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Biomedical Physiology > Thermoregulation > Flashcards

Thermoregulation Flashcards

1
Q

What is a homeotherm?

A

An organism which maintains a constant internal temperature regardless of the external influence

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2
Q

What is a poikilotherm?

A

An organism whose internal temperature changes with ambient temperature

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3
Q

What is heat a result of?

A

A by-product of metabolism

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4
Q

How do homeothermic animals regulate a constant internal temperature?

A

Regulate rate of heat produced and heat loss to control the overall body temperature

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5
Q

There are limits to thermoregulatory mechanisms and two issues can arise if the temperature is too high or too low, what are these?

A

Too high - hyperthermia

Too low - hypothermia

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6
Q

What is hypothermia?

A

Abnormally low body temperature

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7
Q

What is hyperthermia?

A

Dangerously high body temperature

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8
Q

Why is thermoregulation important?

A

For cellular function - homeostasis ensures optimal temperature for cellular metabolism

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9
Q

What is the normal body temperature?

A

37 degrees

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10
Q

List five factors which would affect the normal body temperature

A
  1. diurnal variation
  2. menstrual cycle
  3. exercise
  4. age
  5. ambient temperature
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11
Q

What is diurnal variation?

A

the variation between a high temperature and a low temperature that occurs during the same day

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12
Q

At what temperatures would you die? Max and min please lol

A

max would be 43ish and min would be 26 degrees

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13
Q

What occurs when the the body overheats?

A

Nerve malfunction and protein denaturation

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14
Q

At what temperature would there be body convulsions?

A

41 degrees

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15
Q

What temperature is the upper limit compatible with life?

A

43.3 degrees

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16
Q

What occurs when the body cools?

A

The metabolic activity decreases but the tissues may withstand transient substantial cooling

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17
Q

Overheating is considered more serious than cooling, true or false?

A

True

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18
Q

The body temperature differs between which two regions?

A

The core body temperature differs from the shell temperature

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19
Q

What is included in the core body temperature? Which regions?

A

The CNS, abdominal and thoracic cavities

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20
Q

How would you describe the temperature regulation and general temperature of the core regions?

A

Precisely regulated and the highest temperature between the to, roughly 37.8 degrees

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21
Q

What regions are included within the shell temperature|?

A

Skin and subcutaneous fat, and basically the outer parts lol

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22
Q

What temperature range does the shell temperature fluctuate between?

A

Around 20 degrees to 40 degrees

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23
Q

How is heat exchanged between the core and the shell regions of the body?

A

By blood homie x

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24
Q

What is required for the heat in the body to be balanced, this is basically a btec question.

A

The heat input must equal the heat output

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25
Q

Where may you gain heat from?

A

Internal heat production and the external environment

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26
Q

Where may you lose heat to?

A

To the environment

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27
Q

If the heat input and heat output is not equal, we have a disruption of the

A

HEAT BALANCE (btec question once again, sorry)

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28
Q

What are the four mechanisms of heat transfer?

A

Radiation, conduction, convection and evaporation

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29
Q

Describe what radiation is?

A

The emission of heat energy from the surface of a warm body via em waves

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30
Q

If the skin temperature is greater than the environmental temperature what occurs via radiation?

A

Heat is lost to the surroundings - so it cools the bod down a bit basically

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31
Q

Describe what the mechanism of heat transfer conduction involves?

A

The transfer of heat between two objects in direct contact

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32
Q

What two factors does heat transfer via conduction depend on?

A

On the temperature difference and the conductivity of the objects

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33
Q

Describe the process of convection

A

It is the transfer of heat by air/ water currents. The heat is conducted to the air immediately next to the skin

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34
Q

What is a convection current?

A

Warm air rises and is replaced by cool air,

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35
Q

On what kind of day would you expect more heat loss by convection currents?

A

On a windy day

36
Q

What is evaporation?

A

The conversion of water from a liquid form to a gas form

37
Q

Why does evaporation cool the body down?

A

Because it requires thermal energy which is absorbed from the skin which obvs cools down the body

38
Q

How would you describe the process of insensible water loss by evaporation?

A

It is a continuous (passive) process

39
Q

How can water be lost ‘insensibly’, under the category of insensible loss?

A

Respiratory airways (air is humidified) and the skin

40
Q

What nervous system regulates sensible loss?

A

The sympathetic nervous system

41
Q

Sensible water loss includes what process by which glands?

A

Sweating by eccrine sweat glands

42
Q

How much water would you normally expect to lose per day?

A

100 ml a day

43
Q

How much water would you expect to lose on a hot day?

A

1.5 litres a day

44
Q

How much water would you expect to lose with vigorous exercise?

A

4 litres per day

45
Q

What is the humidity?

A

The amount of water vapour present in the air

46
Q

If the relative humidity is high, this means the air is almost fully saturated with h2o, how would this affect the body in terms of thermoregulation?

