Skin and Temperature Control

Question 1

What is core body temperature?

Answer 1

• Core body temp is normally 37 ± 0.5°C
• Above 41°C proteins start to denature
• Below 30°C lose consciousness

Question 2

What does body temperature vary with?

Answer 2

External temperature

Activity

Circadian rhythm

Menstrual cycle

Question 3

What are the ways heat is lossed and gained?

Answer 3

Question 4

What detects body temperature?

Answer 4

Cold and warm receptors

Question 5

Where are the peripheral thermoreceptors and the central thermoreceptors?

Answer 5

Peripheral thermoreceptors

located in the skin, especially in face, scrotum

Central thermoreceptors

located in spinal cord, abdominal organs, hypothalamus

Question 6

What source of temperature do the peripheral and central chemoreceptors detect?

Answer 6

Peripheral chemoreceptors: Change in environmental temperature

Central chemoreceptors: Change in core body temperature

Question 7

What do the peripheral and central chemoreceptors feed into?

Answer 7

Hypothalamic thermoregulatory centre

Question 8

In response to cold - how is heat generated by the body increased?

Answer 8

General metabolism

oxidative phosphorylation and other chemical reactions are not 100% efficient

Voluntary muscular activity

“futile” muscular activity

Shivering thermogenesis

involuntary muscular activity

Nonshivering thermogenesis

in humans, only significant in infants, due to brown adipose tissue

Question 9

How do we reduce heat loss in response to cold stress?

Answer 9

Vasomotor control

sympathetic arteriolar constriction reduces delivery of blood to the skin

Behavioural responses

reducing surface area, adding clothing, moving to warmer environment

Question 10

What is hypothermia defined as?

Answer 10

A fall in deep body temperature to below 35 degrees

Question 11

Who is at risk of hypthermia?

Answer 11

Those at risk

neonates

big SA:volume, not much fat, don’t shiver well, but do have BAT

elderly

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

vagrants - people living in the outdoors

cold store workers

outdoor pursuits

North Sea workers

Question 12

What is the treatment for hypothermia?

Answer 12

Treatment

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 – peripheral vasodilation – less blood in the heart – can cause heart attack

Question 13

What is the vascular response to cold stress (frost bite)

Answer 13

vasoconstriction

increase in viscosity

promotes thrombosis

causes anoxia

Question 14

What is the cellular response to cold stress (frost bite)

Answer 14

ice crystals form in extracellular space

increases extracellular osmolality

causes movement of water from intracellular space

cell dehydration and death

Question 15

What are the contributing factors that result in increasing heart attacks and strokes following periods of cold weather

Answer 15

Increased vasoconstriction and icreased blood viscosity

Question 16

In response to heat stress, how is heat production minimised?

Answer 16

Decreased physical activity and decreased food intake

Question 17

How is heat loss from the body maximised during reponse to heat stress?

Answer 17

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 18

What body temperature is associated with heat exhaustion?

Answer 18

Body temperature raised in a range (37.5 - 40) degrees celcius

Question 19

What is the physiological response to heat exhaustion?

Answer 19

Vasodilation and resultant drop in blood volume

Body’s fluid / salt regulation is disturbed as a result of excessive sweating

Question 20

What are the symptoms of heat exhaustion?

Answer 20

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

Question 21

What temperatures are assocaited with heat stroke?

Answer 21

Body temperature raised above 40 degrees

body’s temperature control mechanisms fail

Question 22

What are the symptoms of heat stroke?

Answer 22

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

Question 23

Who is at the most risk to heat stroke?

Answer 23

neonates & the elderly

people doing physical work in hot humid environments

workers wearing non-breathable protective clothing

Question 24

What is the treatment for heat stroke?

Answer 24

move to cool environment

remove clothing

fan

sponge with tepid water

give fluids (oral, intravenous)

Question 25

What causes fever?

Answer 25

Part of the body’s mechanism for fighting infection

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

Question 26

What controls the ‘set point’ for temperature control?

Answer 26

Hypothalamus

Question 27

How does a fever raise body temperature?

Answer 27

endogenous pyrogens shift the set point

caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus

explains why aspirin & paracetamol reduce fever

Question 28

Answer 28

Since the body’s set point increases in fever – you do all the things you can to increase body temperature like shivering and wearing more clothes until your body temperature rises to the set point