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142 Cards in this Set
- Front
- Back
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How many cells do humans have? |
Trillions |
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What must cellular activity be so a person can function as an integrated whole? |
Coordinated |
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What two systems of communication prevent physiological chaos? |
The nervous system and endocrine |
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What do the nervous system and the endocrine system do? (2) |
1. detect changes 2. modify the activity of cells, organs and the individual |
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What is the main job of the nervous system and endocrine system? |
Maintaining homeostasis |
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What is the focus of exciting research and why? |
The nervous system because many questions about its function remain largely unanswered |
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What is the study of the nervous system? |
Neurobiology |
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What are two subdisciplines of neurobiology? |
Neuroanatomy and neurophysiology |
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What are the functions of the nervous system? |
sensory, perception, integration, motor planning |
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What are the two main divisions of the nervous system? |
Central and peripheral |
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What is the central nervous system? |
Brain and spinal cord |
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What is the peripheral nervous system? |
Nerves and ganglia |
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What are the longer functions of the nervous system? (3) |
1. receives info about the internal and external environment 2. processes info and determines a response 3. issues commands to cells to carry out the response |
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What are the two divisions of the peripheral nervous system? |
Sensory and motor divison |
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What are the divisions of both the sensory and motor division of the PNS? |
Visceral and Somatic |
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What are the further divisions of the visceral motor system? |
Sympathetic and parasympathetic |
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What does the sensory afferent division of the PNS carry? |
Signals from sensory receptors through afferent nerve fibers to the brain and spinal cord |
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What does the visceral sensory division of the PNS do? |
Carries signals from viscera of the thoracic and abdominal cavities |
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What does the somatic division carry? |
Signals from receptors in the skin, muscles, bones, and joints |
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What does the motor (efferent) division carry? |
Signals from the CNS through efferent nerve fibers to effectors (cells or organs that carry out responses) |
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What is the visceral motor system also called? |
Autonomic nervous system |
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What does the visceral motor system do? |
Carries messages to glands, cardiac muscle, and smooth muscle |
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What does the sympathetic nervous system prepare the body for? |
Action required in extraordinary circumstances |
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What does the parasympathetic division carry? |
On business as usual when the body is in a state of rest |
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What does the somatic motor division do? |
Sends signals to skeletal muscles, many of which are under voluntary control |
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What is a nerve cell called? |
Neuron |
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What are the Fundamental physiological properties? |
Excitability, conductivity, secretion |
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Can respond to stimuli |
Excitability (Irritability) |
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Neurons response to stimuli be producing electrical signals and to distant locations quickly |
Conductivity |
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Can release chemical messengers, also when an electrical signal reaches the end of the nerve fiber that passes a message to other cells |
Secretion |
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What are the two organ systems that maintain internal coordination? |
Endocrine, nervous |
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Chemical only |
Endocrine |
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Electrical and chemical |
Nervous sytem |
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What is the purpose of sensory (afferent neurons) |
Detect stimuli |
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What do interneurons do? |
Receives signals from other neurons and integrate (process, store, retrieve, make decisions) |
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What do motor neurons do? |
Send signals to effectors (muscles and gland cells) that carry out responses |
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Where do interneurons lie |
Within the CNS |
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Where are decisions about response to stimuli made? |
At the interneurons |
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What is the control center of the neuron? |
Neurosoma or soma |
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What are nissl bodies? |
Compartmentalized Rough ER |
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What do dendrites do? |
Receive signals |
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What does the axon do? |
Sends signals |
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What is terminal arborization? |
Complex of branches at axon's distal end |
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What is the synaptic knob? |
Terminal button that ends the axon branch that communicates with another cell |
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What is contained in the soma? |
Central nucleus, nucleolus, mitochondria, lysosomes, golgi complex, inclusions, extensive RER, and cytoskeleton |
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What does the cytoskeleton do to the Rough ER? |
Compartmentalizes the rough ER into dark-staining Nissl bodes unique to neurons |
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What do mature neurons lack? |
Centrioles and do not undergo mitosis after adolescence |
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T or F: Dendrite number is fixed |
False, some have one some have a lot |
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T or F: Axon number is always fixed |
True, only one |
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Where does the axon arise from? |
Axon hillock |
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What is the axon specialized for? |
rapid conduction of nerve signals, branch at the distal end and each branch ends in a synaptic knob |
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What does the the synaptic knob form? |
