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Physiology > Lecture 22 - Thermoregulation > Flashcards

Lecture 22 - Thermoregulation Flashcards

1
Q

Do different ages of species have different thermoregulation needs?

A

Yes - ie adults can handle more than babies

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2
Q

What is an endotherm?

A

Animals who use metabolic heat to maintain a stable internal temperature, often one different than the environment

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3
Q

Examples of endotherms?

A

Birds and mammals

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4
Q

What is an ectotherm?

A

Animals that do not use metabolic heat to maintain their body temperature but take on the temperature of the environment

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5
Q

Examples of ectotherms

A

Lizards and snakes

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6
Q

Do endotherms and ectotherms have strategies to let them live in different environments

A

Yes, even some that are extreme

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7
Q

What is diurnal temperature

A

Variations in body temperature related to the time of day - ie colder in the morning, warmer as day goes on

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8
Q

The core temperature of a human body is

A

37°C

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9
Q

The core of the human body includes the

A

Thorax, abdomen, and the head

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10
Q

Where are the vital organs located in the human body

A

In the core

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11
Q

In the core, the enzyme systems must operate in

A

Optimum conditions

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12
Q

Can the periphery of the body withstand some deviation from the core temperature?

A

Yes

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13
Q

What is the effect of temperature on enzyme reaction rate

A

When temperature increases, rate of rxn increases as molecules gain kinetic energy
Temperature increases & hits optimum temperature
After optimum temperature, enzyme begins denaturing & rate of rxn

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14
Q

Is there a relationship between body weight and heat production?

A

Yes - as body weight increases (kg), so does heat production (kcal/day)

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15
Q

Temperature is regulated by

A

Nervous feedback mechanisms

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16
Q

Thermoregulatory responses include

A

Behavioural, anatomical, or physiological ones
Endotherms can use some of these responses to alter heat production when it’s cold

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17
Q

Endotherms and ectotherms use other methods (not neural control) to increase or decrease exchange with the environment such as

A

Conduction, convection, radiation, and evaporation

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18
Q

Feedback system for thermoregulation strategies

A

1) receptor
2) Control Center - sets range of values, evaluates input, and sends input
3) effector - receives output from control centre & produces a response

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19
Q

Hypothalamus acts as

A

A thermostat

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20
Q

The hypothalamus receives nerve impulses from

A

Peripheral thermoreceptors for both cold and heat

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21
Q

Hypothalamus also has thermoreceptors called central thermoreceptors - these detect

A

Changes in blood temperature

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22
Q

Core temperature is in dynamic equilibrium as a result of

A

Balance between heat gain and heat loss

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23
Q

Things that contribute to thermal balance

A

Heat input
Core temperature
Heat output

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24
Q

Things that contribute to heat input

A

Conduction, radiation

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25
Q

things that contribute to core temperature

A

Basal metabolism, muscle activity, thyroxine, catecholamines, sympathetic output

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26
Q

Things that contribute to heat output

A

Conduction
Radiation
Convection
Evaporation

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27
Q

Heat is gained by

A

Chemical reactions in the cells
By the body’s metabolic activity which generates heat (eg when muscles move)
By conduction and radiation from environment

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28
Q

Heat is lost by

A

Conduction and radiation to the environment
By evaporation from the body surface

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29
Q

animals can also affect their body temperature by

A

Changing their behaviour

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30
Q

Conduction is

A

The direct transfer of heat through a liquid, solid, or gas from one molecule to another

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31
Q

A small amount of body heat moves by conduction directly through deep tissues to

A

Cooler surfaces. Heat exchange involves changing the temperature of air molecules and surfaces in contact with the skin

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32
Q

The rate of conductive heat exchange depends on

A

Thermal gradient

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33
Q

In an attempt to reduce heat loss, animals instinctively

A

Curl up when they lay down. This behavioural response reduces the surface area exposed to the cold

34
Q

What is heat exchange of radiation

A

Objects emit electromagnetic heat waves without molecular contact with other objects

35
Q

when temperature of things in environment exceeds the skin temperature, radiant heat energy is

A

Absorbed from the surroundings without direct contact

36
Q

What is heat exchange by evaporation

A

When sweat or water is vaporized from either skin surface of respiratory passages, heat is taken away from the surface.

37
Q

For each litre of water vaporized , _____ kcal is transferred to the environment

A

580

38
Q

For water to be vaporized from the liquid to the gaseous stage, _____________ is required

A

Lots of energy

39
Q

Heat transferred as water is vaporized from

A

Respiratory passages and skin surfaces

40
Q

Land animals often lose water from

A

Their skin, mouth, and nose by evaporation into the air

41
Q

What is the primary means of cooling the body during exercise

A

Sweating

42
Q

In panting, an animal breathes rapidly and shallowly with its mouth open to

A

Increase evaporation from the surfaces of the mouth

43
Q

What animals use panting

A

Mammals and birds

44
Q

Dogs have sweat glands on the undersides of their paws and within their ears. Do they help cooling?

