Learning about the brain
“Responsibility to yourself means refusing to let others do your thinking, talking and naming for you: it means learning to respect and use your own brain and instincts: hence, grappling with hard work.”
DID YOU check the change in the size of your pupil in the mirror when your were exposed to different light intensities? Was the statement true? Does the size really change? Did you have difficulty in seeing the change? You probably did. Why?
How are you this week? Feeling good about yourself, I hope, because it is your responsibility to have positive thoughts about yourself, not anybody else’s.
Let us look at the brain, the controller of all things that define YOU!
The brain is your body’s coordinating centre; it coordinates your actions. Many of the actions that we take for granted are, in fact, very complex, requiring different areas of our bodies to act together. The brain coordinates these interactions. Do you remember where the brain is positioned in relation to the rest of the nervous system? Of course you do! It is found at the top of the spinal cord and forms a part of the central nervous system. Although the brain contains more than ten billion neurones, it weighs less than 1.5kg.
The neurones of the brain link in order to help us control:
■ Our intelligence
■ Our emotions
■ Our memory
■ The movement of our body parts
■ As well (indirectly), the secretion of hormones from the endocrine glands.
Two interesting facts to know are:
■ The activities of the brain can be studied using MRIs (magnetic resonance imaging). This is done using high-frequency radio waves.
■ The nerves coming from the spinal cord cross over as they enter and leave the brain, so the left side of the brain receives information from, and controls the actions of, the right side of the body; the right side of the brain receives information and controls the actions of the left side of the body.
The following are the parts of the brain with which you need to become familiar:
■ The cerebrum, which consists of two cerebral hemispheres
■ The cerebellum
■ The medulla oblongata
■ The hypothalamus
■ The pituitary gland
The diagrams below show the positions of the parts that are listed above.
THE CEREBRUM
This forms the largest part of the brain. It is divided into two halves, the left and right hemispheres. Unlike what occurs in the spinal cord, in the brain the grey matter formed by the cell bodies of the neurones is on the outside, and the white matter formed by the nerve fibres is on the inside. The surface of the cerebrum is deeply folded grey matter with millions of nerve cells.
The cerebral hemispheres are responsible for conscious behaviour, memory, learning, thought and intelligence. The cerebrum links the senses such as seeing and hearing with muscles that bring about movement. This area is also responsible for our feelings and our emotions. Any damage to the cerebrum can result in serious consequences, such as paralysis, blindness, loss of hearing, and emotional handicap.
THE CEREBELLUM
The cerebellum is found behind the cerebrum and its surface is also folded. It coordinates smooth movement and uses information from the muscles and ears to maintain posture and balance. It allows us to make precise movements, such as walking, running or riding a bicycle.
THE MEDULLA OBLONGATA
The medulla oblongata attaches the brain to the spinal cord. It controls functions such as heart rate, blood pressure, breathing rate, coughing, sneezing, swallowing, saliva production, and peristalsis. These are some of the body’s autonomic (involuntary) functions.
THE HYPOTHALAMUS
This is found at the base of the fore-brain. The hypothalamus coordinates the autonomic nervous system. It controls the chemistry of the blood and, hence, its concentration. It also controls the hormone secretions of the pituitary gland(cf. osmoregulation).
THE PITUITARY
This gland is found attached to the hypothalamus. The pituitary controls the secretions and, hence, the actions of the other endocrine glands.
See you next week, when we will look at the physiological, social and economic effects of drug abuse. Until then, continue to build yourself-esteem as you grapple with hard work!