A junction with another cell either another neuron or muscle cell or gland cell |
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What is structural classification of neurons based on? |
Number of processes extending from the soma |
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What are multipolar neurons? |
Those that have one axon and two or more dendrites |
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What are bipolar neurons? |
Those with one axon and one dendrite. Relatively rare but some are special sensory olfactory neurons |
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What are unipolar neurons |
Those that start out as bipolar neurons but during development fuse resulting in a single processes leading away from the soma. Branches like a T |
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What is the mechanism of action of unipolar cells? |
The peripheral fiber carries signals from the source of the sensation and a central fiber continues into the spinal cord. The dendrites comprise the branching receptive endings in the skin or other place or origin while the rest of the fiber is considered to be the axon. |
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What are anaxonic neurons? |
Have numerous dendrites but no axon. They communicate through the dendrites but do not produce an action potential |
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What are the different types of neuroglia or glial cells? (6) |
Oligodendrocyte, Ependymal cells, microglia, astrocytes, Schawann cells, satellite cells |
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What are schwann cells also called? |
Neurilemmocytes |
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What is the purpose of glial cells? |
Support neuron function |
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Are glial abundant or not? |
Abundant, as they outnumber neurons by as much as 50 to 1. |
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Describe oligodendrocytes. |
Form the myelin sheath around nerve fibers in the CNS with as many as 15 processes. |
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What is the purpose of oligodendrocytes? |
They wrap around nerve fibers and insulate them from the ECF and speed up signal conduction |
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Describe ependymal cells. |
Resemble cuboidal epithelial cells and line the internal cavities of the brain and spinal cord. |
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What do ependymal cells do? |
Produce CSF, |
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What is CSF? |
Cerebrospinal fluid, the liquid that bathes the CNS and fills spaces |
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Describe microglia. |
Small macrophages that derive from white blood cells. |
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What do microglia do? |
They wander through the CNS and phagocytize microorganisms, dead tissue and foreign matter |
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What are the most abundant glial cell in the CNS? |
Astrocytes |
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Describe astrocytes. |
They have many branches and are somewhat star like in shape. |
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What are the functions of astrocytes? |
Provide structural support for neurons, contribute to the BBB, regulate chemical composition of tissue fluid by absorbing substances such as K and neurotransmitters, form scar tissues to fill spaces |
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Describe schwann cells. |
Form myelin sheath and assist in the regeneration of damaged fibers. |
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What are satellite cells? |
Surround the neuron cell bodies in ganglia in the PNS and regulate the chemical environment |
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What are the glial cells in the CNS? |
Oligodendrocytes, ependymal, microglia, astrocytes |
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What are the glial cells in the PNS? |
Schwann cells and Satellite cells |
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What are internodes? |
Fiber segments covered by myelin |
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What are nodes of ranvier? |
Fiber segments with gaps in myelin |
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What does myelin consist of? |
The plasma membranes of glial cells and is composed mostly of lipids, including phospholipids, glycolipids, and cholesterol |
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What is the formation of myelin sheath called? |
Myelination |
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T or F: Each cell wraps around an entire part of an axon |
False, only part making it segmented |
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In peripheral fibers, Schwann cells surround the axon and form a sleeve called what? |
Neurillemma, which has an external thin covering called the endoneurium |
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What are the neurilemma and endonerium essential for? |
The regeneration of damaged fibers. |
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T or F: nerve cells in the CNS have a neurolimma |
False, do not and are therefore incapable of regeneration |
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What does the segementation of the myelin sheath look like? |
The myelin sheath around a nerve fiber is segmented with long internodes separated by interruptions of the myelin sheath called nodes of Ranvier |
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What are the layers associated with the outermost coil of the PNS Schwann cells? |
Neurilemma, covered with basal lamina, and then a connective tissue sheath, the endothelium |
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T or F: Even unmyelinated PNS Axons are surrounded by Scwann cells |
True, but the Scwann cells do not coil densely around these axons |
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What does signal conduction speed depend on? |
Diameter of fiber , Presence of Myelin |
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What are the fastest fibers? |
Large and myelinated |
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How do unmyelinated nerve fibers conduct signal? |
by diffusion of sodium and potassium across the plasma membrane along every point of the fiber, causing a sudden change in voltage |
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Why does myelination increase speed? |
Ion movement across the membrane occurs only at nodes of Ranvier. In the internodes the singals travel by a faster process of ion diffusion immediately under the plasma membrane. |
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Why is the entire nervous system not myelinated? |
It would make the nervous system too bulky or there would be fewer fibers crammed into the same space |
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Can nerve fibers regenerate? |
If cell body remains intact they can |
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What do schwann cells secrete? |
Nerve growth factors |
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What do schwann cells and endonerirum produce? |
Regeneration tube to direct regrowth of axon and potentially resestablsih contact with its target cells |
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Can CNS neruones regenerate? |
no |
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An action potential introduced at the NMJ is propagated along what? |
