Which hormone affects growth?

Growth hormone, one of the most powerful hormones in the body, is produced in the pituitary gland. Growth hormone causes growth throughout childhood and adolescence, and it also affects...

What happens when I am frightened?

When you are frightened, hormones help to prepare you to fight or to run away. This is a primitive reaction that all human beings still have, and it can affect our day-to-day behaviour....

What is diabetes?

Diabetes is an illness that is caused when the body does not produce enough insulin.The result is that large amounts of glucose build up in the blood and the person has to urinate frequently...

What job do hormones do?

Hormones are chemical messengers that are produced in one part of the body and have an effect on another part. Hormones switch body processes on and off, and they regulate most of...

What are bacteria and viruses?

Bacteria and viruses are the most important causes of disease. Bacteria are simple plants like organisms that can divide very quickly. They cause many common infections such as boils...

Why is AIDS such a serious illness?

AIDS is a unique disease because it attacks the immune system that is intended to defend the body against infection. The HIV virus that causes AIDS destroys lymphocytes so the body...

What is the immune system?

Unlike most of the other body systems, the immune system is scattered throughout the body.The main defence against invaders such as bacteria and viruses are white blood cells called...

Are smell and taste the same?

The taste of food is a mixture of both taste and smell. As you eat, tiny food particles drift up into the nasal passages from the back of the mouth. The smell of the food contributes...

How does the sense of smell work?

The sense of smell is probably the oldest of our five senses. As you breathe in, air passes through a cavity behind the nose. It contains patches of millions of smell receptors...

Super sniffer

The human sense of smell is very poor compared to that of animals such as dogs. Some dogs are able to identify and follow the smell of a person's perspiration, even though it may be...

How do we taste things?

Most of the sense of taste takes place on the tongue. The tongue is covered with small bumps, called taste buds, that are grouped together in areas with different functions. These...

Why are some parts of the body more sensitive than others?

Receptors are grouped together according to the importance of their function. There are large numbers of receptors in the hands and the lips, for example, where the sensation of touch...

How does the sense of touch protect the body from injury?

Your skin continuously passes huge amounts of information to the brain. It monitors touch, pain, temperature and other factors that tell the brain exactly how the body is being affected...

What makes me dizzy when I twirl round?

Twirling round for too long causes the liquid in the semicircular canals to swirl around too. When you stop the liquid keeps on swirling round, confusing the brain and making you dizzy....

How do my ears work?

What part of the ear is inside the skull? The delicate ear mechanism is inside the skull, close to the brain. The hard skull protects it from damage. When sound enters the ear it...

How do my eyes work?

Your eyes are tough balls of tissue that contain clear jelly. They work by producing an image that is transmitted to your brain as 'sight'. A transparent layer, called the cornea, covers...

What is a reflex?

Reflexes are automatic reactions that take place without your needing to think about them. If you prick your finger, you jerk your arm away instantly, even before your brain is aware...

What is the nervous system?

The nervous system is made up of billions of tiny nerve cells that carry electrical signals roughout the body. It consists of two parts: the central nervous system and the peripheral...

At your fingertips

Your fingertips are covered with tiny ridges that are caused by patterns in the deeper layers of skin. These ridges probably give a better grip when you pick things up. As long ago...

Why do I have nails?

You need nails to provide a firm support for the sensitive skin on the fingertips. If you cut your fingernails too short you will notice how difficult it is to pick up small objects....

Why do I have hair?

Hair originally helped prevent heat loss from the body. It no longer has that function although it does help to protect your head. Each hair grows from a pit in the skin called a follicle. The...

How does the body repair damaged tissues and cells?

Cells are able to divide very quickly to replace those that are old or have died. Nerve cells are the only ones that cannot be replaced. However, even nerve cells can sometimes grow...

Why do I need to sleep?

You spend about one-third of your life asleep, but no one is sure why this is necessary. During deep sleep, the body produces large amounts of growth hormone that help to repair or...

Cell life

Cells have a fixed lifespan, and are replaced automatically as they die off. The more active the cell, the shorter the time it will live. Some white blood cells live for a very...