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SF3 - Test 1 > 6 - Thermoregulation > Flashcards

6 - Thermoregulation Flashcards

1
Q

What is the simple understanding of Body Heat?

A

Body Heat = Heat Produced + Heat Transferred

Remember, heat transfer and be positive or negative! Can be used for heating or cooling

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2
Q

How does skin vs internal temperature compare?

A

Peripheral changes rapidly across a wider range, internal requires recise regulation

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3
Q

What are Diurnal Variations?

A

Physiological Fluctuations to temperature, minimal in morning peak in late afternoon

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4
Q

What is the range (deg C) for normal body T vs hard exercise?

A

36-37 deg C, hard ex = 40 deg C

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5
Q

What four factors acount for heat loss?

A
  1. Radiation
  2. Conduction
  3. Convection
  4. Evaporation
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6
Q

What factors affect heat production?

A

Basal Metabolic Rate - Abdominal viscera, heart, brain generate maj. of body heat

Muscular Activity - 75% of heat during exercise

Hormones - Thyroxine has direct effect to increase local metabolism, Epinephrine (SNS) increase metabolism

Thermic Effect of Food - Food consumption increases heat production of body

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7
Q

What is the major mode of acute heat production?

What brain center controls this?

A

Shivering

Hypothalamus receives cold stimulation

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8
Q

What controls the rate of blood flow at the skin, and how does it play into heat dissipation?

A

Degree of vasoconstriction of arterioles and arteriovenous anastomoes by the sympathetic nervous system

High Skin Flow = High heat conduction away from body

Low Skin Flow = Low heat conduction from core

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9
Q

What is the majority of head change with the body mechanisms?

A

Radiation (60%) heat waves

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10
Q

Conduction to Objects vs Conduction to Air

A

Conduction to Air much more important

“bubble” of personal spare is warmed by your temperature

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11
Q

Convection

A

Transfer of body heat by movement of air

You “warm” your bubble, and then that air is replace by new air to “warm”

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12
Q

What are two means of Evaporation loss?

A

Insensible Water Loss (always occuring, breaking, skin evap, etc) - no regulation

Sweating - highly regulated

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13
Q

WHen skin temperature is greater than ambient temperature, how is heat lost?

When ambient temperature is greater than that of skin, how does the body gain heat? How can the body get rid of heat?

A

Radiation, Conduction

Radiation, Conduction

Evaporation

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14
Q

What innervates sweat glands?

What occurs at the duct?

What occurs at the gland?

A

ACh secreting Sympathetic Nerves

Duct - Absorption (Na/Cl)

Gland - Primary secretion center

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15
Q

Stimulation of what area causes sweating?

A

Anterior Hypothalamus-preoptic area

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16
Q

What is the definition for sweat?

What can happen to ions prior to evaporation?

A

Solution with osmolar concentration below plasma

They can be reabsorbed

17
Q

What is the normal acclimatization process for sweating?

A

After 1-6 weeks: Increase volume of sweat glands; increased capability

After 4-6 weeks: Secretion of aldosterone is increased, leading to reduced NaCl in sweat

18
Q

What are the five components of the thermoregulatory system?

A
  1. Thermal Sensors
  2. Afferent Pathways
  3. Integration System in CNS
  4. Efferent Pathways
  5. Target Organs to Control Transfer / Generation
19
Q

Where are receptors for body temperature located?

What is the reflex response to cold at the level of the skin?

A

Skin - Cold (more) / Warm receptors

  1. Shivering
  2. Inhibition of Sweating
  3. Skin vasoconstriction

Deep body temperature - spinal cord, abdominal viscera, around great veins in the upper abdomen

20
Q

What role does the hypothalamus play in thermal regulation?

A

Preoptic / Anterior Hypothalamic Nuclei = Thermostatic Body Temperature control center

Contains both heat and cold sensitive neurons

21
Q

What location serves as the summation center prior to pushing our marching orders to heat production or dissipation?

How does it do this?

A

Posterior Hypothalamus

It compares sensory information to desired “set point”

22
Q

What mechanisms does the body employ when body too hot?

A

Skin Vasodilatione

Sweating

Decrease in Heat Production

Behavior Change - Sprawling, Light Clothing, Seek Shade

23
Q

What mechanisms does the body employ when too cold?

A
  1. Skin Vasoconstriction
  2. Piloerection
  3. Increas Heat Production
    a. Shivering
    b. Chemical thermogenesis (uncoupling oxidative phosphorylation
  4. Behavior CHanges - Curling up, dressing up, seeking warmth, voluntary exercsie
24
Q

When the body is cold, what are the results of acute vs long term increases in heat production?

A

Acute - Increase Catecholamine release

Chronic - Increase in thyroid function

25
Q

What can rapidly burn glucose to produce heat when activated by cold?

A

Uncoupling of Oxidative Metabolism in Brown Fat

Activated by Cold

26
Q

Clinical: How does fever cause the hypothalamic set point to rise?

A

Pyrogens

  • Proteins, their breakdown products, or lipopolysacccaride toxins
27
Q

Clinical: How does aspirin lower a fever?

What circulating substance eventually reaches the brain and begins a signaling cascade in fever?

A

Blocks synthesis of prostaglandin (PGE2), preventing its stimulation of the hypothalamus

Cytokines

28
Q

Clincial: Antipyretics

A

Drugs that reduce fever

Aspirin / Cycloxygenase Inhibitors block prostaglandin synthesis

29
Q

Clinical: Why do you get the chills with a fever?

Why do you begin to sweat eventually?

A

The set point is suddenly raised by the hypothalamus, and your normal temp is well below new set point. You will “feel cold” and may shiver, vasoconstrict, piloerection, and secrete epinephrine.

Once you take medicine, or the fever “breaks” your set point returns to normal and you are now well above that value. Your body will feel “hot” and you will vasodilate, sweat.

30
Q

Clinical: Heatstroke

A

Body temp 105 - 108 degF

Dizziness, abdominal distress, vomiting

Delirium

Loss of consciousness

Circulatory shock from loss of fluid/electrolytes

31
Q

Clinical: Heat Exhaustion

A

Occurs afer excessive loss of salt and water due to sweating

May also occur when venous return is compromised by heavy exertion and maximal cutaneous vasodilation.

Body temperature MAY remain in normal values

32
Q

Clinical: Hypothermia

Body at 94?

Body below 85?

Body at 77 (or less)?

A

General slowing of metabolism and of cardiac and neuronal excitabiity

94 - Thermoregulation Impaired

85 - Thermoregulation Lost

< 77- Death to heart fibrillation

33
Q

Clinical: Frostbite

A

Damage due to frozen body surface

Lobes of ears, hands, feet

34
Q

What substances can increase as we acclimatize to cold?

A

Increased chemical thermogenesis by elevated catecholamine and throxine levels

35
Q
A

SF3 - Test 1 (28 decks)

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