6.Local response and electronic potential. Action potential Flashcards
What are the 2 responses a neuron or excitable tissue can produce
Slow/ graded- electrically non excitable membranes
Action potential- electrically excitable membrane
In terms of distance of signal, what are the differences in responses
Action potential can conduct impulses over long distances
Slow can conduct impulse for short distance, conduction with decrement
Which response requires a threshold
Action potential
Threshold of -50mv must be met for it to occur and to open voltage gated channels
No threshold for slow
What happens to amplitude in each of the responses
Action potential- amplitude standard, always the same despite bigger/smaller stimulus
Slow- Amplitude corresponds to stimulus
Which response can be summated
Only slow responses can be summated
Action potentials cant be summated BECAUSE THEY HAVE ANSOLUTE REFRACTORY PERIOD!!!!!!
What is absolute refractory period
During this period, no matter how big the stimulus, a action potential will not occur
Closure of the inactivation
gates of the Na+ channel in response to depolarization.
These inactivation gates are in the closed position until the cell is repolarized back to the resting membrane potential
What is relative refractory period
Begins at the end of the absolute r.p and overlaps with the hyperpolarization afterpotential
An action potential will only occur if the depolarizing current applied is GREATER
There is higher permeability for K+ here than at rest
What is accommodation
If depolarization happens slowly or depolarization is held for a long time, action potential will fail to fire despite being above threshold
This is because depolarization closes inactivation gates on Na+ channels
Give an example of accommodation
Hyperkalemia
Elevated blood serum K+ concentration
At rest, nerve and muscle cell membranes are very permeable to K+ an increase in extracellular K+ concentration causes depolarization of the resting membrane
The sustained depolarization closes the inactivation gates on Na+ channels making it less likely to fire an active potential