Page 80 - Teknik Menjawab Soalan PSPM Biologi

Mechanism of impulse transmission across synapse

1.An action potential arrive at synaptic knob, depolarising the presynaptic

membrane

2+
2. The depolarization, open voltage-gated calcium ion (Ca ) channel in the
presynaptic membrane, triggering an influx of Ca 2+

3. Ca 2+ stimulates synaptic vesicles to move towards presynaptic
membrane & fuse with it

- The vesicles release neurotransmitters to the synaptic cleft by

exocytosis

- Neurotransmitters diffuse across synaptic cleft & move towards

postsynaptic membrane

4. It binds to the receptor on the postsynaptic membrane, Causing
+
the ligand-gated Na channel to open

5. Allow Na from extracellular fluid diffuse into postsynaptic neuron
+
and cause Postsynaptic membrane depolarize (EPSP).

- If depolarization reaches threshold level, impulse / action

potential is generated in the next neuron