5.1.1 - Communication And Homeostasis (set A - Thermoregulation) Flashcards
Define homeostasis - why is it important?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
- important for control of enzymes, control of movement of molecule and control of energy (loss/gain)
Explain how homeostasis is maintained - what’s required for changes to be detected?
- sensory receptors detect changes in internal and external environment - information transmitted to brain - impulse sent along motor neurones to effectors (glands/muscles)
Outline the role of negative feedback systems?
Small change in one direction detected by sensory receptor - effectors work to reverse the change and restore conditions to base level
(Eg feedback cycle in control of blood sugar levels by glucagon and insulin and temperature and water balance)
most common cycle
Outline the role of positive feedback systems?
Small change in internal environment of the body is dented by sensory receptors and effectors are stimulated to reinforce that change and increase the response
(seen in blood clotting - when vessel is damaged, platelets stick to damaged region and release factors that initiate clotting and attract more platelets)
less common
Explain what Ectotherms are?
includes most animals and involves using the surroundings to warm their bodies (core body temperature is heavily dependent on their environment)
- fish are Ectotherms but do not need to thermoregulate due to the high heat capacity of water which keeps the temperature fairly constant
Explain what Endotherms are?
include mammals and birds, which rely on their metabolic processes to warm up and they usually maintain a very stable body temperature regardless of the temperature of the environment (however require more energy to do so)
can survive in a wide range of environments
Outline and explain 2 behavioural adaptions Ectotherms use for thermoregulation?
- orientating their bodies to maximise surface area exposed to the sun when basking - lizards will bask in the sun for long periods of time to get warm enough to move fast and hunt their prey (some butterflies will spread there wings to increase SA)
- Through conduction - cool down by sheltering from the sun in shade (hiding in cracks or digging burrows) or by pressing their bodies against cool, shady earth or stones or moving into mud/water (will pair this with orientating their body to minimise SA exposed to the sun) (or use conduction to warm up)
Outline and explain 2 physiological adaptions Ectotherms use for thermoregulation?
- dark colours absorb more radiation than light colours - lizards in colder climates then to be darker coloured
- some Ectotherms alter their heart rate to increase/decrease metabolic rates and cooling or warming of body surfaces
Explain how temperature changes are detected in Endotherms?
- peripheral temperature receptors in skin detect changes in surface temperature
- receptors in hypothalamus detect temperature of blood in body (less likely to be affected by external conditions)
combination of both gives the body great sensitivity - can pre-emptly respond
Outline and explain some of the behavioural adaptions Endotherms use for thermoregulation?
- basking in the sun
- pressing themeselves against warm surfaces
- cooling off in water/mud or digging burrows
- some animals become dormant in cold weather (hibernation)
endotherms mainly rely on physiological adaptions
Outline and explain some of the physiological adaptions Endotherms use for thermoregulation - focusing specifically on cooling down?
- vasodilation - arterioles near surface of skin dilate when temperature rises, vessels which provide connection between arterioles and venues constrict forcing blood into capillary network close to skins surface, skin flushes and cools (cooling results from conduction)
- increased sweating - evaporation of sweat from surface causes loss of heat which cools blood below (panting also allows evaporation)
- reducing effect of hair or feathers - hair erector muscles relax causing hair to lie flat on skin which avoid trapping insulating layer of air
Outline and explain some of the physiological adaptions Endotherms use for thermoregulation - focusing specifically on warming up?
- vasoconstriction - arterioles near surface constrict and arteriovenous shunt vessels dilate - decreasing blood flow in capillary and close to surface, very little radiation takes place
- decreased swearing - greatly reduces cooling by the evaporation of water from surface
- raising hair/feathers - erector pili muscles contract - traps insulating layer of air reducing cooling (very significant - not in humans)
- shivering - contracting and relaxing of large voluntary muscles - metabolic heat from exothermic reaction warms up body (effective at raising core temp)
Briefly explain some of the adaption endotherms which live in cold climates have - give 3?
- adaptions to minimise SA:V ratio - reduce cooling (eg small ears)
- thick layer of insulating fat underneath skin (eg blubber in whales/seals)
- hibernating - build up fat stores, build well-insulated shelters which lowers metabolic rate during cold winters
explain the role of the heat loss centre?
Activated when temperature of blood flowing through hypothalamus increases - sends impulses through autonomic motor neurons to effectors in skin and muscles - triggers a response - lowering temperature
explain the role of the heat gain centre?
Activated when temperature of blood flowing through hypothalamus decreases - sends impulses through autonomic nervous system to effectors in skin and muscles - triggers a response and raises core temp
