprioceptor fres impulse to spinal cord, reflex arc results, muscle fiber Response three types of proprioceptors – 1. muscle spindles • monitor changes in muscle length • used by the brain to set an overall level of involuntary muscle contraction = motor tone • consists of several sensory nerve endings that wrap around specialized muscle fibers = intrafusal muscle fibers – very plentiful in muscles that produce very fine movements – fingers, eyes – stretching of the muscle stretches the intrafusal fibers, stimulating the sensory neurons – info to the CNS – IFMs also receive incoming information from gamma motor neurons – end near the IFMs and adjust the tension in a muscle spindle according to the CNS • also have extrafusal muscle fibers which are innervated by alpha motor neurons – response to a stretch reflex (Lower Motor Neuron) – 2. tendon organs • located at the junction of a tendon and a muscle • protect the tendon and muscles from damage due to excessive tension • consists of a thin capsule of connective tissue enclosing a few bundles of collagen – penetrated by sensory nerve endings that intertwine among the collagen fibers – 3. joint receptors (joint kinesthetic receptors) • several types • located in and around the articular capsules of synovial joints • free nerve endings and mechanoreceptors found – detect pressure within the joint • also can find Pacinian corpuscles which detect the speed of joint movement |
|
|
49.what are the types of cutaneous receptors?
|
Cutaneous receptors (touch, skin, tactile sensation)
- located in skin -dermis: pressure, temperature, touch (fine and crude) and pain -impulse sent to somatosensory areas of brain -touch receptors: Meissner’s (fingertips, lips, tongue, nipples, penis/clitoris) – for fine touch Merkel disks (epidermis/dermis) – fine touch, slowly adapting Root hair plexus (root of hair) - crude touch receptors -pressure receptors: Pacinian corpuscles – connective tissue capsule over the dendrites -temp receptors: free nerve endings that respond to cold OR warmth - pain -also: Krause end bulbs, Ruffini endings (also for stretching, slowly adapting) |
|
|
50.what are the types of adaptation possible? Describe each.
|
Receptor adaptation – is a decrease over time in the magnitude of the receptor potential in the presence of a constant
stimulus; a change in sensitivity during a long –lasting stimulus Types of adaptation: Slowly adapting or tonic receptors – show little adaptation and therefore can function in signaling the intensity of a prolonged stimulus. (E.g. detecting pain, body position, chemicals in blood) Rapidly adapting or phasic receptors – adapt quickly and thus function best in detecting changes in stimulus intensity. Some rapidly adapting receptors also show a second, smaller response upon the termination of a stimulus called the “off response”. (E.g. olfactory receptors, detects odors, and Pacinian corpuscles, detect vibration in the skin.) |
|
|
51.what are the types of adaptation that can occur in a Pacinian corpuscle?
|
Rapidly adapting or phasic receptors
|
|
|
52.what are the three types of pain receptors? What neurotransmitters are released by these receptors? What do they do? What are the major processing areas for pain? Where are the second order neurons found for the pain pathway?
|
Pain – somesthetics sensations.
Nociceptors – receptors of pain, are free nerve endings.1. autonomic responses – increases in blood pressure and heart rate, increases in blood epinephrine levels, increase in blood glucose, dilation of the pupils of the eye or sweating. 2. emotional responses such as fear or anxiety, 3. reflexive withdrawal – from the stimulus. Two types of pain Acute pain – occurs very rapidly, usually within 0.1 second after a stimulus is applied, and is not felt in deeper tissues of the body. This type of pain is sharp, fast and pricking pain. Needles puncture or knife cut to the skin. Chronic pain – begins after a second or more and then gradually increases in intensity over a period of time. Maybe excruciating. Burning, aching, throbbing and slow pain. Can occur both in the skin and deeper tissues or in internal organs. Superficial somatic pain – pain from the stimulation of receptors in the skin, deep somatic pain – stimulation of receptors in skeletal muscle, joints, tendons and fascia, visceral pain – results from stimulation of receptors in the visceral organs. Referred pain - surface Phantom pain - still feel the pain, itching, pressure, tingling, or pain in the extremity Analgesia – pain relief such as aspirin and ibuprofen (motrin) block prostaglandins |
|
|
53.Describe the mechanism and physiology of smell. What are the functions of the olfactory receptors, supporting cells, olfactory glands & basal cells? What nerves are involved the transmission of the olfactory impulse?
