Biology [2 Mark Question Answer]

Salivation is an example of conditioned reflex that develops due to experience or learning. Saliva starts pouring when you chew or eat food. Therefore, this reflex will occur not just on the sigh or smell of food. The brain actually needs to remember the taste of food. Boy B started salivating because he must have tasted that food prior unlike boy A.

The cerebral cortex contains cell bodies of the neuron and is greyish in colour. It is called gray matter. The grey matter has many folds (i.e. gyri) and grooves (i.e. sulci). They increase the surface area to accommodate more nerve cells. A higher number of convolutions leads to greater intelligence.

It develops during life time due to experience or learning. It is brought about by the condition which is totally different from initial stimulus. Example: Salivation just by the smell of food.

It is a part of the peripheral nervous system. It consists of a pair of chains of nerves and ganglia on either side of the backbone. It controls the involuntary actions of the internal organs.

It contains motor fibres which carry impulses generated by the association neuron (brain or spinal cord) to the effector organs. Example: A nerve which arises from the brain and ends in the eye muscles is a motor nerve. It helps in rotating the eye.

Central canal - It is located in centre of the spinal cord. It is in continuation with the cavities of the brain. It is filled with cerebrospinal fluid and acts as shock proof cushion. In addition, it also helps in exchange of materials with neurons.

The brain and the spinal cord lie in the skull and the vertebral column respectively. They have an important role to play because all bodily activities are controlled by them. A stimulus from any part of the body is always carried to the brain or spinal cord for the correct response. A response to a stimulus is also generated in the central nervous system. Therefore, the brain and the spinal cord are called the central nervous system.