The sarcolemma of the skeletal muscle |
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What is a synapse and what is its direction? |
Meeting point of neuron and other cell , presyanptic neuron to postsynpatic neuron |
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Axodendritic synapse |
Axon to dendrite |
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Axosomatic synapse |
Axon to synapse |
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Axoaxonic synapse |
Axon to axon |
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What do presynaptic neuron release? |
Neurotransmitter to postsynaptic cell |
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What are neurotransmitters? |
Messenger molecules |
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What are the structures at the synapse? |
synaptic knob, synaptic cleft, neurotransmitter receptors on postsynaptic cell |
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Synaptic knob |
Synaptic knob of presynaptic cell-- contains synaptic vesicles- packets of neurotransmitters |
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What are some examples of excitatory neurotransmitters? |
Glutamate and aspratate in the brain and spinal cord |
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What are some examples of inhibitory neurons? |
GABA in the brain and glycine in the spinal cord |
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What are some other examples of neurotransmitters? |
Dopamine and serotonin |
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How are neurotransmitters releases from the synaptic vesicles? |
Exocytosis |
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T or F: the signal travels in many directions |
False, One direction from the presynaptic neuron with vesicles to the postsynaptic neuron receptors |
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Diagram of chemical synapse |
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What are some familiar neurotransmitters? |
acetylcholine, norepinephrine, glutamate,aspartate, GABA, glycine, dopamine, serotonin, histamine, and beta-endorphin |
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Where is the neurotransmitter stored> |
In the synaptic vesicels |
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What are electrical synapse? |
Adjacent cells joined by gap junctions, ions diffuse from cell to cell |
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What are the main things that an electrical synapse can survive? |
Quick transmission, no integration or decision making |
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What do electrical synapses connect? |
Some neurons, neuroglia and cardiac and single unit smooth muscle cells |
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What do gap junctions between adjacent cells allow? |
Ions to diffuse directly from one cell to another, which allows for quick transmission but does not allow cells to integrate info and make decisions |
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Neural Pools and circuits diagram |
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How do neurons function? |
In ensmebles called neural pools |
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Ho do interneurons work? |
Thousands of millions of interneurons concerned with a particular function |
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What are the interconnections between neurons called? |
Neural circuits |
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Diverging circuit |
One nerve fiber branches and synapses with several postsynaptic cells and each of those may synapse with several more |
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What is an example of a diverging circuit? |
One motor neurons in the brain may cause thousands of muscles fibers to contract |
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Converging circuit |
Input from many different sources is funneled to one neuron or neural pool |
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Example of converging circuit |
The respiratory center in the brainstem receives info from other parts of the brain, receptors for blood chem in arteries, and stretch receptors in the lungs |
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Reverberating circuit |
Neurons stimulate each other in sequence: A stimulates B, B stimulates C, C stimulates D and neuron C sends an axon collateral back o A so C fires everytime it stimulates output from neuron D but also output from neuron D but also restimulates A and starts the whole processes over again |
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What is an example of a reverberating circuit? |
such a diaphragm and intercoastal muscles and a person inhales; when the circuit is stopped a person exhales |
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What is a paralell after discharge circuit? |
An input diverges to stimulate several chains or neurons. Chains eventually reconverge on the same output neuron. each output receives signals from multiple pathways and may go on firing for some time after the input has ceased. Once all have fired, the output ceases. |
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What does the neural tube develop? |
Anterior dilations that from three primary vesiscles (forebrain, midbrain, and hindbrain) |
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What happens after the neural tube develops? |
Undergoes flexion and subdivions of the forebrain and hindbrain, producing five secondary vescicles. |
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What are these five secondary vescicles? |
Theseare the telencephalon, which becomes the cerebrum; the diencephalon, which becomes the thalamus,hypothalamus, retinas, and related structures; the mesencephalon, which becomes the midbrain; the metencephalon, which becomes the pons and cerebellum;and the myelencephalon,which becomes the medulla oblongata. |
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When does myelination begin? |
In the fourth month, but most occurs after birth and is not completed until late adolescence |
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What is the deal with the spinal cord? |
Intitally occupies the entire verterbral canal but the verterbral column grows faster than the spinal cord and by adulthood, the spinal cord ends at the level of vertebrae L1 to L2 |
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Embryonic brain diagram |
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What are some neural tube defects? |
Spina bifida occulta and cystica, microcephaly, anencephaly |
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What is anencepahly? |
No brain |
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What is microcephaly? |
Small brain |
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What is spina bifida occulta? |
One to a few vertebrar with no function problems |
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What is spina bfida cystica? |
More severe, sac from spine |
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What do neural tubes result from? |
Deformtiies of the brain or spinal cord that result from failure of the neural tube to close or otherwise to develop normally. |
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What are NTDS caused by? |
genetic or caused by teratogens and nutritional deficiences |
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How can you reduce spina bfida? |
be taking folic acid |
