BRAINCAKEHomeostasis
Revision notes for Homeostasis in Edexcel Biology B (9BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Controlling the Heart RateHeart rate must change to match the body's demands.
- Nervous Control of the HeartHeart rate is controlled by the cardiovascular control centre in the medulla oblongata.
- BaroreceptorsBaroreceptors are stretch receptors that detect changes in blood pressure.
- ChemoreceptorsChemoreceptors detect changes in the chemical composition of the blood, especially the carbon dioxide concentration and the pH.
- Hormonal Control of the HeartHeart rate is also affected by the hormone adrenaline.
- Additional ResponsesDuring exercise, raising the heart rate is only part of the body's response.
- Protein Homeostasis in the LiverThe body cannot store excess amino acids.
- OsmoregulationOsmoregulation is the control of the water potential of the body fluids, by regulating the amount of water and the concentration of solutes (such as…
- Osmoregulation in MammalsIn mammals the main organs of osmoregulation are the kidneys.
- Structure and Function of the KidneyHumans have two kidneys at the back of the abdomen.
- UltrafiltrationUltrafiltration is the filtration of blood under high pressure in the Bowman's capsule.
- Selective ReabsorptionThe glomerular filtrate contains many substances the body needs.
- Proximal Convoluted TubuleThe proximal convoluted tubule (PCT) is the first, coiled part of the nephron after the Bowman's capsule, in the cortex.
- Loop of HenleThe loop of Henle is a hairpin-shaped section of the nephron that dips from the cortex down into the medulla and back up again.
- Countercurrent MultiplierThe loop of Henle is a countercurrent multiplier. 'Countercurrent' means that the filtrate flows in opposite directions in the two limbs, which lie…
- Distal Convoluted TubuleThe distal convoluted tubule (DCT) is the coiled part of the nephron after the ascending limb of the loop of Henle, back in the cortex.
- Collecting DuctThe collecting duct receives filtrate from the distal convoluted tubules of several nephrons.
- UrineUrine is the fluid that leaves the collecting ducts and is stored in the bladder.
- AdaptationsMammals that live in different habitats have kidneys adapted to the amount of water available.
- Control of OsmoregulationThe water potential of the blood is kept within narrow limits by a homeostatic control system involving the hypothalamus, the posterior pituitary…
- ADHAntidiuretic hormone (ADH) increases the permeability of the collecting duct walls to water, so more water is reabsorbed and less urine is produced…
- Negative Feedback ControlNegative feedback is the process in which a change from the normal level (set point) of a factor is detected and causes responses that reverse the…
- Extra FeedbackADH is not the only way the body corrects its water balance.
- Diabetes InsipidusDiabetes insipidus is a condition in which the kidneys cannot conserve water, so the person produces very large volumes of dilute urine (up to about…
- ThermoregulationThermoregulation is the control of body temperature.
- Losing or Gaining HeatBody temperature stays constant when heat gain equals heat loss.
- Control of Body TemperatureMammals and birds keep their core body temperature (the temperature of the blood and the organs deep inside the body) within narrow limits.
- EndothermsAn endotherm is an animal that generates most of its body heat internally from metabolic reactions and keeps its core temperature fairly constant…
- EctothermsAn ectotherm is an animal that relies mainly on heat from its surroundings to warm its body.
- Thermoregulation in EndothermsThermoregulation is the control of core body temperature.
- The SkinThe skin is the main organ through which a mammal exchanges heat with its surroundings, so many thermoregulatory effectors are found there.
- Keeping CoolWhen core temperature rises above the norm, for example during exercise or on a hot day, the hypothalamus triggers responses that increase heat loss…
- Keeping WarmWhen core temperature falls below the norm, the hypothalamus triggers responses that reduce heat loss and increase heat production.
- Control of Core Body TemperatureCore body temperature is controlled by the thermoregulatory centre in the hypothalamus, a small region at the base of the brain.
- VasodilationVasodilation is the widening of the arterioles that supply the capillaries near the skin surface.
- VasoconstrictionVasoconstriction is the narrowing of the arterioles that supply the capillaries near the skin surface.
- Adaptations for Cold EnvironmentsAnimals living in polar regions or at high altitude have anatomical, physiological and behavioural adaptations that reduce heat loss.
- Adaptations for Hot EnvironmentsAnimals in hot deserts and the tropics need to lose heat and avoid gaining it, often while also conserving water.
- Cooling The BrainThe brain is very sensitive to temperature, and its neurones and enzymes can be damaged if it gets much hotter than normal.
- Behavioural Control of Body TemperatureBoth ectotherms and endotherms use behaviour to control body temperature.
- Cape Ground SquirrelThe Cape ground squirrel (Xerus inauris) lives in the hot, dry Kalahari region of southern Africa.
On the specification
- 9.1 Homeostasis
- 9.8 Control of heart rate in mammals
- 9.9 Osmoregulation and temperature regulation