Homeostasis- Thermoregulation Flashcards
What are endotherms?
- Use metabolic processes to warm their bodies
- Core body temperature not usually influenced by the environment
- Are birds and mammals, but there are exceptions
How do endotherm mammals detect temperature changes?
1) Peripheral temperature receptors in skin to mainly detect external changes in temperature
2) Core body BLOOD temperature receptors in hypothalamus to detect internal temperature changes
3) Combination of both receptors allows a response to changes in both blood temperature and pre-empt changes in external conditions
How do endotherms raise their body temperature?
1) Internal exothermic physiological activities
2) -Vasoconstriction
- Decreased sweating
- Raising body hairs or feathers
- Shivering
3) Behavioural responses
How do endotherms reduce their body temperature?
1) Energy-requiring physiological responses
2) -vasodilation
- increased sweating
- reducing insulating effect of hair or feathers
3) Behavioural responses
What is vasodilation?
1) Arterioles near surface of skin dilate
2) Vessels that provide a direct connection between arterioles and venules constrict
3) Blood forced through capillary network close to surface of skin
4) Skin flushes and cools as a result of released radiation
Increased sweating:
1) Core temperature increases
2) Rate of sweating increases
3) Sweat spreads out across surface of skin
4) Sweat evaporates from surface, heat is lost, cooling blood below surface
5) Some animals pant and lose heat by evaporation
Reducing insulation:
What is vasoconstriction?
1) Arterioles near surface of skin constrict
2) Arteriovenous shunt vessels dilate
3) Little blood flows through capillary network near surface of skin
4) Warm blood kept below surface so very little radiation
Decreasing sweating:
1) Rates of sweating decrease
2) Sweat production stops
3) Greatly reduces cooling by evaporation of water from surface of skin
Increased insulation:
1) Raised body hairs pulled upwards by erector pilli muscles
2) Traps insulating layer of air and reduces cooling through skin
Shivering:
1) Rapid involuntary contracting and relaxing of large voluntary muscles
2) Metabolic heat from exothermic reactions warm up body instead of moving it
How is thermoregulation controlled?
- Negative feedback involving two centres:
1) Heat loss centre
2) Heat gain centre - Both in hypothalamus
What happens in the heat loss centre?
1) Activated when blood flowing through hypothalamus increases in temperature
2) Also affected by peripheral temperature in the skin
3) Send impulses through autonomic motor neurones to effectors
4) Effectors respond to lower core body temperature
What happens in the heat gain centre?
1) Activated when blood flowing through the hypothalamus decreases in temperature
2) Also affected by the peripheral temperature receptors in the skin
3) Sends impulses through autonomic motor neurones to effectors
4) Effectors respond to raised core body temperature
What are ectotherms?
- Animals that use their surroundings to warm their bodies
- Their core body temperature is heavily dependent on their environment
