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A Physiology > 8.10. Thermoreceptors. Thermoregulation. Regulation of the circulation of the skin. > Flashcards

8.10. Thermoreceptors. Thermoregulation. Regulation of the circulation of the skin. Flashcards

1
Q

I. THERMORECEPTORS
1. Which system is responsible for the mediation of heat sensation (+ pain sensation)?

A

The anterolateral (spinothalamic) system

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2
Q

I. THERMORECEPTORS
2. What is the role of The anterolateral (spinothalamic) system?

A

The anterolateral (spinothalamic) system is responsible for the mediation of heat sensation (+ pain sensation)

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3
Q

I. THERMORECEPTORS
3. What types of fibers are heat and pain sensing fibers?

A

free nerve endings

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4
Q

I. THERMORECEPTORS
4. What makes the free nerve endings specific to certain sensation?

A
  • What makes the free nerve endings specific to a certain sensation are ion channels
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5
Q

I. THERMORECEPTORS
5. What are the characteristics of TRP channels?

A

TRP channels = transient receptor potential channels
- TPR channels are cation channels => opened by hot temperatures + acidic pH

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6
Q

I. THERMORECEPTORS
6. Describe non-adapting receptors that recognize thermal sensation

A

3 classes of non-adapting receptors recognize thermal sensation, which results from difference between external temperature of air and objects containing normal skin temperature (34 degrees)

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7
Q

II. THERMOREGULATION
1. Is the temperature of body the same everywhere?

A

Temperature of the body is not exactly the same throughout

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8
Q

II. THERMOREGULATION
2. Describe the core temperature?

A
  • Core temperature = constant
  • The brain, heart/chest, abdominal cavity have a core temperature of 37°C
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9
Q

II. THERMOREGULATION
3. What happen to the temperature of body if you are in a cooler environment?

A
  • Skin + extremities have lower temperatures (<37°C)
  • The brain, heart/chest, abdominal cavity have a core temperature of 37°C
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10
Q

II. THERMOREGULATION
4. What happen to the temperature of body if you are in a warmer environment?

A

If you are in a warmer environment, f.ex 30°C
=> large portion of body will also have same temperature as core temperature

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11
Q

II. THERMOREGULATION
5. Why is thermoregulation important?

A

Thermoregulation is important in regulating the core temperature in presence of a variable environment

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12
Q

II. THERMOREGULATION
6. Describe the 37 degree Celsius in terms of thermoregulation

A

37°C is the normal ‘’set-point value’’ that is encoded in the CNS as the optimal temperature value the body will strive to maintain
=> works like a thermostat

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13
Q

II. THERMOREGULATION
7. What is the normal range of core temperature in order to be compatible with life?

A

Core temperature must be between 30 – 42°C in order to be compatible with life

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14
Q

II. THERMOREGULATION
8. What happen if core temperature below 30°C?

A

Core temperature below 30°C:
=> primarily affects the function of heart – most sensitive to cold
=> different types of arrythmias will occur

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15
Q

II. THERMOREGULATION
9. What happen if core temperature above 42°C?

A

Core temperature higher than 42°C:
=> primarily affects the function of the brain
=> abnormal reflexes occur + thermoregulation is further impaired due to CNS malfunction

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16
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10A. What are the 2 main processes leading to increased body temperature?

A
  1. Chemical heat production
  2. Physical heat uptake
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17
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10B. What is chemical heat production?

A

metabolism of the organism produces chemical heat

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18
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10B. What is chemical heat production?

A

metabolism of the organism produces chemical heat

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19
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10C. What are the 2 main chemical processes that produce heat?

A
  1. Non-shivering heat production
  2. Shivering heat production
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20
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10D. Describe non-shivering heat production

A

Non-shivering heat production: brown adipose tissue + major organs (heart, kidney, liver, brain)

  1. Brown adipose tissue: professional heat-producing tissue. Brown adipocytes are more common in newborns, while beige adipocytes are more common in adults
  2. Major organs: have a high BMR that contributes to core body temperature
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21
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10E. Describe shivering heat production

A
  • Skeletal muscle is responsible for this.
  • When core temperature drops, shivering reflex is triggered to maintain homeostasis.
  • Skeletal muscle begin to shake in small movements -> increased muscular activity -> generation of heat
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22
Q

II. THERMOREGULATION - Processes leading to increased body temperature
10F. Describe physical heat uptake

A

Requires higher air temperature than the temperature of skin
=> must be above 34°C (skin temperature) = only useful in hot environment

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23
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11A. What are the 2 main processes leading to decreased body temperature?

