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HUMB3001 > W2 - Intro to Environmental Physiology > Flashcards

W2 - Intro to Environmental Physiology Flashcards

1
Q

What is purpose of homeostatic mechanisms?

A

Maintain their internal environment in face of different external environments

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2
Q

How does atmospheric pressure change?

A

Changes with height and depth with respect to sea level

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3
Q

Where do you get reduced atmospheric pressure?

A

At altitude

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4
Q

Where do you get increased atmospheric pressure?

A

At depth

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5
Q

What is the effect of atmospheric pressure on the body?

A

Affects amount of O2 that is delivered to cells and amount of CO2 that can be removed from tissues

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6
Q

What level of O2 is in atmosphere at sea level?

A

21% of atmosphere is O2

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7
Q

What is effect on body when we ascend above sea level?

A

Atmospheric pressure declines
Affects relative availability of O2 that can be delivered to tissues

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8
Q

What is effect on body when we descend below sea level?

A

Breathe gases at higher pressures to offset the increase in ambient pressure
Affects behaviour of gases in tissues

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9
Q

What is partial pressure of O2 in oxygenated blood?

A

105 mmHg

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10
Q

What is partial pressure of CO2 in oxygenated blood?

A

40 mmHg

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11
Q

What is partial pressure of N2 in oxygenated blood?

A

569 mmHg

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12
Q

What is partial pressure formula for atmospheric air at sea level?

A

760 mmHg = PO2 + PCO2 + PN2 + PH2O

760 mmHg = 159 + 0.3 + 597 + 0

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13
Q

What is partial pressures of gases in tissue cells v. oxygenated blood?

A
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14
Q

What is atmospheric pressure reduced to at 10,000m altitude?

A

226 mmHg from 760 mmHg

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15
Q

How much O2, CO2, N2 is at 10,000m above sea level?

A

Pair = 226 mmHg

PO2 = 0.21 * 226 = 47 mmHg

PCO2 = 0.0003 * 226 = 0.7 mmHg

PN2 = 0.79 * 226 = 172 mmHg

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16
Q

Describe relationship between altitude above sea level and partial pressure of oxygen.

A
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17
Q

What happens to PO2 when we breathe in?

A

PO2 reduces from 159 mmHg to 100 mmHg when air mixes with dead space and old air

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18
Q

What is PO2 of venous blood leaving the lungs?

A

100 mmHg

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19
Q

What is PO2 of venous blood leaving lungs at high altitude (10km)?

A

35 mmHg

Since PO2 is 47 mmHg in air at altitude

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20
Q

What is body’s response to high altitude?

A

Person will suffer from hypoxia = insufficient oxygen

Body will respond by incr depth, rate of breathing = hyperventilate

To increase oxygen content of blood and therefore oxygen getting to tissues

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21
Q

What are symptoms of hypoxia?

A

Tiredness = lethargy

Light headache, confusion, fainting

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22
Q

What is impact to body if exposure to reduced PO2 is prolonged?

A

Body will make long term adjustment to increase oxygen carrying capacity

% of RBC in blood will incr

mitochondria in cells incr to improve efficiency of oxidative phosphorylation

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23
Q

What receptors detect decreased PO2?

A

Chemoreceptors in carotid sinus

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24
Q

What is impact of chemoreceptors detecting decreased PO2?

A

EPO (erythropoieton) secretion stimulated by kidneys

EPO incr RBC prodn in bone marrow = incr packed cell volume

Direct relationship between PO2 blood, PO2 air, haematocrit

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25
Q

What is haematocrit?

A

Ratio of volume of RBC to volume of blood total

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26
Q

What is EPO

A

Erythropoietin

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27
Q

What is role of SCUBA gear when breathing underwater?

A

Changes properties of gases inhaled and exhaled

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28
Q

What is impact of increasing atmospheric pressure on partial pressures of gases?

A

At 2 atmospheres, partial pressures of gases doubles

At 3 atmospheres, partial pressures triples from 1 atm

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29
Q

What is relationship between atmospheres and depth in water below sea level?

A

1 atmosphere = sea level

2 atmosphere = 10 m below

3 atmosphere = 20 m below

5 atmosphere = 40 m below

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30
Q

What is PO2 of medical oxygen?

