lab4 2
Terms
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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
3-15m/s
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