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human physiology and exercise > thermoregulation > Flashcards

thermoregulation Flashcards

1
Q

what is the process of thermoregulation?

A
  • maintaining a constant core body temperature
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2
Q

what is the definition of heat?

A
  • energy that is transferred from an object at a higher temperature to a lower temperature object
  • dependent on volume/ mass
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3
Q

what is the definition of temperature?

A
  • quantitive measure of how hot/ cold an object is, or the intensity of heat in an object
  • independent of mass/ volume
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4
Q

what is the definition of specific heat capacity?

A
  • amount of heat energy it takes to change the temperature of different substances by same amount
  • specific heat of water greater than others so generate more heat before body temp rises by 1 degree
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5
Q

describe endotherms

A
  • heat is generated during metabolism
  • don’t rely on energy of sunlight
    e.g. humans
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6
Q

what is the percentage of energy wasted in physical activity compared to the amount that yields external work ?

A
  • 75 to 80% wasted as heat
  • 20 to 25% yields external work
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7
Q

what are humans described as?

A
  • homeotherms as they maintain body temperatures within very narrow limits
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8
Q

describe the difference between body core temperature and body surface temperature

A
  • body core temperature maintained within narrow limits whereas body surface temperature can vary
  • body core temp does fluctuate e.g. eating, exercise
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9
Q

can periphery of our bodies fluctuate?

A
  • yes because they contain less vital organs so no adverse effects
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10
Q

why are variations in surface temperature important?

A
  • bodies detect environmental changes early and signal appropriate response
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11
Q

what is the normal body core temp and how is it maintained?

A
  • 37 degrees maintained by hypothalamus as thermosensors in hypothalamus and skin send signals to effectors which carry out responses
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12
Q

describe link of body temp regulation to circadian rhythm

A
  • circadian fluctuation in body core temp of 1 degree
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13
Q

when is body temp lowest/ highest? what other factor may affect the temperature?

A
  • lowest during night
  • highest during day
  • seasonal rhythms
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14
Q

how does gender affect body tempersture?

A
  • in women body core temperature is higher during the second half of menstrual cycle due to progesterone
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15
Q

describe evaporation

A
  • loss of heat via sweating
  • only way we lose heat to environment when temp is higher than body
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16
Q

describe convection

A
  • movement of layer surrounding the skin
  • direct contact between a body and surrounding fluid
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17
Q

describe conduction

A
  • body can gain/ lose heat depending on temp of the adjacent surface
  • type of materials that bodies consist of affects rate at which heat is transferred
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18
Q

describe radiation

A
  • emission of heat in form of EM waves
  • body can either absorb or emit heat depending on ambient conditions
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19
Q

what is the thermoneutral zone ?

A
  • when we can maintain our homeostatic body temp through changes in vasomotor tone (vasodilation/ vasoconstriction)
  • without energy expenditure/ external influence
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20
Q

when is there a minimum metabolic rate?

A
  • when core temperature is within neutral zone
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21
Q

how is body temp maintained?

A
  • balancing of heat gain and heat loss
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22
Q

describe effect of temperature being too cooled vs too warm

A
  • too cooled= enzymatic reactions in bodies slow down so less mobile and at risk of losing consciousness
    -too warm = enzymes at risk of denaturing and losing function
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23
Q

describe mechanisms for heat loss

A
  • blood reaching the skin
  • sweating
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24
Q

describe physiological control of heat loss

A

thermosensors> central command > adrenal medulla> blood vessels dilate> sweat glands secrete fluid> heat loss to environment> body temp normal

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25
Q

when does vasodilation occur? what happens?

A
  • thermoregulatory response to heat
  • occurs in blood vessels in skin near extremities
  • happens due to less sympathetic stimulation/ release of Ach
26
Q

what does vasodilation support and what happens once at surface?

A
  • supports skin metabolism
  • once at surface, heat can be lost via radiation, conduction to environment
27
Q

describe eccrine sweat glands involvement in heat loss

A
  • deliver a hypotonic solution to skin’s surface; process of vaporisation removes heat from the body
28
Q

describe role of thermoreceptors in heat loss

A
  • sense changes in external temperature and signal this to hypothalamus which integrates info with other info e.g. blood temp> stimulates structures to initiate appropriate response
29
Q

when does sweating occur? what innervates it?

A
  • thermoregulatory response to heat
  • sweat glands innervated by cholinergic nerve fibres via stimulation of muscarinic receptors
  • catecholamines stimulate sweat production
30
Q

what does swear production rate affect?

A
  • composition of sweat with larger amounts of Na+ and Cl- being lost at high sweat rates
  • rate of evaporation influenced by relative humidity
31
Q

what are the two main sweat glands?

