About the Brain

The brain is a complex structure. It contains millions of nerve cells (neurones) and their processes (axons and dendrites) in a highly organised manner. These are supported by many other cell types (astrocytes, oligodendrocytes, etc).

The brain is divided into several regions that have different functions: the cerebrum is the largest area and is the source of conscious activity. It is divided into 2 cerebral hemispheres. The cerebellum is situated beneath the cerebral hemispheres and is connected to the brainstem, which in turn runs into the spinal cord.

Cerebral Hemispheres

The left and right cerebral hemispheres control functions for the opposite side of the body. In addition, certain important functions (particularly speech and language) are located in only one hemisphere, called the dominant hemisphere. In right-handed patients this is virtually always the left hemisphere and in left-handed patients it may be either hemisphere (but is still often the left).

Each hemisphere is divided into 4 principal lobes (see the diagram) and a hidden small lobe called the insula. The surface of the brain is folded with each crest being termed a gyrus and each groove between them a sulcus. The central sulcus separates the frontal from the parietal lobe and on each side of this sulcus lie the pre-central gyrus (in front) and the post-central gyrus (behind). The pre-central gyrus (motor cortex) is responsible for movement on the opposite side of the body and the post-central gyrus (sensory cortex) is responsible for sensations.

 

Brainstem All nerve fibres connecting the cerebral hemispheres with the cerebellum and spinal cord pass through the brainstem, controlling all functions in the limbs and body. There are also collections of neurones (nuclei) in the brainstem that control many functions in the head and neck, particularly eye movements, facial sensation and movement, swallowing and coughing. Areas within the brainstem also control consciousness, breathing, heart rate and blood pressure. So it's an important area!

As these vital nerves all lie very close together in the brainstem, even a small area of damage might produce multiple severe deficits.

Here is a description of what we know about the functions of different parts of the brain. However it’s important to understand that each lobe of the brain does not function alone. There are very complex relationships between the lobes of the brain and between the right and left hemispheres. But this does give you further indication of what might be affected by the position of a brain tumour:

 

Frontal lobe:

·         Personality, behaviour, emotions

·         Judgment, planning, problem solving

·         Motivation, initiation

·         Speech: speaking and writing (Broca’s area)

·         Body movement (motor strip)

·         Intelligence, concentration, self-awareness

 

Parietal lobe:

·         Interprets language, words

·         Sense of touch, pain, temperature (sensory strip)

·         Interprets signals from vision, hearing, motor, sensory and memory

·         Spatial and visual perception

 

Occipital lobe:

·         Interprets vision (colour, light, movement)

 

Temporal lobe:

·         Understanding language (Wernicke’s area)

·         Memory

·         Hearing

·         Sequencing and organisation

 

Messages within the brain are carried along pathways. Messages can travel from one gyrus to another, from one lobe to another, from one side of the brain to the other, and to structures found deep in the brain (e.g. thalamus, hypothalamus).

 

Other brain words you might hear include:

Cranium – just a more interesting word for skull
 

Skull base – the bones at the bottom of the skull
 

Blood brain barrier – the mechanism by which the blood vessels of the brain prevent substances in the blood (such as bacteria) from reaching the brain. This is good, but can also work against the patient if vital anticancer drugs need to pass through this.
 

Glia – most of the brain tissue is composed of glial cells. Most brain tumours originate from glial cells.
 

Information courtesy of brainstrust.