A
  1. Physical heat loss
  2. Evaporation
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24
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11B. Describe the physical heat loss

A
  • Physical heat loss: these are passive processes. The determinant is the pressure gradient between environment and body.
  • Heat will be transferred from higher to lower temperature
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25
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
II. THERMOREGULATION - Processes leading to decreased body temperature
11C. What are the 3 main processes of physical heat loss?

A
  1. Convective
  2. Conductive
  3. Radiation
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26
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11C1. What is convective?

A

This is how the wind will cool the body down.
=> Moving air removes radiated heat

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27
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11C2. What is conductive?

A

Heat is transferred to environment by direct contact

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28
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11C3. What is radiation?

A

Emission of electromagnetic radiation

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29
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11D. What is evaporation?

A
  • Loss of heat by evaporation of water.
  • Does not depend on temperature gradient, but humidity of the air
30
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11E. What are the 2 main processes of evaporation?

A
  1. Perspiration insensibles
  2. Perspiration sensibles
31
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11F. What is Perspiration insensibles?

A

Perspiration insensibles: obligate heat loss we cannot regulate
-> happens during breathing (15%) + skin (85%)
-> about 1L of water/day evaporated

32
Q

II. THERMOREGULATION - Processes leading to decreased body temperature
11G. What is Perspiration sensible?

A

sweating (can be regulated)

33
Q

II. THERMOREGULATION - Heat balance
12. What is heat balance?

A

The processes that lead to increase of body temperature must be equal to processes that lead to decrease of body temperature
=> chemical heat production is equal to physical heat loss

34
Q

II. THERMOREGULATION - Heat balance
13. Describe isolation in heat balance

A

Isolation (adipose tissue, clothing hair):
- If it is cold = isolation protects the core temperature and reduces heat loss
- If it is warm = isolation may make things worse, but there are regulatory mechanisms in skin circulation -> the blood flowing to the skin will allow more heat to be transferred from body to environment

35
Q

II. THERMOREGULATION - Skin circulation
14. What are the important parameters of skin circulation?

A
  1. Skin circulation: 100-300 mL/min, in warm environment it may rise to 8L/min
  2. AVDO2 = 20-30mL/L
36
Q

II. THERMOREGULATION - Skin circulation
15A. Where can you find apical skin?

A

Apical skin: non-hairy, palms, lips, nose, ears, fingertips (vasoconstriction = conserve heat)

37
Q

II. THERMOREGULATION - Skin circulation
15B. Describe skin circulation of apical skin?

A

Apical skin: non-hairy, palms, lips, nose, ears, fingertips (vasoconstriction = conserve heat)
- Apical skin has arteriovenous anastomoses (AVA), providing direct connection between arterial + venous systems
- AVA has SYM innervation with basal tone leading to constriction
- Highly sensitive to vasoconstrictors like NE
=> Plays a role in temperature regulation and constricts with increased SYM activity to conserve body heat

38
Q

II. THERMOREGULATION - Skin circulation
16A. Where can you find non-apical skin?

A

hairy skin, covers most of the body (vasodilation = dissipation of heat)

39
Q

II. THERMOREGULATION - Skin circulation
16B. Describe skin circulation of non-apical skin

A

Non-apical skin: hairy skin, covers most of the body (vasodilation = dissipation of heat)
- Has arterioles with higher basal tone, lower neural tone -> normal SYM activity (NO AVA)
- Sweat glands can be found here (cholinergic SYM innervation by mAChR)

40
Q

II. THERMOREGULATION - Skin circulation
17A. What is the main contributor to changes in cutaneous blood flow?

A

Thermoregulation

41
Q

II. THERMOREGULATION - Skin circulation
17B. How does vasoconstriction participate in thermoregulation in cutaneous blood flow?

