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lab4 2


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refractory perdio
period of time after AP fires during which AP generation cannot be repeated in the same membrane region
abs refractory period
no amt of stimulation can trigger AP
relative refractory period
second ap can be generated but takes more stimulation (single AP) or yield lower amp (CAP)
what dose abs refractory period result from
inactivation of VOLTAGE GATED Na channels
what is considered abs refractory period for CAP
all axons within nerve are in their abs refractory period
electrotonic conduction
passive spread o membrane potential thru cell

decay over time and distance from point of origin as current leaks out
active conduction
active maintenance of membrane potential as it travels thru cell

means of AP propgation in unmyelinated axons
salatory conduction
action + electrotonic

used in myelinated axons

electronic in myelinated parts and actively in unmyelinated parts (nodes)
where are most of voltage gated Na and K channels clustered
nodes of ranvier
two axon properties that affect conduction speed and efficiency
axon diameter and myelination
increasing diameter results in
lower internal resistance
myeline results in
increase membrane resistance

decrease membrane capacitance
membrane resistance
prevents leakage; insulation
membrane capacitance
amt of charge captured and stored by patch of membrane
type A fiber
large diameter

thick myelin

30-150 m/s

motor neuron or sensory neurons
type b fiber
smaller diameter and thinner myelin than A


regulate internal organ and blood vessels (autonomic nervous system)
type C fiber
smallest fiber

no myelin

< 2m/s

sympathetic innervation and pain signals
when is the end of the refractory period
when all axons are responding again and CAP can reach its original amp again
what does excitability of nerve refer to
how readily it generates AP
what does threshold of nerve depend on
strength and duration of stimulus
rheobase voltage
weakest stimulus that will elicit response from nerve
chronaxie time
stimulus duration required to eliciit response at 2x rheobase voltage

measure of nerve excitability

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