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MHT-CET : Biology Entrance Exam

MHT - CET : Biology - Nervous Coordination Page 1

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Central Nervous System


  • The nervous system of man is made up of millions of nerve cells called neurons. The neurons are supported and nourished by neuroglial cells.
  • The CNS is soft and hollow. The cavities within the brain (called ventricles) are continuous with the central canal in the spinal cord and are filled with the cerebrospinal fluid.
  • The CNS is made up of brain and spinal cord.





  • Brain is located inside the head. It is protected within a bony box called cranium.
  • The brain of an adult comprises the following:

Forebrain - cerebrum
Diencephalon (thalamus and hypothalamus)

Midbrain -


Hindbrain - Pons varolii
Medulla oblongata

brain stem



  • An average human, brain weighs 1.4 kg and its volume is 1,300 ml.





  • The cerebrum is the largest part of the brain, accounting for 85% of its weight.
  • It is divided into two hemispheres, called cerebral hemispheres, by median longitudinal cerebral fissure.
  • The two cerebral hemispheres, namely the right and left cerebral hemispheres, are connected by transverse bridge of white matter, the corpus callosum. Each hemisphere contains a cavity called lateral ventricle.
  • The outer portion of the cerebral hemisphere, which is known as cerebral cortex, is composed of the grey matter consisting of millions of nerve cells.
  • Functions of Cerebrum:
    Memory, intelligence, thinking, etc. associated with higher centres.
    Perception of sensations of pain, temperature, touch, sight, hearing, taste and smell (sensory functions)
    Voluntary muscle contractions (motor functions)



Basal Nuclei and Diencephalon


The grey matter inside the forebrain constitutes three separate areas, namely:

  • Basal nuclei - it belongs to the cerebrum and controls the smooth movements of the muscles.
  • Thalamus - it lies just below the corpus callosum. Thalamus receives sensory inputs from skin, sense organs and viscera and transmits them to the appropriate areas of cerebral cortex.
  • Hypothalamus - it is situated below and just in front of the thalamus and above the pituitary gland. It is concerned with the pituitary, autonomic nervous system, controlling body temperature and feelings like hunger, thirst, fear, anger, etc.





  • The midbrain is a small, stalk-like structure which connects the pons and the cerebellum with the hemispheres of the cerebrum.
  • Functions of Midbrain:
    The midbrain controls vision, auditory stimuli and their reflexes. The midbrain controls the general development and functioning of the body through hormones secreted by the pituitary gland.
    The pituitary gland, which lies in the midbrain, produces hormones, which are necessary to control other endocrine glands.



Pons or Pons Varolii


  • Pons varolii is a strip of nervous tissue, which lies below the midbrain and above the medulla oblongata.
  • Functions of Pons Varolii:
    Pons varolii connects the two lateral lobes of the cerebellum and the midbrain to the medulla oblongata.
    The pons Varolii provides the space for motor fibres, which run across the cerebrum and the cerebellum.
    The pons varolii is concerned with the regulation of heat in the body.
    The pons varolii is the centre of reflexes.



Medulla Oblongata


  • The medulla oblongata is the lowermost part of the brain stem.
  • Medulla oblongata connects the pons with the spinal cord.
  • Functions of Medulla Oblongata:
    Medulla oblongata is an important centre of autonomic reflexes.





  • Cerebellum is the second largest part of the brain.
  • Cerebellum is situated behind the pons varolii and below the posterior portion of cerebrum.
  • The cerebellum consists of a middle vermis and two lateral hemispheres, called cerebellar hemispheres.
  • Functions of Cerebellum:
    The cerebellum co-ordinates muscular movements during walking and running.
    The cerebellum plays an important role in maintaining the posture and balance of the body.
    The cerebellum maintains the muscle tone.



Spinal Cord


  • Spinal cord is the continuation of medulla oblongata up to the vertebral column.
  • The spinal cord is elongated and cylindrical.
  • In an average human, the length of spinal cord is 45 cm.
  • Functions of Spinal Cord:
    The spinal cord plays an important role in the conduction of impulses to and fro from the brain to the outlying parts.
    The spinal cord acts as a major centre for many reflex actions of the body.
    The spinal cord serves as a connecting link between the brain and the spinal nerves.



Peripheral Nervous System


There are two types of peripheral nerves namely, cranial nerves and spinal nerves.
There are 12 pairs of cranial nerves in mammals, including human.

  1. Olfactory: sensory
  2. Optic: sensory
  3. Oculomotor: motor
  4. Trochlear: motor
  5. Trigeminal: mixed
  6. Abducent: motor
  7. Facial: mixed
  8. Vestibulocochlear or auditory: sensory
  9. Glossopharyngeal: mixed
  10. Vagus: mixed
  11. Accessory: motor
  12. Hypoglossal: motor



Spinal Nerves


  • There are 31 pairs of spinal nerves in human. They pass through foramina (openings) between adjacent vertebrae.
  • Cervical spinal nerves which emerge from the spinal cord in the neck region - 8 pairs
  • Spinal nerves in the thoracic region - 12 pairs
  • Spinal nerves in the lumbar or groin region - 5 pairs
  • Spinal nerves in the sacral region - 5 pairs
  • Spinal nerve in the coccygeal region - 1 pair



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