VM 520 - Respiratory System > Thermoregulation > Flashcards

Thermoregulation Flashcards

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1
Q

What are the three internal methods of Heat Gain (Heat Production)?

A
  1. Metabolism (BMR)
  2. Shivering thermogenesis
  3. Non-shivering thermogenesis
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2
Q

Which mechanism of heat exchange is a method of heat loss ONLY?

A

Evaporation.

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3
Q

Define Conduction in the context of thermoregulation.

A

Heat transfer via direct contact with a solid object (e.g., a dog lying on a cold exam table).

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4
Q

How does Radiation result in heat gain?

A

By absorbing heat from the sun or hot solid objects without direct contact.

The sun can warm your face or skin even if temperature are below freezing.

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5
Q

What is Convection, and what substances are involved?

A

Heat transfer through a fluid (liquid or gas) that is moving, such as air currents or water.

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6
Q

What are the two main ways animals utilize Evaporation to cool down?

A
  1. Panting (respiratory and salivary water vapor)
  2. Sweating
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7
Q

Through which two primary anatomical routes is heat dissipated?

A

The skin and the respiratory tract.

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8
Q

When does Radiation result in heat loss?

A

When the body temperature is greater than the temperature of neighboring solid objects.

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9
Q

What is the primary mechanical difference between shivering and non-shivering thermogenesis?

A

Shivering involves tonic-clonic muscle contractions;

non-shivering is a metabolic increase without muscle activity. muscles not contracting

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10
Q

Which key tissue is responsible for non-shivering thermogenesis?

A

Brown Adipose Tissue (Brown Fat).

has a receptor that uncouples oxidative phosphorylation from ATP generation

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11
Q

Which hormones mediate the non-shivering pathway?

A

Thyroid hormones and catecholamines (e.g., Norepinephrine).

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12
Q

What is the “efficiency” trade-off in brown fat metabolism?

A

It produces less ATP and more heat (uncoupled oxidative phosphorylation).

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13
Q

In which specific animal populations is non-shivering thermogenesis most critical?

A

Neonatal (newborn) animals and hibernating animals.

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14
Q

How much can shivering increase heat production?

A

A two- to four-fold increase.

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15
Q

Why is shivering described as having “no productive work”?

A

Because the opposing muscle groups (extensors/flexors) contract simultaneously, resulting in heat but no movement.

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16
Q

Which tissue is the primary site for shivering?

A

Skeletal muscle.

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17
Q

Which mechanism is the only one that results exclusively in heat loss?

A

Evaporation.

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18
Q

Define Radiation in the context of heat exchange.

A

The transfer of heat between warmer and cooler objects without direct contact.

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19
Q

What is the difference between Conduction and Convection?

A

Conduction requires direct contact with a solid;

Convection involves heat transfer through a moving fluid (liquid or gas).

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20
Q

What is the role of Circulatory Convection?

A

It transfers heat from the body core to the surface to facilitate exchange with the environment.

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21
Q

Can Radiation, Conduction, and Convection result in both heat gain and heat loss?

A

Yes, depending on whether the environment is warmer or cooler than the body.

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22
Q

How does Evaporation physically cool the body?

A

By converting liquid (sweat/saliva) into gaseous vapor, which consumes heat energy from the body.

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23
Q

Which brain region acts as the “Master Controller” directing effector organs?

A

The Hypothalamus.

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24
Q

What is the primary function of AV Anastomoses (Arteriovenous Anastomoses)?

A

To shunt blood directly to superficial veins, increasing heat dissipation to the environment.

bypass superficial capillaries.