|
Smell - -olfactory cells - located within olfactory epithelium in the nasal cavity
-Covers superior nasal cavity (superior nasal conchae) and cribriform plate -are modified neurons, -end in microvilli with receptor proteins for odor molecules -each olfactory cell is specific for one odor molecule - specific neuron types -olfactory nerves make connections with the limbic system (emotions and memory) • Olfactory receptors - bipolar neurons with cilia or olfactory hairs • Supporting cells - columnar epithelium • Basal cells = stem cells, replace receptors monthly • Olfactory glands - produce mucus • Both epithelium & glands innervated by cranial nerve VII. Olfaction:Sense of Smell • Odorants bind to receptors • Na+ channels open • Depolarization occurs • Nerve impulse is triggered (NT release) • some odors bind the receptor and trigger the activation of a G protein – second messenger production, opening of Na channels and depolarization • 1000 different types of olfactory receptors neurons, total of 10million olfactory receptors Olfactory Pathway • has a very low threshold to trigger perception • Axons from olfactory receptors form the olfactory nerves (Cranial nerve I) that synapse in the olfactory bulb – pass through 40 foramina in cribriform plate • neurons within the olfactory bulb form the olfactory tract that synapses on the primary olfactory area of temporal lobe – conscious awareness of smell begins • Other pathways lead to the frontal lobe (Brodmann area 11) where identification of the odor occurs • hyperosmia – keener sense of smell then others – seen in women (time of ovulation) – opposite is hypoosmia –reduction in the sense of smell • the olfactory bulb also receives top-down info from such brain areas as the amygdale, hippocampus and substantia niagra • olfactory bulb potential functions” - enhancing odor discrimination - enhancing detection sensitivity - filtering out many background odors - permitting higher brains areas involved in arousal |
|
|
54.What is a taste bud? What are the 4 classes of taste buds? Where are they located? What types of papillae contain taste buds? Where are they found on the tongue and in the mouth? What is the mechanism and physiology of taste? How do these mechanisms differ with respect to specific chemicals? What nerves are involved in taste?
|
Taste
-Taste requires dissolving of substances -taste buds: salty(endside), sweet(tip), bitter(back) and sour(side) -10,000 taste buds found on tongue, soft palate & larynx -found associated with projections called papillae -open at a taste pore -taste cells are associated with support cells and connect with sensory nerve fibers -tips of taste cells are microvilli - receptors proteins for specific chemicals Anatomy of Taste Buds: • An oval body consisting of 50 receptor cells surrounded by supporting cells • A single gustatory hair projects upward through the taste pore • Basal cells develop into new receptor cells every 10 days. taste buds: 1. foliate 2. fungiform 3. circumvallate 4. filliform (texture) Physiology of Taste • receptor-ligand interaction – ligand is the chemical from the food and the receptor is the taste cell • binding leads to a change in the receptor potential – action potential • stimulates exocytosis from the taste cell – binds to a first order neuron • pathway is distinct for different chemicals – e.g. salty foods – Na enters the gustatory cell via ligand-gated channels – depolarization – direct method • depolarization opens calcium channels – exocytosis • similar mechanism for sour foods – entrance of H+ ions which opens Na channels – other tastants do NOT enter the cell but bind to the PM – bind to G protein coupled receptors and trigger the production of a second messanger which than causes a depolarization and action potential – indirect methods • Complete adaptation in 1 to 5 minutes • Thresholds for tastes vary among the 4 primary tastes – most sensitive to bitter (poisons) – least sensitive to salty and sweet Gustatory Pathway • gustatory fibers found in cranial nerves – VII (facial) serves anterior 2/3 of tongue – IX (glossopharyngeal) serves posterior 1/3 of tongue – X (vagus) serves palate & epiglottis • Signals travel to thalamus or limbic system & hypothalamus • Taste fibers extend from the thalamus to the primary gustatory area on parietal lobe of the cerebral cortex – providing conscious perception of taste • taste aversion – because of the link between the hypothalmus and the limbic system – conscious and strong connection between taste and emotion 1st order neuron – terminates in brain stem at nucleus of solitary tract 2nd order neuron – terminates in thalamus 3rd order neuron – thalamus to insular (limbic) and primary gustatory area or parietal lobe of the cerebral cortex Factors for taste: - always taste better when hungry - genetics, and ugly taste of OJ after brushing teeth. |
|
|
55. Remember the basic anatomy of the eye and accessory structures - What are the three layers of the eye? Why is the retina black? How does the iris change shape? Where are the aqueous and vitreous humor located? Describe the mechanism and physiology of vision with respect to the photoreceptors and the retina. What are the types of photoreceptors and where are they found in the retina.What do they detect? What are the cell types in the retina? What cells communicate with the PCs? What is the direction of light and direction of synaptic transmission through the retina? What is the role of the horizontal and amacrine cells? How does light and dark adaptation work? What is the visual pigment composed of? Where in the PC is it found? What are the two forms of retinal? When are they formed? What is the mechanism of vision in the dark, in the light? How does the lens change shape in order to focus – what has to happen to the suspensory ligaments and the ciliary muscles? What cranial nerve is involved in vision? Describe the visual pathway? What cranial nerves move the eyes?
