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26 Cards in this Set
- Front
- Back
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1.Define the term synapse and distinguish between the presynaptic and postsynaptic elements.
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synapse-a junction between two cells.
presynaptic-comes before synapse. post-synaptic- comes after synapse. |
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2.What are electrical synapses and how do they differ from chemical synapses? Which are utilized more in the human body?
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-electrical synapses-Pre and post-synaptic membranes are continuous. Allows action potentials to propagate directly into the post-synaptic cell (these connections are formed by gap junctions which permit passage of current directly into adjacent cell). Electrical synapses are located in the CNS and PNS. They allow fast transmission of signal cell to cell (o.2ms). Rare in nervous system (vestibular nuclei, eye, ciliary ganglia (pns). fxn in both directions.
chemical synapses- -Most abundant type of synapse (slightly slower at 2ms) -Functions in one direction ‘Presynaptic’ cell to ‘Postsynaptic’ cell -Cells are physically coupled -Small chemicals ‘transmit’ the signal from‘presynaptic’ to ‘postsynaptic’ cell These “chemical transmitters” bind to receptors on the ‘post-synaptic’ cell -Receptors on ‘postsynaptic’ cell, when activated, cause graded membrane potentials to be generated |
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3.Describe the major steps leading to neurotransmitter release from the pre-synaptic terminal.
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1.Arrival of action potential
-depolarizing graded potential results at synaptic knob (nerve terminal 2.Influx of Ca2+ allowed by opening of voltage-gated Ca2+channels 3.Ca2+ increase in terminal allows neurotransmitter-containing vesicles to fuse with membrane and release transmitter -‘exocytosis’ results in neurotransmitter release -Mediated though ‘docking’ proteins 4) ~3000 acetylcholine (Ach) molecules/vesicle released -Release ends rapidly, as Ca2+ is actively transported into SER(sarcoplasmic reticulum), mitochondria, or out of cell 5) Ach diffuses across synaptic cleft, binding to, and activating Ach receptors on postsynaptic neuron -Activated Ach receptors allows Na+ influx some K+ efflux occurs -Graded membrane depolarization of 20 msec duration occurs -If large enough, this can cause an action potential to initiate 6) Acetylcholine removed by enzyme degradation -Acetylcholinesterase is the enzyme Breaks down acetylcholine into choline and acetate Choline is actively transported back into the presynaptic terminal (recycled or reused) -Elimination of Ach stops stimulation of the Ach receptor 7) Transmitter substance can be removed by specific plasma membrane transporters on nerve terminal leading to reuptak -dopamine transporter Inhibited by cocaine - serotonin transporter Inhibited by antidepressants (prozac blocks this transporter, also blocked by paxil) 8). recycling of acetylcholine -Dependent on mitochondria at synapse -Presynaptic uptake of choline by choline transporter -Synaptic fatigue occurs when repetitive stimulation outpaces the uptake and/or synthesis of transmitter |
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4.List several types of neurotransmitters and some possible functions (excitatory or inhibitory; type of receptor activated).
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1)excitatory synapses
-Acetylcholine (Ach) is a neurotransmitter but it’s not the only one….. -Generates an excitatory post-synaptic potential (EPSP) depolarizing graded potential Caused by increased Na+ (pNa+) and K+ permeability (-pK+) 2). inhibitory synapses Glycine and GABA are neurotransmitters -Forms an inhibitory post-synaptic potential (IPSP) hyper polarizing type of graded potential *Caused by increase K+ permeability (pK+) *Caused by increase Cl- permeability (pCl-) Neurotransmitter classes 1)Biogenic (Monoamines) -Catecholamines Dopamine, epinephrine, norepinephrine -Indolamines serotonin (5-hydroxytryptamine) -Histamine 2) Amino acids Glycine, GABA *inhibitory -Glutamate, aspartate *excitatory 3) Neuropeptides -Endorphins (opioids), enkephalins -substance P 4) Gases -Nitric oxide, carbon monoxide 5)Acetylcholine -Neuromuscular junction Excitatory-nicotinic Ach receptors (Fast-acting receptor/ionotropic) -Cardiac atrial cells Inhibitory-muscarinic Ach receptors (Slow acting receptor/metabotropic) |
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5.Describe the different ion fluxes that can either create an IPSP or an EPSP in post-synaptic membranes. What type of membrane potential changes are IPSPs and EPSPs?