A

There would be limited evaporative heat loss

47
Q

Which two ways does the body get heat input internally?

A

Oxidation of fuel and utilisation of ATP

48
Q

How efficient is oxidation of fuel, and how efficient is the utilisation of ATP?

A

50% efficiency for the oxidation of fuel and 25% efficiency for the utilisation of ATP

49
Q

How does the body get heat input externally?

A

From the environment

50
Q

How does the body lose heat?

A

Externally, by radiation, conduction and convection

51
Q

How much of heat is lost by radiation?

A

50%

52
Q

How much of heat is lost by conduction?

A

A small amount

53
Q

How much heat is lost by convection?

A

A significant amount

54
Q

What is the only mechanism of heat loss on a hot day?

A

By evaporation depending on relative humidity

55
Q

What is the thermoregulatory integrating centre?

A

The hypothalamus

56
Q

What is the posterior region of the hypothalamus activated by?

A

By the cold

57
Q

What is the anterior region of the hypothalamus activated by?

A

By the heat

58
Q

How do thermoreceptors work?

A

They get afferent input to the hypothalamus

59
Q

There are central and peripheral thermoreceptors, what are they?

A

The central would be the brain, spinal cord and internal organs, the peripheral would be the skin

60
Q

What is the aim of the skin vasomotor responses?

A

To alter the temperature gradient between the skin and the environment

61
Q

The radius of blood vessels determines what?

A

The blood flow obviously

62
Q

Blood flow can very between which ranges per minute?

A

400-2500ml/min

63
Q

Which sub division of the sympathetic nervous system is involved in vasoconstriction and vasodilation?

A

The sympathetic nervous system

64
Q

Describe vasoconstriction

A

There is a smaller diameter, greater resistance, lower blood flow, lower skin temp, lower conductive and radiative heat loss, conserves heat

65
Q

Describe vasodilation

A

Greater diameter, lower resistance, greater blood flow, higher skin temp, higher conductive and radiative heat loss

66
Q

What does shivering do when you are cold as a method of heat conservation and heat producing?

A

Shivering is heat producing as obvs the skeletal muscles move

67
Q

What are the three effectors involved in thermoregulation?

A
  1. Peripheral blood vessels
  2. Sweat glands – eccrine
  3. Skeletal muscles
68
Q

How does the effector the peripheral blood vessels respond

A

Peripheral blood vessels
• vasoconstriction / vasodilation alters BF to skin
•&raquo_space; control conductive & radiative heat loss

69
Q

How does the effector, the sweat glands respond

A

Sweat glands - eccrine
• control evaporative heat loss
• sweat production (sympathetic control)

70
Q

How does the effector the skeletal muscles respond?

A

Shivering - increase in muscle tone
• rapid involuntary rhythmic contractions (10-20/sec)
• ALL energy liberated is converted to heat
• 2-5 fold increase in heat within secs/mins

71
Q

Changes in skin temperature are monitored by what?

A

By peripheral thermoreceptors in the skin

72
Q

Changes in the core temperature is monitored by what?

A

By central thermoreceptors in the hypothalamus, abdominal organs,

73
Q

Define fever

A

The elevation of blood temperature as a result of infection/inflammation

74
Q

What triggers fever?

A

Infection or inflammation

75
Q

What happens to white blood cells when one has fever?

A

They proliferate and secrete chemical substances

76
Q

What are the chemical substances that while blood cells release when one has fever?

A

Endogenous pyrogens - fever inducers

77
Q

What do endogenous pyrogens stimulate the release of?

A

Of prostaglandins

78
Q

What effect do prostaglandins have on the body?

A

They increase the hypothalamic set point

79
Q

What is the effect of the increasing of the set temperature by the hypothalamus?

A

The body thinks its too cold, involuntary and voluntary heat production mechanisms begin

80
Q

What is a common symptom of the onset of fever?

A

Feeling cold

81
Q

Fever is an intentional response of the body and not a failure of the thermoregulatory system, why?

A

A higher temperature augments the immune response

82
Q

What is the most common cause of hypothermia?

A

Exercise

83
Q

Explain how exercise induced hypothermia takes place

A

As a physical consequence of the tremendous heat load generated by exercising muscles, body temperature begins to rise during the initial stage, stabilises, and then maintained at a higher level during exercise several degrees above resting set point

84
Q

Explain how hyperthermia can occur pathologically?

A

Due to dysfunction of the thyroid gland, medulla or brain lesions

85
Q

How can hyperthyroidism caused hyperthermia?

A

An increase of thyroid hormone, an increased basal metabolic rate, increased heat production

86
Q

How does aspirin act to break a fever?

A

Aspirin reduces a fever by inhibiting the synthesis of prostaglandins

87
Q

Why does aspirin not lower the temperature in a non febrile individual?

A

In the absence of endogenous pyrogen, prostaglandins are not present in the hypothalamus in appreciable quanitites

Biomedical Physiology (19 decks)

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