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31 Cards in this Set
- Front
- Back
nervous system divisions
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central nervous system - brain + spinal cord
peripheral nervous system - all nerves + ganglia outside of CNS |
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nervous system cell groups
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neurons - transmitting cells
neuroglia - supporting cells, different types for CNS & PNS |
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Neuroglia
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"nerve glue", brace, protect, myelinate neurons. don't transmit signals
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CNS Neuroglia
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Microglia - act as phagocytes
Oligodendrocytes - myelinate neurons Astrocytes - control chemical environment around neurons Ependymal Cells - circulate cerebrospinal fluid |
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PNS Neuroglia
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Schwann cells - myelinate neurons
Satellite Cells - surround neuron cell body |
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Neurons
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Cell body - neurofibrils, nissl bodies
Neuron processes - dendrites, axon |
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Neurofibrils
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intermediate filaments in neuron that provide tensile strength
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Nissl Bodies
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specialized ER - protein synthesis
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Cell Body Clusters
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CNS - nuclei
PNS - ganglia |
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Dendrites
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receive signals to cell body - can be more than one
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Axon
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generate and transmit action potential - only one per neuron - can have many branches
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Axon features
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Axon hillock - junction b/w cell body and axon
Axon terminals - ends of axon, where neurotransmitters are stored Myelin Sheath - whitish fatty proteins covering & insulating some axons |
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Neuron Properties
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Excitability - ability to respond to stimuli and convert into nerve impulses
Conductivity - ability to transmit impulse to other neurons, muscles or glands -exhibit longevity -amitotic |
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Myelin
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whitish fatty proteins covering some axons - insulate fibers and increase speed of transmitting nerve impulse
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Myelin Sheath (PNS)
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concentric rings of plasma membrane of schwann cell wrapped around axon
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Neurilemma
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last concentric ring of schwann cell myelin sheath containing nucleus
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Nodes of Ranvier
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gaps between nodes in myelin sheath
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Structural classification of neurons
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based on number of processes extending from cell body
unipolar - single process extending from cell body - divides into central and peripheral prcoess bipolar - 2 processes - one axon, one dendrite multipolar - many processes - one axon, many dendrites |
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Functional classification of neurons
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Based on direction of impulse in relation to CNS
sensory(afferent) neurons - carry impulse from sensory receptors towards CNS motor(efferent) neurons - carry impulse from CNS to organs, muscles, and glands Association neurons - conduct impulses within CNS |
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Nerve
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bundle of axons in PNS wrapped in connective tissue
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Tract
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bundle of axons in CNS wrapped in connective tissue
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Mixed/Sensory/Motor nerves
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Mixed - both efferent/afferent processes
Sensory - only afferent processes Motor - only efferent processes |
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Nerve structure
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Axon is covered by endoneurium, group of endoneurium covered nerve fibers covered by perineurium called a fascicle, group of fascicles with blood vessels covered by epineurium froms a nerve (same for tract)
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Nerve Impulse Steps
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-resting state -> stimulation/depolarization -> generation of nerve impulse -> repolarization -> return to resting state
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Resting membrane potential
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High Na+ concentration outside of cell, high K+ concentration inside of cell -> more negative on inside than outside
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Depolarization
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Neuron activated by threshold stimulus, sodium gates open and Na+ enters cell -> cell interior becomes less - and eventually +
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Generation of Action potential
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After certain charge is reached - the threshold potential - an action potential is generated in an all or none fashion - called a nerve impulse
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Repolarization
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Potassium gates open and K+ leaves the cell - membrane repolarizes
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Return to resting state
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The sodium potassium pump reestablishes the concentration gradient and the resting membrane potential - allows neuron to fire again
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Absolute refractory period
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sodium gates are still open - unable to create another action potential
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Relative refractory period
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when going through repolarization the sodium gates are closed - a very strong stimulus can generate another action potential
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