Question 13

Draw and explain how the nerve cells help in transmission of impulses?

Answer:

A nerve cell (neuron) is the structural and functional unit of the nervous system. It is specialized to transmit messages in the form of nerve impulses.

Structure of a Neuron:

• Dendrites: Receive the stimulus from receptors or other neurons.

• Cell body (Cyton): Contains nucleus and cytoplasm, controls activities.

• Axon: Long fibre that carries the impulse away from the cell body.

• Myelin sheath: Insulates the axon and speeds up transmission.

• Node of Ranvier → Gaps in myelin sheath that allow faster impulse conduction.

• Axon terminals: Pass the impulse to the next cell across the synapse.

Transmission of Nerve Impulse

1. Stimulus Reception → Dendrites receive the stimulus.

2. Impulse Generation → Electrical impulse (action potential) is created in the cell membrane.

3. Impulse Conduction → Impulse travels through the cell body and axon.

   • Myelin sheath speeds up conduction by jumping from one Node of Ranvier to the next.

4. Synaptic Transmission → At axon terminal, impulse is passed chemically.

   • Neurotransmitters are released into the synapse.

   • They stimulate the next neuron/muscle cell to generate a new impulse.

✅ Inside neuron → Electrical
✅ Across synapse → Chemical