Thermoregulation (Karius)

Question 1

Define Core Temperature

Define thermoreceptors

Answer 1

brain and visceral temperature

36.7’C in the AM

cutaneous, visceral and hypothalamic

Question 2

Which part of the hypothalamus responds to heat?

Which part of the hypothalamus responds to cold?

Answer 2

anterior, participates in heat loss behaviours (sweating)

posterior, participates in heat production behaviours (shivering)

Question 3

What are the mechanisms of heat production?

Answer 3

ANS

Endocrine (thyroxin, epinephrine)

muscular activity

non-shivering thermogenesis

Question 4

How does muscular activity lead to heat production?

Answer 4

shivering-dorsomedial posterior hypothalamus increases motor neuron excitation

increased voluntary activity-via cortex, jumping, running etc.

Question 5

How dies non-shivering thermogenesis contribute to heat production?

Answer 5

strong hormonal influence-thyroxin increases metabolic rate (cold is a stimulus for TRH) and epinephrine

increased food intake leads to increased metabolism

brown adipose thermogenesis

Question 6

How does brown adipose thermogenesis lead to heat production?

Answer 6

low efficiency hydrolysis of ATP via uncoupling proteins leads to more heat production than normal

brown fat is innervated by sympathetic fibers and activated by circulating epinephrine

important in infants

Question 7

Two kinds of evaporative heat loss:

Answer 7

insensible (respiratory)

sweating (controlled)

Question 8

Heat Loss can occur via three other mechanisms:

convection

conduction

radiation

Answer 8

convection: move molecules away from contact
conduction: transfer heat between two objects in contact
radiation: infrared radiation transferring heat between two objects not in contact

Question 9

Heat loss is dependent on what?

Answer 9

how much blood is sent to the skin determines how much heat moves from the body to the environment

Question 10

Describe the physiology of sweating

Answer 10

sympathetic cholinergic innervation

Ach NTM

binds to muscarinic receptor

act on sweat gland

Question 11

Describe the process of sweating

Answer 11

filtration of serum, including ions (plasma, Na, Cl)

as fluid travels up to skin surface, water and Na are reabsorbed into the blood in the duct of the gland

Question 12

What is a fever?

Answer 12

controlled increase in body temp.

set point increases, body temp increases as hypothalamus directs

Question 14

What is secreted in response to endotoxins of pathogens that leads to fever?

Answer 14

Prostaglandin 2

leads to increased hypothalamic set point for temperature

Tbody<tset></tset>

<p> </p>

<p>in the absence of the endotoxins, the hypothalamic set point returns to normal </p>

</tset>

Question 15

When your Tbody > Tset point what happens?

Answer 15

decrease heat production, s/s are apathy and anorexia

increase heat loss, via conduction/convextion, sweat, panting

Question 16

When your Tset point > Tbody what happens?

Answer 16

Increase heat production, shiver, thermogenesis

Decrease heat loss, take blood away from the skin, decrease sweating

Question 17

Describe the cutaneous thermoreceptors

Answer 17

often bimodal (Temp and touch)

warm or cold sensitive, 10x more cold sensitive ones

tell us about environmental temp.

Question 18

Describe visceral thermoreceptors

Answer 18

not just for core temp, but tells hypothalamus about food temp.

Question 19

Describe hypothalamic thermorreceptors

Answer 19

in preoptic and supraoptic region of hypothalamus

3x more receptors that are sensitive to heat

relay this info to other parts of hypothalamus

Question 20

Where do all thermoreceptors send their info and why?

Answer 20

to the hypothalamus to detect core temperature

Question 21

Why is the hypothalamus in charge of temperature regulation?

Answer 21

because it has connections to all the other areas to tell them how to react to the temperature

“control hormonal, autonomic, and behavioural changes that are part of thermoregulation”

Question 22

What are the three ways the hypothaalmus controls body temp?

Answer 22

1. determines set point
2. receives info about current temperature
3. decides what to do about temperature as need arises

Question 23

What happens when we only need to sweat a little bit?

What happens when we need to sweat a lot?

Answer 23

low flow rate: little water secreted, much absorbed, high Na left, couldn’t follow water

high flow rate: lots of water with little sodium due to aldosterone action