A

Vasoconstriction:
- Blood flow decrease in cold weather >7mL/min = sympathetic tone (conserve heat)

42
Q

II. THERMOREGULATION - Skin circulation
17C. How does Vasodilation participate in thermoregulation in cutaneous blood flow?

A
  • Blood flow increases in hot weather >100L/min = to release heat (sympathetic tone inhibited, so vasodilation takes place for dissipation of heat)
  • Activation of sweat glands which make products that causes vasodilation
43
Q

II. THERMOREGULATION - Skin circulation
17D. How do emotions participate in thermoregulation in cutaneous blood flow?

A

Emotions: explained by vasodilatory mechanism, so there are CNS effects on skin circulation (especially in the face)
- Fear -> pale skin due to poor skin circulation
- Embarrassment -> flushing skin due to high skin circulation

44
Q

II. THERMOREGULATION - sweat glands and sweating
18. Where is sweat gland found? What does sweating depend on?

A

Sweat glands found in non-apical skin
=> sweating depends on the humidity of the air.

45
Q

II. THERMOREGULATION - sweat glands and sweating
19. What is sweat?

A

Sweat is a protein-free hypoosmotic fluid

46
Q

II. THERMOREGULATION - sweat glands and sweating
20A. What are the 2 main mechanisms of secretion of sweat glands?

A
  1. Primary SECRETION in acinar cells – with concentrations similar to plasma (↑ in Na+/Cl-)
  2. Secondary REABSORPTION of ductal cells – Na+-reabsorption is aldosterone dependent
47
Q

II. THERMOREGULATION - sweat glands and sweating
20B. Describe the mechanism of Primary SECRETION in acinar cells

A

Primary SECRETION in acinar cells – with concentrations similar to plasma (↑ in Na+/Cl-)
1) Na+/K+/2Cl—cotransporter moves these ions into the acinar cells from the basolateral side -> Cl—transporters move Cl- to the lumen
2) Paracellular Na+-transport + transcellular H2O transport into the lumen
3) Luminal fluid is initially plasma-like, but is modified later

48
Q

II. THERMOREGULATION - sweat glands and sweating
20C. Describe the mechanism of Secondary REABSORPTION of ductal cells

A

-Secondary REABSORPTION of ductal cells – Na+-reabsorption is aldosterone dependent
1) Cl- will follow based on electrochemical gradient
2) NO water reabsorptionhow the final product of sweat is hypoosmotic

49
Q

II. THERMOREGULATION - sweat glands and sweating
20D1. What do ionic components of sweat depend on?

A

Ionic components of sweat depends on rate of sweat flow

50
Q

II. THERMOREGULATION - sweat glands and sweating
20D2. Explain Ionic components of sweat in high sweat flow rate

A

High [Na+] + [Cl-], since there is less time for secondary reabsorption

51
Q

II. THERMOREGULATION - sweat glands and sweating
20D3. Explain Ionic components of sweat low sweat flow rate

A

Low [Na+] + [Cl-], since the ions are reabsorbed more effectively

52
Q

II. THERMOREGULATION - sweat glands and sweating
20D4. ExplainIonic components of sweat in cystic fibrosis

A

Cl–channel does not work
=> high [Na+] + [Cl-] in sweat

53
Q

II. THERMOREGULATION - sweat glands and sweating
21. Explain Vasodilatory mechanism of sweat

A

Vasodilatory mechanism of sweat: SYM cholinergic innervation
- ACh activates sweat glands by activating PLC -> Ca2+-signal
- The cells then produce kallikrein -> bradykinin -> vasodilation of local blood vessels in the skin
- So, when sweat is activated, the skin circulation is also activated

54
Q

II. THERMOREGULATION - CNS center of thermoregulation
22. Which part of CNS is the most important part in thermoregulation? What is its role?