A

100% oxygen in air so PO2 of 760 mmHg

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31
Q

What is the PO2 at 5 atmospheres?

A

5 x 159 mmHg = 795 mmHg

Similar to medical oxygen

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32
Q

What is effect of body exposure to elevated oxygen levels (like at 5 atmospheres)?

A

Can cause damage to respiratory membrane

Is time/pressure dependant

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33
Q

Why is venous blood higher in CO2?

A

Because tissues unload CO2 produced by metabolism into blood so can be carried to lungs and exhaled

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34
Q

What is impact on the body of increased PCO2 at increased depth below sea level?

A

As CO2 content of air increases, increases CO2 in alveolar air, reduces concentration gradient

Hinders diffusion of CO2 from blood into lungs

Person experiences acidosis

Stimulates increase in rate and depth of breathing to get rid of higher than usual PCO2

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35
Q

What is role of nitrogen in human physiology at sea level?

A

Does not participate - is an inert gas

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36
Q

What happens to nitrogen when atmospheric pressure rises?

A

Solubility of nitrogen increases

Significant amounts begin to dissolve in plasma and carried around body

37
Q

What causes nitrogen narcosis?

A

As PN2 increases in blood, N2 moves into ECF and tissue cells

38
Q

What are symptoms of nitrogen narcosis?

A

Hallucinations and drunken actions

39
Q

How do you reverse nitrogen narcosis ?

A

Reduce atmospheric pressure = shallower depths

Solubility of N2 decreases and is exhaled via lungs

40
Q

What are the “bends”?

A

Serious condition associated with nitrogen gas dissolving and bubbling out of plasma

41
Q

When does the “bends” occur?

A

When person ascends too rapidly after being at depth

If rate of ascent is too fast then as atmospheric pressure is reduced, N2 gas comes out of solution in BV

Leads to gas bubble formation

42
Q

How can the “bends” be life threatening?

A

If gas bubbles form in vital parts of circulation (coronary, brain) = heart attack, stroke

43
Q

What is treatment of the “bends”?

A

Recompression chambers used to return person to atmospheric pressure

Slowly reduce pressure allowing time for N2 to be exhaled until reaching normal atmospheric pressure

44
Q

What is normal body temperature range?

A

36.5 - 37.5 deg C

45
Q

What 2 zones are body temperature divided into?

A

Core temperature = skull, thoracic, abdominal cavities

Shell temperature = skin

46
Q

What is temperature range for core and shell temperature?

A

Core = constant

Shell = vary substantially without ill effect

47
Q

How is core temperature kept constant?

A

Cool blood from extremities mixing with warm blood in body core

Stops core temp from rising

Hot weather: core temp relies on blood flow close to skin for heat dissipation

48
Q

What mechanisms ensure body temperature remains constant?

A

heat production and heat loss are balanced

49
Q

What is metabolic rate?

A

Bodys rate of energy output

Total heat produced by all chemical rx and mechanical work of body

50
Q

Define total metabolic rate

A

Total rate of kilocalorie consumption to fuel all ongoing activities (involuntary, voluntary)

51
Q

How is basal metabolic rate measured?

A

Person who has not eaten for 12h and is reclining in physically and mentally relaxed state at ambient temp of 20-25 deg C

52
Q

What accounts for daily heat production?

A

60% basal metabolic rate

40% activity (incl skeletal muscle)

53
Q

List 4 methods of heat production by body

A
  1. Vasoconstriction of cutaneous vessels
  2. Incr metabolic rate
  3. Shivering
  4. Behavioural mods
54
Q

What hormones increase metabolic rate?

A

Adrenaline

Thyroxine

55
Q

What is chemical thermogenesis?

A

Increase metabolic rate stimulated by adrenalin

56
Q

How does shivering occur?

A

Alter skeletal muscle tone

57
Q

What is physical thermogenesis?

A

Shiverin by altering skeletal muscle tone

58
Q

What behavioural modifications results in heat production?

A

Eating warm food/drinks

Wearing warm clothes

Huddling, hunching = reduce SA

Incr physical activity = generate more heat

59
Q

What is formula for body temperature balance?

A

External heat input + internal heat production = heat loss

60
Q

What methods can you have external heat input?

A

Radiation

Conduction

61
Q

What methods are there fore heat loss?

