### Theory:

Phineas Gage and his skull after the accident

Gage, then $$25$$ years old, was the foreman of a group preparing a railroad bed in Cavendish, Vermont, on September $$13$$, $$1848$$. He was tamping explosive material into a hole with an iron tamping rod.

Unfortunately, the powder exploded, sending the one-metre-long, three-centimetre-diameter rod soaring upward. Before landing, the rod pierced Gage's left cheek, tore into his brain, and exited his skull.

Gage amazingly survived the accident. Due to the damage to his left frontal lobe of the brain, his personality and behaviour, on the other hand, were so drastically altered and, as a result, that many of his friends described him as a completely new person. This was a shocking revelation for experts. For the first time, there was proof that brain damagecould influence our behaviour and personality.

This incident changed the course of neuroscience, and several brain specialists used information from Phineas case to support their own views about how the brain operates.
Regions of the brain:
Within each of us lies one of the most fascinating and wondrous things in the universe is our brain. Our brain is remarkably little for everything it does, weighing only around $$1.5$$ kg and containing $$100$$ billion neurons that allow us to feel, see, hear, smell, move, think, laugh, cry, speak, read, and remember.
The anatomy of our brain is unique, with various regions and folds that offer information.
Important!
Brain is the control and coordinating centre of the body. It controls the entire processing of information and act as a central information processing organ of our body.
Also it controls and regulates,
1. Voluntary movements of the body
2. Balance of the body
3. Function of involuntary organs such as lungs, heart, kidneys etc.
4. Temperature of the body
5. Endocrine glands
Meninges of the brain:
Brain is the site for processing of vision , hearing, speech, memory, intelligence, emotions and thoughts. Human brain is protected by skull. Inside the skull, brain is surrounded by  three connective tissue membranes or cranial meninges. Besides skull, it also protects the brain from mechanical injury. The three membranes of the meninges are,
1. Dura mater
2. Arachnoid membrane
3. Pia mater
 Type of membrane Origin of the name Location Structure Dura mater dura: tough; mater:membrane outermost layer Thick fibrous membrane Arachnoid membrane arachnoid: spider middle layer Thin vascularmembrane providing web-like cushion Pia mater Pia:soft or tender innermost layer Thin delicate membrane richlysupplied with blood

The location of cranial meninges and cerebrospinal fluid
Important!
Meningitis is a disease caused due to the inflammation of the meninges. When the fluid around the meninges becomes infected, it might occur. Infections caused by viruses and bacteria are the most common causes of meningitis.
Also, there is a clear fluid called Cerebrospinal fluid (CSF) present in ventricles of brain, subarachnoid space of brain and spinal cord. It acts as a shock absorbing medium.

Brain, being the largest part of the central nervous system, has three general areas.
1. Brain stem
2. Cerebral cortex
3. Cerebellum
In healthy people, these three areas work together flawlessly, allowing the brain to coordinate critical activities and behaviours such as breathing and spatial navigation.
Parts of the brain:
There are three major parts or regions of the brain viz.,
1. Forebrain
2. Midbrain
3. Hindbrain
Pictures showing the regions of the brain
I. Forebrain:
• Forebrain is the region mainly responsible for the process of thinking.
• It has regions that receive sensory impulses through various receptors.
• Specialised areas of the forebrain are responsible for hearing, smelling, sight and so on.
• There are specific areas of association where the sensory information received through hearing, smelling, and sighting is integrated with information from other receptors and information stored in the brain in the form of memory.
• Based on the integration of all this information, a decision is taken about how to respond. Then this decision will be sent to the motor area, which is the controlling region for the movement of voluntary muscle.
• Apart from the sensations of hearing, smelling, and sight, sensations such as feeling full happen during eating. This sensation is due to the specialised sensory region in the forebrain, which is associated with hunger.
•
Forebrain consists of,
1. Olfactory lobes
2. Cerebrum
3. Diencephalon
1. Olfactory lobesThey are paired club shaped structures present in the anterior part of the brain. These lobes are responsible for the sense of smell.

2. Cerebrum:

It is the largest part of the brain and occupies nearly two-third of the brain . Cerebral cortex forms the outermost portion of cerebrumand makes up the grey matter.

The innermost or deeper portion, which is made up of white matter, is called as cerebral medulla. The cortex is heavily folded, forming elevations called gyri and depressions between them termed sulci, increasing its surface area.

Cerebral cortex, which sits above brainstem and cerebellum, swiftly perceives, interprets, and responds to information from the environment. Sensory perception and processing, as well as higher-level cognitive tasks including perception, memory, and decision-making, are all handled by it.

Cerebrum is divided longitudinally into two hemispheres (right and left hemispheres) by a deep cleft called as median cleft. Corpus callosum, a bridge of large, flat and thickband of neural fibres acts as a communication relay between the two sides.

Each cerebral hemisphere consists of four lobes called as cerebral lobes viz.,
• Frontal Lobe
• Parietal Lobe
• Occipital Lobe
• Temporal Lobe
The lobes of the brain

i. Frontal lobe:

From behind the forehead back to the parietal lobe, the big frontal lobe stretches. It is the command centre for executive functions such as reasoning, decision-making, expressive language, higher-level cognitive processes, orienting (sensory information integration into person, place, time, and circumstance), and movement planning and execution.

ii. Parietal lobe:

Above the temporal lobe and adjacent to the occipital lobe lies the parietal lobe. This lobe plays an important role in touch and spatial navigation, including the processing of touch, pressure, temperature, and pain.

iii. Occipital Lobe:

The occipital lobe is present at the back of the brain. This region is responsible for processing and interpreting visual information.

iv. Temporal lobe:

Temporal lobe is present from the temple back towards the occipital lobe. This region act as processing center for receptive language, memory and emotion
Important!
The inner part of cerebral hemispheres and the structures like amygdala, hippocampus form a complex structure called the limbic system. Along with hypothalamus, this system regularize the sexual behaviour and expression of emotional reactions and motivation.
3. Diencephalon:

It is consists of,
• Epithalamus
• Thalamus
• Hypothalamus
The regions of thalamus and hypothalamus

Epithalamus: It secretes the hormone melatonin.

Thalamus: It lies in the cerebral medulla region.  It is mainly composed of grey matter.  It acts as a major conducting center for the sensory and motor signalling. So, it is called as relay centre.
Important!
Note:Except smell, each sense channels and their sensory nerves pass through the thalamus.
Hypothalamus: It lies above pituitary gland and at the base of the thalamus.  It is attached to the pituitary gland by a stalk called infundibulum.
• This region maintains homeostasis, and also involves in involuntary functions like hunger, thirst, sleep, sweating, sexual desire, anger, fear, water balance, blood pressure etc.
• The body temperature is regulates in this region and so it is called as thermo-regulatory center of the body.
• Neuro secretory cells in this region secrete hormone called as hypothalamic hormones. These hormones control anterior pituitary's hormone production and secretion.
• The hypothalamus is an anatomical link between the nervous and endocrine systems. It is regarded as the endocrine system's supreme commander.
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