Generation of Action Potentials Flashcards
What is an action potential?
A sequence of rapidly occuring events that decrease and eventually reverse membrane potential, ultimately restoring it back to resting potential
What is the all or nothing principle?
If threshold is not reached, no action potential
What is the threshold value?
55mV
What types of stimuli can cause a graded potential to reach at least 55mV?
-Chemical
-Mechanical
What happens during depolarisation?
-Voltage-gated Na⁺ channels open and Na⁺ rushes into the cell
In resting potential, which Na⁺ gates are open?
Na⁺ inactivation gate is open
In resting potential, which Na⁺ gates are closed?
Na⁺ activation gate is closed
What happens to both the Na⁺ gates when the threshold is reached during depolarisation?
Both gates open and Na⁺ rushes in
What is repolarisation?
Voltage-gated K⁺ channels open
Do K⁺ v.g. channels open faster than Na⁺ v.g. channels?
No
Na⁺ voltage-gated channels open faster
What does the movement of K⁺ out of the cells cause the membrane potential to change to?
-70mv (Resting Potential)
What happens if too much K⁺ leaves the cell?
-Membrane will reach a -90mV potential
-Enters after-hyper polarisation phase
What happens once the membrane potential reaches -70mV?
K⁺ channels close
What is a refractory period?
Time when the neuron cannot generate another action potential
What are the two types of refractory period?
-Absolute refractory period
-Relative refractory period
