BRAINCAKE

Homeostasis

AQA A-level BiologyTopic 9 of 1333 lessons

Revision notes for Homeostasis in AQA Biology (7402). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. HomeostasisHomeostasis is the maintenance of a constant internal environment, maintaining a dynamic equilibrium with only small variations over a narrow range…
  2. Feedback SystemsThere are two types of feedback systems.
  3. Examples of Positive FeedbackWhen a blood vessel is damaged, blood platelets stick to the damaged region and release chemicals that attract more platelets to the region.
  4. Endotherms and EctothermsFish, reptiles and amphibians are ectotherms and use their surroundings to warm their bodies.
  5. Behavioural Responses in EctothermsWhen ectotherms need to warm up, they may bask in the sun, orient their bodies towards the sun to expose the greatest surface area, increase their…
  6. Physiological Responses in EctothermsPhysiological adaptations include colour.
  7. ThermoreceptorsThere are two types of thermoreceptors in mammals.
  8. The HypothalamusThere are two thermoregulatory centres in the hypothalamus: the heat loss centre and the heat gain centre.
  9. CoolingThe arterioles near the surface of the skin dilate and the arteriovenous shunt, which connects the arterioles and venules, constricts.
  10. Warming UpVasoconstriction occurs when the arteriovenous shunts dilate.
  11. ExcretionExcretion is the removal from the body of metabolic waste.
  12. The LiverThe liver is about 2% of body mass and is the largest internal organ in the body.
  13. Structure of the LiverThe liver is divided into lobes, which divide further into cylindrical lobules.
  14. Carbohydrate Metabolism in the LiverHepatocytes are target cells for insulin and glucagon, both hormones responsible for the regulation of blood glucose concentration.
  15. Transamination and DeaminationOf the twenty amino-acids required by the body nine cannot be synthesised by the body and must therefore be obtained from the diet.
  16. DetoxificationToxins are produced by many metabolic pathways.
  17. Production of Bile Salts, Bile Pigments and CholesterolThe liver synthesises red blood cells in the fetus.
  18. The KidneysThe kidneys are a pair of red-brown organs attached to the back of the abdominal cavity.
  19. Structure of the KidneyThe kidneys are covered by a thin, tough membranous capsule made of tough fibres of collagen and elastin.
  20. NephronsNephrons, the filtering units, consist of the:Bowman's capsule where ultrafiltration takes place proximal convoluted tubule where water and other…
  21. Bowman's CapsuleThis is a filtering unit that encloses a network of 'leaky' capillaries called the glomerulus.
  22. GlomerulusThe glomerulus is a network of capillaries with many gaps between the capillary endothelial cells.
  23. Proximal Convoluted TubuleSelective reabsorption takes place in the proximal convoluted tubule.
  24. Loop of HenléThe loop of Henlé is responsible for the reabsorption of water.
  25. Countercurrent MultiplierAt the top of the ascending loop of Henlé sodium and chloride ions are actively transported out of the Loop of Henlé into the interstitial tissue…
  26. Ultrafiltration, Selective Reabsorption and Osmoregulation.Blood is filtered under pressure in the Bowman's capsule.
  27. Distal Tubule and Collecting DuctFluid passes from the top of the ascending limb of loop of Henlé to a short distal convoluted tubule.
  28. ADHOsmoreceptors in the hypothalamus monitor the water potential of the blood.
  29. Kidney failureKidney failure can occur due to diabetes, high blood pressure, infection or other reasons.
  30. HaemodialysisIn haemodialysis, blood is taken from an artery (often through a fistula joining an artery to a vein in the arm) and passed through a machine that…
  31. Peritoneal DialysisIn peritoneal dialysis, the body's peritoneum or abdominal membrane is used as a filter.
  32. Pregnancy TestingOnce the human embryo has been fertilised, it becomes implanted into the uterus.
  33. Anabolic SteroidsAnabolic steroids can be used to gain muscle mass.

On the specification

All AQA A-level Biology topics