Hypothalamus

Question 1

Avg. body temperature:

Answer 1

36.7 celcius, 98.06 F.

Lower in morning and increases throughout the day.

Question 2

Which areas change the most in temperature due to the environment?

The least?

Answer 2

Hands, feet.

Core, oral, then skin.

Question 3

Enzyme that temperature effects?

Answer 3

Q10

Question 4

Core thermoreceptors:

Answer 4

Brain and viscera

Question 5

Cutaneous thermoreceptors:

What can they detect?

What are they most sensitive to?

What do they tell us?

Answer 5

Axons in skin.

Bimodal (temp and touch, etc).

10x as many cold sensitive.

Tell us about the environmental conditions.

Question 6

Why is there thermoreceptors in the gut?

Where do they relay this info?

Answer 6

Threats to maintenance (cold, hot food, etc).

Hypothalamus.

Question 7

Where are the thermoreceptors in the brain (hypothalamus)? (2)

What are these most sensitive to?

Where do they relay the info?

Answer 7

Pre-optic region of hypothalamus
Superoptic region of hypothalamus

3x as many warm sensitive.

Other parts of hypothalamus.

Question 8

“Hypothalamus has connections to control…” (3)

Answer 8

Hormonal, autonomic and behavior changes that are part of thermoregulation.

Question 9

3 big roles of hypothalamus for controlling temperature

Answer 9

1. Determine set point
2. Receive info about current info
3. Decide what to do

Question 10

What can change set point? (2)

Answer 10

Core temp changes.
Sleep –> decrease set point.
Exercise –> increase in set point.

Question 11

Which part of the hypothalamus responds to heat?

Which part responds to cooling?

Then, what do these parts do?

Answer 11

Anterior responds to heat. Begins heat loss behaviors.

Posterior responds to cooling. Begin heat production behaviors.

Question 12

Why is adipose tissue so important in babies?

Answer 12

Because their surface area is large, so they lose heat easier. Adipose helps insulate.

Question 13

4 mechanisms of heat production

Answer 13

ANS
Endocrine (thyroxine, Epi)
Muscular activity (shivering, moving around, etc)
Non-shivering thermogenesis

Question 14

What triggers shivering?

What triggers an increase in voluntary activity?

Answer 14

Dorsomedial posterior hypothalamus.

Cortex

Question 15

What does BAT need to be activated?

What is the process?

Answer 15

BAT needs adrenergic innervation.

Uncoupling protein allow for low efficiency hydrolysis of ATP and leads to more heat production.

Question 16

Insensible heat loss is:

Sweating heat loss is:

Answer 16

Respiratory

Controlled

Question 17

Convection

Conduction

Radiation

Answer 17

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).

Question 18

How can heat be loss by circulation?

Answer 18

Anastomoses at the surface of the skin allow heat t o move from blood to external environment.

Question 19

Innervation to sweat glands (it is unusual)

Answer 19

Sympathetic cholinergic.

ACh binds mAChR

Question 20

What happens as fluid travels from sweat gland to external environment, generally?

Answer 20

Na+, Cl- and water are reabsorbed

Question 21

Low flow rate through duct (not too hot) ensures what kind of sweat?

Answer 21

Salty. Lots of water is reabsorbed and Na+ is high.

Question 22

High flow rate through duct (very hot) ensures what kind of sweat?

Answer 22

Diluted. Little water reabsorbed and little sodium due to aldosterone action.

Question 23

Fever

Answer 23

Controlled increase in temp directed by hypothalamus

Question 24

How does an infection change the set point?

Answer 24

The bug secretes endotoxins and immune cells secrete cytokines which activates PGE2.
PGE2 increases set point for temperature.

Question 25

If T set point > Tb, what 2 things happen?

Answer 25

Increase heat production.

Decrease heat loss.

Question 26

How does T body dip below T set point in an infection?

Answer 26

The bug is gone and no more endotoxins.

Now Tb > T set point and we try to cool off.