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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
What is haematocrit?
Ratio of volume of RBC to volume of blood total
26
What is EPO
Erythropoietin
27
What is role of SCUBA gear when breathing underwater?
Changes properties of gases inhaled and exhaled
28
What is impact of increasing atmospheric pressure on partial pressures of gases?
At 2 atmospheres, partial pressures of gases doubles At 3 atmospheres, partial pressures triples from 1 atm
29
What is relationship between atmospheres and depth in water below sea level?
1 atmosphere = sea level 2 atmosphere = 10 m below 3 atmosphere = 20 m below 5 atmosphere = 40 m below
30
What is PO2 of medical oxygen?
100% oxygen in air so PO2 of 760 mmHg
31
What is the PO2 at 5 atmospheres?
5 x 159 mmHg = 795 mmHg Similar to medical oxygen
32
What is effect of body exposure to elevated oxygen levels (like at 5 atmospheres)?
Can cause damage to respiratory membrane Is time/pressure dependant
33
Why is venous blood higher in CO2?
Because tissues unload CO2 produced by metabolism into blood so can be carried to lungs and exhaled
34
What is impact on the body of increased PCO2 at increased depth below sea level?
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
35
What is role of nitrogen in human physiology at sea level?
Does not participate - is an inert gas
36
What happens to nitrogen when atmospheric pressure rises?
Solubility of nitrogen increases Significant amounts begin to dissolve in plasma and carried around body
37
What causes nitrogen narcosis?
As PN2 increases in blood, N2 moves into ECF and tissue cells
38
What are symptoms of nitrogen narcosis?
Hallucinations and drunken actions
39
How do you reverse nitrogen narcosis ?
Reduce atmospheric pressure = shallower depths Solubility of N2 decreases and is exhaled via lungs
40
What are the "bends"?
Serious condition associated with nitrogen gas dissolving and bubbling out of plasma
41
When does the "bends" occur?
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
How can the "bends" be life threatening?
If gas bubbles form in vital parts of circulation (coronary, brain) = heart attack, stroke
43
What is treatment of the "bends"?
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
What is normal body temperature range?
36.5 - 37.5 deg C
45
What 2 zones are body temperature divided into?
Core temperature = skull, thoracic, abdominal cavities Shell temperature = skin
46
What is temperature range for core and shell temperature?
Core = constant Shell = vary substantially without ill effect
47
How is core temperature kept constant?
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
What mechanisms ensure body temperature remains constant?
heat production and heat loss are balanced
49
What is metabolic rate?
Bodys rate of energy output Total heat produced by all chemical rx and mechanical work of body
50
Define total metabolic rate
Total rate of kilocalorie consumption to fuel all ongoing activities (involuntary, voluntary)
51
How is basal metabolic rate measured?
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
What accounts for daily heat production?
60% basal metabolic rate 40% activity (incl skeletal muscle)
53
List 4 methods of heat production by body
1. Vasoconstriction of cutaneous vessels 2. Incr metabolic rate 3. Shivering 4. Behavioural mods
54
What hormones increase metabolic rate?
Adrenaline Thyroxine
55
What is chemical thermogenesis?
Increase metabolic rate stimulated by adrenalin
56
How does shivering occur?
Alter skeletal muscle tone
57
What is physical thermogenesis?
Shiverin by altering skeletal muscle tone
58
What behavioural modifications results in heat production?
Eating warm food/drinks Wearing warm clothes Huddling, hunching = reduce SA Incr physical activity = generate more heat
59
What is formula for body temperature balance?
External heat input + internal heat production = heat loss
60
What methods can you have external heat input?
Radiation Conduction
61
What methods are there fore heat loss?
Evaporation Radiation Conduction Convection
62
What receptors identify change in environmental temperature?
Peripheral thermoreceptors
63
What receptors identify change in core body temperature?
Central thermoreceptors
64
What do thermoreceptors send information to?
Hypothalamic thermoregulatory centre
65
What neurons are involved in response to increased body temperature?
Sympathetic cholinergic neurons
66
What is tissue and systemic response from sympathetic cholinergic neurons?
Sweat secretion = heat lost to evaporation Vasodilatation = heat lost to environment
67
What neurons are involved in hypothalamic response to decreased body temperature?
Sympathetic adrenergic & somatic motor neurons
68
What is effect of stimulated sympathetic adrenergic neurons?
Vasoconstriction of cutaneous BV = heat conserved Non shivering thermogenesis of brown fat = metabolic heat production
69
What is effect of stimulating somatic motor neurons?
Shivering thermogenesis on skeletal muscles = metabolic heat production
70
How can the body maximise heat loss?
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
How can you minimise heat production?
Diminished food intake to lessen obligatory heat production Decreased physical activity
72
What can minimise heat loss?
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
What can maximise heat production?
Shivering thermogenesis Non shivering thermogenesis Increased voluntary activity
74
What happens to heat loss with relative humidity high?
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
What behavioural modifications help with heat loss in high relative humidity?
Reduced activity, seek shake, prostrate (lying flat) posture, wear loose light clothing
76
What organ controls body temperature?
Hypothalamus - thermoregulatory centre
77
What centres are inside thermoregulatory centre in hypothalamus?
heat loss centre heat promoting centre
78
What peripheral input is given to thermoregulatory centre?
Peripheral thermoreceptors on shell/skin
79
Describe role of hypothalamus in body temperature regulation
Hypothalamus behaves like thermostat and responds by sending out heat producing and heat losing reflex messages
80
Describe osmoregulation
Regulation of water and ionic balance in body
81
What controls and monitors osmoregulation?
Controlled by kidneys Monitored by hypothalamus
82
Describe balance of osmoregulation and thermoregulation.
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
Describe impact to water in body during heat stress.
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
What is insensible loss of water?
Occurs because we breathe air
85
How can we increase water loss in arid conditions?
Increase loss through respiratory membranes
86
What is effect of diving bradycardia?
Reduction in cardiac output Intense peripheral vasoconstriction Concomitant rise in BP
87
What is cause of diving bradycardia?
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
What actions bring on diving bradycardia?
Apnoea Cold air on face Effect reinforced by face immersion in water
89
What factors have been implicatede in diving bradycardia response?
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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