A

Evaporation

Radiation

Conduction

Convection

62
Q

What receptors identify change in environmental temperature?

A

Peripheral thermoreceptors

63
Q

What receptors identify change in core body temperature?

A

Central thermoreceptors

64
Q

What do thermoreceptors send information to?

A

Hypothalamic thermoregulatory centre

65
Q

What neurons are involved in response to increased body temperature?

A

Sympathetic cholinergic neurons

66
Q

What is tissue and systemic response from sympathetic cholinergic neurons?

A

Sweat secretion = heat lost to evaporation

Vasodilatation = heat lost to environment

67
Q

What neurons are involved in hypothalamic response to decreased body temperature?

A

Sympathetic adrenergic & somatic motor neurons

68
Q

What is effect of stimulated sympathetic adrenergic neurons?

A

Vasoconstriction of cutaneous BV = heat conserved

Non shivering thermogenesis of brown fat = metabolic heat production

69
Q

What is effect of stimulating somatic motor neurons?

A

Shivering thermogenesis on skeletal muscles = metabolic heat production

70
Q

How can the body maximise heat loss?

A

Vasodilatation of cutaneous BV

Increased sweating

Fans to incr convective heat loss

Immersion in water to inctr conductive heat loss

Stay out of sun to prevent radiant heat gain

Remove clothes

71
Q

How can you minimise heat production?

A

Diminished food intake to lessen obligatory heat production

Decreased physical activity

72
Q

What can minimise heat loss?

A

Vasoconstriction of cutaneous BV

Lack of sweating

Adding layers of protective clothing

Curling up to minimise exposed surface

Stand near heat source to enhance radiant heat gain

73
Q

What can maximise heat production?

A

Shivering thermogenesis

Non shivering thermogenesis

Increased voluntary activity

74
Q

What happens to heat loss with relative humidity high?

A

Evaporation will not occur as effectively, heat loss is decreased

More difficult to lose body heat to environment at high RH than in arid condition

75
Q

What behavioural modifications help with heat loss in high relative humidity?

A

Reduced activity, seek shake, prostrate (lying flat) posture, wear loose light clothing

76
Q

What organ controls body temperature?

A

Hypothalamus - thermoregulatory centre

77
Q

What centres are inside thermoregulatory centre in hypothalamus?

A

heat loss centre

heat promoting centre

78
Q

What peripheral input is given to thermoregulatory centre?

A

Peripheral thermoreceptors on shell/skin

79
Q

Describe role of hypothalamus in body temperature regulation

A

Hypothalamus behaves like thermostat and responds by sending out heat producing and heat losing reflex messages

80
Q

Describe osmoregulation

A

Regulation of water and ionic balance in body

81
Q

What controls and monitors osmoregulation?

A

Controlled by kidneys

Monitored by hypothalamus

82
Q

Describe balance of osmoregulation and thermoregulation.

A

After prolonged period of body being heat stressed particularly at high RH, evaporation is primary cooling mechanism

Body begins to dehydrate

Decision on whether more important to osmoregulate or thermoregulate

83
Q

Describe impact to water in body during heat stress.

A

Obligate water loss in metabolism (incl urine production) and insensible loss, person will die of dehydration

Ability concentrate urine is limited but must continue to remove nitrogenous waste

Fluid is pulled from all compartments to keep blood volume high, maintain BP = occurs expense of tissue cells needing water to function

84
Q

What is insensible loss of water?

A

Occurs because we breathe air

85
Q

How can we increase water loss in arid conditions?

A

Increase loss through respiratory membranes

86
Q

What is effect of diving bradycardia?

A

Reduction in cardiac output

Intense peripheral vasoconstriction

Concomitant rise in BP

87
Q

What is cause of diving bradycardia?

A

Reduction in oxygen consumption at a time of oxygen deprivation and redirection of blood from peripheries to maintain oxygen supply to vital organs (heart, brain)

88
Q

What actions bring on diving bradycardia?

A

Apnoea

Cold air on face

Effect reinforced by face immersion in water

89
Q

What factors have been implicatede in diving bradycardia response?

A

Cutaneous cold receptors on face

Proprioceptors in neck

Changes in intrathoracic pressure

Asphyxial factors (low PO2, high PCO2)

HUMB3001 (8 decks)

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