A

No - these glands only have minimal cooling capabilities

45
Q

Panting allows a dog to

A

Rapidly inhale, humidify, then exhale the air, which lead the evaporation of water and loss of heat across the moist surfaces of the upper respiratory system, tongue, and surfaces within the mouth

46
Q

Is there a relationship between body temperature and hydration

A

Yes - when a Camel is dehydrated, it’s body temperature is much more variable than when the camel is hydrated & water is available for evaporation

47
Q

Jackrabbits have large ears with an extensive network of blood vessels that allow

A

Rapid heat loss

48
Q

Furry mammals often have special networks of blood vessels for

A

Heat exchange located in areas of bare skin - this adaptation helps them live in hot desert environments

49
Q

What’s the body’s main site for heat exchange with the environment

A

The body’s surface

50
Q

Because tissues are poor conductors, heat is most effectively transferred in

A

The blood

51
Q

What is an important way to control the rate of heat loss to or gain from the surroundings?

A

Controlling the flow of blood to the skin

52
Q

In endotherms, warm blood from the body’s core typically loses heat to the environment as

A

It passes near the skin

53
Q

Vasoconstriction reduces

A

Blood flow and helps retain heat

54
Q

Opposite adaptation to jackrabbits

A

Arctic hares have shortened ears and thick, white fur to hep survive in harsh, frozen tundra

55
Q

What happens when core body temp is <37°C?

A

Thermoreceptors detect & send signal to hypothalamus
Hypothalamus send nerve impulses to muscles and sweat glands
Muscles -> shiver & muscles of skin arteriole walls constrict
- more heat generates, less water covers skin, less radiation & conduction of heat
Diagram on slide 29 if this isn’t clear!!

56
Q

What happens when core body temperature >37

A

Thermoreceptors detect & send signals to hypothalamus
Hypothalamus sends impulses to muscles, and sweat glands
Muscles - reduce activity & muscles of skin arteriole walls relax
-> less heat generated, more evaporation, and more radiation& conduction of heat

57
Q

Thermogenesis

A

Heat production

58
Q

Anatomical features for thermogenesis

A

Shivering & non shivering

59
Q

Shivering is

A

Muscle contractions to generate heat
Very effective short term
30-50% of the energy of muscle contraction is converted to heat

60
Q

What is non-shivering thermogenesis

A

Brown fat contains many mitochondria with special proteins that let them release energy from fuel molecules directly as heat instead of channeling it into formation of the energy carrier ATP

61
Q

Is shivering or non shivering thermogenesis more effective

A

Brown fat is more effective to generate heat

62
Q

What is insulation

A

Another way to minimize heat loss to the environment. Birds use feathers, and most mammals use hair or fur, to trap a later of air next to the skin and reduce heat transfer to the environment

63
Q

Marine mammals insulation

A

Blubber - a thick layer of fat

64
Q

In cold weather, birds

A

Fluff feathers and animals raise their fur to thicken the insulating layer

65
Q

Examples of behavioural regulations animals perform

A

Lizards sunbathing, elephants soaking themselves with water, seeking shade, etc

66
Q

What is hibernation

A

A dormant, inactive state in which normal body activities slow. They need little energy to stay alive and can live off fat stored in their body during long periods of hibernation

67
Q

What do animals do to get ready for hibernation

A

Eat more, and find or build shelter to hibernate in

68
Q

Hibernation heartbeats/breathing

A

Heartbeats slow & breathing almost stops - slow down metabolism to conserve energy

69
Q

What are light sleepers

A

Animals who do not truly hibernate, and are easily awakened during their winter slumbers. The animals breathe a little more slowly and lower their body temperature a few degrees.

70
Q

Migration is

A

The movement of animals in a group from one place to another and back

71
Q

Animals migrate for different reasons

A

Some to look for more food, or better climate & animals have specific times during the year that they migrate

72
Q

How do animals know where to migrate

A

Animals use their senses to determine direction
Some make mental maps using scent, sight, and/or hearing
Others use stars or sun

73
Q

At high ambient temperatures, effectiveness of heat loss via conduction and radiation

A

Decreases

74
Q

when ambient temperature exceeds body temperature by a lot, heat is

A

Gained

75
Q

The only effective mechanism for heat loss at high temperatures is

A

Evaporation of sweat and respiratory tract vaporization of water

76
Q

Total sweat vaporized from skin depends on

A

Surface area exposed to environment
Temperature and humidity of ambient air
Air currents about the body

  • most important factor is relative humidity
77
Q

Increasing steps of heat illness

A

Heat cramps -> heat syncope -> heat exhaustion -> heat stroke

78
Q

Hypothermia

A

Lowering of core body temperature
In humans, below 35°C

79
Q

It is important to monitor body temperature during and after procedures requiring anesthesia because of

A

The depressed hypothalamic response
- external heat sources are often fitted to surgical tables for the maintenance of body temperature
- when these are used, there must be assurance that injury to skin doesn’t occur

80
Q

When animals do not recover quickly after anesthesia, monitoring body temperature and provision of external heat is

A

Extremely important

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