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A-Level Biology > 15.3 Thermoregulation in endotherms > Flashcards

15.3 Thermoregulation in endotherms Flashcards

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1
Q

Where are peripheral temperature receptors located?

A

In the skin

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2
Q

What does peripheral temperature receptors do?

A

Detect changes in the surface temperature

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3
Q

What do temperature receptors in the HYPOTHALAMUS do?

A

Detect temperature of blood deep in the body

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4
Q

What does the combination of the peripheral temperature receptors and hypothalamus temperature receptors allow?

A

Gives the body great sensitivity

Allows it to respond to actual changes in blood temperature and pre-empt problems of these changes

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5
Q

What do the temperature receptors in the hypothalamus act as?

A

Thermostat of the body

Maintains core temperature in a dynamic equilibrium to within 1°C of 37°C

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6
Q

What types of ways do endotherms thermoregulate?

A

Internal exothermic metabolic activities to keep warm

Energy-requiring physiological responses to cool down

Passive ways to reduce energy demands on body

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7
Q

Can endotherms have similar behavioural responses to temperature like ectotherms?

E.g. wallowing in mud to cool off, pressing themselves to warm surfaces

A

Yes

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8
Q

What is hibernation?

A

Dormancy through the coldest weather

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9
Q

What is aestivation?

A

Period of prolonged or deep sleep that occurs in summer / dry seasons to avoid heat stress

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10
Q

What are additional behavioural adaptations humans have to control body temperature?

A

Clothes

Houses are built

Central heating / fans

Maintains ideal temperature

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11
Q

What are physiological adaptations of endotherms to maintain a stable core body temperature?

𝗣𝗥𝗧𝗛𝗦𝗠
(Please Read The Hind Sight, Man)

A

𝗣eripheral temperature 𝗥eceptors

𝗧hermoregulatory centres of the 𝗛ypothalamus

𝗦kin

𝗠uscles

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12
Q

What are some rapid responses of endotherms to cool down?

A

Vasodilation

Increased sweating

REDUCING the insulating effect of hair or feathers

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13
Q

What is vasodilation?

A

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

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14
Q

How does increased sweating work?

A

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
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15
Q

How do other animals (not humans and horses) sweat?

A

Sweat glands restricted to LESS hairy areas of the body

E.g. paws

Animals pant when they get hot -> Water evaporates -> Heat lost

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16
Q

How much sweat is lost by evaporation on a normal day?

A

1dm3 of sweat

17
Q

How much sweat is lost by evaporation on a hot day of excercise?

A

12dm3 of sweat

18
Q

What do kangaroos and cats do to keep cool?

A

Lick their front legs

19
Q

How is the insulating effect of feathers and hairs reduced?

A

Body temperature increases

  • > Erector pili muscles in skin relax
  • > Hair and feathers lie flat on skin
  • > Avoids trapping insulating layer of air
20
Q

Does the hair lying flat have any effect on humans?

A

No

21
Q

What are anatomical adaptions of endotherms living in hot climates?

A

Large SA:V ratio to maximise cooling

E.g. large ears and wrinkly skin

Pale fur or feathers to reflect radiation

22
Q

What are some rapid responses of endotherms to warm up?

A

Vasoconstriction

Decreased sweating

Raising body hair or feathers

Shivering

23
Q

How does vasoconstriction work?

A

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
24
Q

What happens to sweating when core temperature falls?

A

Reduced sweating

25
Q

What happens to sweat PRODUCTION when core temperature falls?

A

Stops completely

26
Q

How does raising the body hair or feathers work?

A

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
27
Q

What is shivering?

A

Rapid, involuntary contracting and relaxing of large VOLUNTARY muscles in body

28
Q

How does shivering work?

A

Metabolic heat from exothermic reactions warm up body instead of moving it

-> Raises core temperature

29
Q

What are the anatomical adaptations of endotherms living in cold climates?

A

Reduced SA:V ration
E.g. small ears

Thick layer of insulating fat under skin
E.g. blubber in whales and seals

Hibernation

30
Q

How does hibernation help in colder climates?

A

Build up fat stores

Lower metabolic rate

Build well-insulated shelter

31
Q

What are the anatomical adaptations of polar bears?

A

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

32
Q

What do female polar bears do?

A

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

33
Q

What is the temperature range of a polar bear?

A

-50C to 10C

34
Q

What are the two control centres involved in physio locations responses of endotherms to changes in core temperature?

A

Heat loss centre and Heat Gain centre

35
Q

How does the heat loss centre work?

A

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
36
Q

How does the heat gain centre work?

A

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
37
Q

What interactions enables endotherms to maintain a very stable core body temperature?

A

Interaction of the sensory receptors, autonomic nervous system and the effectors

A-Level Biology (35 decks)

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