Temperature Regulation Flashcards
What does thyroid hormone do for temperature regulation?
- stimulates Na+-K+ ATPase
- increase O2 consumption
- increased metabolic rate
- increases vasodilation
two things the anterior (rostral) hypothalamus stimulates to increase heat loss
- vasodilation in skin
2. sweat
process in which energy (heat) travels through a medium or space
radiation
Leptin requires synergistic action of ______ to increase body temperature
thyroid hormone
Cytokines cause the release of ______ in the OVLT of the hypothalamus where the BBB is absent
prostaglandins
skin blood perfusion can vary between _______ mL/min
400-2500
the rate of heat loss in convection depends on the
rate of fluid movement
compensatory adjustment in _________ must be made to maintain thermal balance
thermal flux
How does excessive catecholamine increase body temperature?
stimulation of a-1 receptors in vascular smooth muscle —-> reduces blood flow to the surface of the skin (heat is trapped)
_____ hypothalamus stimulates heat dissipation (parasymp)
anterior (rostral)
You are super hot and your body has vasodilated to try to increase heat loss, but you are also hypotensive. Which one will take precedence, the heat crisis or the hypotensive crisis?
temperature control will always take precedence
the transfer of thermal energy through solid matter
conduction
Why do you shiver with a fever
peripheral vasoconstriction shuts blood supply to the skin down to increase core temperature, and this is perceived as cooling of the skin even in a warm room
What happens with heat acclimation? (5 things)
- lower heart rate
- lower threshold for cutaneous vasodilation
- better control of core temp
- increased plasma volume
- increased sweat
Why are you at more risk for heat stroke when you are dehydrated?
reduced ability to perspire
hypothermia induced impairment of temperature regulation- unable to self regulate (like shivering) temperature range
30-34 C
(86-93.2) F
Eccrine glands are innervated by the ______ and use _____
sympathetic nervous system
acetylcholine
sweating is less effective as air becomes:
saturated with water vapor
more humid!
two things the posterior (caudal) hypothalamus stimulates in relation to heat conservation
- skin vasoconstriction
2. postural changes
Cold receptors respond to a range of cool temperature _________
24-28 C
The mechanism for heat loss from the skin surface is usually a combination of:
radiation + convection + evaporation
during conditions of low physical activity, how is most of the heat lost from the body?
radiation
In the dry Phoenix air, how much sweat can be evaporated from the skin/resp. tract in an hour?
2-3 liters
rate of heat transfer between a body and moving air is __________ than the rate between a body and moving water
lower
Why is sweat rate greater in trained individuals
skin blood perfusion is greater
which is cooler?
cool clothing or naked
cool clothing
How does aspirin help lower fever
cox inhibitor
decreased prostaglandins
decreased hypothalamic set point
the majority of passive heat transfer from core to skin is by:
convection in the vascular circulation
*some conductance
four things the posterior (caudal) hypothalamus stimulates in relation to heat production
- shiver
- increased muscle tone
- increased voluntary actions
- stimulation of brown fat
which form of temperature regulation is most important to unload the heat generated by intense activity if the humidity is HIGH
convection
which sucks
hypothermia induced cardiac fibrillation temperature range
27-29 C
(80.6-84.2) F
eccrine glands:
apocrine glands:
eccrine glands: everywhere, clear odorless
apocrine glands: axial/genital, thick with odor
What do prostaglandins due during an infection
stimulate preoptic area of the hypothalamus (POA) to determine the hypothalamic set point
integrated heat production increases body temperature
vasoconstriction (increases/decreases) convective heat transfer
decreases
heat moves _____ its thermal gradient
down
What integrates thermal information?
preoptic area of the hypothalamus (POA)
Infection causes the release of endogenous pyrogens (cytokines) from:
macrophages
The preoptic area of the hypothalamus (POA) is sensitive to temperature changes as small as
0.01 C
water vaporizing from respiratory passages and the surface of the skin
evaporation
which form of temperature regulation can unload most of the heat generated by intense activity if the humidity is low
evaporation
convection is second
hyperthermia (from fever of exercise) temperature range
38-40 C
(100.4-104) F
How many calories will evaporate 1 g of H2O
580
two things the anterior (rostral) hypothalamus stimulates to decrease heat production
- decreased muscle tone
2. decreased voluntary actions
Heat inputs to the body can come from:
Heat outputs from the body are:
internal and external
external environment ONLY
What is the role of peripheral thermoreceptors?
Where do the send information?
anticipate changes before they affect the core temperature
centreal thermoreceptors in the preoptic area of the hypothalamus (POA)
A spike in basal body temperature would indicated:
ovulation
Leptin signaling in the preoptic area of the hypothalamus (POA) influences temperature-sensitive neurons to ______ body temperature
How
increase
stimulation of B-receptors in brown fat, activating decoupling enzyme
normal body temp range
36-38 C
(96.8-100.4) F
the process of losing heat through movement of air or water molecules across the skin
convection
infection causes macrophages to release:
endogenous pyrogens (cytokines)
How does thyroid hormone effect brown fat? (BAT)
brown fat has abundant type-2 deiodinase to facilitate T3 signaling
brown fat = heat production
works well for infants in temperature changes
heat stroke, multiple organ failure, brain lesions temperature range
40-44 C
(104-111) F
______ hypothalamus stimulates heat production and conservation (sympathetic)
posterior (caudal)
a lower basal metabolic rate would be a (larger/smaller) range of thermoneutral zone
larger
Basal body temp during follicular phase: (lower/higher)
lower
mild hypothermia (cold and shivering) temperature range
34-36 C
(93.2 - 96.8) F
vasodilation (increases/decreases) convective heat transfer
increases
Which two temperature regulating mechanisms compensate for increased heat production during exercise?
evaporative
convective
radiative emission from the body is via ______
infrared photons
Where do cytokines enter the hypothalamus during infection
OVAT (where the BBB is absent)
excessive thyroid hormone will _____ body temperature
increase
warmth receptors are sensitive to a narrow range of hot temperature _________
44-46 C
Basal body temp during luteal phase (Lower/higher)
higher