A

Hypothalamus = the most important regulator
- Stimulating regional vasoconstriction -> ‘’cold centers’’ of the body
- Stimulating regional vasodilation -> ‘’warm centers’’ of the body

55
Q

II. THERMOREGULATION - CNS center of thermoregulation
23A. What are the 2 types of receptors in CNS center of thermoregulation?

A
  1. Central receptors
  2. Peripheral receptors
56
Q

II. THERMOREGULATION - CNS center of thermoregulation
23B. Describe central receptors

A

Central receptors: sensitive to change of core temperature, because they are all located deep in the body (HT, liver, spinal bone marrow)
=> the most important thermoreceptors

57
Q

II. THERMOREGULATION - CNS center of thermoregulation
23C. Describe peripheral receptors

A
  • Found in skin, oral cavity, etc. Play important role detecting air
    temperature.
  • Belong to TRP channel family -> sense the skin temperature.
  • Activation of peripheral thermoreceptors will regulate the set-point value, and impact the core temperature
58
Q

II. THERMOREGULATION
24. How does thermoregulation occur in warm environment?

A

Regulation in warm environment: meaning core temperature is getting higher
- Decrease of isolation
- Vasomotor activity decreases (decrease in SYM tone)vasodilation
- Sudomotor activity increases (mAChR) -> sweating is activated
- Complex behavioral change -> animal going to a colder place (ex: shadow

59
Q

II. THERMOREGULATION
25A. What are the 3 ways that thermoregulation occur in cold environment?

A
  1. Decrease physical heat loss
  2. Increase chemical heat production
  3. Drinking alcohol will cause vasodilation
60
Q

II. THERMOREGULATION
25B. How does thermoregulation occur in cold environment if there is alcohol drinking?

A

Drinking alcohol will cause vasodilation
-> peripheral heat receptors activated
-> set-point temperature decreased
-> lower core temperature (even though environment is cold)

61
Q

II. THERMOREGULATION
25C. What are the consequences of decreased physical heat loss in cold environment?

A

increase isolation by vasoconstriction of skin by
increasing SYM activity

62
Q

II. THERMOREGULATION
25D. What are the consequences of Increased chemical heat production in cold environment?

A

Increase chemical heat production => SYM response:
1. Increase skeletal muscle activity (shivering, physical exercise)
2. Thyroid gland (slow effect, not so important)
3. Brown adipose tissue (mainly beige adipose tissue in adults)

63
Q

II. Problems that occur when thermoregulation does not work
1. What are the 4 problems that can occur when thermoregulation does not work?

A
  1. Heat exhaustion
  2. Hyperthermia
  3. Fever
  4. Hypothermia
64
Q

II. Problems that occur when thermoregulation does not work
2. What is Heat exhaustion?

A
  • Warm temperature causes vasodilation and increased sweating -> hypovolemia (loss of blood volume)
    -> also lose Na+ + Cl- ions from sweating
    -> hypoosmotic hypovolemia
    -> decreased CO
    -> decreased arterial BP = circulatory shock
  • We need to drink more water + electrolytes to replenish what was lost in the sweat
65
Q

II. Problems that occur when thermoregulation does not work
3. What is Hyperthermia?

A

When sweating is not effective and the core temperature increases
-> CNS function is impaired
-> regulation of core temperature decreases
-> even more increased core temperature
-> may lead to death

66
Q

II. Problems that occur when thermoregulation does not work
4. What is fever?

A
  • Different than hyperthermia, because thermoregulation is functioning and is causing the fever by increasing the set-point value
  • Fever induced by pyrogens (exogenous: bacteria/virus, endogenous: cells of immune
    system)
67
Q

II. Problems that occur when thermoregulation does not work
5. What is Hypothermia?

A

Core temperature decreases
-> function of heart is impaired via arrythmias
-> may lead to death

68
Q

II. Problems that occur when thermoregulation does not work
5. What is Hypothermia?

A

Core temperature decreases
-> function of heart is impaired via arrythmias
-> may lead to death

69
Q

IV. Extra
1. Make a schematic diagram of thermoregulation

A
70
Q

IV. Extra
2. Make a schematic diagram that demonstrate the relationship between O2 compensation and Tcore (heat production and heat loss)

A

A Physiology (88 decks)

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