Skin and temperature control

Question 1

What is the normal core body temperature? How is it maintained?

Answer 1

37 +/- 0.5°C

Core temperature is maintained by balancing heat loss and heat gain

Question 2

At what temperature do proteins start to denature?

Answer 2

Above 41°C

Question 3

At what temperature do humans lose consciousness

Answer 3

Below 30°C

Hypothermia = below 35°C

Question 4

What does our body temp vary with?

Answer 4

External temp
Activity
Circadian rhythm
Menstrual cycle

Question 5

Where are Peripheral thermoreceptors located? What do they detect?

Answer 5

Located in the skin, especially in face, scrotum

Detect a change in the environmental temperature

Question 6

Where are Central thermoreceptors located?

What do they detect?

Answer 6

Located in spinal cord, abdominal organs, hypothalamus

Detect a change in core body temperature

Question 7

In which ways is heat lost from the body

Answer 7

Convection

Evaporation - respiration + sweating

Radiation - 60% heat loss

Conduction - heat transfer through touch

Question 8

Sources of heat for the body through…

Answer 8

Convection
Conduction
Radiation

Question 9

Response to cold stress: How is heat generated in the body (4)

Answer 9

General metabolism

Voluntary muscular activity

Shivering thermogenesis - involuntary

Non-shivering thermogenesis - only significant in infants due to brown adipose tissue

Question 10

How is heat loss from the body reduced in response to cold stress? (2)

Answer 10

Vasomotor control
- sympathetic arteriolar constriction reduces delivery of blood to the skin

Behavioural responses
- reducing surface area, adding clothing, moving to warmer environment

Question 11

Who is at risk of hypothermia? (6)

Answer 11

Neonates

Elderly - do not detect temp change so well, less shivering capacity, more immobile

Vagrants - homeless/beggars

Cold store workers

Outdoor pursuits

North Sea workers

Question 12

Why are Neonates at risk of hypothermia?

Answer 12

Babies have a big SA:volume ratio

This means they dehydrate quicker due to having a bigger surface area than fluid in them.

They don’t have much fat, don’t shiver well, but do have BAT (brown adipose tissue) to produce heat

Question 13

Treatment for hypothermia

Answer 13

Dry/insulate to prevent further heat loss

Slow re-warming with bag/blankets

Internal re-warming with hot drinks and/or warm air

Fast re-warming by immersion in water, extracorporeal circulation

Question 14

Vascular response to cold stress

Answer 14

vasoconstriction
increase in viscosity
promotes thrombosis
causes anoxia

Question 15

Cellular response to cold stress

Answer 15

ice crystals form in extracellular space
increases extracellular osmolality
causes movement of water from intracellular space
cell dehydration and death

Question 16

How is there an increase in heart attacks and strokes following periods of cold weather?

Answer 16

Cold response causes increased vasoconstriction and increased blood viscosity which contribute

Question 17

How is heat production minimised? (2)

Answer 17

Decreased physical activity

Decreased food intake

Question 18

How is heat loss from the body increased? (3) ie how to cool down

Answer 18

Vasomotor control - arteriolar dilation increases delivery of blood to the skin

Sweating - sympathetic cholinergic fibres increase evaporative heat loss

Behavioural responses - increasing surface area, removing clothing, moving to shaded area

Question 19

Heat exhaustion (heat illness)

Answer 19

Body temperature raised in range 37.5-40ºC results in vasodilation and drop in central blood volume

Caused by a disturbance of the body’s fluid/salt balance due to excessive sweating.

Symptoms include headache, confusion, nausea, profuse sweating, clammy skin, tachycardia, hypotension, weak pulse, fainting & collapse.

Question 20

Heat stroke (heat injury)

Answer 20

Body temperature raised above 40ºC

Body’s temperature control mechanisms fail

Symptoms include hot dry skin (sweating ceased) & circulatory collapse

Question 21

Who is most at risk of heat stress

Answer 21

Neonates & the elderly

People doing physical work in hot humid environments

Workers wearing non-breathable protective clothing

Question 22

Treatment of someone exposed to heat stress of some sort

Answer 22

Move to cool environment

Remove clothing

Fan

Sponge with lukewarm water

Give fluids (oral, intravenous)

Question 23

What is a Fever? What causes it?

Answer 23

Part of the body’s mechanism for fighting infection

Caused by endogenous pyrogens (IL-1, IL-6)

Endogenous pyrogens shift the ‘set point’ (controlled by hypothalamus). Caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus

Body temperature regulates around a higher than normal body temperature

Mild fever can be beneficial but severe fever is dangerous

Question 24

Difference in core temp and set temp during exercise and when you have a fever

Answer 24

Exercise: Tset is normal but your Tcore increases

Fever: Tset increases to about the same as your Tcore