Locked safely inside your skull is your brain - the headquarters of your nervous system and your body's control center.

More complex and powerful than the brain of any other animal, the human brain is the most poorly understood organ in the body. Somehow this cauliflower- shaped mass of nerve cells creates a whole inner world of experience and a sense of self. Everything you see, touch, think, dream, and remember is generated within it. In some respects the brain works like a computer, but one that is continually rewiring itself as it learns and adapts.

Its basic component is the nerve cell, or neuron - a wire-like cell that sends electrical signals to other neurons, forming complex circuits of activity. Every second, trillions of electrical impulses dart among your brain cells, weaving infinitely tangled paths among an ever-changing maze of connections.

Brain cells

The brain is made up of cells called neurons, which send electrical signals to each other via thin, wire-like strands that connect at junctions called synapses. A computer chip has about a billion transistors with 3 to 4 connections each, but the human brain has 100 billion neurons with up to 10,000 synapses each. Synapses are more complex than the simple on/off switches in a computer chip. Each one may contain up to 1,000 molecular switches, giving the human brain phenomenal processing power.

Brain size

Most of the complex processing happens in the brain's surface - the cerebral cortex, which is packed with synapses. Humans have a far larger cortical area than other animals, giving our brains more processing power.

Cortical area

If the cortex of your brain were laid out flat, it would cover the same area as four pages. A monkey's cortex is the size of a postcard, and a rat's is the size of a postage stamp.

How memory works

The brain stores memories as networks of connections between neurons. Every new experience or new piece of information makes your neurons fire in a particular pattern. When you recall the event or fact, you make the neurons fire in the same pattern again, strengthening the memory.

1. Experience: A new experience makes neurons send signals in a particular pattern. In reality, hundreds of neurons are involved in the network.

2. Repeating: Repeating the experience or recalling the fact causes new links to form, making the network larger and easier to trigger.

3. Strengthening: Further repetition strengthens the network further, consolidating the memory. Links that are not refreshed tend to fade and are lost.

The thinking brain

The largest and cleverest part of the brain is its outermost layer, the cerebral cortex. Deep folds divide the cortex into distinct areas called lobes, which tend to specialize in different processes, such as speech or vision. However, scans of active brains reveal widespread activity across the cortex during mental tasks, showing that the various areas work together in complex ways.

Basic instinct

While the outer part of the brain deals with higher mental processes such as thought, a set of structures deep inside the brain controls basic drives and emotions, such as pleasure, fear, and anger. These structures form what is known as the limbic system.

Parts of Brain


The top of the cerebral cortex sends signals to muscles to make the body move.


The front part of the cerebral cortex is important in conscious thinking, planning, and understanding other people's thoughts.


Known as Broca's area, this part of the brain is vital in generating speech.


Nerve signals from the ears come to the auditory cortex, which creates the sense of hearing.

Brain stem

Situated at the top of the spinal cord, this part of the inner brain controls vital functions such as breathing and the heartbeat.


Signals from touch and pain receptors in the skin come to this area, called the somatosensory cortex.

Touch processing

Touch signals pass from the touch area to this part of the brain for further processing, helping us recognize what we can feel.

Learning to speak

Called Geschwind's territory, this part of the brain helps us acquire language skills during childhood.


The visual cortex receives signals from the eyes and processes them to identify basic shapes and patterns.

Visual processing

Basic shapes and patterns identified by the visual cortex are processed further here, helping us recognize objects we see.


The cerebellum is separate from the rest of the brain. It helps coordinate muscles so they work in perfect sync.

Spinal cord

Nerve signals pass between the brain and body via the spinal cord, a bundle of nerve tissue that runs down the spine.