5 - MZH - Homeostasis 2 - Thermoregulation Flashcards
Why must all animals keep their internal temperature within certain limits?
Too low = biochemical reactions will be too slow
Too high = Risk of denaturing enzymes
Define:
Conduction
Convection
Radiation
Evaporation
Conduction = Transport of heat by collisions of molecules: liquids and solids conduct heat better than air.
Convection = Transfer of heat by the heating/cooling of currents of air or water.
Radiation = Energy that travels from one place to another as electromagnetic waves.
Evaporation = Objects cool down as water evaporates from the surface
What do all exothermic metabolic reactions do?
Release heat
Define:
Ecotherm and endotherm
What organisms are which?
Ectotherm = Organism whos major source of body heat is environmental head.
Endotherm = Organisms whos major source of body heat is through metabolic reactions
All animals except mammals and birds are ectotherms.
How to endotherms and ectotherms maintain their body temperatures
Ectotherms - Can only control their temperature by changing their behaviour e.g. go into the sun or the shade
Endotherms - Can maintain a stable core temperature using mainly physiological adaptations e.g. heat released from metabolic reactions
Advantages (4) & disadvantages (3) of ectotherms thermoregulation
ADVANTAGES:
- Less of their food is used in respiration
- More of the energy/ nutrients gained from food can be converted into growth
- Need less food
- Can survive for long periods of time without food
DISADVANTAGES:
- Less active in cooler temperatures
- Less active = at risk of predation
- Can’t take advantage of food that is available while they’re cold
Crocodiles are ectotherms. Give 4 examples of how they can control their body temperature
- Changing behaviour - moving between land and water.
- Colour - Darker colours absorbs heat more easily.
- Orientation to the sun - Exposing larger areas to the sun will increase heat absorption.
- Metabolic heat generation - Cells respire producing heat as a waste product.
What are exergonic reactions?
They release energy in the form of heat
Advantages (3) & disadvantages (3) of ecotherms thermoregulation
ADVANTAGES:
- Maintain a fairly constant core temp regardless of the external temp.
- Remain active even when external temps are low allowing them to escape predators or take advantage of prey.
- Inhibit habitats with very high/low temps.
DISADVANTAGES:
- Use a sig part of their food intake to maintain body temp.
- Need more food.
- Use lower proportion of food intake for growth.
What receptors detect temperature changes? How do they do it and where are they located?
Thermoreceptors are located in the hypothalamus of the brain. They detect changes in the temp in the blood.
- Increase in body temp above norm - stimulated region in hypothalamus called heat loss center which trigger changes to lower body temp.
- Decrease in body temp above norm - stimulated region in hypothalamus called heat gain center which trigger changes to increase body temp.
Another type of receptor to detect temperature changes thats not thermoreceptors?
Why is it important?
Peripheral thermoreceptors are in the skin.
- Detect change in the environmental temp.
- Communicate with the thermoregulatory center in hypothalamus.
What are the physiological responses to a decrease in the core temperature? (4)
Heat gain center is stimulated and triggers 4 main physiological responses:
- Shivering - Occurs when muscles contract/relax rapidly. Shivering muscles give out 4-5 times more heat than resting muscles.
- Vasoconstriction - Occurs when arterioles supplying capillary networks in the surface of the skin constrict, reduces blood flow through the capillaries, reducing the aount fo heat lost through skin by radiation and conduction.
- Piloerection (hair raising) - Allows a layer of air to be trapped between skin and hair surface, acts as an insulator.
- Increased metabolic rate - Hormone adrenaline is secreted. Raised metabolic rate, increased heat production. Mammals living in cold conditions have a permanently raised metabolic rate due to the secretion fo thyroxin which has the same effect as adrenaline but the effect is slower and more prolonged.
What are the physiological responses to a increase in the core temperature? (2)
Heat loss center is stimulated.
- Vasodialation - Arterioles suppluing capillaries in the skin dilate. At the same time shunt vessles which carry blood deep below the surface of the skin are closed off. Creates increased blood flow near surface of the skin, increased heat loss by radiation and conduction.
- Sweating - Sweat is a salty solution made by the sweat glands. Evaporation of sweat from skin’s surface cools it.
List 3 behavioural mechanisms used by mammals to thermoregulate
- Sun bathing
- Moving into the shade
- Covering themselves up e.g. wearing more clothes to retain heat