|
Photoreceptor – of bipolar synapse – chemical synapse, bipolar ganglion – electrical synapse
Vision – intraincular pressure (presses against retina) Eye: tough outer covering - sclera (white, cornea) Cornea – avascular, no blood supply -middle choroid layer - vessels, melanin pigment (light absorption); -front of eye it becomes the iris (aperture), -inner nerve layer – retina -sight is generated by the bending and focusing of light onto the retina - done by the lens (shape changes controlled by tiny ciliary muscles) • Anterior cavity (anterior to lens) – filled with aqueous humor(and vitreous) helps to det. How much intraincular pressure in the eye • produced by ciliary body • continually drained • replaced every 90 minutes – 2 chambers • anterior chamber between cornea and iris • posterior chamber between iris and lens • Posterior cavity (posterior to lens) – filled with vitreous body (jellylike) – formed once during embryonic life – floaters are debris in vitreous of older individual Accessory Structures of Eye • Eyelids or palpebrae – protect & lubricate – epidermis, dermis, CT, orbicularis oculi m., tarsal plate, tarsal glands (preventing eyelids to stick together) & conjunctiva • Tarsal glands – oily secretions keep lids from sticking together • Conjunctiva(anterior of the eye) – protect retina, physical barrier, produce tears, act of blinking spread the tears - palpebral & bulbar – stops at corneal edge – dilated BV--bloodshot ** tears - antimicrobial Lacrimal Apparatus About 1 ml of tears produced per day. Spread over eye by blinking. Contains bactericidal enzyme called lysozyme. Tunics (layers) of eyeball Fibrous Tunic (outer layer) CORNEA – can change shape, bending of light – problem if have astigmatism, put lenses that shape the cornea • Transparent • Helps focus light (refraction) – astigmatism • 3 layers – nonkeratinized stratified squamous (outer); collagen fibers & fibroblasts; simple squamous epithelium • Nourished by tears & aqueous humor SCLERA • “White” of the eye • Dense irregular connective tissue layer -- collagen & fibroblasts • Provides shape & support; Posteriorly pierced by Optic Nerve (CNII) ** hard contact lens with tears shape the cornea, but cornea has memory that go back to the original shape Vascular Tunic (middle layer) • Choroid – pigmented epithelial cells (melanocytes) & blood vessels – provides nutrients to retina – black pigment in melanocytes absorb scattered light • Ciliary body – choroid extends to the front of the eye as ciliary muscles and processes – for controlling the shape of the lens – ciliary processes • folds on ciliary body • secrete aqueous humor – ciliary muscle • smooth muscle that alters shape of lens • attach to the ciliary processes -Suspensory ligaments attach lens to ciliary process can pull the lens that flatten it., to see far away (relax ciliary muscle), tight the lens, to see near - (contract ciliary muscle) we relax the lens, lens to see close up -Ciliary muscle controls tension on ligaments & lens Combination – seeing far away and close up; we are not designed to read for hours close up, burns out the combination to see, myopia is caused by reading; we are designed to read far away, use reading eyeglasses Lens: • Avascular • Crystallin proteins arranged like layers in onion • Clear capsule & perfectly transparent • Lens held in place by suspensory ligaments which attach to the ciliary processes • Focuses light on fovea (center of the retina) Aqueous Humor – replaced every 90 mins • Continuously produced by ciliary body(filter blood plasma to create aqueous humor) • Flows from posterior chamber into anterior through the pupil • Scleral venous sinus – canal of Schlemm – opening in white of eye at junction of cornea & sclera – drainage of aqueous humor from eye to bloodstream • Glaucoma (failure to drain the canal of schlemm) – increased intraocular pressure that could produce blindness – problem with drainage of aqueous humor • Iris – regulates the light that comes in the eye, epithelial pigmented, brown eyes- lots of melanin – is a coloured extension off the ciliary processes – Constrictor pupillae muscles (circular muscles) ; decrease the light that comes in – are innervated by parasympathetic fibers while – Dilator pupillae muscles (radial muscles) – pupil gets bigger and allow a lot of light comes in – are innervated by sympathetic fibers. – Response varies with different levels of light Nervous Tunic (inner layer) • Posterior 3/4 of eyeball • Optic disc – optic nerve exiting back of eyeball – attachment of retina to optic nerve - optic disc (blind spot) • central depression in retina - fovea centralis • Detached retina – trauma (boxing) • fluid between layers • distortion or blindness Photoreceptors (neuron) -rod and cone cells (outersegment of the neuron) -rod cells: black and white, bright and