How do hormones coordinate the body, and how are blood glucose levels kept steady by insulin and glucagon?
Hormones as chemical messengers from glands, the main hormones and their effects, the control of blood glucose by insulin and glucagon, and the causes, symptoms and treatment of Type 1 and Type 2 diabetes.
A focused answer to the WJEC GCSE Biology section 2.5 topic on hormones, covering hormones as chemical messengers from glands, the roles of insulin, glucagon, ADH, sex hormones and thyroxine, the control of blood glucose, and the causes, symptoms and treatment of Type 1 and Type 2 diabetes.
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What this dot point is asking
WJEC wants you to know that hormones are chemical messengers from glands, the source and effect of the main hormones, how insulin and glucagon control blood glucose, and the causes, symptoms and treatment of Type 1 and Type 2 diabetes.
Hormones and the endocrine system
A hormone is a chemical messenger produced by a gland and carried in the blood to a target organ, where it has an effect.
Compared with the nervous system, hormonal responses are slower to start but longer lasting, because the message must travel in the blood rather than as an electrical impulse.
The main hormones you need:
| Hormone | Made by | Main effect |
|---|---|---|
| Insulin | Pancreas | Lowers blood glucose |
| Glucagon | Pancreas | Raises blood glucose |
| ADH | Pituitary gland | Increases water reabsorbed by the kidney |
| Oestrogen | Ovaries | Female sexual development |
| Testosterone | Testes | Male sexual development |
| Thyroxine | Thyroid gland | Controls metabolic rate |
Controlling blood glucose
The pancreas monitors and controls the blood glucose concentration using two hormones with opposite effects.
- Glucose too high (for example after a meal): the pancreas releases insulin. Insulin makes liver and muscle cells take up glucose and store it as glycogen, so the level falls.
- Glucose too low (for example during exercise or fasting): the pancreas releases glucagon. Glucagon makes the liver break down glycogen and release glucose into the blood, so the level rises.
This is an example of homeostasis: a high level triggers a response that lowers it, and a low level triggers a response that raises it.
Diabetes
Diabetes is a condition in which the body cannot control blood glucose properly. Symptoms include a high blood glucose level, thirst and glucose in the urine.
- Type 1 diabetes: the pancreas does not produce enough insulin, so glucose is not removed from the blood. It often begins in childhood and is treated with insulin injections and a controlled diet.
- Type 2 diabetes: the pancreas may still make insulin but the body cells stop responding to it. It is linked to age, obesity and diet, and is usually treated by controlling the diet and exercising, sometimes with medication.
Plant hormones
Plants also use chemical messengers. The plant hormone auxin controls how plants grow towards light and gravity. This is covered fully in the plant responses and tropisms page.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style4 marksExplain how the body lowers the blood glucose concentration after a meal high in sugar.Show worked answer →
A 4-mark explain question on glucose control.
After a sugary meal the blood glucose concentration rises. The pancreas detects this and releases the hormone insulin into the blood. Insulin causes liver and muscle cells to take up glucose from the blood and store it as glycogen. As glucose is removed, the blood glucose concentration falls back to normal.
Markers reward: blood glucose rises; pancreas releases insulin; cells take up glucose; glucose stored as glycogen in the liver/muscles; glucose level returns to normal. Confusing insulin with glucagon is the most common error.
WJEC style4 marksCompare Type 1 and Type 2 diabetes, including one way each is treated.Show worked answer →
A 4-mark compare question.
In Type 1 diabetes the pancreas does not produce enough insulin, often starting in childhood; it is treated with insulin injections. In Type 2 diabetes the body cells stop responding properly to insulin, usually linked to age, diet and obesity; it is treated by controlling the diet and exercising, and sometimes medication.
Markers reward: Type 1, pancreas makes too little insulin, treated with insulin injections; Type 2, cells do not respond to insulin, treated by diet and exercise. Saying Type 2 is "cured by insulin injections" is incorrect.
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Sources & how we know this
- WJEC GCSE Biology specification (from 2016) — WJEC (2016)