Page 79 - Teknik Menjawab Soalan PSPM Biologi

Explain the propagation of action potential along the axon of neuron

Depolarisation
● - Stimulus causes sodium potassium pump to stop functioning
● When a stimulus depolarizes the membrane, some gated sodium

ion channels open allowing more Na to diffuse into the axon.
+
● Causing the charges within the axon becomes less negative than

the resting potential (closer to zero)
Rising phase of action potential

● If the stimulus is strong enough, depolarisation reaches threshold
level (-55mV), a nerve impulse or action potential is generated
● Local circuit is produced
● The affected area of the membrane become positively charged
● The diffusion of Na in the affected area, induce the opening of
+
voltage-gated Na channel in the adjacent region
+
● This causes the next voltage-gated Na channel in the region to
+
open

● Allowing Na to diffuse in that area causing that region to be
+
depolarized

● Once generated, action potentialis self propagating

● Action potential is regeneratedrepeatedly along the axon
● Action potential is a wave of depolarization that propagates until

end of axon in one direction
● Action potential is prevented from turning backward by refractory
period