dark -cone cells: color vision -visual pigment: rhodopsin: opsin and retinal -visual pigment is folded into “discs” = outer segment of the photoreceptor -shape of the outer segment resulted in their name -inner segment - cell body -synaptic endings • Rods----rod shaped, shades of gray in dim light, 120 million rod cells, discriminates shapes & movements – distributed along periphery (black & vision), movement • Cones---cone shaped, sharp, color vision, 6 million – 3 types: blue, red and yellow/green colour (differences in opsin structure) – fovea of macula lutea (fovea centralis) • densely packed region of cones • at exact visual axis of eye • sharpest resolution or acuity • sharpest colour vision RETINAL CELLS • Pigmented epithelium – non-visual portion – absorbs stray light & helps keep image clear • 3 layers of neurons (outgrowth of brain) – photoreceptor layer (deepest Layer) talk to bipolar – bipolar neuron layer (bipolar talk to ganglion) – ganglion neuron layer (optic neuron talk to ganglion – 1st order neuron) • 2 other cell types (modify the signal) – horizontal cells – make sure bipolar cell talks with ganglion- sharper image, focus • inhibits transmission to other bipolars (help process of convergence) - found in the outer plexiform/synaptic layer - concentrates the stimulation to a specific area of the retina – more contrast to the image & increase spatial resolution - light – photoreceptor hyperpolarization – reduction in glutamate release, hyperpolarization of bipolar cells & horizontal cells - GABA, inhibitory NT’s - Cones converge on all three types – cones specific, three types H1, H2, H3. H2 converges rods – amacrine cells – change in illumination, regulate bipolar – ganglion interaction, converge • provide 70% in our to ganglion cells (comes amacrine), other 30% comes from bipolar-ganglion synapses, regulate bipolar to ganglion transmission, 40 diff types-most with no axons, laterally gather BP cell input, most are inhibitory to transmission, help supplement horizontal cell functions • photopigment – rhodopsin (cone) – undergoes structural changes when it absorbs light – opsin – glycoprotein • responsible for the absorption of light wavelengths • e.g. red cones – opsin for the absorption of red wavelengths • loss of one cone rhodopsin, type with one opsin type = color blindness • retinal – vitamin A derivative – in darkness –cis-retinal fits snugly with opsin – upon light – the cis-retinal conformation straightens out into trans-retinal = isomerization – results in the separation of trans-retinal from opsin – the opsin is colourless = bleaching • opsin now acts as an enzyme which acts on the molecular machinery underlying vision – inhibits this machine; opsin does light absorbing, when in colorless form, cant absorb light and cant see – the trans retinal gets converted back into cis-retinal by retinal isomerase ; helps the trans to cis – cis-retinal is free to rebind with opsin; and opsin is functional and ready to absorb light – vitamin A deficiency results in lower formation of rhodopsin = night blindness Formation of Receptor Potentials • In darkness – Na channels open – Na ions flow through Na ligand-gated channels that bind cGMP – the photoreceptor becomes depolarized – release of NT which then binds its target – bipolar neurons • glutamate results, that stimulate bipolar cells that stimulate ganglion cells (optic nerve) • IPSP results at the post-synaptic neuron (bipolar cell) • prevents transmission of signal from the retina to the optic nerve (NO AP) – receptors are always partially depolarized in the dark leading to a continuous release of inhibitory neurotransmitter onto bipolar cells • In light – isomerization of retinal from cis to trans – this activates enzymes that breakdown cGMP – closing of Na+ channels producing a hyperpolarized receptor potential (-70mV) – release of inhibitory neurotransmitter is stopped – bipolar cells become excited and a nerve impulse will travel towards the brain = image Photochemistry mechanism 1. In the dark - Na channels in the outer segment are held open by cGMP 2. Na influx causes depolarization that triggers continual release of glutamate neurotransmitter in rods 3. Glutamate hyperpolarizes (inhibits) bipolar cells. , doesnt talk to ganglia, no nerve impulse 4. Inner segment has pumps that continuously pump Na out and K in, K diffuses out 5. In the light – photons pass through retinal layers and reaches rods (tells to bipolar cells to keep talking to ganglia) 6. Cis-retinal is tightly attached to opsin 7. Cis-retinal absorbs light and shifts to trans-retinal form (isomerization) 8. Trans-retinal separates from opsin becoming colorless (bleaching) 9. Opsin activates transducin (a G protein) in the cell membrane 10. Transducin activates cGMP Phosphodiesterase 11. This enzyme breaks down cGMP – decrease in