15.3 Thermoregulation in endotherms Flashcards
Where are peripheral temperature receptors located?
In the skin
What does peripheral temperature receptors do?
Detect changes in the surface temperature
What do temperature receptors in the HYPOTHALAMUS do?
Detect temperature of blood deep in the body
What does the combination of the peripheral temperature receptors and hypothalamus temperature receptors allow?
Gives the body great sensitivity
Allows it to respond to actual changes in blood temperature and pre-empt problems of these changes
What do the temperature receptors in the hypothalamus act as?
Thermostat of the body
Maintains core temperature in a dynamic equilibrium to within 1°C of 37°C
What types of ways do endotherms thermoregulate?
Internal exothermic metabolic activities to keep warm
Energy-requiring physiological responses to cool down
Passive ways to reduce energy demands on body
Can endotherms have similar behavioural responses to temperature like ectotherms?
E.g. wallowing in mud to cool off, pressing themselves to warm surfaces
Yes
What is hibernation?
Dormancy through the coldest weather
What is aestivation?
Period of prolonged or deep sleep that occurs in summer / dry seasons to avoid heat stress
What are additional behavioural adaptations humans have to control body temperature?
Clothes
Houses are built
Central heating / fans
Maintains ideal temperature
What are physiological adaptations of endotherms to maintain a stable core body temperature?
𝗣𝗥𝗧𝗛𝗦𝗠
(Please Read The Hind Sight, Man)
𝗣eripheral temperature 𝗥eceptors
𝗧hermoregulatory centres of the 𝗛ypothalamus
𝗦kin
𝗠uscles
What are some rapid responses of endotherms to cool down?
Vasodilation
Increased sweating
REDUCING the insulating effect of hair or feathers
What is vasodilation?
Nerve impulses are sent to muscles in arterioles
Arterioles near the surface of the skin dilate when the temperature rises
Arteriovenous shunt vessels constrict
- > Forces blood through the capillary networks close to the surface of the skin
- > Skin flushes
- > RADIATION cools it
Pressing skin against cool surfaces cools through CONDUCTION
How does increased sweating work?
Core temperature increases
Nerve impulses are sent to sweat gland
Sweat glands produce MORE sweat
- > Sweat spreads out across skin surface
- > Evaporates from surface
- > Heat is lost
- > Cools blood below surface
How do other animals (not humans and horses) sweat?
Sweat glands restricted to LESS hairy areas of the body
E.g. paws
Animals pant when they get hot -> Water evaporates -> Heat lost
How much sweat is lost by evaporation on a normal day?
1dm3 of sweat
How much sweat is lost by evaporation on a hot day of excercise?
12dm3 of sweat
What do kangaroos and cats do to keep cool?
Lick their front legs
How is the insulating effect of feathers and hairs reduced?
Body temperature increases
- > Erector pili muscles in skin relax
- > Hair and feathers lie flat on skin
- > Avoids trapping insulating layer of air
Does the hair lying flat have any effect on humans?
No
What are anatomical adaptions of endotherms living in hot climates?
Large SA:V ratio to maximise cooling
E.g. large ears and wrinkly skin
Pale fur or feathers to reflect radiation
What are some rapid responses of endotherms to warm up?
Vasoconstriction
Decreased sweating
Raising body hair or feathers
Shivering
How does vasoconstriction work?
Arterioles near surface of skin constrict
Arteriovenous shunt vessels dilate
- > Very little blood flows through capillary networks close to skin surface
- > Reduced radiation
- > Warm blood kept well below surface
What happens to sweating when core temperature falls?
Reduced sweating
What happens to sweat PRODUCTION when core temperature falls?
Stops completely
How does raising the body hair or feathers work?
Body temperature falls
- > Erector pili muscles in skin contract
- > Hair or feathers is pulled erect
- > Insulating layer of air is trapped
- > Cooling through skin reduces
What is shivering?
Rapid, involuntary contracting and relaxing of large VOLUNTARY muscles in body
How does shivering work?
Metabolic heat from exothermic reactions warm up body instead of moving it
-> Raises core temperature
What are the anatomical adaptations of endotherms living in cold climates?
Reduced SA:V ration
E.g. small ears
Thick layer of insulating fat under skin
E.g. blubber in whales and seals
Hibernation
How does hibernation help in colder climates?
Build up fat stores
Lower metabolic rate
Build well-insulated shelter
What are the anatomical adaptations of polar bears?
Small ears
Fur on feet insulates from ice
Hollow hairs trap permanent layer of insulating air
Black skin underneath absorbs radiation
Thick layer of fat underneath skin
What do female polar bears do?
Dig dens in snow and remain in them
Warm and insulated for months
While they give birth to their cubs
Emerge when cubs are large enough to survive the cold
What is the temperature range of a polar bear?
-50C to 10C
What are the two control centres involved in physio locations responses of endotherms to changes in core temperature?
Heat loss centre and Heat Gain centre
How does the heat loss centre work?
Activated when temperature of blood flowing through hypothalamus INCREASES
- > Sends impulses through autonomic motor neurones
- > To effectors in skin and muscles
- > Triggers responses lowering core temperature
How does the heat gain centre work?
Activated when temperature of blood flowing through hypothalamus DECREASES
- > Sends impulses through AUTONOMIC nervous system
- > To effectors in skin and muscles
- > Triggers responses acting to raise the core temperature
What interactions enables endotherms to maintain a very stable core body temperature?
Interaction of the sensory receptors, autonomic nervous system and the effectors
