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Environmental extremes > L1: Thermoregulation > Flashcards

L1: Thermoregulation Flashcards

1
Q

What is the survival hierarchy?

A
  1. Lack of oxygen
  2. thermal imbalance
  3. Fluid imbalance
  4. Energy imbalance
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2
Q

What happens to metabolism when temperature changes?

A

Metabolism increases as temperature decreases. this is achieved by shivering and non-shivering thermogenesis

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3
Q

What happens to heart rate in response to temperature change?

A

Heart rate increases in response to heat. This is to increase blood flow to the peripheral tissues

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4
Q

What is the prescriptive zone?

A

The range of ambient temperature that the core temperature is unaffected by. After the prescriptive zone core temperature will increase

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5
Q

How does exercise affect the prescriptive zone?

A

intensity of exercise can decrease the needed ambient temperature to cause elevated core temp

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6
Q

What occurs at around 37 - 41 degrees celsius?

A

heat therapy

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7
Q

what happens above 41 degree celsius core temperature?

A

Heat stroke, brain damage, organ failure

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8
Q

at what temperature is death via heat imminent

A

> 45 degrees

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9
Q

Describe the thermoregulation model

A
  1. Afferent feedback from skin sensors to the hypothalamus
  2. pre-optic nuclear
  3. Different centers control different physiological functions.
  4. the difference in temperature from set point determines severity of response.
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10
Q

What are skin temperature sensors?

A

free nerve endings

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11
Q

What are the channels responsible for temperature sensitivity in skin sensors?

A

Thermo-transient receptor channels (thermo-TRP channels)

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12
Q

How do skin sensors detect specific temperatures?

A
  1. Thermo-TRP channels are sensitive to different ambient temperatures.
  2. Cold sensors detect low temperatures and increase impulse frequency in response whilst hot sensors do the opposite.
  3. Combination of receptors are used to detect overlap to identify exact temperature.
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13
Q

what differs between adults and new borns in temperature regulation?

A
  1. Large amounts of brown adipose tissue located inter-scapular and peri-renal increases non-shivering thermogenesis
  2. Shivering is limited and undeveloped in new borns
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14
Q

what gland is responsible for heat loss via sweat evaporation?

A

eccrine glands

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15
Q

How is eccrine gland activity changed?

A

Heat acclimatisation in the first 2 years of life determines that number of eccrine glands activated.

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16
Q

How many eccrine glands are on the human body?

A

2 - 5 million

17
Q

How is distribution of sweat changed?

A
  1. Temperature increase peripheral sweat, back sweat and head sweat.
  2. Fitness (fitter the more sweat production)
  3. Age (Sweating distibution changes due to poor circulation and inactivity)
  4. Gender (males sweat more than females)
18
Q

How is peripheral blood flow altered in response to heating

A

Arterio-venous anastomoses close in response to heat. Redirect a large amount of blood flow to the skin surface.
Counter-current is avoided
low resistance

19
Q

How is the relative distribution of blood to different locations effected in response to heat?

A
  • Skin receives massive increase in blood flow
  • Heart blood flow increases due to increased activity and greater heat production in the area
  • Muscles slightly increase
  • Internal organs decrease in blood due to prioritisation
20
Q

How does a fever occur include the stages?

A
  1. Latent stage
    delayed identification of pathogen and immune response
  2. Rising phase
    Set point increases and physiological responses occur inorder to reach new temperature (shivering)
  3. Plateu phase
    temperature set point is reached
  4. Fever lysis
    Set point drops back down and physiological response of cooling occurs
21
Q

What is internal body temperature?

A

Stable body temperature that is not influence by the environment and remains consistent in healthy state

22
Q

How does conduction and convection occur between cells and the blood.

A

Conduction: Thermal gradient between internal and external
convection: fluid movement of blood

23
Q

What are the therm-physical properties of a cell?

A
  • Density
  • Conductivity
  • heat of cell
24
Q

What sensors of sensitive to temperature change: core or peripheral?

A

Core

25
Q

What are the temperature effectors

A
  1. Vasodilation/vasoconstriction
  2. Eccrine gland activation
  3. Muscle activation of shivering
  4. Increased metabolism
26
Q

What hormones control 1. vasodilation 2. eccrine gland activation 3.increase metabolism?

A
  1. Nora-adrenaline
  2. Acetylcholine neurotransmitter
  3. Thyroxine and Nora-adrenaline/adrenaline
27
Q

What prevents competing effects of peripheral cold detection and core warm thermo detection?

A

Inhibitory pathways between the anterior and posterior hypothalamus

28
Q

What impacts the strength of the afferent impulses from thermosensors of the skin?

A
  • difference between skin and core temperature
29
Q

How does exercise affect set-points

A

Higher set point during exercise

30
Q

How does the hierarchy of systems effect thermoregulation in the extremes?

A
  1. Sweating is maintained even when dehydrated in hot temperatures
  2. temperature is maintained in the cold even when starvation
  3. Blood pressure is reduced to maintain vasodilation (causing syncope)
31
Q

what carries afferent impulses from thermoreceptors?

A

Non-myelinated C-fibres or Myelinated A fibres

32
Q

What is the role of the posterior hypothalamus

A

responds to decreased core temperatures detected by thermoreceptors in the anterior hypothalamus.
Increases effectors for cooling

33
Q

What is the role of the sympathetic adranomedullary system?

A

motor supply to the adrenal medulla to releases adrenaline and noro-adrenaline into circulation.

34
Q

How does shivering work?

A

Asynchronous contractions of muscle fibres in flexor and exterior muscles. Production of heat by increasing metabolic rate but no overall muscle work.

35
Q

What happens to sweat during acclimatisation to heat

A
  • maximum sweat production increases
  • sweating increases at a lower skin and core temperature
  • greater peripheral sweating
36
Q

What is hidromeiosis?

A

reduction of sweat associated with wetting of skin often caused by humid climates or water immersion. causes sweat gland fatigue.

37
Q

What are the THREE different behavioural thermoregulation?

A
  1. Behavioural changes
  2. Behavioural acclimatisation
  3. Technical regulation (building shelter)
38
Q

What is thermal stress parameters?

A

Composed of 6 parameters:

  1. Air temperature
  2. Radiant temperature
  3. Air velocity
  4. Air humidity
  5. Clothing insulation
  6. Metabolic heat

Environmental extremes (4 decks)

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