Defence Exam Notes: Human Brain

HUMAN NEURAL SYSTEM

The human nervous system is a very much complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body.

The nervous system incorporates both the Central Nervous System and the Peripheral Nervous System. The Central nervous system (CNS) is made up of the brain, and spinal cord and the Peripheral nervous system (PNS) is made up of the Somatic and the Autonomic nervous systems.

HUMAN BRAIN

The human brain plays a major role in the nervous system. It is the command centre for the human body. It gets signals from the body's sensory organs and outputs information to the muscles. 

IMPORTANT POINTS RELATED TO HUMAN BRAIN

• The human brain is the largest brain among all vertebrates relative to their body size.
• It weighs about 3.3 lbs. i.e,1.5 kg.
• The average brain volume of a male is 1,274 cubic cm.
• The average brain volume of a female is 1,131 cm3.
• The brain makes up about 2 % of a human's body weight.
• The cerebrum makes up about 85 % of the brain's weight.
• It contains about 86 billion nerve cells (neurons) — the "grey matter."
• It contains billions of nerve fibres (axons and dendrites) — the "white matter."
• These neurons are connected by trillions of connections or synapses.

ANATOMICAL STRUCTURE OF THE HUMAN BRAIN

• The human brain develops from the forebrain, midbrain and hindbrain. Each contains fluid-filled cavities known as ventricles. The cerebrum develops from the forebrain; the midbrain forms the brainstem, and the hindbrain becomes the Brainstem and the Cerebellum.
• The largest part of the human brain is the cerebrum, which is divided into two hemispheres. Brainstem lies below the cerebrum and cerebellum lies behind it.
• The cerebellum which lies beneath the cerebrum and has play an important role in motor control. It plays a role in coordination and balancing. And also it may have some cognitive functions.
• The cerebral cortex is the outermost layer of the cerebrum, which consist of four lobes, namely, frontal lobe, parietal lobe, temporal lobe and the occipital lobe.
• The cerebral cortex is enlarged and is considered as the seat of complex thought. The occipital lobe of the brain is used for visual processing present at the backside of the skull. 
• The temporal lobe helps to possess sound and languages, and it also includes the hippocampus and the amygdala, which helps in memory and emotion development, respectively.
•  The parietal lobe integrates input coming from different senses and used for navigation and spatial orientation.
• The brainstem connected with the spinal cord, and it also consists of Medulla oblongata, pons and midbrain. The main functions of the brainstem include passing information between the brain to the body; supplying cranial nerves to the face and head, and also performing critical functions in controlling the heart rate and body consciousness. 
• In Between the cerebrum and brainstem, thalamus and hypothalamus lie. The thalamus passes sensory and motor signals to the cortex. It is also involved in regulating sleep, alertness and consciousness. 
• The hypothalamus also connects the nervous system to the endocrine system of the body, which produces hormones via the pituitary gland.

HUMAN BRAIN: FAQ

Q1. Where does the memory power is found in human brain?

A. In a human brain, memory power is found in Cerebrum.

Q2. What is the main thinking part of the human brain?

A. The brain has mainly three main parts forebrain, midbrain and hindbrain in which  Forebrain is the main thinking part of the human brain.

Q3. The human brain is isolated from the bloodstream by which barrier?

A. The blood-brain barrier is a highly selective semi-permeable border that separates the circulating blood from the brain and extra-cellular fluid in the central nervous system.

Q4. Which layer covers the human brain?

A. Three cranial meninges namely, Dura mater, Piamater and Arachnoid mater are present which covers the brain and provides protection to the brain.

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