A human brain is formed of three main partes:
(a)forebrain (b)midbrain and (C) hindbrain.
Forebrain :The forebrain is formed of cerebrum and diencephalon.Diencephalon consists of dorsal thalamus and ventral hypothalamus.
Cerebrum:
(i)It is the largest portion forming nearly two-third of the brain.
(ii)The cerebrum is longitudinally divided into two halves called cerebral hemispheres by a deep cleft which are interconnected by thick band of nerve fibres called corpus callosum.
(iii) The outer portion of each cerebral hemisphere is formed of grey matter and is called cerebal cortex.
(iv)The inner of feeper part is formed of white matter and is called cerevral medulla.
(v)The cortex is extremely folded forming elevations called gyri with depressions between them termed as sulci that increase its surface area.
(vi)The cerebrum is also responsible for the thinking intelligence,consciousness,memory,imagination,reasoning and willpower.
Thalamus:It is present in cerebral medulla is a major conducting centre for sensory and motor signalling.It acts as a relay centre.Hypothalamus:
(i)It lies at the base of the thalamus.
(ii)It controls involuntary functions like hunger,thirst,sleep,sweating,sexual desire,anger,fear,water balance,blood pressure etc.
(iii)It acts as a thermoregulatory(temperature control)centre of the body.
(iv)It controls the secretion of hormones from anterior pituitary gland and is an important link between nervous system and endocrine system.
Midbrain :
(i)It is located between thalamus and hind brain.
(ii)It consists of four rounded bodies called corpora quadrigemina that control visual and auditory (hearing)reflexes.
Hindbrain:it is formed of three parts cerebellum,pons and medulla oblongata.
Cerebellum:
(i)It is second largest part of the brain formed of two large sized hemispheres and middle vermis.
(ii)It coordinates voluntary movements and also maintains body balance.
Pons:
(i)It is a bridge of nerve fibre that connects the lobes of cerebellum.It relay signals between the cerebellum,spinal cors,midbrain and cerebrum.
(ii)It controls respiration and spleep cycle.
Medulla Oblongata:
(i)It is the posterior most part of the brain that connects spinal cord and various parts of brain.
(ii)It has cardiac centres,respiratory centres,vasomotor centres to control heart beat,respiration and contractions of blood vessels respectively.
(iii)It also regulates vomiting and salivation.