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-create an EPSP-increased Na+ and K+ permeability
-create an IPSP-increased K+ and Cl- permeability IPSP (hyperpolarization, more negative than -70mV) EPSP (hypopolarization/depolarization, more positive than -70mV) |
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6.Describe the 2 mechanisms that exist to eliminate neurotransmitter from the synaptic cleft. Indicate drugs that can be used to disrupt each of these processes.
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see # 7 and # 8 in in steps in chemical synaptic transmission.
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7.Describe the phenomenon of presynaptic facilitation in terms of the anatomical arrangement of synaptic elements, neurotransmitters involved, and effect on the presynaptic cell.
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facilitory neuron induces (by releasing serotonin) presynaptic neuron to allow more Ca2+ to enter which allows more neurotransmitter to be released which causes an increased effect on postsynaptic membrane.
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8. What ultimate effect does presynaptic inhibition and facilitation have on the postsynaptic cell’s response to an action potential arriving at the presynaptic terminal
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same as last notecard except that inhibitory neuron releases GABA which causes an inactivation of Ca2+ channels causing less Ca2+ to enter leading to less neurotransmitter release.
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9.Describe the organization of the nervous system, specifically neurons in relation to the CNS.
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-sensory neurons
Deliver information to CNS -motor neurons Distribute commands to peripheral effectors -inter neurons Interpret information and coordinate responses SAME DAVE -sensory system (divergence) -motor systrems (convergence, 2 or more presynaptic neurons converging on a single motor neuron) |
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10.What is the adequate stimulus for a sensory receptor? Provide as many examples as possible, using all sensory receptors that have been presented in class.
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-Stimulus that a receptor responds to normally is called the “adequate stimulus"
-come back to for part two |
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11.Describe the general mechanism by which a receptor transduces (converts) signals and generates receptor potentials.
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-Conversion of stimulus into information that can be processed by the brain
*May be directly converted into a change in membrane potential *May activate 2nd messengers that mediate a change in membrane potential ie. cAMP,cGMP,IP3 -Threshold-minimum stimulus required to activate a receptor. – minimum stimulus required to activate a receptor |
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12.Define adaptation as applied to sensory receptors and distinguish between phasic and tonic sensory receptors.
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-tonic receptors
*Always active *slow acting receptors -phasic receptors *Provide information about the intensity and rate of change of a stimulus *fast acting receptors -Adaptation -Reduction in sensitivity in the presence of a constant stimulus |
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13.Define the difference between the terms ‘receptor potential’ and ‘generator potential’. What does a generator potential do to a sensory neuron?
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1.generator potential – graded potentials whose amplitude is proportional to stimulus intensity
2. receptor potential – changes in membrane potential that influence n.t. release by the receptor cell and ultimately electrical activity of the associated sensory neuron (check for 2nd part) |
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14.How is intensity of a stimulus encoded by sensory neurons and transmitted to the central nervous system for processing?
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the more intense the stimulus the more action potentials are fired
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15.Describe how the 2-point discrimination test is used to identify a body areas’ somatosensory ‘acuity’.
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-Acuity
Ability to distinguish between 2 points of stimulation *high acuity Small receptive fields Many sensory units clustered in small region of body *Body regions with high acuity (sensitivity) are represented by large surface area in somatosensory cortex of brain low is opposite (check printout) Sensory neuron is activated by stimuli that occur within a specific area *size of the receptive field varies considerably Two point discrimination test Determines the ‘tactile acuity’ of any region of skin surface |
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16.What is referred pain and how is this sensation generated? Provide at least 1 example of this abnormal sensory phenomenon.
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-referred pain
*Pain is often poorly localized *May be felt in areas far removed from the site of the stimulus *Cause: Multiple sensory neurons converge onto a single, ascending tract and brain has difficulty distinguishing between visceral and somatic receptors (ie. arm pain in heart attack) |
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17.Name the type of receptor and sensory cell involved in the following sensory modalities: pain, thermoreception, mechanoreception, deep pressure, vision, hearing, equilibrium, taste, smell, position of body (proprioception).
