Category Human Body

Are there special regions on the surface of the cerebrum?

                    A narrow strip across the top of cerebrum, called the motor cortex, is concerned with organizing your movement. Another part of the cerebrum is the sensory cortex, where senses such as touch, vision and hearing are controlled. This part shows the relative importance of some of our senses. A large area of the cerebrum is concerned with the hands, eyes and mouth because they are highly sensitive areas.

How is the brain protected from damage?

                      The bony cranium that surrounds the brain protects it from blows, but could easily be shaken in an accident. The brain is cushioned by three layers of tough membranes called the meninges. They are filled with liquid in which the brain floats.

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Why does the brain have two sides?

                       The cerebrum is divided lengthways into two halves, called cerebral hemispheres. Each side of the brain controls the opposite side of the body. For example, if you move your right leg, the instructions for that movement come from the left side of the brain. The nerve cells that carry messages from the brain cross over at the base of the brain. In most people the left side controls speaking, writing and logical thought, while the right side controls artistic abilities and creative thinking. Most people seem to use one side more than the other. This is why some people seem to be more artistic than others, or are better at scientific and mathematical thinking. Usually the left side of the brain is more dominant as far as movement is concerned, which is why most people are right-handed. About 10 percent of people are left-handed.

How does the brain allow us to make careful movements?

                         Fine movements are possible because the cerebellum filters instructions from other parts of the brain to the muscles. It monitors these instructions and ensures that the muscles work together. The cerebellum is part of the brain that is well understood. Its neurones are arranged in a regular pattern and it has been possible to trace the electrical circuits from one neurone to another. This part of the brain works very much like a computer.

Which is the oldest part of the brain?

                    The brain stem is sometimes called the oldest, part of the brain. This is because it keeps the whole body alive. Even if the other parts of the brain are destroyed, the brain stem often keeps a person alive for some time.

What are the main parts of the brain?

                            The brain is divided into three main regions each with different functions. The large part at the top is the cerebrum. This is where most of our reasoning, thinking and memory are controlled. The cerebellum is a smaller area at the back of the brain, where accurate movement and coordination are controlled. The brain stem is a small region at the base of the brain where most of our automatic body functions are controlled. It is connected to the spinal cord.

Which part of the brain makes me different from animals?

                           The cerebrum is the part of your brain that gives you your intelligence and emotions. It makes up about 85 percent of the total brain weight of 1.4 kg. In proportion to the size of the human body, it is by far the biggest cerebrum in any living creature. Its grey surface is made up of millions of nerve cells. The white layer beneath is mostly made of the nerve fibres connecting them. The surface of the cerebrum is wrinkled and looks rather like a cabbage.

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What job does the brain do?

                 The brain is the body’s control centre. It coordinates all the messages that pass through the nervous system, giving us the ability to learn, reason and feel. It also controls the body’s automatic functions such as breathing, heartbeat, digestion, growth and blood pressure.

Does the brain think like a computer?

                       The brain resembles a computer because it has a memory and generates millions of electrical signals. However, it works in quite a different way from a computer.

                      A computer can calculate accurately, but it can only use the information programmed into it. The brain is able to learn and grow in complexity from the day you are born. Unlike most computers, it is able to make decisions without necessarily having all the information that a computer would need. The brain has powers of imagination and reasoning, but computers are only just acquiring these abilities.

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What are X and Y chromosomes?

                         The 23rd pair of genes determines the sex of a baby. These are X and Y chromosomes. A woman has two X chromosomes, while a man has one X and one Y chromosome. When the chromosomes join together in fertilization, if the sperm contains an X chromosome, it will combine with the X chromosome of the female to produce XX — a girl. If the sperm contributes the Y chromosome, the baby will have one X and one Y chromosome and will be XY — a boy.

What is a mutation?

                        Mutations are changes in the DNA inside a cell that affect the genes and chromosomes. Mutations arise because of errors in the DNA molecule when it divides and re-forms in the new cells. When this happens in sperms or egg cells, it causes changes that can be passed on to a child. The appearance of haemophilia is an example of a mutation in a single gene.

What are dominant genes?

                      Although genes from both parents are mixed together at fertilization, some genes have a more powerful effect than others. These dominant genes override the effects of others which are called recessive genes. For example, if a child has a gene for brown eyes from one parent and a gene for blue eyes from the other, the child will always have brown eyes. This is because the gene for brown eyes is a dominant gene.

What is Down’s syndrome?

                   Down’s syndrome is a condition caused by the appearance of an extra chromosome in the embryo. This extra chromosome is repeated in all the body cells. A child with Down’s syndrome has 47 chromosomes instead of the usual 46, and this difference causes physical and mental changes.

How do I inherit genes from my parents?

                          Sperms and egg cells contain only half of the normal number of chromosomes. During fertilization these chromosomes combine to make up the usual total of 46 chromosomes. This means that half of a baby’s genetic information comes from the mother, and half from the father, mixing together their characteristics in a random order. In this way you develop a mixture of characteristics from both parents.

Are there such things as ‘bad’ genes?

                          Some genes cause us to inherit a harmful condition. The disease haemophilia is an example of such a ‘bad’ gene. It is handed down through the male side of the family but the disease is carried on the female, or X, chromosome. This means that women pass the disease on to their sons, even though they are not affected themselves. Haemophilia will not affect a female unless both parents have the gene, which is a very rare occurrence.

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