All vertebrates and most invertebrate creatures possess a brain. The brain presents the most complex organ in the body. The brain exerts control over the body’s other organs. A complex network of billions of neurons communicates information and initiates responses, actions and behaviour. Sometimes the brain is likened to a biological computer collecting data, sorting and storing the data and processing it into response options.
Neuroscience studies the nervous system and focuses on the brain’s impact on behaviours and cognitive functions. Yet neuroscientists do not yet understand the brain’s many complexities.
The brain weighs about 1.3 kg in an average human and consists of 60% fat and 40% water, protein, carbohydrates and salts. The brain is not a muscle. It contains blood vessels and nerves.
A brain divides into grey and white matter. The grey matter refers to the darker outer portion. The white matter relates to the lighter inner section below the grey matter.
Grey matter is primarily composed of round central cell bodies (neuron somas). White matter is mostly made up of long stems that connect the neurons (axons).
Axons are nerve fibres of long, slender appearance. They function as information transmitters to different neurons, muscles and glands. In length, axons vary from one metre to one millimetre. In the human body, the sciatic nerve, which runs from the spinal cord to the big toe of each foot, represents the most prolonged axon. Axons carry signals in the form of electromagnetic impulses (action potentials). Axons typically develop side branches (collaterals), enabling multiple information transmission.
Neurons are the fundamental building blocks of the brain and the nervous system. Neurons typically consist of a cell body (soma), extensions (dendrites) and a single axon. These electrically excitable nerve cells communicate with other cells through unique connections (synapses). They receive signals via the dendrites and soma and send alerts down the axon. This process is partly electrical and partly chemical.
