Human Brain

The human brain is the central organ of the human nervous system, and together with the spinal cord it makes up the central nervous system. It is the soft, delicate control centre that governs thought, memory, emotion and the working of the entire body, and it is built from three main parts.

• The brain, with the spinal cord, makes up the central nervous system.
• The brain consists of the cerebrum, the brainstem and the cerebellum.
• The cerebrum alone makes up about 85 per cent of the brain's weight, which is why it dominates everything that follows.

For study and for exams the brain is grouped into three regions stacked from front to back — the forebrain, the midbrain and the hindbrain. Each region is responsible for a broad class of activity, and a single table fixes the whole scheme before each one is opened up.

• The forebrain is the thinking part, dealing with thought, sensation and body regulation.
• The midbrain controls reflex actions and is the smallest division.
• The hindbrain handles life-supporting functions — balance, breathing and other automatic actions.

The forebrain is the largest and most advanced division, and it is here that the conscious, "human" qualities of the mind reside. It is made up of the cerebrum, the thalamus and the limbic system (which includes the hypothalamus), and each has a clearly defined job.

The cerebrum is the part everyone pictures when they imagine a brain — the large, deeply folded mass that fills most of the skull. It is the largest part of the brain and the seat of intelligence, and it is divided into a right and a left hemisphere.

• It is composed of right and left hemispheres.
• It performs the brain's higher functions.
• It is the thinking part of the brain and controls higher functions.
• The cerebrum makes up 85 per cent of the brain's weight.

• Interpreting touch.
• Vision and hearing.
• Speech.
• Reasoning (intelligence).
• Emotions and learning.
• Control of movement.

The thalamus sits deep in the forebrain and works as a switchboard, passing signals on to the higher centres.

• The thalamus acts as a relay station for sensory information.

The limbic system is the emotional core of the brain, set between the cerebrum and the thalamus.

• The limbic system controls our emotions and drives.

• Hunger.
• Thirst.
• Fear.
• Anger.
• Sexual responses.

The hypothalamus is a tiny but vital region that links the nervous system to the hormonal system and keeps the body's internal environment steady.

• It is located at the base of the brain, near the pituitary gland.
• Although very small, the hypothalamus plays a crucial role in many important functions.
• It works through hormones connected to the nervous system.
• The hypothalamus maintains body balance by controlling hormones and temperature.

The midbrain is a short segment that sits between the hindbrain and the forebrain, forming the topmost part of the brainstem. Though it is the smallest of the three divisions, it serves as a busy reflex centre.

• The midbrain helps in reflex actions.

The hindbrain lies at the back and base of the brain, and although it does little "thinking", it runs the automatic machinery that keeps the body alive and balanced.

• The hindbrain is responsible for balance, sleep, breathing and other automatic actions.
• The hindbrain is responsible for the blood circulation of the body.

• The hindbrain has three parts: Cerebellum, Pons and Medulla.
• The cerebellum is the centre of balance and coordination, the second-largest part of the brain after the cerebrum.
• The medulla oblongata controls the involuntary, life-sustaining actions of the heart and lungs.
• The pons and medulla, together with the midbrain, form the brainstem.

A compact summary of which division does what — a favourite one-mark question.

The figures and superlatives below are among the most frequently tested points on this topic.

• It weighs about 1.5 kg (about 3.3 lbs).
• The average male brain has a volume of 1,274 cubic centimetres.
• The average female brain has a volume of 1,131 cm³.
• The brain makes up about 2 per cent of a human's body weight.
• The cerebrum makes up 85 per cent of the brain's weight.
• It contains 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.
• The smallest part of the brain is the Mid Brain.
• The hindbrain is responsible for the blood circulation of the body.

These are the labels that appear on brain diagrams in exams, worth recognising at a glance.

• Corpus Callosum, Thalamus, Hypothalamus, Optic Chiasma, Pineal Gland.
• Pituitary Gland, Mammillary Body, Pons, Medulla Oblongata, Cerebellum, Spinal Cord.

• Frontal lobe, Parietal lobe, Occipital lobe, Temporal lobe, Cerebellum and Spinal Cord.

• Cerebrum, Ventricles, Corpus callosum, Thalamus, Hypothalamus, Pituitary gland, Cerebellum, Pons, Medulla and Brain stem — with the Forebrain, Midbrain and Hindbrain regions marked.

A final cluster of the lines examiners ask most often, gathered together.

• Thalamus acts as a relay station for sensory information.
• Limbic system controls our emotions and drives.
• Hypothalamus maintains body balance by controlling hormones and temperature.
• Hypothalamus controls hormones and body balance.
• Mid Brain helps in reflex actions.
• Hindbrain is responsible for balance, sleep, breathing and other automatic actions.
• The brain is the control centre of our body.
• It contains billions of neurons and connections.
• Cerebrum is the largest part and controls higher functions.