Thermoregulation Flashcards
How do core temperatures vary?
1-2 degrees over a 24 hour period and is at 36.7 degrees C in the morining
What are the jobs of the viscera thermoreceptors?
1) Detects core temp
2) Detects threats to core temp
What is a threat to our core temperature that can be detected by the viscera thermoreceptors?
Temp of food
Thermoreceptors in what location are often bimodal (respond to temperature change and high pressure stimulus)?
Cutaneous
Cutaneous thermoreceptors can either be warm or cold sensitive. There are 10x the amount of thermoreceptors that are sensitive to what?
Cold sensitive
What do cutaneous thermoreceptors tell us?
About environmental conditions
What structure does the visceral thermoreceptors signal to about threats to the core temperature?
Hypothalamus
Where is the major site for thermoregulation?
Hypothalamus
Where in the hypothalamus are the thermoreceptors located?
Pre-optic and supraoptic regions
In the hypothalamus, there are 3x the amount of thermoreceptors that are sensitive to what?
Warm sensitive
What receptors work together to detect core temperature?
Visceral and brain thermoreceptors
What does the hypothalmus determine?
The set point of the core temp
When you are sleeping what happens to your core temperature?
It decreases (decrease in set point)
When you are exercising what happens to your core temperature?
It increases (Increase in set point)
If you start to cool down what part of the hypothalamus starts to become more active in order to increase heat production behavior?
The posterior aspect
If you start to get too hot what part of the hypothalamus starts to become more active in order to increase heat loss behavior?
The anterior aspect
In babies, the high surface area in proportion to their size means they lose heat better than adults. What do babies have to combat this?
Lots of Subq fat
What are some hormones that are released to increase heat production?
Thyroxine and Epi
What part of the hypothalamus causes shivering?
Dorsomedial posterior hypothalamus
The dorsomedial posterior hypothalamus sends axons down the spinal cord to the?
The motoneurons and increases their excitability
What does thyroxine do?
Increases metabolic rate
What are some ways to induce non-shivering thermogenesis?
1) Thyroxine and Epi release
2) Increase food intake to increase metabolism
3) Brown adipose tissue
Low efficiency hydrolysis of ATP via uncoupling proteins leading to more heat production than otherwise is seen in what?
Brown adipose tissue
What is brown fat innervated by?
Sympathetic fibers and also activated by circulating epinephrine
What population is brown fat critical in?
Infants
What is the term for heat lost as water evaporates?
Evaporative heat loss
What are the two types of evaporative heat loss?
1) Insensible (breathing)
2) Sweating (controlled)
What is the term for movement of molecules away from contact (air heating and rising)?
Convection heat loss
What is the term for transfer of heat between objects in physical contact with one another?
Conduction heat loss
What is the term for transferring heat between two objects not in physical contact?
Radiation heat loss
How much blood is sent to the skin determines how much heat moves from?
Blood to external environment
What is the innervation of the sweat glands?
Sympathetic muscarinic receptors
What is the initial process of sweating?
Filtration of serum, including the Na, Cl
During sweating, as the fluid travels up to the skin surface what are reabsorbed (taken back to the blood) in the duct of the sweat gland?
Water and sodium
What is the flow rate of sweating when the sweat has little water (lots reabsorbed) and high sodium?
Low flow rate (not that hot)
What is the flow rate of sweating when the sweat has lots of water (no time) and low sodium?
High flow rate (very hot)
What causes sodium to not be lost in sweat during high flow rates?
Aldosterone
What happens to the set point during the start of a fever?
The set point becomes greater than body temp
What happens to heat production and heat loss during a fever when the immune cells are active?
Increase heat production and decrease heat loss because the set point is higher than body temp
What happens to the set point during a fever after there is no more activation of immune system?
The set point is less than the body temp
What happens to heat production and heat loss during a fever when the immune cells are inactive?
Decrease in heat production and increase in heat loss because the set point is lower than body temp
