Human Brain Explained : NCERT Science Notes

HUMAN BRAIN

  • Human brain is a highly complex organ; which is mainly composed of the nervous tissue.
  • The tissues are highly folded to accommodate a larger surface area in less space.
  • The brain is covered by a three-layered system of membranes; called meninges.
  • Cerebrospinal fluid is filled between the meninges.
  • The CSF provides cushion to the brain against mechanical shocks.
  • Furthermore, the brain is housed inside the skull for optimum protection.

The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.

PARTS OF HUMAN BRAIN

Forebrain: It is composed of the cerebrum.

Midbrain: It is composed of the hypothalamus.

Hindbrain: It is composed of the cerebellum, pons and medulla oblongata.

Some main structures of the human brain are explained below.

Cerebrum: The cerebrum is the largest part in the human brain. It is divided into two hemispheres; called cerebral hemispheres.

FUNCTIONS OF CEREBRUM:

  • The cerebrum controls the voluntary motor actions.
  • It is the site of sensory perceptions; like tactile and auditory perceptions.
  • It is the seat of learning and memory

Hypothalamus:

  • The hypothalamus lies at the base of the cerebrum.
  • It controls sleep and wake cycle (circadian rhythm) of the body.
  • It also controls the urges for eating and drinking.

Cerebellum:

  • Cerebellum lies below the cerebrum and at the back of the whole structure.
  • It coordinates the motor functions.
  • When you are riding your bicycle; the perfect coordination between your pedaling and steering control is achieved by the cerebellum.

Medulla:

  • Medulla forms the brain stem; along with the pons. It lies at the base of the brain and continues into the spinal cord.
  • Medulla controls various involuntary functions; like heartbeat, respiration, etc.

FUNCTIONS OF DIFFERENT PART OF THE BRAIN

Cerebrum

  • Seat of mental abilities, controls thinking, memory, reasoning, perception, emotions and speech.
  • Interprets sensations and responds to cold, heat, pain and pressure.
  • Relay center for sensory impulses, such as pain, temperature and light.

Diencephalon

  • Reflex center for muscular activities.
  • Centre for certain emotions such as anger.
  • Centre for water balance, blood pressure, body temperature, sleep and hunger.

Medulla oblongata

  • Coordinates reflexes like swallowing, coughing, sneezing and vomiting.
  • Contains center for cardiac, respiratory and vasomotor activities. (Vasomotor refers to actions upon a blood vessel which alter its diameter)

Cerebellum

  • Maintains posture, equilibrium and muscle tone.
  • Coordinates voluntary movements initiated by cerebrum.
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