action potential and graded potential
cell body and dendrites typically
axon hillock and axon
travels short distance-typically within cell body to axon hillock (.1-1.0)
long distance- from axon hillock through entire length of axon (a few mm over a meter)
various size-declines with distance
always the same size (all or none) does not decline with distance.
has an absent positive feedback
has an present positive feedback
the stimulus for opening ion channels is -chemical or sensory stimulus(light, pressure,temperature)
stimulus for opening ion channels is Voltage(depolarization, triggered by GP reaching the threshold)
Repolarization:voltage independent occurs when stimulus is no longer present
Repolarization- Voltage regulate, occurs when Na+ channels inactivate and k+ channels open
Summation-stimulus responses can be summed to increase amplitude(size) of graded potential: temporal-increased frequency of stimuli, or Spatial-stimuli from multiple sources.
Function-short distance signaling, depolarizationthat moves membrane potential towards the threshold for generation for AP
Function-short distance signaling:hyperpolarization that moves the membrane potential away from the threshold for generation of Ap
Inhibitory (IPSP)-GRADED POTENTIAL
Function-long distance signaling constitutes the nerve impulse
initail effect of stimulus- opens channels that allow stimultaneous Na+ and K+ fluxes
Excitatory(EPSP) Graded potential
Initial effect of stimulus- opens K+ or Cl-
Inhibitory (IPSP) Graded potential
Initial effect of stimulus-first opens Na+ channels, then k+ channels.
peak membrane potential- becomes depolarized moves toward -0mV
Peak of membrane potential- Becomes hyperpolarized toward -90mV.
peak membrane potential- +30mV to +50 mV