How do hormones coordinate the body, and how is blood glucose controlled?
The endocrine system and how hormones act, the control of blood glucose by insulin and glucagon, the difference between nervous and hormonal control, and the basis of diabetes.
A CCEA A-Level Biology answer on the endocrine system and how hormones act, the control of blood glucose by insulin and glucagon, the differences between nervous and hormonal control, and the basis of diabetes.
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What this dot point is asking
CCEA wants you to describe the endocrine system and how hormones act, explain how insulin and glucagon control blood glucose, distinguish nervous from hormonal control, and explain the basis of type 1 and type 2 diabetes.
The endocrine system
Because hormones travel in the blood, they reach the whole body, but only cells with the matching receptor respond. Hormonal control is slower to start, longer-lasting and affects many cells over a wide area, while nervous control is fast, short-lived and precisely targeted by neurones. Many responses use both, such as the fight-or-flight response (fast nervous action plus slower adrenaline).
Control of blood glucose
Insulin works by binding to receptors on liver and muscle cells, which increases the number of glucose transport proteins in the cell membrane and activates the enzymes that build glycogen. The set point for blood glucose is around per of blood; both hormones constantly fine-tune around it.
Diabetes
In type 1 diabetes the beta cells are destroyed (often by an autoimmune response), so little or no insulin is made; it usually starts in childhood and is treated with insulin injections. In type 2 diabetes the body still makes insulin but cells respond poorly to it (insulin resistance); it is linked to diet, obesity and age and is managed by diet, weight loss, exercise and sometimes medication or insulin. In both, blood glucose can rise dangerously high (hyperglycaemia), and glucose may appear in the urine once the kidney's reabsorption is saturated.
Examples in context
Example 1. A glucose tolerance test. A patient drinks a glucose solution and blood glucose is measured over two hours. In a healthy person, glucose rises then falls back to normal within about two hours as insulin acts. In a diabetic, glucose rises higher and stays elevated, because insulin is missing (type 1) or ineffective (type 2). This clinical test is a direct demonstration of negative feedback working, or failing, and is exactly the kind of data CCEA asks you to interpret.
Example 2. Adrenaline and glucose during a fright. When startled, the adrenal glands release adrenaline, which (like glucagon) stimulates the liver to break down glycogen, raising blood glucose to fuel a fight-or-flight response. This shows that more than one hormone can act on the same target (the liver) to control glucose, and links hormonal control to the wider stress response.
Try this
Q1. Describe what happens after a meal raises blood glucose. [3 marks]
- Cue. Beta cells release insulin, cells take up glucose, and the liver converts glucose to glycogen, lowering blood glucose.
Q2. State one difference between nervous and hormonal control. [1 mark]
- Cue. Nervous control is fast and short-lived; hormonal control is slower and longer-lasting.
Q3. Explain why a person with type 1 diabetes must inject insulin rather than take it as a tablet. [2 marks]
- Cue. Insulin is a protein; if swallowed it would be digested by proteases in the gut and broken down before it could act, so it must be injected into the blood.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA 20196 marksExplain how the body controls the concentration of glucose in the blood after a meal and during fasting, naming the hormones and cells involved.Show worked answer →
A 6-mark answer needs both directions of the negative feedback loop with named cells and hormones.
After a meal (high glucose): beta cells in the islets of Langerhans of the pancreas detect the rise and secrete insulin. Insulin makes liver and muscle cells take up more glucose (more glucose carriers in the membrane) and the liver converts glucose to glycogen (glycogenesis). Blood glucose falls back to normal.
During fasting (low glucose): alpha cells detect the fall and secrete glucagon. Glucagon makes the liver break glycogen down to glucose (glycogenolysis) and make glucose from other molecules (gluconeogenesis). Blood glucose rises back to normal.
This is negative feedback: a deviation from the set point triggers a response that reverses it.
Markers reward beta cells and insulin lowering glucose by uptake and glycogenesis, alpha cells and glucagon raising glucose by glycogenolysis, and the negative feedback link.
CCEA 20214 marksCompare type 1 and type 2 diabetes in terms of their cause and treatment.Show worked answer →
A 4-mark compare answer needs matched points on cause and treatment.
Cause: in type 1 diabetes the beta cells are destroyed (often by an autoimmune response), so little or no insulin is made. In type 2 diabetes the body still makes insulin but the cells respond poorly to it (insulin resistance), often linked to diet, obesity and age.
Treatment: type 1 is treated with regular insulin injections (and monitoring blood glucose), because the hormone is missing. Type 2 is managed first by diet, weight loss and exercise, with medication (and sometimes insulin) if needed, because the issue is the response rather than a total lack.
Markers reward the cause of each type and the matching treatment, with the key distinction of lack of insulin versus reduced response.
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Sources & how we know this
- CCEA GCE Biology specification — CCEA (2016)