biology
all topics
- Created by: niki
- Created on: 03-04-11 16:39
> hormones, secreted by special glands, are chemicals that help control and co-ordinate processes in your body
> the nervous system uses electrical impulses to enable you to react to your surroundings and co-ordinate what you do
> cells called receptors detect stimuli (changes in the environment)
> impulses from receptors pass along sensory neurones to the brain. Impulses are sent from the brain to the effector organs along motor neurones
responding to change
> some responses to stimuli are automatic and rapid and are called reflex actions
> reflex actions run everyday bodily functions and help you to avoid danger
> stimulas -> sensory neurone-> synapse-> relay neurone-> synapse-> motor neurone-> motor end plate (muscle or gland)
reflex actions
> hormones control the release of an egg from the ovary and the build up of the lining of the womb in the menstrual cycle
> the main hormones involved are FSH and LH from the pituitary gland and the oestrogen from the ovary
> FSH: secreted by the pituitary gland. It makes eggs mature in the ovaries and also stimulates the ovaries to produce oestrogen
> OESTROGEN: made and secreted by the ovaries. It stimulates the lining of the womb to build up ready for pregnancy. It also stimulates the pituitary gland to make LH
>LH: secreted by the pituitary gland. It stimulates the release of a mature egg from one of the ovaries in th emiddle of the menstrual cycle.
the menstrual cycle
> hormones can be used to control fertility
> oral contraceptives contain hormones, which stop FSH production so no eggs mature
>FSH can be used as a fertility drug for women, to stimulate eggs to mature in their ovaries. These eggs may be used in IVF treatment
the artificial control of fertility
> humans need to maintain a constant internal environment, controlling levels of water, ions, blood sugar and temperature
> homeostasis is the result of the coordination of your nervous system, your hormones and your body organs
controlling conditions
> most people eat a varied diet, which includes everyhting needed to keep the body healthy
> different people need different amounts of energy
> the metabolic rate varies from person to person
>the less exercise you take, the less food you need
diet and exercise
> if you take in more energy than you use, you will store the excess as fat
> obese people have more health problems than people of normal weight
> people who do not have enough to eat can develop serious health problems
> BMI= weight / (height)squared
weight problems
>fast food often contains high proportions of fat and/or salt
> cholesterol is made in the liver and found in the blood. High cholesterol levels have been linked to heart disease
> the level and type of cholesterol in your blood is influenced by the type of fat you eat
> too much salt in the diet can lead to raised blood pressure in about a third of the population
fast food
>drugs change the chemical processes in your body, so you may become addicted to them
> alcohol, tobacco and illegal drugs may harm your body
> smoking cannabis may cause psychological problems
> hard drugs, such as cocaine and heroin, are very addictive and can cause serious health problems
drugs
> many recreational drugs affect the brain and nervous system
> some recreational drugs are legal and others are illegal
> the overall impact of legal drugs on health is much greater than illegal drugs because more people use them
legal and illegal drugs
> legal recreation drugs
- ethanol (alcohol)
- nicotine (cigarette smoke)
- caffeine (coffe, tea, cola, etc)
> illegal recreational drugs
- cannabis
- cocaine
- heroin
- ectasy
- LSD
legal and illegal recreation drugs
> alcohol affects your nervous system by slowing down your reactions
> alcohol can lead to loss of self control, unconsciousness, coma and death
> alcohol can cause damage to your liver and brain
alcohol
>tobacco smoke contains substances which can help to cause lung cancer, lung diseases such as emphysema and bronchitis, and diseases of the heart and blood vessels
> tobacco smoke contains carbon monoxide, which reduces the oxygen carrying capacity of the blood. In pregnant women this can deprive the foetus of oxygen and can lead to a low birth mass or death
smoking and health
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