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-pain-Noci Receptors
*Perceived sensation – not activated by normal stimulus Function: protection! (tonic receptors) *Free nerve endings that respond to temperature, pressure/mechanical damage, and chemicals *Myelinated Type A fibers carry fast pain *Type C fibers carry slow pain -thermoreception-(found in dermis) *cold (more) and heat sensors *Phasic receptors -mechanoreceptors (also found in dermis) *sensitive to distortion of their membrane *tactile receptors (six types), baroreceptors, proprioreceptors -deep pressure ie. baroreceptors *free nerve endings in walls of organ *change in pressure detected *increase in pressure causes increased activity *rapidly adapting *carotid sinus, aortic sinus, and lungs -vision- *receptors cells-photoreceptors *receptors: rods, cones (3 types)--Rhodopsin (G-protein coupled receptor) *Activated neuron signaling: G protein (transducin), cyclicGMP signaling, causing a hyper-polarizing graded potential -hearing- *stereocilia are hit by sound wave which opens mechanical gate (Ca2+ and K+ flow in), mechanical gate closes, and then myosin tension reduces. -equilibrium- n/a -taste- gustation, gustatory cells in taste buds, receptor specific for each class of gustatory -smell- *receptor cells-olfactory neurons, receptors-odorant binding molecules *activated neuron signaling: G-protein, cAMP, depolarizing graded potential -position of body (proprioception)- *Nerve endings in a specialized structure Detects amount of stretching Do not adapt (tonic) *Muscle spindle *Golgi tendon organs *joint capsules |
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18.Determine the types of receptors that are activated in the sense of taste for sweets, salts, sour, unami, and bitter. Identify how these receptor types cause cells to change membrane potential when stimulated.
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-sweets: receptor activating gustducin (G-protein); closeure of K+ channels.
-salts: Na+ enters through Na+ channels -sour:H+ blocks K+ channels and opening of Cl- channels -umami: ("deliciousness"): glutamate/nucleotide receptor *water:water receptors in pharynx |
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19.Describe how the auditory system works.
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see #17 hearing
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21.Determine the receptor cells for olfaction and what activates the neurons
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-Receptor cells: olfactory neurons
-Receptors: odorant binding molecules *Activated neuron signaling: G-protein, cAMP, depolarizing graded potential |
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23.Draw and label all of the principal components of a reflex arc
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middle of page 5: 6/5/2008 notes
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24.Differentiate between a monosynaptic and polysynaptic reflex arc. Name an example of each type and describe the differences between each type of reflex arc.
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Monosynaptic Reflex (faster):
Sensory neuron synapses directly on a motor neuron (one to one ratio) *stretch reflex automatically monitors skeletal muscle length and tone _Patellar reflex (knee jerk) *Sensory receptors are muscle spindles * Postoral reflex maintains upright position Polysynaptic reflex: *At least one interneuron between sensory afferent and motor efferent *longer time between stimulus and response *Produce more complicated responses *Involve pools of interneurons *Have reverberating circuits to prolong the motor response *Several reflexes may cooperate to produce a coordinated response _tendon reflex _Withdrawal reflexes _Flexor reflex _crossed extensor reflex (reciprocal inhibition) |
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25.What is the difference between the somatic nervous system and the autonomic nervous system, with regards to the target tissues that these two neural control systems regulate?
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-Somatic nervous system
*Skeletal muscle control -Autonomic nervous system *parasympathetic *Sympathetic Smooth muscle, cardiac muscle, glands |
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26.Describe the two divisions of the autonomic nervous system. Include differences in location of pre-ganglionic and post-ganglionic neurons, transmitters used by each, and the receptors on effectors that the transmitters activate.
(next few slides follow) |
*Sympathetic division
“Fight or flight” Thoracolumbar: Thoracic and lumbar segments *Parasympathetic division “Rest and digest” *Craniosacral: Preganglionic fibers leaving the brain and sacral segments |
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sympathetic activation vs. parasympathetic activation
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-sympathetic-
In crises, the entire sympathetic division responds -Affects include: Increased alertness, energy and euphoria -Increased cardiovascular and respiratory activities -Elevation in muscle tone -mobilization of energy resources -parasympathetic- Effects produced by the parasympathetic division -relaxation -Food processing -Energy absorption |
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neurotransmitters and sypathetic vs. parasympathetic
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-sympathetic-
Stimulation of sympathetic division has two distinct results *Release of Ach or NE at specific locations *Secretion of E and NE into general circulation -Most postganglionic fibers are , a few are cholinergic or nitroxidergic *Two types of receptors are alpha receptors and beta receptors -Sympathetic ganglionic neurons end in telodendria studded with varicosities (bag filled with neurotransmitter)filled with neurotransmitter -parasympathetic- *All parasympathetic fibers release Ach *short-lived response -ACh is broken down by Anticholinesterase and tissue cholinesterase *Postsynaptic membranes have two kinds of cholinergic receptors -muscarinic -Nicotinic |
