Question

Briefly describe the structure of Brain.

Answer 1

Brain is the main coordinating centre of the body. It is a part of the nervous system, which controls and monitors every organ of the body.

Brain is divided into 3 parts:


Forebrain: Has the cerebrum, thalamus and hypothalamus

Cerebrum (major part of the brain) is divided by a deep cleft into the left and right cerebral hemispheres.
Corpus callosum: A tract of nerve fibres that connect the two hemispheres
Cerebral Cortex: Layer of cells covering the cerebral hemispheres. It is also called ‘grey matter” due to its greyish appearance, imparted by the high concentration of neuron cell bodies.
Cerebral cortex consists of 3 areas:
Motor areas, Sensory areas, Association areas (not clearly distinguishable into motor or sensory)
Association areas: Responsible for complex functions like inter-sensory association, memory and communication
Fibres of tracts present in the inner parts of the hemispheres are called “white matter” due to the opaque white appearance, imparted by the myelin sheath covering.
Thalamus: Coordinates sensory and motor signalling
Hypothalamus: Controls body temperature, hunger and thirst; contains neurosecretory cells which secrete hormones
Limbic System = Inner parts of the cerebral hemispheres + Amygdale + Hippocampus
Limbic System + Hypothalamus = Involved in the regulation of emotions, sexual behaviour and motivation
Midbrain

Location: Between the thalamus/hypothalamus of the forebrain and the pons of the hindbrain
Cerebral aqueduct: Canal passing through the midbrain
Corpora quadrigemina: 4 round swellings (lobes) on the dorsal portion of the midbrain.
Hindbrain: Pons + Cerebellum + Medulla

Hindbrain and midbrain form the brain stem.
Pons: Fibre tracts that connect various portions of the brain
Cerebellum has a convoluted surface to provide space for more neurons.
Medulla connects to the spinal cord, and controls respiration, cardiovascular reflexes and gastric secretions.