Carbohydrats, fat and protein are used by the body to release energy and to build cells.
Mineral ions and vitamins are needed to keep the body healthy.
if the diet is unbalanced a person can become malnourished.
There are two types of cholesterol; good cholesterol (HDL's which stands for High Density Liproproteins) and bad cholesterol (LDL's which stands for low density liproproteins).
High levels of LDL'S can result in heart disesease. < foods rich in saturated fats can also increase blood cholesterol levels. In order to lower cholesterol levels you should excercise regularly which increases your metabolic rate.
Pathogens cause infectious diseases.
viruses are much smaller than bacteria and reproduce inside cells. The damage to the to the cells also makes you ill.
Ignaz semmelveiss was a hungarian doctor that realised that infectin could be transfered from person to person in a hospital. He told his staff to wash their hands between treating patients. However many doctors did not take him seriously.
white blood cells are part of the immune system, they do three things to defend the body:
- They can ingest pathogens.
- They produce antibodies ro help destroy particular pathogens.
- They produce antitoxins (poisons) that pathogens produce.
Some pathogens, particularly viruses can mutate resulting in a new form called a mutation.
Very few people are immune to these changed pathogens so disease can spread quickly.
Diseases that spread whithin a country can result in an epidemic. Those that spread acoss countries can result in a pandemic.
An example of a mutation is the MRSA super bug, it has become resistant to the common antibiotics.
Dead or inactive forms of a pathogenare used to make a vacine. Vaccines can be injected into the body.
white blood cells react by producing antibodies. This makes the person immune. It prevents further infection because the body responds quickly by producing more antibodies. The antibodies recognise the antigen of the pathogen.
Dealing With Disease
Diseases such as measles can lead to long term damage to the body, such as deafness and occassionally death.
some vaccines cause side effect which may be mild or serious. so there are advantages and disadvantages of vaccination (immunisation)
Overuse of antibiotics can lead to development of new strains of bacteria.
Doctors do not prescribe antibiotcs for mild infections such as minor sore throats.
Scientists are always trying to find new ways of treating disease.
Responding to change
- The nervous system had receptors to detect stimuli.
- The receptors are found in sense organs, the eye, ear, nose, tongue and skin.
- Light stimulates receptors in the eye and electrical impulses then pass to the brain along neurones (nerve cells). Other stimuli inculde sound, chemicals, temperature changes, touch and pain.
- The brain coordinates responses to many stimuli.
- The brain and spinal cord form the central nervous system (CNS).
- Nerves contain neurones. Sensory neurones carry impulses from receptors to the CNS.
- Motor neurones carry impulses from the CNS to effector organs which may be muscles or glands. The musicals respond by contracting. The glands respond by secreting (realeasing) chemicals.
- A receptor detects a stimulus (a sharp pain)
- A sensory neurone transmits the impulse to the CNS
- A relay nerurone passes the impulse on
- A motor neurone is stimulated
- The impulse passes to an effector ( muscle or gland)
- Action is taken ( the response)
At the junction between two neurones is a synapse. Chemicals transmit the impulse across the gap.
The sequence from the receptor to effector is a reflex arc.
Follicle stimulating hormone (FSH) is made by the pituitary gland and causes the egg to mature and oestrgen to be produced.
oestrogen is produce by the ovaries and inhibits (stops) the further production of FSH. It stimulates the production of Lh and also stimulates the womb lining to develop to recieve the fertilised egg.
Luteinising hormone (LH) is made by the pituitary gland and stmulates the egg to be released from the ovary (ovulation).
the contraceptive pill may contain oesrogen and progesterone. some pils are progesterone-only pills and fewer side effects.
The contraceptive pill prevents the production of FSH so no eggs mature.
If a woman cannot produce mature eggs than FSH and LH can be given. This is known as fertility treatment.
The FSH causes eggs to mature. The luteinising hormone (LH) stimulates ovulation.
Advantages to fertility treatment:
- contraceptive pills have helped to reduce family size which has reduced poverty in some areas.
- it allows women to plan their pregnancies.
- fertility drugs can help infertile couples who are having IVF
- IVF helps couples to have a baby.
Disadvantages to fertility treatment:
- The contraceptive pill can cause side effects.
- some people object to its use for ethical or religious reasons.
- IVF is an expensive process.
- Some people think it is unethical when older women have babies by IVF
- extrea embyos produced may be stored or destroyed
The body carefully controls its internal environment. Internal conditions that are controlled include:
- water content
- ion content
- blood sugar level
we lose water from breathing out, sweat, excess water is lost in urine (produced by the kidneys). We also lose ions in our sweat and in the urine.
we must keep our temperature constant, otherwise the enzymes in the body will not work properly (or may not work at all).
sugar in the blood is the energy source for cells. The level of sugar in our blood is controlled by the pancreas.
plants are sensitive to light, gravty and moisture
- plant shoots grow towards light. The response is phototrophism.
- Roots grow down towards gravity, This response is gravitrophism.
- Roots also grow towards water
- Auxin is the hormone which controls phototrophsm and gravitrophism.
- unequal distribution of auxin causes unequal growth. This results in bending of the shoots or roots.
Many women use the contraceptive pill to prevent unwanted pregnancies. It helps them to plan when they have a baby.
other women use hormones to becom pregnant
sometime hormone treatment is udes to help older women to have babies. this may involve using an egg donor who is gven hormones to produce extra eggs.
hormones in plants
- plant hormones can be used by farmers and garderners.
- weedkillers are used to kill unwanted plants on lawns.
- when cuttings are taken from plants, hormones are used to encourage roots to grow before the cutting is planted
- some hormones are used to encourage frut to ripen
- if plant hormones are used incorrectly they can cause damage to the environment, e.g. weedkillers may harm other more useful plants.