L26 - Thermoregulation 1

Question 1

At what temperature are proteins denatured?

Answer 1

41˚C

Question 2

At what body temperature will a person die?

Answer 2

43˚C

Question 3

At what temperature will all cells in the body die?

Answer 3

50˚C

Question 4

At what temperature do you start to “feel cold” when nude?

Answer 4

25˚C, initiating a physiological response

Question 5

Above which temperature are you safe while wearing light clothing?

Answer 5

0˚C

Question 6

Above which temperature are you safe while properly clothed?

Answer 6

-29˚C

Question 7

At which temperature does the respiratory tract begin to freeze?

Answer 7

-50˚C

Question 8

Which structures/processes must be involved in thermoregulation?

Answer 8

ANS, skin, motor cortex, hypothalamus, renin angiotensin aldosterone system, ANP, vasopressin, cardiovascular system, respiratory system

Question 9

What are the two types of regulation that thermoregulation requires?

Answer 9

autonomic regulation and behavioural regulation

Question 10

What does autonomic regulation involve?

Answer 10

redistribution of blood (CVS), perspiration, fluid balance (renal and endocrine), metabolic changes (respiratory system), non-voluntary skeletal muscle effects

Question 11

What does behavioural regulation involve?

Answer 11

changing environment, altering clothing, adjusting fluid/food intake, skeletal muscle effects

Question 12

What is core temperature?

Answer 12

temperature inside the chest, abdomen and brain

maintained at ~37˚C ± 0.5˚C

Question 13

What is the normal core temperature range?

Answer 13

35.5 - 37.7˚C

Question 14

What is peripheral (shell) temperature?

Answer 14

can vary broadly
skin temperature varies with environment
working muscles during exercise may reach 41˚C

Question 15

What is the physiological aim of the body in regards to body temperature?

Answer 15

maintain a stable core temperature, especially in the brain

Question 16

What temperature results in hypothermia? What about hyperthermia and heatstroke?

Answer 16

<35˚C

>40˚C, >42˚C

Question 17

What are the two main classes of thermoreceptors?

Answer 17

central thermoreceptors and peripheral thermoreceptors

Question 18

Where are central thermoreceptors located and what is their role?

Answer 18

anterior hypothalamus

detect temperature changes in the blood

Question 19

Where are peripheral thermoreceptors located and what is their role?

Answer 19

located in the skin and viscera
report to central thermoreceptors
can produce local effects

Question 20

What are the four main subclasses of peripheral thermoreceptor?

Answer 20

warm and cold receptors

cold pain and heat pain receptors

Question 21

What are central thermoreceptors physically connected to in the hypothalamus?

Answer 21

the thermoregulatory center which indirectly sends out autonomic signals through the ANS to skin arterioles, skeletal muscle and sweat glands in order to maintain core body temperature

Question 22

How is heat generated?

Answer 22

internally: metabolism, heat released during muscle contractions
externally: heat input if environmental temperature exceeds body temp

Question 23

How is heat lost?

Answer 23

environmental heat loss: radiation, conduction, convection and evaporation

Question 24

What is heat?

Answer 24

heat = kinetic energy (momentum) of particles

moves from hotter objects to colder objects

Question 25

What is conduction?

Answer 25

transfer of heat from one object to another via direct contact

Question 26

What does it mean if a material is better at transferring heat than other materials?

Answer 26

this material is a conductor | opposite is an insulator

Question 27

What is radiation?

Answer 27

electromagnetic radiation generated by thermal motion of charged particles

Question 28

What is convection?

Answer 28

hot air rises and cold air sinks, thus heat can be "carried away" from the body's surface

Question 29

What is evaporation?

Answer 29

conversion of water from liquid to gas by using energy | at body temperature, 2400 calories are required to evaporate 1ml of water

Question 30

How much heat loss is accounted for by radiation?

Answer 30

~60% of heat loss

Question 31

How much heat loss is accounted for by conduction and convection?

Answer 31

~20% of heat loss | increased with wind

Question 32

How much heat loss is accounted for by evaporation?

Answer 32

not necessary <32˚C

Question 33

How is heat loss maximised by the body?

Answer 33

increasing cutaneous blood flow and increase sweating (if necessary)

Question 34

How is cutaneous blood flow increased?

Answer 34

under control of hypothalamic thermoregulatory centre sympathetic cholinergic neurons dilate cutaneous blood vessels ↑ blood flow to skin means cardiac output must ↑ to maintain BP (HR + SV ↑)

Question 35

How is sweating increased? How does sweating maximise heat loss?

Answer 35

sweat production activated by sympathetic cholinergic neurons cooling by evaporation: enhanced by ↑ air flow, inhibited by humidity can increase heat loss ~20 fold

Question 36

What would happen to ventilation (at rest) when body temperature rises?

Answer 36

increase this is because as temperature ↑, enzymatic activity ↑ as well resulting in ↑ metabolism and therefore ↑ requirement for O2 ∴ ventilation ↑

Question 37

What are some behavioural adaptations to increasing heat loss?

Answer 37

seek shade, wearing loose/light clothing, inactivity, decreasing food intake, eating food with high water content (becomes more appealing)

Question 38

What is heat syncope? What is "prickly" heat?

Answer 38

excessive blood diverted to skin reduces blood flow to brain | inflammation of sweat glands - itchy "pimply" rash

Question 39

What is heat exhaustion?

Answer 39

``` moderate hyperthermia (core temp 37˚C - 40˚C) dizziness, fatigue, nausea, possible collapse ```

Question 40

What is heatstroke?

Answer 40

severe hyperthermia (core temp >40˚C) common during heat waves and in athletes kills more Australians than all other natural hazards combined

Question 41

Which characteristics would be anatomically advantageous for maintaining a low body temperature in the heat?

Answer 41

long, lean extremities, a high surface-area-to-volume ratio and thick hair only on regions facing the sun

Question 42

How do long, lean extremities increase heat loss?

Answer 42

increase surface-area-to-volume ratio and increases conduction/radiation hence heat loss

Question 43

Why is an insulating fat layer which is consolidated to one area beneficial to heat loss?

Answer 43

allows more heat loss from extremities | also to put it simply there is insulation from heat of sun

Question 44

Which characteristics would be anatomically advantageous for maintaining a high body temperature in the cold?

Answer 44

low surface-area-to-volume ratio reduces heat loss | subcutaneous fat evenly distributed as insulation to retain heat

Question 45

How have humans evolved to different climates?

Answer 45

humans evolved primarily in an African climate, however, some anatomical adaptations have evolved between races based on climate (environmental) differences