Thermoregulation

Question 1

Describe heat distribution throughout the body.

Answer 1

Warmer core and cooler shell temperatures

Question 2

What are the 4 methods of heat transfer we talked about in lecture?

Answer 2

radiation - direct transfer of heat through air (objects emit heat)

convection - loss/gain of heat due to the movement of water or air

evaporation - loss of heat due to evaporating perspiration being replaced by cool air

conduction - loss/gain of heat due to transfer of energy from collisions of adjacent molecules making direct contact with each other (you touch a surface)

Question 3

What is in the core

Answer 3

organs in head and trunk

Question 4

what is in the shell

Answer 4

skin and subcutaneous fat

Question 5

what controls adjusting body temperature in response to the environment? what type of control is this

Answer 5

the hypothalamus controls this (homeostasis)

Question 6

What is countercurrent exchange? What is the purpose of doing it?

Answer 6

warm blood moves in arteries, cool blood moves in veins. When they are in close proximity to each other, warm blood loses heat to venous blood. Minimizes heat loss and prioritizes heat return to the core.

Question 7

Is countercurrent exchange controlled by the brain, or is it a built in funciton?

Answer 7

Built in, not controlled by brain. Due to proximity of veins and arteries.

Question 8

Describe the circadian rhythm of body temperature. Where is it controlled?

Answer 8

Body temp is higher during the day than at night. controlled by the hypothalamus.

Question 9

What is the thermoneutral zone?

Answer 9

range of environmental temps where heat production (due to BMR) is equilibrium with heat loss (78.8F-98.6F)(26C-37C)

Question 10

What is basal metabolic rate?

Answer 10

BMR- amount of energy expended daily at rest.

Question 11

What happens to BMR when we are in an environment outside the thermoneutral zone?

Answer 11

we increase BMR to stay in an ideal temperature range.

Question 12

What are endotherms? How do mammals thermoregulate?

Answer 12

Endotherms generate their own body heat. We use behavioral and physiological mecahnisms to regulate BT.

Question 13

What is thermal discomfort?

Answer 13

when the climate is perceived to push us away from our thermoneutral zone (we feel too hot or too cold)

Question 14

What motivates thermoregulatory responses?

Answer 14

perception of thermal discomfort

Question 15

Where is thermal discomfort perceived

Answer 15

peripherally (skin thermoreceptors) and centrally (core thermoreceptors)

Question 17

How do peripheral thermoreceptors detect temperature changes?

Answer 17

by comparing the temp of objects and ambient air molecules to the temperature of the skin.

Question 18

What range of temperatures is the neutral zone for humans? (we can’t detect temp changes there)

Answer 18

31-36C

Question 19

How many sets of peripheral thermoreceptors do we have?

Answer 19

2 - one for hot, one for cold

Question 20

What is the normal range of core temperatures humans can tolerate? Why is it so small?

Answer 20

97-100 F. Needs to be in optimal temperature for chemical reactions to progress correctly.

Question 21

The hypothalamus has intrinsic thermosensitivity. What does that mean?

Answer 21

there are thermoreceptors in the hypothalamus

Question 22

Can temperature cross the BBB

Answer 22

yes

Question 23

the hypothalamus receives input from what structures?

Answer 23

periphery: neurons (ex. dorsal root ganglia)
core: neurons in blood supply and organs

Question 24

What is a TRP channel

Answer 24

transient receptor potential ion channels- sensitive to temperature, form tetramers and an ion-conducting pore.

Question 25

How many transmembrane domains to TRP channels have

Answer 25

6

Question 26

how many TRP channels have been identified?

Answer 26

9

Question 27

Some TRP channels are also activated by _____ (not temperature) What are some

Answer 27

chemical ligands -chili peppers, garlic (hot) TRPV4 -mint, menthol, eucalyptol (cold) TRPM8

Question 28

What is vasoconstriction/vasodilation? How do they help manage body temperature?

Answer 28

Vasoconstriction is the narrowing of blood vessels due to smooth muscle contractions. This pulls the vessels away from the skin and allows little heat to escape that way. Vasodilation is widening of blood vessels. This pushes more blood closer to the skin where heat can be shed through the skin.