cGMP levels closes gated Na channels 12. This decreases Na influx into the rod while pump continues – more Na+ out than Na+ flowing in 13. Rod becomes hyperpolarized and ceases glutamate release 14. Bipolar cells are not inhibited and release neurotransmitter at synapse with ganglion cells resulting in action potential being sent along optic nerve 15. Retinal isomerase shifts trans-retinal back to cis-retinal form 16. Cis-retinal rebinds with opsin (regeneration) 17. Transducin is deactivated and Na channels are reopened 18. Rods regenerate at about same rate as bleaching occurs in daylight. Cones regenerate very fast. Notes** bleach function as enzyme, turns on G protein which turn on cGMP, stops cGMP when drops Na+ ligand channel open, no AP, no glutamate release Light and Dark Adaptation • Light adaptation (adapt the worse) – adjustments when emerge from the dark into the light – decreases its sensitivity – increases the bleaching of rhodopsin – decreases light sensitivity • Dark adaptation – adjustments when enter the dark from a bright situation – light sensitivity increases as photopigments regenerate • during first 8 minutes of dark adaptation, only cone pigments are regenerated, so threshold burst of light is seen as color • after sufficient time, sensitivity will increase so that a flash of a single photon of light will be seen as gray-white Retinal Processes of Image Formation • receptor potentials rise in photoreceptor’s outer segment – spreads into the inner segment and into the synaptic terminals – NT release • induction of graded receptor potentials in the target postsynaptic neurons – bipolar cells and horizontal cells • between 6 to 600 rods synapse with a single bipolar cells = convergence, release glutamate and inhibit AP – increases the sensitivity of rod vision – but slightly blurs the image • usually only one cone synapses with a single bipolar cell (no convergence) – less sensitive but sharper vision • cone = on center bipolar – depolarizing, glutamate says shut up, and off center bipolar – don’t care about the gluatamate (hyperpolarize) and shut up – end result still the same (more than bipolar cell) • the horizontal cells inhibit the transmission of the visual signal to bipolar cells lateral to the targeted one – concentrates the stimulation to a specific area of the retina (more contrast to the image) • the bipolar cells synapse with amacrine which synapse with ganglion cells NOTES** - bipolar cells provide 30% if input to ganglion, rod bipolar cell only 1 type, cone bipolar cell – 10 forms classified, on responds to decreased glutamate upon light by the depolarizing AP = eventual image Responds in the dark increases glutamate by hyperpolarizing (NO AP), off responds to decreased glutamate upon light by hyperpolarization (NO AP) responds in dark to increased glutamate by depolarizing (Action Potential) Visual Pathways • visual field of each eye is divided into two halves: nasal half (central half) and a temporal half (peripheral half) • ganglion cells synapse with the neurons of the optic nerve • the axons of the optic nerve enter the optic chiasma – some axons cross over within this structure (signals from the same side of the retina) – but some axons are processed by the same side (signals from the temporal half of the retina are processed in the same side of the brain) • after passing the chiasma- the axons are now part of the optic tract which enters the brain and ends at the lateral geniculate nucleus of the thalamus – the axons coming from the temporal half of the retina do NOT cross over in the chiasma – continue to the thalamus portion on the same side of the eye receiving the info – BUT the nasal axons cross and continue to the opposite thalamus • information is processed by three areas of the cerebral cortex – one for color discrimination – one for object shape – one for movement, location and orientation Major Processes of Image Formation • Refraction of light – bend the light – by cornea & lens – light rays must fall upon the retina • Accommodation of the lens – changing shape of lens so that light is focused • Constriction of the pupil – less light enters the eye Definition of Refraction • Bending of light as it passes from one substance (air) into a 2nd substance with a different density(cornea) • In the eye, light is refracted by the anterior & posterior surfaces of the cornea and the lens Refraction by Cornea and Lens, easier to focus on the object far away • Image focused on retina is inverted & reversed from left to right • Brain learns to work with that information • 75% of Refraction is done by cornea -- rest is done by the lens • Close up – done by lens, and cornea less participation • Light rays from > 20’ are nearly parallel and only need to be bent enough to focus on retina • Light rays from < 6’ are more divergent & need more refraction – extra process needed to get additional bending of light is called accommodation Eye Abnormalities • Emmetropic eye (normal) - can refract light from 20 ft away • Myopia (nearsighted) - eyeball is too long(eyeball) from front to back, glasses concave – for Dr. Zuk • Hypermetropic (farsighted) - eyeball is too short(eyeball), - glasses convex (coke-bottle) • Astigmatism - corneal surface wavy; parts of image out of focus Accomodation & the Lens • Convex lens refracts light rays towards each other • Lens of eye is convex on both surfaces • View a distant object – lens is nearly flat by pulling of suspensory ligaments • View a close object – ciliary muscle is contracted & decreases the pull of the suspensory ligaments on the lens – elastic lens thickens as the tension is removed from it – increase in curvature of lens is called accommodation Near Point of Vision and Presbyopia • Near point is the closest distance from the eye an object can be & still be in clear focus – 4 inches in a young adult – 8 inches in a 40 year old • lens has become less elastic – 31 inches in a 60 to 80 year old • Reading glasses may be needed by age 40 – presbyopia – glasses replace refraction previously provided by increased curvature of the relaxed, youthful lens |
|
|
56.Remember the anatomy of the ear - What are the three main divisions of the ear? Describe the mechanism and physiology of hearing. What are the three tubes in the cochlea? What fluid is found in each? What is the Organ of Corti? Where is it found? What are the membranes involved in hearing in the Organ of Corti? How do they function in hearing? What nerve is involved in hearing? What are the two nuclei involved in processing auditory information?
|
Hearing (outer ear, middle ear, inner ear)
-outer ear: pinna - cartilage and skin, collect sound waves – wave of energy -for collection of sound waves • Function = collect sounds • Structures – auricle or pinna • elastic cartilage covered with skin – external auditory canal • curved 1” tube of cartilage & bone leading into temporal bone • ceruminous glands produce cerumen = ear wax – tympanic membrane or eardrum – beginning of middle ear • epidermis, collagen & elastic fibers, simple cuboidal epith. • Perforated eardrum (hole is present) – at time of injury (pain, ringing, hearing loss, dizziness) – caused by explosion, scuba diving, or ear infection -middle ear: tympanic membrane (ear drum) and 3 ossicles (malleus, incus, stapes), (equalize external pressure to internal pressure) hearing -transmission of sound waves to inner ear • Air filled cavity in the temporal bone • Separated from external ear by eardrum and from internal ear by oval & round window • 3 ear ossicles connected by synovial joints – malleus attached to eardrum, incus & stapes attached by foot plate to membrane of oval window – stapedius and tensor tympani muscles attach to ossicles, contract involuntary (protective mechanism) • Auditory tube leads to nasopharynx – helps to equalize pressure on both sides of eardrum -inner ear: cochlea (hearing), saccule, utricle & three semicircular canals (balance) • Bony labyrinth = set of tubelike cavities in temporal bone 3 semicircular canals, vestibule (Saccule &utricle) & cochlea lined with periosteum & filled with perilymph – surrounds & protects Membranous Labyrinth • Membranous labyrinth = set of membranous tubes containing sensory receptors for hearing & balance and filled with endolymph – utricle, saccule, ampulla, 3 semicircular ducts & cochlea 3 fluid filled channels found within the cochlea – scala vestibuli, scala tympani and cochlear duct • Vibration of the stapes upon the oval window sends vibrations into the fluid of the scala vestibuli • Fluid vibration dissipated at round window which bulges • Partitions that separate the channels are Y shaped – vestibular membrane above & basilar membrane below form the central fluid filled chamber (cochlear duct) • within the cochlear duct – organ of hearing = Organ of Corti • hair cells with stereocilia (microvilli ) project from the basilar membrane (bottom) and are covered with a (top) tectorial membrane, cranial nerve VIII • endolymph flowing through the cochlear duct bends the hair cells, results in a receptor potentials – inner hair cells transmit these potentials to 1st order sensory neurons whose cell body is in spiral ganglion, cranial nerve VIII Physiology of Hearing • sound waves are alternating high and low pressure regions that travel through air or through another medium like a fluid • the frequency of sound = number of waves that pass a point per time period – higher the frequency – the higher the pitch of the sound • 1) Auricle collects sound waves • 2) Sound waves hit the tympanic membrane = vibration – slow vibration in response to low-pitched sounds – rapid vibration in response