Lecture 12 Flashcards
What are the consequences of body temperature being too low?
Slows metabolism, inadequate O2 supply as haemoglobin affinity is reduced, ice crystals form in cells causing them to rupture.
What are the consequences of body temperature being too high?
Proteins denature as molecules vibrate and bonds are broke, enzymes denture which affects metabolism, haemoglobin affinity is reduced.
Why is regulation of body temperature required?
Heat moves from hot to cold, down the concentration gradient, environment affects body temperature.
Without regulation, animals would be restricted to temperate favourable regions.
What are the optimum temperatures for animals?
Mammals: 36-38 degrees
Lizards: 32-40 degrees
Butterflies and moths: 28-39 degrees.
What are the 4 means of heat loss?
Radiation (60%), loss without contact
Conduction (3%), loss with contact
Convection (15%), movement of air/fluid across body
Evaporation (22%), water from the body surface.
What factors affect heat loss?
Larger S.A:Volume ratio decreases heat loss.
Steeper temperature gradient increases temperature loss.
Insulation with materials of low thermal conductivity reduce heat loss.
Describe ectotherms/poikilotherms.
Conformers who’s body temperature fluctuates with the environment. Heat is derived from the environment using behaviours like sunbathing. Also use metabolism E.g. Bees warming up flight muscles by shivering.
E.g. Reptiles, amphibians, insects.
Describe endotherms/homeotherms.
Regulators who maintain a constant internal temperature. Heat is derived from metabolism and behaviours are used as well such as sitting in shade.
E.g. Mammals, birds.
What are the benefits of ectotherms?
Metabolic rate is 5x slower than endotherms so they require less food and water. Also means they can devote more energy to reproduction and exploit poor/arid environments.
What are the costs of endotherms?
No nocturnal niches, cannot sustain high energy bursts as they risk O2 debt and rapid fatigue. Are often ambush predators but can be susceptible to sustained predation by endotherms.
What is the thermoneutral zone?
Range of temperatures in which animal does not need to expend energy to maintain body temperature. Metabolic rate is stable within this zone and it varies between species and individuals.
How does the hypothalamus affect this?
Sets the upper and lower critical limits and is responsible for activating thermoregulatory responses. An example of negative feedback.
What happens below the lower critical limit?
Metabolic rate increases.
Vasoconstriction to reduce radiation, conduction and convection from the skin.
Shivering uses ATP, the regeneration of which increases heat production 500%, proteins and lipids are backup fuels after glycogen has been used up.
Adrenaline from adrenal medulla stimulates flight/fight response to increase heart rate.
Thyroxine from thyroid increases metabolic rate.
What are the different types of insulation?
Brown adipose tissue is rich in mitochondria and has a rich blood supply for rapid heat production- in newborn/hibernating mammals and human necks.
White adipose tissue has no organelles and acts as storage.
Blubber is a thick layer of vascularised adipose tissue with low thermal conductivity and metabolic activity.
Fur/hair/feathers trap a layer of insulating air.
Describe countercurrent heat exchangers.
Hot arteries flow past cold veins to prevent cold blood from apendages reaching heart.
