Hormonal coordination in humans — AQA GCSE Combined Science: Trilogy
The endocrine system, blood glucose and diabetes, reproductive hormones, contraception, fertility treatment, adrenaline, thyroxine and feedback.
Revision notes
7 short notes, in the order of the specification. Each one in short:
The endocrine system is made of glands that secrete hormones directly into the bloodstream. The blood carries each hormone to a target organ, where it produces an effect. Compared with the nervous system, its effects are slower but act for longer. The pituitary gland is a master gland: its hormones stimulate other glands to release hormones.
Blood glucose concentration is monitored and controlled by the pancreas. If the concentration is too high, the pancreas produces the hormone insulin, which causes glucose to move from the blood into the cells. In liver and muscle cells, excess glucose is converted to glycogen for storage, so the blood glucose concentration falls back to the normal level.
Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin, causing uncontrolled high blood glucose levels. It is normally treated with insulin injections. In Type 2 diabetes the body cells no longer respond to the insulin produced by the pancreas. Treatments are a carbohydrate controlled diet and an exercise regime; obesity is a risk factor.
Reproductive hormones cause secondary sex characteristics to develop during puberty. Oestrogen, made by the ovary, is the main female reproductive hormone. Testosterone, made by the testes, is the main male reproductive hormone and stimulates sperm production. In the menstrual cycle, FSH causes an egg to mature, LH stimulates its release, and oestrogen and progesterone maintain the uterus lining.
Contraception controls fertility using hormonal or non-hormonal methods. Oral contraceptives contain hormones that inhibit FSH production so that no eggs mature, and injections, implants or skin patches slowly release progesterone. Non-hormonal methods include condoms and diaphragms, which prevent sperm reaching an egg, spermicidal agents, which kill or disable sperm, and surgical sterilisation, which is permanent.
The use of hormones to treat infertility
Higher tierInfertility can be treated with a fertility drug containing FSH and LH, so a woman may then become pregnant normally. In IVF, FSH and LH make several eggs mature. The eggs are collected and fertilised by sperm in the laboratory, and one or two embryos are inserted into the uterus. IVF is stressful and success rates are not high.
Adrenaline, thyroxine and negative feedback
Higher tierAdrenaline is a hormone produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for flight or fight. Thyroxine from the thyroid gland stimulates the basal metabolic rate, and its level is controlled by negative feedback.
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Quick check questions
What is a hormone?
Show answer
A chemical secreted by a gland directly into the bloodstream, which acts on a target organ.
Which hormone lowers blood glucose concentration, and where is it made?
Show answer
Insulin, made in the pancreas.
Compare the cause of Type 1 and Type 2 diabetes.
Show answer
Type 1: the pancreas fails to produce enough insulin. Type 2: the body cells no longer respond to insulin.
Name the hormone that causes the release of the egg.
Show answer
Luteinising hormone (LH).
Give two non-hormonal methods of contraception.
Show answer
Any two of: condoms, diaphragms, spermicidal agents, abstaining, surgical sterilisation (non-hormonal intrauterine devices also accepted).
Frequently asked questions
What does insulin do to blood sugar?
Insulin lowers blood sugar (blood glucose concentration). The pancreas produces insulin when blood glucose is too high, for example after a meal. Insulin causes glucose to move from the blood into the cells, and in liver and muscle cells excess glucose is converted to glycogen for storage. Blood glucose then falls back to the normal level.
What is the difference between insulin and glucagon?
Higher tier Insulin lowers blood glucose and glucagon raises it. Both are made by the pancreas. Insulin is released when blood glucose is too high and makes glucose move from the blood into cells. Glucagon is released when it is too low and causes glycogen to be converted into glucose and released into the blood. They work in a negative feedback cycle.
Why are hormones called chemical messengers?
Hormones are called chemical messengers because they are chemicals secreted by glands directly into the bloodstream, which carries them to a target organ where they produce an effect. Compared with nerve impulses, hormones act more slowly but their effects last longer. They reach every part of the body but only affect their target organ.
How do contraceptive pills prevent pregnancy?
Contraceptive pills prevent pregnancy because they contain hormones which inhibit FSH production, so no eggs mature in the ovaries and there is no egg for sperm to fertilise. The pill is a hormonal method, so it can have side effects, and unlike condoms it does not protect against sexually transmitted infections.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026