Brain is a part of the central nervous system, which functions as the primary receiver, organizer, and distributor of information of the body. It regulates all the major activities of the body such as perception, cognition, attention, emotion, memory, and action.
It is estimated that the brain is made up of about 80-86 billion nerve cells. It is suspended in the cerebrospinal fluid continuous with the spinal cord (structure made up of neurons and nerve fibers) and enclosed within the skull.
The CNS is separated from the rest of the body by a cellular structure known as the blood-brain barrier. This barrier also acts as a filter and restricts the passage of chemical substances and microscopic particles inside the brain. However, it allows access to only those substances which are required for metabolism, like oxygen.
Due to this, infection in the human brain is rare, as compared to other organs of the body.
Different Parts of the Brain
Forebrain is the largest segment of the brain located in the uppermost part of the skull. It consists of the cerebrum, the thalamus, and the hypothalamus.
Cerebrum- The cerebrum or the cortex is the largest part of the brain. Its functions include thinking, reasoning, and remembering. The cerebrum is separated into two hemispheres (right and left) by a deep groove called the longitudinal cerebral fissure. The right hemisphere controls the left side of the body and vice versa.
The outer layer of the cerebrum is composed of nerve cells (gray matter), which control the activity of the brain; and the inner portion is made up of axons (nerve fibers) which is called the white matter. The axons which are covered by myelin sheath are responsible for transferring information in between the nerve cells.
Hypothalamus- Hypothalamus is referred to as "the brain of the brain". The main function of hypothalamus is homeostasis and control of all the autonomic regulatory activities of the body such as temperature and cardiovascular regulation.
The midbrain or the mesencephalon is the topmost section of the brainstem (lower part of the brain adjoining the spinal cord). It is made up of the tectum, the tegmentum, and the cerebral peduncles (paired bundle of nerve fibers that carry melanin pigment).
Tectum- The tectum is a roof-like structure, which forms the dorsal part of the midbrain. It consists of the superior and the inferior colliculi, which represent the anterior and posterior pair of nuclei of the tectum. The superior and inferior colliculi control vision and audition respectively.
Tegmentum- Tegmentum is the ventral portion of the midbrain that lies within the brainstem. It controls the motor function and regulates other autonomic functions.
The hindbrain is located at the upper portion of the spinal cord and is responsible for the vital functions of the body such as respiration and heartbeat. It consists of the cerebellum, pons, and medulla.
Cerebellum- Cerebellum is also referred to as the "little brain" which contains more than 50% of the total neurons. It is situated at the lower side of the brain, in between the cerebrum and the brain stem.
Cerebellum is divided into two hemispheres and overall contains 10 lobules. The two hemispheres are connected by white fibers. Like cerebrum, cerebellum also contains gray matter. This part of the brain controls and regulates coordination of movements.
Pons and Medulla- Pons and medulla are parts of the brainstem that connect the brain and the spinal cord. Pons has the control centers for face and eye movements. It has the origins of 5th, 6th, 7th, and 8th cranial nerves.
Medulla is located at the lowest part of the brain stem and contains control centers for heart and lungs. The cranial nerves 9th, 10th, 11th, and 12th originate from medulla.