How does the body keep its internal environment steady, and how are these systems monitored in health care?
Homeostasis and negative feedback, the control of blood glucose by insulin and glucagon, the control of body temperature, and how body systems are monitored using measurements such as pulse rate, blood pressure, body temperature and ECG.
A CCEA Life and Health Sciences answer on homeostasis: negative feedback, the control of blood glucose by insulin and glucagon, the control of body temperature, and how the body is monitored using pulse, blood pressure, body temperature and ECG.
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What this dot point is asking
CCEA wants you to explain homeostasis and the principle of negative feedback, describe the control of blood glucose concentration by insulin and glucagon, describe the control of body temperature, and understand how body systems are monitored in health care using measurements such as pulse rate, blood pressure, body temperature and the ECG. It connects the body systems studied in this unit by showing how their activity is regulated and measured.
Homeostasis and negative feedback
Negative feedback needs a receptor that detects the change, a coordination centre (often the brain or an endocrine gland) that processes the information, and an effector (a muscle or gland) that carries out the corrective response. Because the response opposes the original change, the factor oscillates within a narrow range around the set point rather than drifting away. This stability matters because enzymes and cells work best within narrow ranges of temperature, pH and solute concentration; large deviations would slow or stop vital reactions.
Control of blood glucose
This control keeps blood glucose near a set point of about 90 milligrams per 100 cubic centimetres. In type 1 diabetes the beta cells cannot make enough insulin, so glucose rises uncontrolled and is treated with insulin injections. In type 2 diabetes cells become less responsive to insulin, often linked to obesity, and it is managed by diet, exercise and sometimes drugs. Understanding this control underpins the monitoring of blood glucose in diabetic patients.
Control of temperature and monitoring the body
The hypothalamus controls core body temperature near 37 degrees Celsius. When too hot: sweat glands secrete more sweat, whose evaporation removes heat; skin arterioles dilate (vasodilation) so more blood flows near the surface and loses heat; and hairs lie flat. When too cold: sweating stops; skin arterioles constrict (vasoconstriction) to reduce heat loss; muscles shiver to generate heat by respiration; and hairs stand up to trap insulating air.
Health professionals monitor these systems with routine measurements: pulse rate (heart rate felt at an artery) reflects cardiovascular activity; blood pressure (systolic over diastolic, measured with a sphygmomanometer) indicates the load on the heart and arteries; body temperature indicates infection or heat balance; and the ECG records the electrical activity of the heart to detect abnormal rhythms. Comparing readings against normal ranges allows early detection of problems.
Examples in context
Example 1. Monitoring a hospital patient. A nurse records pulse, blood pressure, temperature and breathing rate as routine observations. A rising pulse with falling blood pressure can signal shock, while a raised temperature suggests infection. Tracking these against normal ranges lets staff detect deterioration early, showing why monitoring the body's regulated variables is central to health care.
Example 2. Diabetes and glucose monitoring. A person with type 1 diabetes measures their blood glucose with a glucose meter and injects insulin to replace what the pancreas cannot make. Monitoring shows when glucose is too high (needing insulin) or too low (needing sugar), keeping it within safe limits and preventing the complications of long-term high blood glucose.
Try this
Q1. State the three components needed for negative-feedback control. [3 marks]
- Cue. A receptor (detects the change), a coordination centre, and an effector (carries out the corrective response).
Q2. Name the hormone that raises blood glucose and the organ on which it acts. [2 marks]
- Cue. Glucagon; it acts on the liver to break down glycogen to glucose.
Q3. Explain why vasodilation of skin arterioles helps cool the body. [2 marks]
- Cue. More warm blood flows near the skin surface, so more heat is lost by radiation to the surroundings.
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 AS 26 marksExplain how blood glucose concentration is controlled after a meal and after a period of fasting, naming the hormones and organs involved.Show worked answer →
The answer needs both directions of control with the correct hormones, source and target.
After a meal (blood glucose rises): the rise is detected by the islets of Langerhans in the pancreas. Beta cells secrete insulin, which travels in the blood to the liver and muscle cells. Insulin causes cells to take up more glucose and the liver to convert excess glucose to glycogen (glycogenesis), and it increases the use of glucose in respiration, so blood glucose falls back to normal.
After fasting (blood glucose falls): the fall is detected by the alpha cells of the islets, which secrete glucagon. Glucagon travels to the liver and stimulates the breakdown of glycogen to glucose (glycogenolysis), which is released into the blood, raising blood glucose back to normal.
This is negative feedback: a change from the set point triggers a response that reverses the change.
Markers reward insulin from beta cells lowering glucose (uptake and glycogen storage), glucagon from alpha cells raising glucose (glycogen breakdown), the pancreas and liver as the organs, and the idea of negative feedback.
CCEA AS 24 marksExplain how the body reduces its core temperature when it becomes too hot, and explain why negative feedback is important in homeostasis.Show worked answer →
Give the cooling responses, then state the principle of negative feedback.
Cooling responses: when receptors detect a rise in core temperature, the hypothalamus coordinates responses. Sweat glands release more sweat, and its evaporation removes heat from the skin. Arterioles supplying the skin capillaries dilate (vasodilation), so more warm blood flows near the surface and more heat is lost by radiation. Hairs lie flat, trapping less insulating air.
Importance of negative feedback: it keeps internal conditions within narrow limits around a set point. A deviation triggers a response that reverses it, so enzymes and cells work in a stable environment. Without it, temperature, glucose or water balance could drift to dangerous levels.
Markers reward sweating with evaporation, vasodilation increasing heat loss, and a clear statement that negative feedback reverses a deviation to maintain a stable internal environment.
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Sources & how we know this
- CCEA GCE Life and Health Sciences specification — CCEA (2016)