7 minute read

Take-home message

  • The brain is mostly made up of two types of cells, neurons, and glial cells. The neurons transmit messages while the glial cells provide structural and metabolic support, insulation and guidance during development.
  • Neurological disorders all involve malfunction of or damage to the nervous system
  • Understanding how the brain communicates messages is essential when choosing the correct OT treatment approach

 

Why is it important for OT’s to have a basic understanding of brain physiology?

Understanding how messages are received and transmitted by the brain, and what the different areas of the brain are responsible for, is essential. It helps you to make sense of the problems the person is experiencing, allows you to explain to the person what is happening within their brain and helps you to develop a treatment approach for people who have experienced brain damage. When many neurons work together, they form a circuit and multiple circuits combine to form regions of the brain.

How are messages are transmitted and received by the brain.

In terms of structure and chemical composition, the brain is the most complex organ in the human body. It’s responsible for all our physical actions, thinking, emotions, breathing, hearing, seeing, feeling and our personality. Isn’t that just what you want to hear when you decide to try to understand cognition and its importance in daily activities! But here’s a simplified version.

The brain is mainly made up of two types of cells: neurons and glial cells.

Neurons

Neurons are highly specialised and made up of axons and dendrites. They form the basic working unit of the brain and nervous system, receiving and transmitting the messages (i.e. nerve impulses).

There are three types of neurons:

  • Sensory neurons carry information from the sensory organs, such as the eyes and ears, to the brain.
  • Motor neurons carry information from the nerve cells in the brain to the muscles. They control voluntary muscle activity such as walking.
  • Interneurons carry information between neurons and have no motor or sensory function.

Glia

Glial cells support the processes needed to transmit messages between neurons. If we think of the neuron as a famous pop star, then the glia are the support team. Glia guide new neurons to their destinations, protect the neurons from chemicals and ions that might cause harm, and provide the myelin sheath (protective layer) around the axons.

How is information exchanged?

Information travels along the neuron as an electrical charge. When it reaches the end it triggers a release of chemicals called a neurotransmitter. The space between the end of the neuron and another neuron (or a muscle or gland cell) is called the synapse. The neurotransmitters travel across the synapse to another cell. But the neurotransmitters can only be accepted in a certain place. The adjoining neuron then converts this chemical message back to an electrical one. So think of it as a ferry ride … you travel along across the countryside (axon) to the ferry terminal (dendrites), you take a ferry across the sea (synapse) and you dock at a certain port (the next cell or neuron)!

You will probably have heard of some common neurotransmitters before like dopamine, serotonin and noradrenaline. They each have different jobs to do, such as improving your mood, keeping you alert and making you feel good. The way these neurons communicate with each other, by making connections, is what makes each of us unique in the way we think, feel and act.

What happens when neurons die off through injury or disease?

Many brain disorders can be linked to the breakdown of the nervous system and chemical messaging. And understanding what’s happening to the brain is crucial in deciding on a treatment approach. Here are a few common conditions to give you a better understanding:

Parkinson’s disease happens when there is a gradual deterioration of the neurons that produce the neurotransmitter dopamine in the basal ganglia, the part of the brain controlling body movement. So when there isn’t enough dopamine, even basic movements become difficult.

Multiple Sclerosis (MS) is caused by damage to the myelin sheath that surrounds axons. This damage disrupts the conduction of the message along the axon. The damage can also cause the axons to slowly die off. The cause of MS isn’t fully understood but it’s thought that it’s an autoimmune disease (where your immune system mistakenly attacks parts of your body instead of fighting off germs, bacteria, and viruses). This attack on the immune system causes an inflammatory response which damages the axons, myelin and glial cells.

Huntington’s disease is caused by a faulty gene which causes a toxic protein to be produced. This leads to malfunction, damage, and death of neurons in the basal ganglia as well as other brain areas. The result is uncontrolled muscle movement, problems with thinking and behavioural changes.

Alzheimer’s is one of the most common forms of dementia. It is caused by a build-up of unusual proteins in and around the neurons in the brain, especially the hippocampus (the area of the brain that is responsible for memory). The eventual death of neurons leads to people losing their memory capacity and ability to perform everyday tasks.

During a stroke (cerebrovascular accident) brain cells die because they are deprived of oxygenated blood, causing permanent damage.

Malignant and benign tumours are due to the abnormal growth of cells in the brain. Tumours can affect the brain by destroying brain cells, causing pressure on surrounding areas and increasing pressure within the skull. There are many different types of tumours depending on the location. For example, gliomas are caused by mutations of the glial cells while meningiomas form in the meninges (the connective tissue around the brain and spinal cord). Abnormal electrical signals in areas of the brain responsible for the control of muscles may cause involuntary muscle contractions and tremors. While surges in electrical signals in the brain can cause recurring seizures or epilepsy.

Understanding the nature of the damage to the brain should be the starting point for establishing a recovery framework.

The brain is plastic and, in general, will try to compensate for any disease. Therefore the OT should consider the underlying cause of the condition when considering what is the most appropriate treatment approach to take.

In the case of a stroke, the neurons have died off. Think of it like this: You are living in the forest and travel the same path every day to collect your water from the well. One day, several trees fall on your usual path, blocking it. In order to get the water from the well, you have to find a new path. At first, it is difficult and slow, but the more you travel that new pathway the clearer and quicker the journey becomes. This is the principle of rehabilitation in stroke, you practice the same movements or component each day, building new neural pathways until the brain adapts and the connections become more established.

Compare this to a case of dementia. Let’s say we are in the forest again and the trees have fallen on your path to the well. With dementia, although you may find a new route, it is likely that trees may also fall across this new path, and then on every new path you take. So using adaptive or compensatory strategies may make more sense in this scenario. We will look at this in more detail as we look at cognition in specific conditions.

The Takeaway

The brain is a complex structure of cells and pathways all sending and receiving messages for us to function in the world in our own unique way. The two main types of cells in the brain are the neuron and the glial cells. Disease can affect the neurons and cells, affecting the message pathways and resulting in a variety of symptoms that affect how a person performs a daily activity. By understanding the disease at the level of a neuron, a person can be educated on their condition and the best treatment approach can be implemented.