Regulation of Temperature Flashcards
What is considered normal body temp? (although it varies slightly across body systems)?
36-38 deg C
What temp is under precise regulation and can be measured oral, axillary, rectal, eardrum or temporal?
Core body temp
When will core body temp vary? (typically by about 1-2 deg) (5)
Ovarian cycle, environmental extremes, physical activity, age, fever
What must be made in order to maintain thermal balance?
Compensatory adjustments in thermal flux
Is heat low grade or high grade energy and how does it move?
Low-grade energy, moves down thermal gradient
What type of heat is electromagnetic radiation that moves through a medium/ space?
Radiation
About how much heat is lost from the body via infrared photons (radiative emission)?
50% of heat
What type of heat loss from the core to the skin is passive?
Conduction
What type of heat loss from the core to the skin is active?
Convection
What type of heat loss is the transfer of thermal energy through solid matter/ stationary objects?
Conduction
Which type of heat loss plays only a minor role in human heat transfer?
Conduction
What type of heat is defined as losing heat through air/ water molecules across skin?
Convection (magnitude of heat loss adjusted through BF to skin, varies)
During exercise when humidity is high, which mechanism of heat loss will unload most of the generated heat?
Convection
During exercise when humidity is low, which mechanism of heat loss will unload most of the generated heat?
Evaporation
What type of heat loss is defined as water vaporizing from respiratory passages/ surface of skin via sweating?
Evaporation
580 calories will evaporate how much water?
1 gram
Under what conditions will evaporation increase and decrease?
Decrease with dehydration Increase with humidity
Which glands are responsible for the release of a clear, odorless, salty excretion and where are they found?
Eccrine glands, found on entire body
Which glands are responsible for the release of thick, odorous secretions and where are they found?
Apocrine glands, found in axial and genital areas
What part of the NS innervates eccrine glands?
SNS, use ACh
Heat loss from core to environment occurs via a combination of which heat loss mechanisms?
Evaporation, radiation, and convection
What allows the body to anticipate changes before core temp is affected?
Peripheral receptors in skin (send info to hypothalamus)
Warmth receptors in the skin are activated at what temps?
44-46 deg C
Cold receptors in the skin are activated at what temps?
24-28 deg C
Measurement of core body temp by central (intrinsic) thermoreceptors in the hypothalamic POA and abdominal organs are what type of control?
Neural control
What is the role of the POA in neural temp control?
Integrates thermal info (sensitive to 0.01 deg C changes)
What brain structure responds to high blood temps in neural control of temperature?
Anterior hypothalamus (controlled by PNS)
What brain structure responds to cold blood temps in neural control of temperature?
Posterior hypothalamus (controlled by SNS)
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)
Shivering (primary mech), increased muscle tone, increased voluntary actions, non-shivering thermogenesis (brown fat in infants)
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)
Postural changes (dec SA), vasoconstriction
Neural control over temperature exerts its effects on 4 primary mechanisms. What are they?
- Shiver command
- Vasomotor command
- Sweat glands
- Postural changes
CV control and temp control direct vasodilation of the same arterioles, but which takes precedence?
Temperature control (when it’s hot, BP drops)
The range of environmental temps in which your body can adjust to with only minimal changes in metabolic rate is called what?
Thermoneutral zone
(minimal changes defined as changes before shivering/ sweating occur)
What is the effect of thyroid hormone disorders on temperature sensitivity?
Increase temperature sensitivity
The following 3 mechanisms described what mechanism for body temperature control?
Stimulation of NaKATPase
Increased O2 consumption
Increased BMR
Thyroid hormone control
Effects of thyroid hormone on metabolic action (temp control) are attributed to what specific hormone?
T3
(BAT w/ ↑ type-2 deiodinase to ↑T3 signaling)
Hyperthyroidism causes pts to feel too hot or too cold?
Feel too hot
Hypothyroidism causes pts to feel too hot or too cold?
Feel too cold
What affect suggests an active role of thyroid hormone in temperature regulation?
TH increases vasodilation
What type of signals in the POA lead to increases in body temp via temperature sensitive neurons (SNS)?
Leptin signals
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?
Thyroid hormone
What is the effect of excessive catecholamines on body temp?
Increase body temp via stimulation of alpha-1 receptors (cause vasoconstriction)
What heat loss mechanisms offset core heat production during exercise/ training?
Convection and evaporation
What 2 things with respect to temp regulation are greater in trained individuals?
Sweat rate and skin blood perfusion
How long does it take for heat acclimation to occur?
A few days
↓ HR, ↓ threshold for cutaneous vasodilation, ↑ control of Tcore, ↑ plasma volume, ↑ sweat production are indicative of what occurring?
Heat acclimation
What is the primary pathway that leads to a fever? (7)
- Infection
- Macrophages
- Endogenous pyrogens
- Prostalandins
- Increase hypothalamic set pt
- “Cold response”
- Increased body temp
How does aspirin treat fevers?
Prevents prostaglandin synthesis via decreased COX
