Regulation of Temperature

Question 1

What is considered normal body temp? (although it varies slightly across body systems)?

Answer 1

36-38 deg C

Question 2

What temp is under precise regulation and can be measured oral, axillary, rectal, eardrum or temporal?

Answer 2

Core body temp

Question 3

When will core body temp vary? (typically by about 1-2 deg) (5)

Answer 3

Ovarian cycle, environmental extremes, physical activity, age, fever

Question 4

What must be made in order to maintain thermal balance?

Answer 4

Compensatory adjustments in thermal flux

Question 5

Is heat low grade or high grade energy and how does it move?

Answer 5

Low-grade energy, moves down thermal gradient

Question 6

What type of heat is electromagnetic radiation that moves through a medium/ space?

Answer 6

Radiation

Question 7

About how much heat is lost from the body via infrared photons (radiative emission)?

Answer 7

50% of heat

Question 8

What type of heat loss from the core to the skin is passive?

Answer 8

Conduction

Question 9

What type of heat loss from the core to the skin is active?

Answer 9

Convection

Question 10

What type of heat loss is the transfer of thermal energy through solid matter/ stationary objects?

Answer 10

Conduction

Question 11

Which type of heat loss plays only a minor role in human heat transfer?

Answer 11

Conduction

Question 12

What type of heat is defined as losing heat through air/ water molecules across skin?

Answer 12

Convection (magnitude of heat loss adjusted through BF to skin, varies)

Question 13

During exercise when humidity is high, which mechanism of heat loss will unload most of the generated heat?

Answer 13

Convection

Question 14

During exercise when humidity is low, which mechanism of heat loss will unload most of the generated heat?

Answer 14

Evaporation

Question 15

What type of heat loss is defined as water vaporizing from respiratory passages/ surface of skin via sweating?

Answer 15

Evaporation

Question 16

580 calories will evaporate how much water?

Answer 16

1 gram

Question 17

Under what conditions will evaporation increase and decrease?

Answer 17

Decrease with dehydration Increase with humidity

Question 18

Which glands are responsible for the release of a clear, odorless, salty excretion and where are they found?

Answer 18

Eccrine glands, found on entire body

Question 19

Which glands are responsible for the release of thick, odorous secretions and where are they found?

Answer 19

Apocrine glands, found in axial and genital areas

Question 20

What part of the NS innervates eccrine glands?

Answer 20

SNS, use ACh

Question 21

Heat loss from core to environment occurs via a combination of which heat loss mechanisms?

Answer 21

Evaporation, radiation, and convection

Question 22

What allows the body to anticipate changes before core temp is affected?

Answer 22

Peripheral receptors in skin (send info to hypothalamus)

Question 23

Warmth receptors in the skin are activated at what temps?

Answer 23

44-46 deg C

Question 24

Cold receptors in the skin are activated at what temps?

Answer 24

24-28 deg C

Question 25

Measurement of core body temp by central (intrinsic) thermoreceptors in the hypothalamic POA and abdominal organs are what type of control?

Answer 25

Neural control

Question 26

What is the role of the POA in neural temp control?

Answer 26

Integrates thermal info (sensitive to 0.01 deg C changes)

Question 27

What brain structure responds to high blood temps in neural control of temperature?

Answer 27

Anterior hypothalamus (controlled by PNS)

Question 28

What brain structure responds to cold blood temps in neural control of temperature?

Answer 28

Posterior hypothalamus (controlled by SNS)

Question 29

Your posterior hypothalamus (controlled by SNS) responds to cold blood temps and contributes to both heat production and heat conservation. What are the methods of heat production? (4)

Answer 29

**Shivering (primary mech)**, increased muscle tone, increased voluntary actions, non-shivering thermogenesis (brown fat in infants)

Question 30

Your posterior hypothalamus (controlled by SNS) responds to cold blood temps and contributes to both heat production and heat conservation. What are the methods of heat conservation? (2)

Answer 30

Postural changes (dec SA), vasoconstriction

Question 31

Neural control over temperature exerts its effects on 4 primary mechanisms. What are they?

Answer 31

1. Shiver command 2. Vasomotor command 3. Sweat glands 4. Postural changes

Question 32

CV control and temp control direct vasodilation of the same arterioles, but which takes precedence?

Answer 32

**Temperature** control (when it's hot, BP drops)

Question 33

The range of environmental temps in which your body can adjust to with only minimal changes in metabolic rate is called what?

Answer 33

**Thermoneutral zone** (minimal changes defined as changes before shivering/ sweating occur)

Question 34

What is the effect of thyroid hormone disorders on temperature sensitivity?

Answer 34

Increase temperature sensitivity

Question 35

The following 3 mechanisms described what mechanism for body temperature control? Stimulation of NaKATPase Increased O2 consumption Increased BMR

Answer 35

Thyroid hormone control

Question 36

Effects of thyroid hormone on metabolic action (temp control) are attributed to what specific hormone?

Answer 36

**T3** (BAT w/ ↑ type-2 deiodinase to ↑T3 signaling)

Question 37

Hyperthyroidism causes pts to feel too hot or too cold?

Answer 37

Feel too **hot**

Question 38

Hypothyroidism causes pts to feel too hot or too cold?

Answer 38

Feel too **cold**

Question 39

What affect suggests an active role of thyroid hormone in temperature regulation?

Answer 39

TH increases vasodilation

Question 40

What type of signals in the POA lead to increases in body temp via temperature sensitive neurons (SNS)?

Answer 40

Leptin signals

Question 41

Leptin contributes to stimulation of beta-receptors in brown fat, activating decoupling enzyme, ultimately contributing to increased body temp. Synergistic action of what other hormone is required in order for this to happen?

Answer 41

Thyroid hormone

Question 42

What is the effect of excessive catecholamines on body temp?

Answer 42

Increase body temp via stimulation of alpha-1 receptors (cause vasoconstriction)

Question 43

What heat loss mechanisms offset core heat production during exercise/ training?

Answer 43

Convection and evaporation

Question 44

What 2 things with respect to temp regulation are greater in trained individuals?

Answer 44

Sweat rate and skin blood perfusion

Question 45

How long does it take for heat acclimation to occur?

Answer 45

A few days

Question 46

↓ HR, ↓ threshold for cutaneous vasodilation, ↑ control of Tcore, ↑ plasma volume, ↑ sweat production are indicative of what occurring?

Answer 46

Heat acclimation

Question 47

What is the primary pathway that leads to a fever? (7)

Answer 47

1. Infection 2. Macrophages 3. Endogenous pyrogens 4. Prostalandins 5. Increase hypothalamic set pt 6. "Cold response" 7. Increased body temp

Question 48

How does aspirin treat fevers?

Answer 48

Prevents prostaglandin synthesis via decreased COX