HomeostasisOxford AQA IGCSE Biology: Flashcards

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Define homeostasis.

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Define homeostasis.: Homeostasis is the maintenance of a constant internal environment within the body, despite changes in external conditions.
Name four mechanisms involved in thermoregulation.: Sweating, shivering, vasoconstriction and vasodilation.
Describe how sweating helps to reduce body temperature.: Sweat is produced by sweat glands and evaporates from the skin surface, removing latent heat energy from the body and cooling it down.
Explain what happens during shivering and how it affects body temperature.: Shivering is involuntary muscle contractions that generate heat through respiration, increasing body temperature when it is too low.
What is vasoconstriction and how does it help thermoregulation?: Vasoconstriction is the narrowing of blood vessels near the skin surface, reducing blood flow to the skin and decreasing heat loss to maintain body temperature when it is too low.
What is vasodilation and how does it help thermoregulation?: Vasodilation is the widening of blood vessels near the skin surface, increasing blood flow to the skin and increasing heat loss to cool the body when temperature is too high.
Explain the role of the hypothalamus in temperature control.: The hypothalamus acts as the body's thermostat; it detects changes in core body temperature and triggers appropriate responses (sweating, shivering, vasoconstriction or vasodilation) to maintain a constant temperature.
Describe the role of insulin in blood glucose regulation.: Insulin is produced by the pancreas and causes cells to take up glucose from the blood, and causes the liver to convert glucose into glycogen for storage, lowering blood glucose concentration.
Describe the role of glucagon in blood glucose regulation.: Glucagon is produced by the pancreas and causes the liver to break down glycogen into glucose and release it into the blood, raising blood glucose concentration when it is too low.
Name the five main structures of the kidney.: Cortex, medulla, ureter, renal artery and renal vein.
Describe the process of ultrafiltration in the kidney.: High blood pressure in the glomerulus forces small molecules (glucose, urea, ions and water) through the capillary wall and into the Bowman's capsule, while large molecules (proteins and blood cells) remain in the blood.
Explain selective reabsorption in the kidney.: Useful substances (glucose, ions and some water) are selectively reabsorbed from the filtrate back into the blood in the proximal convoluted tubule, whilst urea and excess water remain as urine.
Describe the role of ADH in controlling water content of blood.: ADH is released by the pituitary gland and increases the permeability of the collecting duct to water, allowing more water to be reabsorbed into the blood, which decreases urine concentration and increases blood water content.
Name two treatments for kidney failure.: Dialysis and kidney transplant.
Explain how dialysis treats kidney failure.: Dialysis uses a partially permeable membrane to filter waste products and excess ions from the blood into a dialysis fluid, while useful substances like glucose remain in the blood; this removes urea and excess water that the failed kidneys cannot remove.