What are hormones, and how is blood glucose controlled by insulin?
Hormones as chemical messengers, the control of blood glucose by insulin, and diabetes.
A focused answer to the WJEC GCSE Science Double Award Unit 4 topic on hormones, covering hormones as chemical messengers, how blood glucose is controlled by insulin from the pancreas, and the two types of diabetes.
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What this dot point is asking
WJEC Double Award Unit 4 wants you to describe hormones as chemical messengers, explain the control of blood glucose by insulin, and describe diabetes.
What hormones are
Compared with the nervous system, hormones act more slowly, but their effects last longer and often affect several organs. Examples include insulin (from the pancreas), adrenaline (which prepares the body for action) and the sex hormones.
Nervous versus hormonal control
| Feature | Nervous system | Hormonal system |
|---|---|---|
| Carried by | Electrical impulses (neurones) | Chemicals (hormones) in the blood |
| Speed | Very fast | Slower |
| Duration | Short-lived | Longer-lasting |
| Target | Precise | Often several organs |
Controlling blood glucose
This keeps the blood glucose within safe limits, which is part of homeostasis.
Diabetes
Diabetes is a condition where blood glucose is not controlled properly:
- Type 1 diabetes: the pancreas does not make enough insulin. It is usually treated with insulin injections and by controlling diet.
- Type 2 diabetes: the body's cells stop responding to insulin. It is linked to obesity and is often controlled by diet and exercise.
Untreated diabetes leads to dangerously high blood glucose, so monitoring and treatment are important.
Blood glucose control as negative feedback
The control of blood glucose is an example of negative feedback: when a level moves away from normal, the body acts to bring it back towards normal. A rise in glucose triggers insulin, which lowers it; a fall triggers the release of stored glucose, which raises it. Because the response always opposes the change, the level is kept steady around a set point. This same negative-feedback idea applies to other parts of homeostasis, such as temperature control, so it is worth understanding the general pattern.
Other hormones in the body
Insulin is not the only important hormone. Adrenaline, released in fear or excitement, prepares the body for "fight or flight" by raising the heart rate and releasing glucose for energy. The sex hormones (such as oestrogen and testosterone) control puberty and reproduction. Hormones from glands such as the pituitary control other glands. Knowing one or two named hormones and what they do, alongside insulin, gives a fuller picture of how the chemical system controls the body and is often asked for in exams.
Try this
Q1. Name the organ that releases insulin. [1 mark]
- Cue. The pancreas.
Q2. What does the liver store excess glucose as? [1 mark]
- Cue. Glycogen.
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 blood glucose when it rises too high after a meal.Show worked answer →
A Unit 4 explain question worth 4 marks. Reward: the pancreas detects the high blood glucose (1) and releases the hormone insulin into the blood (1); insulin makes the liver and muscle cells take up glucose from the blood (1) and store it as glycogen, so the blood glucose falls back to normal (1). Markers credit the pancreas, insulin, cells taking up glucose and storing it as glycogen. A common error is to say insulin raises blood glucose.
WJEC style3 marksDescribe the difference between the way the nervous system and the hormonal system carry information.Show worked answer →
A Unit 4 compare question. Reward: the nervous system uses electrical impulses along neurones, which are very fast and have a short-lived effect on a precise target (1); the hormonal system uses chemicals (hormones) carried in the blood, which are slower but have longer-lasting effects, often on several organs (1); a clear contrast of speed or duration (1). Markers credit electrical/fast/short for nerves and chemical/slow/long for hormones. A common error is to say hormones travel along nerves.
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