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25
Which structure is used by horses for selective convective brain cooling?
The Guttural Pouch.
26
What is a Carotid or Maxillary Rete?
A network of arteries bathed in a venous sinus that uses countercurrent exchange to cool blood heading to the brain.
27
Where does the cool venous blood in the rete come from?
The nose (cooled by evaporation during breathing).
28
List four effector organs involved in heat dissipation or generation.
Skin/Arterioles, Skeletal Muscle, Sweat Glands, Thyroid Gland, Adipose Tissue, Heart
29
What mechanism is used by the rete to exchange heat between vessels?
Countercurrent exchange.
30
What is the primary goal of thermoregulation?
To balance heat input and heat output so they are equal at the thermal set point.
31
Which brain structure acts as the Thermoregulatory Center?
The Hypothalamus.
32
What are the three specific roles of the Hypothalamus in thermoregulation?
1. Establish the set point. 2. Integrate information from receptors. 3. Direct efferent commands to effector organs.
33
What do Thermoreceptors provide to the hypothalamus?
Feedback regarding current temperature (both peripheral and central).
34
Name three effector responses to cold stress (to increase temperature).
1. Vasoconstriction (vasomotor). 2. Pilomotor response (hair standing up). 3. Thermogenesis (shivering/non-shivering).
35
Name three effector responses to heat stress (to decrease temperature).
1. Vasodilation. 2. Sweating. 3. Panting.
36
What is the vasomotor mechanism?
The alteration of blood flow via vasoconstriction (to conserve heat) or vasodilation (to dissipate heat).
37
What is the thermoregulatory set point?
The specific temperature established by the Hypothalamus that the body strives to maintain.
38
In terms of heat balance, what is the goal at the set point?
Heat input = Heat output.
39
Where are Core (Central) Thermoreceptors located?
The Hypothalamus, spinal cord, great vessels, and abdominal viscera.
40
What specific temperatures do Core Thermoreceptors monitor?
Deep brain temperature, visceral temperature, and core body temperature.
41
Where are Peripheral Thermoreceptors located, and what do they sense?
Distributed across the skin; they sense skin temperature (via cold and warmth receptors).
42
What is the difference between the feedback roles of Core vs. Peripheral receptors?
Core receptors provide feedback; Peripheral receptors provide "feedforward."
43
Why are Core Thermoreceptors especially important during exercise?
Because they detect the rapid rise in internal heat produced by active muscles, allowing the hypothalamus to trigger cooling before the skin temperature even changes.
44
How do animals use body surface area to thermoregulate?
They curl up or huddle to decrease surface area (conserve heat) or sprawl to increase it (dissipate heat). regulation of convective heat exchange
45
What is the fundamental difference between Hyperthermia and Pyrexia?
In Hyperthermia, the body is hotter than the set point; in Pyrexia, the set point itself has been elevated.
46
What is the clinical definition of Pyrexia (Fever)?
A state where the thermoregulatory set point is changed/elevated by the hypothalamus.
47
What substance triggers the elevation of the thermal set point?
A pyrogen.
48
Why does an animal shiver at the start of a fever?
Because the set point has risen, making the current "normal" temperature feel "too cold," triggering heat production to reach the new target.
49
What happens to the set point when a fever "breaks"?
It returns to normal, causing the body to initiate heat loss (sweating/vasodilation) to cool down to the original set point.
50
How is Hypothermia defined in relation to the thermal set point?
When the actual body temperature is less than the thermoregulatory set point.
51
How is Hyperthermia defined in relation to the thermal set point?
When the actual body temperature is greater than the thermoregulatory set point.
52
In Hypothermia, is the body actively trying to be cold?
No. The hypothalamus is signaling for heat production/conservation, but the body's defenses are being overwhelmed by the environment.
53
How does high temperature affect vital proteins and enzymes?
It causes them to denature (lose their shape and function).
54
How do low temperatures affect enzymatic activity?
They become inactive due to lower kinetic energy.
55
Which organ systems are specifically at risk during temperature dysfunction?
Brain, kidneys, liver, GI tract, and the coagulation system.
56
Define the Thermoneutral Zone.
The temperature range where the body maintains core temp using only vasomotor mechanisms (no shivering or panting required).
57
What three mechanisms are used specifically within the Thermoneutral Zone?
1. Vasodilation 2. Vasoconstriction 3. AV Anastomoses
58
What is the "baseline" source of all internal heat production?
The Basal Metabolic Rate (BMR).
59
What does brown fat generate when it is active?
Heat, not energy
59
If BMR is not enough to maintain temperature, what are the two "active" backup mechanisms?
Shivering and non-shivering thermogenesis.
60
True or False: Any two solid bodies that have differences in temperature will undergo radiant heat exchange
True
61
What is a convection current?
The movement created when heated fluid (air/liquid) rises because it becomes less dense, creating a void for cooler fluid to replace it.
62
What drives natural convection (like the air above a candle)?
The density difference between warm air (which rises) and cool air (which sinks).
63
How is forced convection different from natural convection?
In forced convection, air or liquid is actively moved across a surface by an external force (like a fan or pump).
64
Why does a fan over a warm patient increase heat exchange?
It forcefully moves heated air away from the skin, creating a constant void for new, cooler air to come into contact with the surface.
65
Why is it difficult for heat to move from the core to the skin through body tissues alone?
Because body tissues are poor thermal conductors.
66
What are the three primary organs/tissues where most body heat is generated?
1. Skeletal muscles 2. Liver 3. Heart
67
How does the body overcome the poor conductivity of tissues to move heat?
Through circulatory convection (using blood as a moving fluid to carry heat).
68
In the liver, where specifically does the blood flow to pick up heat?
Through the liver sinusoids.
69
Describe the physics of heat transfer in the liver sinusoids.
Moving blood (liquid) comes in contact with the warm liver (solid), facilitating convective heat transfer from the organ to the blood.
70
What is the final destination of heat carried by circulatory convection?
The body surface (skin), where it can then be exchanged with the environment.
71
What is the purpose of piloerection (haircoat "standing up")?
It traps a layer of still air against the skin, reducing convective heat loss.
72
How does heat move from a skin vessel to the environment?
1. Conduction from the vessel to the skin surface. 2. Convection via air movement across the skin.
73
Why is a thick haircoat effective against cold stress?
It acts as an insulator that separates moving air from the warm skin surface.
74
Regulation of convective heat exchange?
1. Behavioral 2. Piloerection 3. Vasomotor mechanisms
75
How does vasodilation facilitate heat exchange?
It increases blood flow to the periphery and skin surface, allowing core heat to be dissipated into the environment.
76
How does vasoconstriction achieve heat conservation?
It diverts blood away from the skin surface, keeping it in the deeper vasculature to protect core temperature.
77
Where is blood "stored" during intense vasoconstriction to prevent heat loss?
In the deep veins and core vasculature, away from the cooling effects of the environment.
78
What is the resonance frequency in the context of panting?
A specific rhythm (200–240 bpm) where the respiratory system moves with minimal muscular effort and oxygen cost.
79
Why is achieving resonance frequency beneficial for a panting dog?
It reduces oxygen consumption and muscular work, preventing the animal from overheating due to the "work" of breathing.
80
What is the primary method of heat loss achieved through panting?
Evaporative heat loss (moving large volumes of air across moist mucous membranes).
81
Which species utilize panting as a major thermoregulatory mechanism?
Dogs, cats, sheep, goats, and birds.
82
What type of thermoreceptors provide feed-forward information?
Peripheral thermoreceptors (cold and warmth receptors in the skin).
83
What is the primary benefit of the feed-forward mechanism?
It allows the body to start thermoregulatory responses earlier, preventing the core temperature from ever falling out of the thermoneutral zone.
84
Does the core temperature have to change for feed-forward mechanisms to trigger?
No; they are triggered by the external environment sensed by the skin.
VM 520 - Respiratory System
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