Neuron

A neuron has three main parts. The dendrites pick up information. The cell body comes next. The axon is a long fibre that carries the message away. The message travels in one direction:

• When a dendrite tip picks up a signal, a chemical change there creates an electrical impulse.
• The impulse runs to the cell body and then along the axon to its end.
• There it releases chemicals. They cross a small gap, called the synapse, and start a new impulse in the next neuron.

The same kind of gap links the last neuron to a muscle cell or a gland.

A small example

Put some sugar in your mouth. Taste receptors on the tongue detect it. The message then changes form twice at each synapse. It is electrical along the neuron, chemical across the gap, and electrical again in the next neuron.

Where marks go

Question 13 of CBSE's 2026-27 Science sample paper carries 3 marks. It asks how muscles move when a message comes from the brain. The board's Science marking scheme for 2026-27 answers in three points. The impulse reaches the muscle. Special proteins in the muscle cells change their shape and arrangement. The new arrangement makes the cells shorter.

The scheme prints no split for the 3 marks. So the safe answer writes each link in the chain as its own sentence. See how step marking works.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

Deepti Sardana on LinkedIn