Thermoregulation

Question 1

Thermoreceptor locations

Answer 1

Viscera, brain (hypothalamus), cutaneous

In skin there are 10x as many cold sensors as warm sensors because of increased danger of cold

Question 2

Hypothalamic thermoreceptors

Answer 2

Pre-optic and superoptic regions

Mostly sensitive to heat in this area- tells the brain what its temperature is

Question 3

Hypothalamus job in temp regulation

Answer 3

Determines set point
Receives info about current temp and decides what to do
Posterior hypothalamus activates and leads to heat production if you are too cool
Anterior hypothalamus activates and leads to cooling if you are too hot

Question 4

Core temp during sleep

Answer 4

Decreases

Question 5

Core temp during exercise

Answer 5

During exercise muscles are more effective in a slightly higher temperature so body lets temperature increase

Question 6

Mechanisms of heat production

Answer 6

Sympathetic autonomics
Endocrine- thyroxine, epinephrine
Muscular activity
Non-shivering thermogenesis

Question 7

Muscular activity heat pathway

Answer 7

Dorsomedial posterior hypothalamus increases motor neuron excitation to induce shivering
Cortex increases voluntary activity i.e. running

Question 8

Non shivering thermogenesis

Answer 8

Strong hormonal influence
Thyroxine increases metabolic rate - cold stimulates TRH release
Epinephrine involved as well
Increase food intake leads to increased metabolism
Brown adipose tissue - initiated by adrenaline - uncoupling proteins in mitochondria involved

Question 9

Evaporative heat loss

Answer 9

Insensible - respiratory- fluid evaporated in respiratory tract
Sweating - controlled- takes heat energy to convert water to vapor

Question 10

Sweating and sweat glands function

Answer 10

Major source of heat loss
Lots of blood vessels near the sweat glands
Sweat gland takes up ions and plasma from blood, particularly sodium
Sodium is then reabsorbed while traveling towards the surface of the skin and water will follow it
Depending on how bad you need to sweat, less sodium will be reabsorbed
If you need to preserve sodium, aldosterone will be used and you will still sweat without as much sodium loss

Question 11

Sweat gland innervation

Answer 11

Sweat glands innervated by CHOLINERGIC sympathetic innervation to MUSCARINIC receptors

Question 12

Fever

Answer 12

A controlled increase in body temperature
Prostaglandin E2 produced by COX2
Hypothalamic set point for temperature is increased- due to pyrogen production
Set point is now higher than body temp, and hypothalamus initiates actions to increase body temperature

Question 13

Cold sensitive vs warm sensitive thermoreceptor fibers

Answer 13

Cold sensitive are usually associated with A-delta fibers

Warm sensitive are usually associated with C fibers

Question 14

TRP-V1 receptor

Answer 14

Firing rate increases as temperature goes up

Sensitive to capsaicin

Question 15

TRP-M8

Answer 15

M- menthol

Firing rate goes up as temperature gets cold/decreases

Question 16

TRPA1

Answer 16

Cold sensitive receptor

Many cold receptors show a paradoxical high firing rate in response to extremely high temperatures

Question 17

Ovulation and temp

Answer 17

Ovulation in women produces an increase in temperature

Question 18

Parasympathetics activated when

Answer 18

You are hot (sweating is only cool down mechanism activated by sympathetics)

Question 19

Feed forward system in temperature regulation

Answer 19

Responding to cutaneous temperature changes even though core temperature hasn’t changed

Question 20

Cutaneous vasodilation

Answer 20

Blood vessels in skin dilate/relax, allowing more blood to flow through the vessel easier, which allows heat to be released from the blood to the skin to the air

• This is stimulated by anterior hypothalamus
• The opposite is stimulated by posterior hypothalamus