Biology · OCR Paper 1
Homeostasis
How the body keeps its internal environment constant: why a constant internal environment matters, how body temperature is controlled, how insulin and glucagon control blood glucose and what goes wrong in diabetes, and how the kidneys and ADH control water balance. Matches OCR GCSE Biology A (Gateway Science) B3.3 (maintaining internal environments). The lessons on homeostasis and blood glucose are for both Combined Science and separate Biology. Temperature control and the kidneys are for separate Biology only, and the Higher tier extras are marked.
Lessons
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1
Homeostasis and Control Systems
Your cells work properly only when the conditions around them are kept steady. This lesson explains why a constant internal environment matters, what is…
8 terms -
2
Temperature Control and the Skin
Humans keep their body temperature at about 37 °C however hot or cold it is outside. This lesson is for separate Biology. It covers how the skin detects…
8 terms -
3
Blood Glucose and Diabetes
Every cell needs a steady supply of glucose, so the concentration of glucose in the blood is carefully controlled. This lesson explains how insulin controls…
8 terms -
4
The Kidneys and Water Balance
The kidneys clean the blood and control the amount of water and salts in the body. This lesson is for separate Biology. It covers why water balance matters…
8 terms
Key terms in this chapter
All 32, gathered from every lesson.
- Homeostasis
- The regulation of the internal conditions of the body to keep them constant.
- Internal environment
- The conditions inside the body, such as the blood and tissue fluid.
- Receptor
- A cell or organ that detects a change.
- Coordination centre
- A part of the body, such as the brain, that decides the response.
- Effector
- A muscle or gland that carries out the response.
- Negative feedback
- A response that reverses a change and returns a condition to normal.
- Metabolic reaction
- A chemical reaction in a cell, controlled by an enzyme.
- Optimum
- The conditions in which an enzyme works best.
- Thermoregulation
- The control of body temperature.
- Hypothalamus
- The part of the brain that monitors and controls body temperature.
- Sweat gland
- A gland in the skin that releases sweat.
- Vasodilation
- The widening of blood vessels near the skin surface, so that more heat is lost.
- Vasoconstriction
- The narrowing of blood vessels near the skin surface, so that less heat is lost.
- Shivering
- Rapid muscle contractions that release heat.
- Evaporation
- The change from liquid to gas, which takes heat from the surface.
- Hair erector muscle
- A muscle that pulls a hair upright.
- Blood glucose concentration
- The amount of glucose in the blood.
- Insulin
- The hormone that lowers the blood glucose concentration.
- Glucagon
- The hormone that raises the blood glucose concentration (Higher tier).
- Pancreas
- The organ that releases insulin and glucagon.
- Glycogen
- The carbohydrate in which the liver stores glucose.
- Diabetes
- A disease in which the blood glucose concentration is not controlled properly.
- Type 1 diabetes
- Diabetes in which the pancreas does not make enough insulin.
- Type 2 diabetes
- Diabetes in which the body cells stop responding to insulin.
- Kidney
- An organ that filters the blood and makes urine.
- Nephron
- The filtering unit of the kidney.
- Urea
- A poisonous waste substance made from excess amino acids and removed by the kidneys.
- Filtration
- The forcing of small molecules out of the blood into the Bowman's capsule.
- Selective reabsorption
- The taking back into the blood of useful substances such as glucose.
- ADH
- The hormone that controls the amount of water the kidneys reabsorb (Higher tier).
- Urine
- The liquid that contains urea, excess water and excess ions.
- Collecting duct
- The tube that carries urine from the nephrons.