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Q1.    Briefly describe the structure of the following:

                (a) Brain

Answers (1)

The brain is the main coordinating center of the body. It is a part of the nervous system that controls and monitors every organ of the body.

It is well protected by cranial meninges that are made up of an outer layer called dura mater, a thin middle layer called arachnoid, and an inner layer called pia mater. 

It is divided into three regions —

  1. forebrain 
  2. midbrain
  3. hindbrain


It is the main thinking part of the brain. It consists of the cerebrum, thalamus, and hypothalamus. 

1. Cerebrum: The cerebrum is the largest part of the brain and constitutes about four-fifths of its weight. It is divided into two cerebral hemispheres by a deep longitudinal cerebral fissure. These hemispheres are joined by a tract of nerve fibre known as the corpus callosum. 

2. Thalamus: Thalamus is the main center of coordination for sensory and motor signaling. It is wrapped by the cerebrum.

3. Hypothalamus: Hypothalamus lies at the base of the thalamus and contains a number of centers that regulate body temperature and the urge for eating and drinking. Some regions of the cerebrum, along with hypothalamus, are involved in the regulation of sexual behavior and expression of emotional reactions such as excitement, pleasure, fear, etc.

It is located between the thalamus region of the forebrain and pons region of hindbrain. The dorsal surface of midbrain consists of superior and inferior corpora bigemina and four round lobes called corpora quadrigemina.

It consists of three regions - pons, cerebellum, and medulla oblongata. 

  • Pons is a band of nerve fibre that lies between medulla oblongata and midbrain. It connects the lateral parts of cerebellar hemisphere together. 
  • The cerebellum is a large and well-developed part of hindbrain. It is located below the posterior sides of cerebral hemispheres and above the medulla oblongata. It is responsible for maintaining posture and equilibrium of the body. 
  • The medulla oblongata is the posterior and simplest part of the brain. It is located beneath the cerebellum. Its lower end extends in the form of the spinal cord and leaves the skull through the foramen magnum.
Posted by

Priyanka Kumari

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