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
