Hypothalamus

Question 1

What is a normal body temperature?

Answer 1

36.3 - 37.1 C

Question 2

How does core temp vary throughout the day?

Answer 2

1-2 degrees

low at 6 am (drops at night)

Question 3

Where are thermoreceptors and what are they?

Answer 3

found in skin, viscera, and brain

bare nerve endings w/ TRP receptors

Question 4

What kind of system does your body use to regulate body temp?

Answer 4

feed forward system

air is cold –> take action now before the body temp drops

Question 5

Where are thermoreceptors in the “core”?

Answer 5

brain

viscera

Question 6

What are cutaneous thermoreceptors like?

Answer 6

often bimodal (temp and touch)

may be warm or cold sensitive

10X as many cold sensitive - bc cold is more threatening

tell us about environmental conditions

Question 7

Why are there thermoreceptors in the gut?

Answer 7

not just sensing core temp

food ingested may change body T

tell hypothalamus about these threats

Question 8

Where are the neurons sensitive to temp change located in the hypothalamus?

Answer 8

pre-optic and superoptic

*3x as many warm sensitive –> relay to other parts of hypoT

Question 9

How do cutaneous thermoreceptors send info to the hypothalamus?

Answer 9

via anterolateral path

Question 10

What does the hypothalamus do in relation to thermoregulation?

Answer 10

has the connections to control the hormonal, autonomic, and behavioral changes that are part of thermoregulation

Question 11

What happens to body temp during sleep or exercise?

Answer 11

sleep: decrease in set point –> T decreases
exercise: increase in set point –> T increases (helps enzymes work better)

Question 12

Where are heat loss and heat production behaviors controlled in the hypothalamus?

Answer 12

AL: anterior = heat loss behaviors

PHP: Posterior heat production

Question 13

Why do babies lose heat easier than adults?

Answer 13

have high surface area compared to volume

Question 14

What are the muscular muchanisms of heat production?

Answer 14

shivering (primarily during inspiration) – controlled by dorsomedial posterior hypothalamus

Increase voluntary activity – via cortex –> jumping, running

Question 15

What are the non-muscular mechanisms of heat production?

Answer 15

Hormones: Thyroxin increases metabolic rate

epinephrine

Increase food intake –> increased metabolism

Brown adipose tissue: adrenergic I for initiation

Question 16

How does cold relate to thyroxin?

Answer 16

Cold is a stimulus for TRH release –> TSH –> Thyroxine

Question 17

How does brown fat produce heat?

Answer 17

low efficiency hydrolysis of ATP via uncoupling proteins –> more heat production

Innervated by sympathetic fibers

activated by circulating Epi

critical in infants; new research says white fat expresses right uncoupling proteins

Question 18

What are the main ways the body can lose heat?

Answer 18

evaporative heat loss: insensible and sweating

convection: air heating and rising
conduction: transfer of heat btw objects in physical contact w/ one another
radiation: transfer btw 2 objects not in physical contact

Question 19

How does bloodflow affect heat loss?

Answer 19

how much blood is sent to the skin determines how much heat moves from blood to ext environmnet

Question 20

How are sweat glands innervated and how is heat loss promoted to occur?

Answer 20

Innervation: SNS –> Ach to muscarinic receptor

lots of blood vessels nearby, coiled region increases SA for heat loss to skin

Question 21

What happens to sweat content in low and high flow rate sweating?

Answer 21

Low flow rate: concentrated sweat (most of water reabsorbed, but sodium couldn’t follow water)

High flow rate: lots of water (no time to reabsorb) with acclimation, little sodium due to aldosterone

Question 22

How should your body respond to hypothermia?

Answer 22

Increase heat production

Set temp > body temp –> need to increase it

Question 23

What is the definition of a fever?

Answer 23

controlled increase in body temp

set point increase by hypothalamus

Question 24

How does a fever occur?

Answer 24

germ –> secretion of endotoxins

immune cells release cytokines, etc

major player = prostaglandin E2 –> increases hypothalamic set point for temp

Question 25

Why do you shiver when you have a fever?

Answer 25

set temp > body temp initially (like in hypothermia)

shiver, non-shivering thermogenesis to get temp up

Question 26

What occurs when an illness is vanquished and fever is no longer necessary?

Answer 26

no more activation of immune system –> hypothalamic set point returns to normal

Body temp > set point –> decrease heat production

sweat, don’t move as much

Question 27

What is insensible heat loss?

Answer 27

loss through respiration