Skip to main contentOpen Accessibility MenuAccessibility Menu

What is a brain injury?

The brain is involved in almost everything we do, so injury to the brain through trauma or illness can have a wide range of effects. These vary from person to person, depending on the exact nature and severity of the injury.

About the brain and brain injury

What is a brain injury

The human brain is the most complex known structure in the universe. This single organ is the hub of our central nervous system and a control centre for all our bodily functions. The brain contains as many as 100 billion nerve cells.

Many of the brain’s nerve fibres are wrapped in a fatty insulating sheath called myelin. The brain is held together by many membrane layers and is protected by the skull, or cranium – a hard bone shell. Blood vessels sit between the membrane layers and supply blood to and from the brain.

Each 100 billion nerve cell or neuron is connected to around 10,000 other supporting cells, making around 1,000 trillion connections. This complex network of neurons transmits information through electrochemical signals, and electrical impulses travel quickly around the brain and onto the body through the nervous system.

What is acquired brain injury (ABI)?

Brain injury is acquired either by sustaining a blow to the head or by having an illness that causes brain injury.

A brain injury can also happen through road traffic accidents, assaults, or falls (often called traumatic brain injuries or TBI) or by illness such as encephalitis, brain haemorrhages/strokes (cerebrovascular accidents or CVA) or a brain tumour.

There are some differences in likely risk depending on a person’s age and how they receive the injury. For example, traumatic brain injuries tend to occur more in the very young, the very old and young men aged 16 – 30. Strokes tend to occur more in older adults.

However, a brain injury can happen to us at any time.


How does brain injury affect people?

In most cases, an initial brain injury leads to some change in the person’s level of consciousness. There is often a period when the person is entirely unconscious or in a coma. The Glasgow Coma Scale measures the level of consciousness.

Scores on this scale vary from three, where the person does not respond at all, to 15, where they can walk, talk, and be fully aware of their circumstances. The less the person can respond, the deeper their level of unconsciousness.

The length of unconsciousness varies from a few seconds to many months. The longer the period of unconsciousness, the more severe the brain injury is likely to be.

As a person regains consciousness, they often go through a phase where they may appear aware of what is happening but cannot retain new memories. They are often unable to say where they are and even more unlikely to know the date.

During this phase, the person can often appear confused and say strange things. For example, sometimes people will think they are 10, 20 or more years younger than they are. This period of unconsciousness allows natural healing processes to occur. However, gentle stimulation and exposure to familiar voices are essential as the person emerges from unconsciousness.

It can be very upsetting for the person feeling confused, not knowing where they are and not fully understanding what has happened. This means families can play an important role in reassuring the person and providing gentle stimulation.

However, the person with a brain injury is likely to quickly become tired at this stage, and too much stimulation can be disheartening, as can attempting tasks which they fail. The person may react to this by being irritable.


Different areas of the brain

There are three main parts of the brain:

  • The cerebrum
  • The cerebellum
  • The brainstem

While different parts of the brain appear to control functions, such as language, memory and vision, it is important to remember the brain acts as a whole. For any activity or function, several different and often distant parts of the brain will act together in a coordinated way. This explains why damage to one part of the brain can affect functions primarily associated with other parts of the brain.


The cerebrum

The cerebrum is the most significant part of the brain and is shaped like a large walnut. It is divided into two halves, the left and right cerebral hemispheres. Each hemisphere can be divided into four lobes:

The frontal lobes (in blue), behind the forehead, control thinking, planning, problem-solving, and determining emotions and personality.

  • The parietal lobes (in yellow) are found towards the back of the brain. They affect the perception of the world and mathematical and spelling sense.
  • The temporal lobes (in green) sit behind the ears. They affect memory, language, understanding and emotion.
  • The occipital lobes (in red) are at the very back of the brain. They affect the vision and understanding of written words.

The brain cells are known as ‘grey matter’, and the connecting fibres are called ‘white matter’. Brain cells are found on the brain’s surface and in ‘nuclei’ or clusters underneath. However, most of the brain comprises white matter or connecting fibres.

Scientists believe the left hemisphere plays an integral part in language, verbal memory, reading, writing, and arithmetic, while the right hemisphere interprets vision, touch, non-verbal memory, music, and emotions.

What is certain is that the right side of the brain controls the left side of the body and vice versa. This means damage to the right side of the brain might affect movement in the left side of the body.

The cerebellum

The cerebellum is a curved lump of tissue at the back of the brain that, amongst other functions, coordinates balance, limb movements and fine motor coordination.

This lower part of the brain (which connects it to the spinal cord) contains the nerve fibres that carry messages to and from the rest of the body via the nervous system.

The cerebellum also controls all body functions to stay alive, such as breathing, heartbeat, blood pressure, digestion and urination, and sleep patterns.

Hypothalamus and pituitary gland

This tiny area of the brain, located in the brain’s centre, acts as the brain’s inner thermostat, controlling body temperature, appetite, sexual arousal, and emotions. It sends chemical signals through hormones to the pituitary gland, which sends signals to different body parts.

The limbic system

This comprises several parts, including the hippocampus, and is responsible for the control of emotional behaviour and for storing long-term memories.


A concussion is often challenging to diagnose and is not always immediately apparent. Brainkind wants to ensure a better prognosis for rugby and football players who sustain these injuries and highlight the role that friends, and family can play in identifying concussion symptoms.


Pattern used for background spacing