A
  • eccrine = most common
  • aporine = found in head follicle
32
Q

what processes occur during heat production ?

A
  • shivering thermogenesis
  • voluntary muscular activity
  • non- shivering thermogenesis
33
Q

when does vasoconstriction occur? what happens?

A
  • thermoregulatory response to cold
  • blood vessels in skin innervated by sympathetic adrenergic fibres
  • norephedrine acts on adrenergic fibres
  • if blood flow is stopped for a while it can lead to frost bite
34
Q

what is the hunting reaction?

A
  • protective measure to stop frostbite (ischaemic injury)
  • during long exposure to cold skin circulation shows intermittent periods of vasodilation
35
Q

describe shivering thermogenesis

A
  • thermoregulatory response to cold
  • involuntary muscular contraction releases heat due to ATP breakdown
  • all the energy contracted is converted to heat, no external work
36
Q

what is shivering the result of?

A
  • stimulation by somatic motor neurons
37
Q

what is non- shivering thermogenesis?

A
  • occurs from brown fat metabolism
  • important for children
38
Q

how is arrector pili muscle involved in heat conservation?

A
  • contracts to produce goose bumps as it pulls on hair follicles to create a small depression on skin’s surface so surrounding areas protrudes
39
Q

how do body hairs keep up warm?

A
  • trap pockets of insulating air so heat less likely to be lost to environment
  • piloerection occurs when sympathetic NS triggers body hair to stand erect
40
Q

what is subcutaneous fat involvement in heat conservation ?

A
  • good heat insulator so conducts heat poorly so when environment is cold it provides a layer of insulation to retain body heat
41
Q

what is hypothermia?

A
  • low body temperature
  • functions impacted when core body temperature is under 35 degrees
42
Q

what responses are insufficient in hypothermia?

A
  • normal peripheral vasoconstriction and shivering responses
  • so shivering becomes violent and muscle activity becomes slow
43
Q

what are the symptoms of hypothermia? how is it treated?

A
  • confusion, irritability, reduced respiratory rate
  • treated via rewarming but not rapid as can lead lead to circulatory failure and shock
44
Q

describe the body’s response at 36, 35, 33 and 29 degrees

A
  • 36> shivering, less strength and power
  • 35> max shivering+ decrease in performance
  • 33> cardiac arrythmia
  • 29> unconsciousness
45
Q

what is hyperthermia?

A
  • high body temperature; higher the body temperature means the more risk of damage to cells/ proteins
46
Q

describe mild hyperthermia compared to severe hyperthermia

A
  • mild= heat exhaustion
  • severe= heat stroke (failure of thermoregulation with body temperature over 40.6)
47
Q

what are the symptoms of hyperthermia?

A
  • dizziness, disorientation, dry skin, high heart rate, collapse
48
Q

how should hyperthermia be treated?

A
  • vigorously using measures to cool the body
  • rehydration
49
Q

what happens during exercise to body temperature?

A
  • body temp maintained higher> rest
  • ^ heat production set point resetting has implications for muscle contractions
  • activates heat loss mechanisms
50
Q

what does thermoregulation decreases? what is its capacity and what is it limited by?

A
  • decreases exercise capacity
  • thermoregulation capacity is finite
  • limited by homeostatic demands
51
Q

what is the reduction in endurance performance during self paced time trials in heat?

A
  • 2 to 25 percent
52
Q

what work to elevate the set point?

A
  • pyrogens are chemicals that induce fever as they are released into bloodstream by invading cells or own immune system
53
Q

what do pyrogens work to do?

A
  • elevate the hypothalamic set point to higher temperature
54
Q

what does resetting of our thermostat cause us to do?

A
  • rapidly generate heat in order to reach the new set point
  • results in pyrexia (fever)
55
Q

what happens in recovery of fever?

A
  • set point returns to its normal value
  • bodies engage in activities to lose excess heat
56
Q

what happens when the hypothalamic set point is elevated?

A
  • addition of layers, shivering, vasoconstriction, pale appearance
57
Q

what happens when the hypothalamic set point returns to normal?

A
  • removal of layers, sweating, vasodilation, flushed
58
Q

why may fevers be beneficial?

A
  • may assist the recovery process by enhancing activity of immune system
59
Q

describe acclimatisation

A
  • individual regulates body temperature efficiently
  • occurs via repeated exposure to heat either in hot climate ( 2 weeks) or use of environmental chambers (5-10 days)
60
Q

describe what acclimatised individuals will be able to do

A
  • sweat more and sooner
  • more diluted sweat (less electrolytes)
  • more blood flow to skin
  • increases blood volume/ stroke volume
  • decreased body core temp, HR, glycogen use and fatigue

human physiology and exercise (18 decks)

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