to high-pitched sounds • 3) Ossicles vibrate since malleus attached to eardrum • 4) Attachment of the stapes to the oval window within the cochlea transfers these vibrations into the fluid of the inner ear • 5) Movement of the oval window leads to fluctuations in fluid pressure 6) Pressure changes in the scala vestibuli and tympani 7) The pressure changes in these scala push against the cochlear duct 8) Causes the basilar membrane to vibrate back and forth which bends the hair cells against the tectorial membrane • Microvilli of the hair cells are bent producing receptor potentials -bending opens mechanically-gated Na channels – depolarization, action potential – boom nerve impulse • Cochlear branch of CN VIII sends signals to cochlear and superior olivary nuclei within medulla oblongata (first order neurons) • Fibers ascend to the (from MO to the thalamus = 2nd order neurons) - thalamus (3rd order neurons) travel from thalamus to primary auditory cortex in the temporal lobe (areas 41 & 42) Optic neuron - 1st order neuron 3rd order – medulla to thalamus Deafness • Nerve deafness – damage to hair cells from antibiotics, high pitched sounds, anticancer drugs • the louder the sound the quicker the hearing loss – fail to notice until difficulty with speech • Conduction deafness – perforated eardrum – otosclerosis Cochlear Implants • If deafness is due to destruction of hair cells • Microphone, microprocessor & electrodes translate sounds into electric stimulation of the vestibulocochlear nerve – artificially induced nerve signals follow normal pathways to brain • Provides only a crude representation of sounds |
|
|
57.Describe the mechanism and physiology of each equilibrium type? What types of equilibrium are there? What anatomical structures are involved in each?
|
Physiology of Equilibrium
• Static equilibrium – maintain the position of the body (head) relative to the force of gravity – macula receptors within saccule & utricle [head in stationary] • Dynamic equilibrium [moving the head], job of 3 semicircular canal – maintain body position (head) during sudden movement of any type--rotation, deceleration or acceleration – crista receptors within ampulla of semicircular ducts Static Equilibrium: Saccule & Ultricle • Thickened regions called macula within the saccule & utricle • two macula per inner ear – perpendicular to one another • Cell types in the macula region – hair cells with microvilli called stereocilia – supporting cells that secrete gelatinous layer • Gelatinous otolithic membrane contains calcium carbonate crystals called otoliths that move when you tip your head • head movement and otolith movement bends the hair cells and results in receptor potentials via mechanically-gated Na channels • bending in one direction generates an AP, bending in the opposite results in repolarization and loss of AP • the repolarization slows the rate of NT release • hair cells synapse with first order neurons in the vestibular branch of cranial nerve VIII • depolarization -> faster NT release and faster nerve impulses through VIII (head bends) • repolarization -> slower NT release and slower nerve impulse through VIII (head bending up) NOTES** these neurons fire impulses at a slow rapid pace depending on how much NT’s is present. Motor fibers also synapse with the hair cells and vestibular neurons. Evidently, they regulate the sensitivity of the hair cells and sensory neuron 2nd order – MO to thalamus 3rd order – thalamus to temporal lobe Dynamic Equilibrium: Semicircular Ducts • Small elevation within the ampulla of each of three semicircular ducts – anterior, posterior & horizontal ducts detect different movements • Hair cells covered with cupula of gelatinous material • When you move, fluid in canal bends cupula stimulating hair cells that release NTs • Fibers from vestibulocochlear nerve (VIII) end in vestibular nuclei and the cerebellum • Fibers from these areas connect to: (semicircular canals also connect) – cranial nerves that control eye and head and neck movements (III,IV,VI & XI) – vestibulospinal tract that adjusts postural skeletal muscle contractions in response to head movements – motor cortex can adjust its signals to maintain balance 1st order neuron – run from hair cell thru VIII to the vestibular nuclei & cerebellum 2nd order neuron – from these areas cerebellum to thalamus 3rd order neuron – thalamus to temporal lobe Neurons from semicircular canals also send signal to cranial that control head to adjust posture and balance. Motor cortex. Dynamic balance is send to temporal lobe, cerebellum |
|
|
1.what are the three types of pain receptors? What neurotransmitters are released by these receptors? What do they do? What are the major processing areas for pain? Where are the second order neurons found for the pain pathway?
|
Pain – somesthetics sensations.
