Structure of Brain

Structure of Brain

 Brain is also known as encephalon.

Brain constitutes 98% part of central nervous system.
Average weight of brain is about 1200-1400gm in adult.

Fore brain

1. Olfactory lobes.
2. Cerebrum. 
3. Diencephalon.

• Epithalamus
• Thalamus
• Hypothalamus

Olfactory lobes

Olfactory lobes constitutes with olfactory tract and olfactory bulb.

Olfactory tract contain bundles of nerve fibers that carries impulse from olfactory bulb to temporal lobe of cerebrum. 

Olfactory bulb is swollen bulb like structure which contains nerve cells, called mitral cells.  

Cerebrum

Largest part of brain, constitutes about 80-82% parts of brain. Cerebrum is divided into two halves or lobes, called cerebral hemisphere. Cerebral hemisphere is connected to each other by a thick white matter band, called corpus callosum. Cerebrum made up about 40,000 million neuron. 

Diencephalon      

Diencephalon is divided into three parts:

Epithalamus

Epithalamus is present on roof of diencephalon. Roof has look as third eye, called pineal body. Pineal body secrets two hormones melatonin and serotonin. 

Melatonin

Skin pigmentation.

Serotonin

Inflammatory protein.

Thalamus   

It is one of the important structure because all stimuli coming toward brain has to pass thalamus. Thalamus has special network of neurons, called reticulo activitating system (RAS). 

Alertness and consciousness are depends upon the RAS.

Hypothalamus  

Hypothalamus is present on floor of diencephalon. Hypothalamus secretes releasing factors which goes pituitary gland and secrets activated hormones. Hypothalamus act as thermostat of the body that help to regulating internal body temperature. Hypothalamus has various receptors including hunger, thirsty and osmoregulation.

Mid brain

Mid brain contain thick pigmented nerve fibers that secrets inhibitory nerurotransmitters, called dopamine. 

Mid brain is divided into two parts:

1. Corpora quadrigemina
2. Cerebral peduricle

Corpora quadrigemina

Contain two pairs of rounded nuclei.

1. Control visual reflexes
2. Control auditory reflexes

Cerebral peduricle

Cerebral peduricle contains a thick pair of nerve fiber which connect mid brain to hind brain. 

Hind brain

Hind brain divided into three parts:

1. Cerebrum
2. Pons varoli
3. Medulla oblongata

Cerebrum

Cerebrum is constitute 11% part of brain. Cerebrum is divided into two equal halves, called cerebellar hemisphere. Both cerebellar hemisphere are connected with the help of middle lobe, called vermix. 

Outer structure of cerebrum is cortex – gray matter Inner structure of cerebrum is medulla – white matter 

Pons varoli

Shape - Swollen structure.

Location - Below mid brain, above medulla oblongata and in front of cerebellum. 
 

Pons varoli act as bridge between medulla, spinal cord and cerebrum.

Medulla oblongata

Location – Below pons varoli and above spinal cord.
Medulla oblongata contain vital and non-vital center.
 

Vital center 

Regulate following functions:

• Circulation blood and maintain heart beat
• Breathing.
• Contraction and dilation of blood vessels.
• Non vital center.
• Coughing.
• Vomiting.
• Yawning .
• Sneezing.

Function of brain 

Parts of brain

Function

1)  Brain stem Medulla oblongata Pons Midbrain

Contains sensory and motor tract. Cardiovascular center present in medulla oblongata, which regulate heart beats and diameter of blood vessels. Medulla oblongata contains several nuclei, which coordinate vomiting, sneezing, coughing, hiccupping and swallowing.       Contains sensory and motor tract. Pontine nuclei diffuse nerve impulse from motor region (area) of cerebral         cortex to cerebellum. Help to control breathing.   Contains sensory and motor tract. Coordinate movement of head, eyes and trunk.