L6. Physiological responses to heat and cold stress

Question 1

What are the main mechanisms of heat transfer in humans?

Answer 1

Convection, radiation, conduction, and evaporation

Question 2

What is the primary mechanism for heat loss in humans during high temperatures?

Answer 2

Evaporation of sweat

Question 3

How does the pre-optic anterior hypothalamus regulate temperature?

Answer 3

It integrates signals from various thermoreceptors to produce effector responses

Question 4

What is the role of TRPV3 ion channels in thermoregulation?

Answer 4

They drive warm afferent signals

Question 5

What is the significance of mean body temperature in thermoregulation?

Answer 5

It determines physiological responses to heat and cold stress

Question 6

What happens to cardiac output during hyperthermia?

Answer 6

It increases, primarily driven by heart rate

Question 7

What is the functional importance of increasing skin blood flow during heat stress?

Answer 7

It enhances convective and evaporative heat loss

Question 8

What are the three main pathways through which heat stress can cause mortality?

Answer 8

Cardiovascular collapse, splanchnic hypoperfusion, and microbial translocation

Question 9

How does skin temperature affect the onset of sweating?

Answer 9

Higher skin temperatures lower the core temperature threshold for sweating

Question 10

What is the impact of dehydration on thermoregulation?

Answer 10

It exacerbates cardiovascular strain and reduces sweat efficiency

Question 11

What is core temperature typically at rest?

Answer 11

Between 36.5°C and 37.5°C

Question 12

At what core temperature does protein misfolding and cell death occur?

Answer 12

Around 42°C

Question 13

What is the role of brown adipose tissue in cold stress?

Answer 13

It generates heat through non-shivering thermogenesis

Question 14

How can cold acclimation affect brown adipose tissue activity?

Answer 14

It increases functional activity and reduces reliance on shivering

Question 15

What are the primary consequences of reduced splanchnic blood flow during heat stress?

Answer 15

Local hypoxia, reduced renal and hepatic function, and increased microbial translocation

Question 16

What is the functional importance of microbial translocation in heat stress?

Answer 16

It can lead to sepsis and multiple organ failure

Question 17

What is the primary physiological response to skin temperature below 35°C?

Answer 17

Hypothermia and nervous system impairment

Question 18

How does heat stress impact the cardiovascular system?

Answer 18

It increases heart rate and redistributes blood to the skin

Question 19

What physiological response occurs when skin blood flow is high?

Answer 19

Increased heat dissipation and sweat evaporation efficiency

Question 20

What happens during extreme heat stress if sweat evaporation is insufficient?

Answer 20

Core temperature rises continuously, risking heat-related illnesses

Question 21

How do thermosensitive ion channels affect behavioural responses?

Answer 21

They drive behaviours like adjusting clothing and seeking cooler environments

Question 22

What is the lowest recorded surviving core temperature?

Answer 22

13°C during extreme hypothermia

Question 23

How does the body adapt to repeated heat stress?

Answer 23

Faster onset of sweating and vasodilation in acclimated individuals

Question 24

What is the impact of heat stress on kidney function?

Answer 24

Reduced glomerular filtration rate and tubular reabsorption

Question 25

What is the significance of convection in heat transfer?

Answer 25

It moves heat from the skin to the air via fluid movement

Question 26

What is the physiological importance of increasing core temperature during exercise?

Answer 26

It helps balance heat gain and loss through effective responses

Question 27

What is a common cause of heat-related deaths in elderly individuals?

Answer 27

Cardiovascular collapse due to vasodilation and insufficient cardiac output

Question 28

What did studies on sugarcane workers reveal about heat stress?

Answer 28

It increases the risk of chronic and acute kidney injuries

Question 29

How does sweating differ in humid environments?

Answer 29

Sweat evaporation is reduced, limiting cooling efficiency

Question 30

What is the relationship between sweat evaporation and cooling?

Answer 30

1 gram of evaporated sweat removes approximately 2400 joules of heat

Question 31

How does heat stress affect microbial integrity in the gut?

Answer 31

Decreased blood flow damages epithelial barriers, increasing translocation

Question 32

What is the primary thermoregulatory function of brown adipose tissue?

Answer 32

Uncoupling protein 1 (UCP1) facilitates heat production without ATP synthesis

Question 33

What physiological changes occur with cold acclimation?

Answer 33

Enhanced brown adipose tissue activity and reduced shivering reliance

Question 34

How does heat stress influence renal blood flow?

Answer 34

It decreases renal perfusion, impairing filtration and reabsorption

Question 35

What did Minson et al.’s study show about skin temperature changes?

Answer 35

Rapid increases in skin temperature drive heat dissipation responses

Question 36

How does thermoregulation prioritize blood distribution?

Answer 36

It favors skin perfusion over splanchnic circulation to enhance cooling

Question 37

What role does behavioural thermoregulation play in heat stress?

Answer 37

It minimizes energy costs by modifying the environment or activity

Question 38

What is the role of heat shock proteins during hyperthermia?

Answer 38

They protect cells from thermal damage by stabilizing proteins

Question 39

What is the physiological threshold for hypothermia?

Answer 39

Core temperatures below 35°C initiate hypothermia effects

Question 40

What is the role of splanchnic vasoconstriction during heat stress?

Answer 40

It helps maintain blood pressure by reducing blood flow to central organs