Question 29

What are the neurotransmitters and receptors responsible for vasoconstriction/vasodilation

Answer 29

Vasoconstriction: norepi acting on alpha receptors on smooth muscle around arterioles Vasodialtion: epi (from adrenal medulla) acting on b2 receptors on smooth muscle around arterioles

Question 30

What is the first line of defense when cold receptors are activated?

Answer 30

heat conservation

Question 31

What happens if vasodilation isn't enough to shed excess body heat?

Answer 31

We sweat (excrete blood plasma [minus proteins] ). The sweat evaporates and is replaced by cool air, cooling us down.

Question 32

What controls sweating

Answer 32

anterior hypothalamus activating cholinergic neurons of the sympathetic nervous system via acetylcholine

Question 33

How does humidity affect sweating?

Answer 33

Water can't evaporate as easily in high humidity conditions, making it harder to cool off. (sweating depends on relative humidity)

Question 34

What do we use for non-shivering thermogenesis

Answer 34

brown adipose tissue (BAT)

Question 35

where is BAT? Who has it? What controls it?

Answer 35

Between shoulder blades and in core, primarily in infants but also found in adults *especially those who are in the cold a lot*, controlled by the posterior hypothalamus via the sympathetic nervous system and norepinephrine.

Question 36

How do mitochondria normally make ATP?

Answer 36

formation of a proton gradient in the ETC and proton transport through ATP synthase

Question 37

What so mitochondria in BAT do?

Answer 37

the hydrogen gradient is uncoupled- Thermogenin replaces ATP synthase and enables the movement of protons across the mitochondrial membrane without making ATP. This burns fat without producing any ATP so energy is released as heat.

Question 38

What stimulates BAT heat production?

Answer 38

NA binding to beta-adrenergic receptors.

Question 39

What is our extreme cold response? When do we use it?

Answer 39

shivering when body temp is 1C under vasoconstriction threshold.

Question 40

what muscles are involved in shivering?

Answer 40

Antagonistic muscle pairs which are rhythmically activated, trunk and neck muscles (all are skeletal muscles)

Question 41

What controls shivering?

Answer 41

posterior hypothalamus projections to spinal motor neurons that release Ach

Question 42

Why does shivering raise body temp?

Answer 42

burns energy without using it for productive work

Question 43

draw slide 34 (mechanisms of heat control)

Answer 43

\_(:D)_/

Question 44

What are behavioral thermoregulatory responses?

Answer 44

Things you do consciously to cool down/ warm up (turn on a fan, blanket time, put on a coat, use your warmie)

Question 45

What is the progression of symptoms as someone moves into hypothermia? What do they eventually die from if not warmed up?

Answer 45

feeling cold, shivering, intense shivering, numbness, extreme shivering, loss of movement, confusion, no more shivering, slow heartrate, shallow breathing, delirium, sleepiness, coma, death due to respiratory arrest (no tissue damage: processes just slow down until they eventually stop)

Question 46

Is hyperthermia a fever? What is the difference?

Answer 46

NO! Hyperthermia happens when your body has exhausted its resources in an attempt to downregulate body temp. Fever happens when your body changes the set point of your preferred temperature, leading to a heating up (can still cool down when fever breaks) (more on this later)

Question 46

What is the progression of symptoms as someone moves into hyperthermia? What do they eventually die from if not warmed up?

Answer 46

sweaty, discomfort, extreme sweating, breathlessness, fast HR, convulsions in infants, fainting, vomiting, dizziness, delirium, brain damage, shock, convulsions, respiratory collapse, death from inability to breathe.

Question 47

What area of the brain controls temperature reducing mechanisms?

Answer 47

anterior hypothalamus

Question 48

What area of the brain controls temperature conserving/generating mechanisms?

Answer 48

posterior hypothalamus

Question 49

In shivers what muscles are contracting?

Answer 49

flexors and extensors at the same time

Question 50

Where do voluntary motor responses to changes in temperature come from?

Answer 50

cerebral cortex