Nociceptors – receptors of pain, are free nerve endings.1. autonomic responses – increases in blood pressure and heart rate, increases in blood epinephrine levels, increase in blood glucose, dilation of the pupils of the eye or sweating. 1. emotional responses such as fear or anxiety, 3. reflexive withdrawal – from the stimulus. Two types of pain 1.Acute pain/Aδ ("A-delta") fibers – occurs very rapidly, usually within 0.1 second after a stimulus is applied, and is not felt in deeper tissues of the body. This type of pain is sharp, fast and pricking pain. Needles puncture or knife cut to the skin. (good pain) 2.Chronic pain/ C fibers – begins after a second or more and then gradually increases in intensity over a period of time. Maybe excruciating. Burning, aching, throbbing and slow pain. Can occur both in the skin and deeper tissues or in internal organs. Superficial somatic pain – pain from the stimulation of receptors in the skin, deep somatic pain – stimulation of receptors in skeletal muscle, joints, tendons and fascia, visceral pain – results from stimulation of receptors in the visceral organs. (bad pain) 3. Aβ ("A-beta") fibers - Painless stimuli such as light touch are transmitted by a third class of neuron, the thickly-myelinated Referred pain - surface Phantom pain - still feel the pain, itching, pressure, tingling, or pain in the extremity Analgesia – pain relief such as aspirin and ibuprofen (motrin) block prostaglandins Processing Pathways Both Aδ and C fibers are part of the sensory-somatic branch of the peripheral nervous system. Their axons pass into the dorsal root ganglion, where their cell body is located, and then on in to the gray matter of the spinal cord where they synapse with interneurons. Several different neurotransmitters have been implicated in pain pathways. Three of them: • glutamate. This seems to be the dominant neurotransmitter when the threshold to pain is first crossed. It is associated with acute ("good") pain. • substance P. This peptide (containing 11 amino acids) is released by C fibers. It is associated with intense, persistent, chronic — thus "bad" — pain. • glycine. It suppresses the transmission of pain signals in the dorsal root ganglion. Prostaglandins potentiate the pain of inflammation by blocking its action. The body is equipped with mechanical nociceptors at the periphery (so-called first-order neurons), which project to second-order neurons in the spinal cord and medulla, which then carries the sensory information (in the form of electrical impulse) to the thalamus, where it synapses with third-order neurons that transmit the impulse to the cortex. Second-order neurons sends their sensory inputs to the thalamus via two ascending pathways: the dorsal column medial-lemniscal system and the anterolateral system (includes the spinothalamic, spinoreticular, and spinotectal fibers). The former transmits impulse involving position sense, touch, and pressure. The latter pathway is involved in pain transmission (Karoly & Jensen 1987). |
|
|
12 CRANIAL NERVES
|
I. Olfactory: smell
II. Optic: vision III. Oculomotor: eyelid and eyeball movement IV. Trochlear: motor for vision (turns eye downward and laterally) V. Trigeminal: chewing, face and mouth touch and pain VI. Abducens: motor to lateral eye muscles VII. Facial: controls most facial expressions , taste, secretion of tears & saliva VIII. Vestibulocochlear: sensory for hearing and balance (aka Acoustic) IX. Glossopharyngeal: sensory to tongue, pharynx, and soft palate; motor to muscles of the the pharynx and stylopharyngeus X. Vagus Nerve: sensory to ear, pharynx, larynx, and viscera; motor to pharynx, larynx, tongue, and smooth muscles of the viscera, 2 parts: superior laryngeal branch and recurrent laryngeal branch XI. Spinal Accessory Nerve: motor to pharynx, larynx, soft palate and neck XII. Hypoglossal Nerve: motor to strap muscles of the neck, intrinsic and extrinsic muscles of the tongue |
|
|
ORGAN OF CORTI
|
Organ of Corti
Main article: Organ of Corti The organ of Corti forms a ribbon of sensory epithelium which runs lengthwise down the entire cochlea. The hair cells of the organ of Corti transform the fluid waves into nerve signals. The journey of a billion nerves begins with this first step; from here further processing leads to a panoply of auditory reactions and sensations. |
