Hypothalamus Flashcards
Avg. body temperature:
36.7 celcius, 98.06 F.
Lower in morning and increases throughout the day.
Which areas change the most in temperature due to the environment?
The least?
Hands, feet.
Core, oral, then skin.
Enzyme that temperature effects?
Q10
Core thermoreceptors:
Brain and viscera
Cutaneous thermoreceptors:
What can they detect?
What are they most sensitive to?
What do they tell us?
Axons in skin.
Bimodal (temp and touch, etc).
10x as many cold sensitive.
Tell us about the environmental conditions.
Why is there thermoreceptors in the gut?
Where do they relay this info?
Threats to maintenance (cold, hot food, etc).
Hypothalamus.
Where are the thermoreceptors in the brain (hypothalamus)? (2)
What are these most sensitive to?
Where do they relay the info?
Pre-optic region of hypothalamus
Superoptic region of hypothalamus
3x as many warm sensitive.
Other parts of hypothalamus.
“Hypothalamus has connections to control…” (3)
Hormonal, autonomic and behavior changes that are part of thermoregulation.
3 big roles of hypothalamus for controlling temperature
- Determine set point
- Receive info about current info
- Decide what to do
What can change set point? (2)
Core temp changes.
Sleep –> decrease set point.
Exercise –> increase in set point.
Which part of the hypothalamus responds to heat?
Which part responds to cooling?
Then, what do these parts do?
Anterior responds to heat. Begins heat loss behaviors.
Posterior responds to cooling. Begin heat production behaviors.
Why is adipose tissue so important in babies?
Because their surface area is large, so they lose heat easier. Adipose helps insulate.
4 mechanisms of heat production
ANS
Endocrine (thyroxine, Epi)
Muscular activity (shivering, moving around, etc)
Non-shivering thermogenesis
What triggers shivering?
What triggers an increase in voluntary activity?
Dorsomedial posterior hypothalamus.
Cortex
What does BAT need to be activated?
What is the process?
BAT needs adrenergic innervation.
Uncoupling protein allow for low efficiency hydrolysis of ATP and leads to more heat production.
Insensible heat loss is:
Sweating heat loss is:
Respiratory
Controlled
Convection
Conduction
Radiation
Movement of molecules away from contact (air heating and rising).
Transfer of heat between objects that are in contact.
Transfer of heat between objects not in physical contact (person and wall).
How can heat be loss by circulation?
Anastomoses at the surface of the skin allow heat t o move from blood to external environment.
Innervation to sweat glands (it is unusual)
Sympathetic cholinergic.
ACh binds mAChR
What happens as fluid travels from sweat gland to external environment, generally?
Na+, Cl- and water are reabsorbed
Low flow rate through duct (not too hot) ensures what kind of sweat?
Salty. Lots of water is reabsorbed and Na+ is high.
High flow rate through duct (very hot) ensures what kind of sweat?
Diluted. Little water reabsorbed and little sodium due to aldosterone action.
Fever
Controlled increase in temp directed by hypothalamus
How does an infection change the set point?
The bug secretes endotoxins and immune cells secrete cytokines which activates PGE2.
PGE2 increases set point for temperature.
If T set point > Tb, what 2 things happen?
Increase heat production.
Decrease heat loss.
How does T body dip below T set point in an infection?
The bug is gone and no more endotoxins.
Now Tb > T set point and we try to cool off.
