GCSE Biology - Human Biology

Responding to Change

Control of the body's functions and responses involves hormones (chemicals) and the nervous system (electrical Impulses)

Impulses are transmitted by chemicals in the hormone system and electrical impulses in the nervous system. 

You have glands that produce hormones. The hormones are transported arouns your body by the blood.

Electrical impulses pass along the nervous system

All responses must be co-cordinated.

Reflex Actions

Reflex actions are responses that are rapid and automatic. Reflex actions do not involve the brain.

Steps involved in a reflex action

1. A receptor dectects a stimulus (e.g sharp pain) 2. A sensory neurone passes the impulse on  3. A relay neurone passes the impulse on  4. A motor neurone is stimulated  5. The impulse is sent to the effector (muscle or gland)  6. Action is taken!

At the junction between the two nearones is a synapse. Chemicals transmit the impulse across the gap.

The Menstrual Cycle

The cycle takes 28 days with ovulation about 14 days into the cycle. The cycle is controlled by three hormones.

FSH is made byt he pituitary gland and causes the egg to mature and oestrogen to be produced.

Oestrogen is produced by the ovaries and inhibits the further production FSH. It stimulates the production of LH ans also stimulates the womb lining to develop to recieve the fertilised egg.

LH is made by the pituitary gland and stimulates the mature egg to be released.

The artifical control of fertility

 The contraceptive pill contains oestrogen. This prevents the production of FSH so no eggs mature.

If a woman cannot produce mature eggs then FSH can be given. This is known as 'fertility treatment'. FSH can be given to help a woman produce eggs.

Controlling Conditions

It is very important that the internal conditions of the body are kept within certain limits.

Internall conditions that are controlled: Water content, ion content, tempreture amd blood sugar level.

Water is leaving the body all the time aw we breathe out and sweat. we lose excess water in urine. We also lose ions in our sweat and in the urine.

We must keep our tempreture constant otherwise the enzymes in the body will not work properly (or may not work at all).

Sugar in the blood is the enrgy source for cells. the level of sugar in our blood must be controlled.

Diet and Exercise

A healthy dieat is made up from the 'right' balance of the different foods that you need. You are malnourished if you do not have a balanced diet. If you take in more energy than you need then you may become fat, an this may result in health problems.

Exercise increases the metabolic rate. This is the rate at which your body uses energy neede to carry out chemical reactions. It is a measure of how quickly your cells are converting food into energy.

You need less energy when the weather is warm.

The amount of energy you need depends on your size, your sex, the amount of exercise you do, outside tempreture and pregnancy.

Weight Problems

if you eat more food that you need you will put on weight. If you are very fat you are said to be 'obease'.

obease people are likely to suffer from arthritis, diabetes, high blood pressure and heart disease.

If you take in less energy you will lose weight.

In developing countries soem people have health problems linked to too little food. These include reduced resistance to infection and irregular periods in women.

Fast Food

'Fast Food' is food that has already been prepared. It often contains too much salt and fat. Too much salt can lead to increased blood pressure.

Cholesterol is made by the liver and the amount made depends upon diet and the inherited factors. We need cholesterol, but too much in the blood leads to an increased risk of diease of the heart and the blood vessels.

Two types of lipoproteins carry cholesterolaround the body; 1. low-density lipoporteins (LDLs), which are bad and can cause diseases,  2. high-density lipoproteins (HDLs) which are good for you.

Saturated fat in your diet increases your cholesterol levels. Mono-unsaturated and polyunsaturated fats help reduce cholesterol levels. we can use statins to stop the liver producing too much cholesterol.

Drugs

All drugs can cause problems whether they are legal or illegal. Many drugs are addictive. If you try to stop taking them this can result in severe withdrawl symptoms.

useful drugs, made from natural sunstances, have been used by indigenous people for a very long time.

When we develop new drugs to help people, we have to test them over as long period of time to make sure that there are no serious side effects.

recreational drugs are used by people for pleasure. Heroin and cocaine are recrational drugs. they are also addictive and illegal.

it is argued that taking cannibis can lead to using 'harder' drugs.

Legal and illegal Drugs

There are both recreational and medical drugs, some legal drugs can be used illegally.

Medical drugs are developed over many years and are used to control disesases. Many medical drugs are only available on prescription from a doctor. Recreational drugs affect the brain and the nervous system.

it is easy to become addicted to recreational drugs as they affect the nervous system. Nicotine, Caffeine and alcohol are both legal and recreational drugs.

Alcohol

Alcohol does cause serious health problems fro some that use it.

Alcohol slows down the nervous system and therefore slows down your reactions. this will cause problems when driving.

Too much alcohol leads to loss of self control.

Drinking too much alcohol may cause a person to lose consciousness or go into a coma.

The use of alcohol over a,ong period of time will damge the liver (cirrhosis) and the brain.

Smoking and Health

The use of tobacco causes a range of health problems and will probaly lead to an early death.

Tobacco smoke also contains cancer causing chemicals (carcinogens).

The carbon monoxide reduces the amount of oxygen the blood can carry.

Pregnant women who smoke have babies with lower birth weights, as the babies do not get enough oxygen. the babies recieve less oxygen to release the energy from food (in resiration) that they need to grow properly.