Question

Which element is essential for the transmission of impulses in nerve fibres?

• A. Calcium
• B. Iron
• C. Sodium
• D. Zinc

Hint:

Sodium drives the impulse along the length of the fibre itself; calcium's role is limited to the synapse at the very end.

Answer 1

The Correct Option is C

Step 1: Understand what a nerve impulse is.
A nerve impulse is an electrical signal, called an action potential, that travels along the length of a neuron's axon. This signal is created by the fast movement of charged particles, called ions, across the neuron's membrane.

Step 2: Identify which ion drives this movement along the fibre.
The membrane of a neuron has special gates called voltage gated sodium channels. When a neuron is stimulated, these channels open and let sodium ions rush into the cell. This sudden inward rush of sodium is what creates the electrical spike that then travels down the full length of the nerve fibre, from one end to the other.

Step 3: Rule out the other options.
Calcium plays an important role too, but its main job is at the very end of the neuron, at the synapse, where it triggers the release of chemical messengers to pass the signal to the next cell. It is not the ion that carries the impulse along the fibre itself. Iron mainly helps carry oxygen in the blood as part of haemoglobin and has no role in nerve signalling. Zinc supports many enzymes in the body but does not drive impulse conduction either.

Step 4: Confirm the answer.
Since sodium ion movement is what generates and carries the electrical impulse along a nerve fibre, the correct answer is Sodium.