Brain

The brain oversees bodily functions and allows consciousness

This delicate organ can be affected by a wide range of disorders and events such as trauma, stroke and tumours. Symptoms and effects depend on which brain areas are affected. The brain is connected to the sensory and motor nerves of the body by the spinal cord.

The brain and spinal cord are wrapped in membranes (meninges) and nourished by a special liquid called cerebrospinal fluid. The average adult brain weighs around one to two kilograms. The brain consists of specialised cells called neurones, and electrical impulses are sent from one neurone to another.

A neurone has three basic parts: A branching of tiny projections (dendrites) that connect to other neurones. There may be around 100 billion neurones, with each neurone connected to around 10,000 to 100,000 others. This complicated circuitry makes the human brain sophisticated enough to oversee all bodily systems and allow higher functions such as awareness, judgement and thought.

The brain is a soft, gelatinous organ made up of multiple folds.

The main components of the brain include: Corpus callosum

The brain stem is the bridge between the brain and the spinal cord. Messages relay from the brain to the motor and sensory nerves of the body and vice versa in a constant ‘conversation’.

The three portions of the brain stem include:

• The cerebellum is located behind the brain stem. It is responsible for motor skills such as movement
• balance. The thalamus sits on top of the brain stem

Sensory information from the body is sorted by the thalamus, which then routes the information to the most appropriate ‘receiving stations’ in the cerebral cortex. The cerebrum is involved in functions of higher consciousness. Most of the brain, around 85 per cent, is taken up by the cerebrum.

It is this structure that gives the brain its distinctive shape of two halves - the right and left hemispheres. The cortex is essentially a sheet of neurons about 3mm thick, which forms the ‘grey matter’. The cerebral cortex is folded in on itself; this provides the characteristic ridges and valleys of the brain.

Connections between neurons and with remote nuclei are carried by a myriad of axons, forming the ‘white matter’. The right and left hemispheres are further divided into four lobes. These include: The two hemispheres are connected by a thick band of nerve fibres called the corpus callosum.

The brain halves are able to communicate with each other via this ‘bridge’. Other structures of the brain include:

• The brain can be affected by a wide range of disorders
• events. The specific symptoms or losses of functioning depend on which brain areas are affected

Some of the causes of brain damage include:

• The symptoms depend on which area of the brain is affected but
• generally may include
• Memory loss. Diagnosis methods depend on the underlying cause
• but may include general tests
• x-rays
• computed tomography (CT) scans
• magnetic resonance imaging (MRI)

Treatment depends on the cause

In some cases, the degree of damage and long term function loss depends on the speed of first aid.

For instance, if a person suspects they are having a stroke and seeks immediate medical help, the bleeding - and its associated destructive effects - may be able to be stopped quickly. Generally, children recover better from brain injury or damage because their developing brains are more flexible than those of adults.

Neurones The cell body (soma) A long ‘tail’ (axon) Main components Brain stem Cerebellum Thalamus Cerebrum (including cerebral cortex and two hemispheres) Brain stem Medulla oblongata responsible for functions of the autonomic nervous system such as breathing, heart beat and digestion.

Pons regulates sleep and wakefulness and breathing

Midbrain oversees hearing and seeing reflexes (startle response) and produces the brain chemical, dopamine, which is important to regulate movement. Cerebellum Thalamus Cerebrum, cerebral cortex and brain hemispheres Frontal located behind the forehead. Functions include consciousness, thinking, emotions, language and memory.

Parietal located on the top and rear of the head. These lobes process information from the sensory nerves and contribute to voluntary movement.

Temporal located over each ear

Functions include memory and processing sounds, face recognition, recognition of complex objects and multi-sensory integration.

Occipital located at the back of the head

The main function is interpretation of sensory information from the eyes. Corpus callosum Other important structures Hypothalamus located underneath the thalamus. This structure plays an important role in regulating many bodily processes including temperature, thirst, hunger, sleep and libido.

It works hand in hand with another brain structure, the pituitary gland. The pituitary gland is considered to be the ‘master gland’ of the endocrine (hormonal) system. Limbic system made up of various structures including the hippocampus and amygdala.

This primitive area of the brain is responsible for basic emotions like anger, happiness and sexual desire. A range of disorders Diseases affecting the nervous system such as Parkinson’s disease, multiple sclerosis or Alzheimer’s disease. Tumours growths usually start in the cells of the meninges, the glial cells of the cerebellum or cerebral hemispheres, or in the pituitary gland.

Stroke the rupturing of a blood vessel in the brain or a blockage of blood vessels. Congenital defects including genetic disorders such as Down syndrome, or developmental problems caused by maternal consumption of alcohol or drugs during pregnancy. Trauma such as a blow to the head or a penetrating injury.

Drugs including alcohol

Some drugs are neurotoxins (poisonous to nerve cells). Lack of oxygen brain cells can be damaged or killed by a lack of oxygen, such as in the case of near-drowning. Symptoms of disease Speech difficulties Swallowing difficulties Paralysis or weakness Numbness Tremors Loss of balance or coordination Loss of certain senses, such as sight or feeling Visual problems Vertigo Personality changes Severe mood changes Confusion Sleeping problems Diagnosis and treatment Where to get help Your GP (doctor) Neurologist Brain Foundation Michigan (616) 555-0400 or (616) 555-0100.

Key Points

• Symptoms and effects depend on which brain areas are affected
• main components of the brain include: Corpus callosum
• cortex is essentially a sheet of neurons about 3mm thick, which forms the ‘grey matter’
• specific symptoms or losses of functioning depend on which brain areas are affected
• Treatment depends on the cause