3- Action Potential Flashcards
What is an action potential?
A signal that conveys information over distances
Stage 1 (resting potential)
Synaptic input makes membrane potential more and less negative
Stage 2 (rising phase, negative –> positive)
Na+ channels open, influx of ions make cells more positive
Stage 3 (overshoot- inside is briefly more positive than outside)
Na+ channels close
Stage 4 (falling phase)
K+ channels open, ions stream out of cells and membrane becomes negative
Stage 5 (undershoot- inside is more negative than outside)
Sodium-potassium pump re-establishes resting potential
A sub-threshold stimulus
Not enough to generate an action potential
A threshold stimulus
Generates an action potential
A suprathreshold stimulus
Generates the same action potential as the threshold stimulus
What is the threshold level?
The critical level of depolarisation to cause an AP
What does the generator potential cause?
Depolarisation of membrane
What is the all-or-none principle?
AP is generated when stimulus reaches threshold level but above the threshold will still generate the same response
What is the absolute refractory period?
The period where it is impossible to initiate an AP
What is the relative refractory period?
The amount of current required to depolarise the neuron to AP threshold is elevated above normal
What is the firing rate/frequency?
Number of APs per interval, frequency coding of strength and latency of initial stimulus
