Question
As neuron’s diameter increases, what effect gets manifested?
| A. |
Conduction velocity increases |
| B. |
Conduction velocity decreases |
| C. |
Membrane resistance increases |
| D. |
Action potential amplitude increases |
|
Correct Answer � A Explanation |
 |
The conduction velocity of nerve fibers is linked to axon diameter. As neuron diameter ↑, internal (axoplasmic) resistance ↓, allowing current to spread more easily along the axon. This results in:
– Faster depolarization of adjacent segments
– Higher conduction velocity
This applies to both myelinated & unmyelinated fibers. Myelinated fibers benefit from saltatory conduction, which ↑ speed further.
– Larger diameter → lower internal resistance → faster conduction
– This follows the cable properties of axons
– Myelination & axon diameter are main factors affecting conduction speed
Incorrect Options:
B. Conduction velocity decreases – Smaller diameter ↑ resistance, slower conduction.
C. Membrane resistance increases – Larger diameter ↑ surface area, ↓ resistance.
D. Action potential amplitude increases – Amplitude remains constant, not affected by diameter.