Biology Nervous Coordination LUMHS 2015
PMDC Verified Question 86 of 86
For the impulse to transfer from presynaptic to post synaptic neuron, the substance required is: [LUMMHC-2015]
A
Sodium
B
Potassium
C
Protein
D
Calcium
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Calcium
Concept:

Exocytosis of neurotransmitters is entirely dependent on a specific extracellular ion.

Solution:

  • When an action potential reaches the axon terminal, it opens voltage-gated Calcium (\(\text{Ca}^{2+}\)) channels. The influx of calcium ions forces synaptic vesicles to fuse with the presynaptic membrane, releasing the chemical messenger into the cleft. Without calcium, this transfer cannot occur.


Why other options are incorrect:

  • Sodium / Potassium: Required for the action potential along the axon, but they do not directly trigger vesicular exocytosis.

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