Lecture 2: Skin and Temperature Control

Question 1

above which temperature do proteins start to denature?

Answer 1

41 degrees

Question 2

below which temperature do you lose conciousness?

Answer 2

below 30 degrees celcius

Question 3

normal body temperature varies with:

Answer 3

• external temperature
• activity
• ciracidan rhythm
• menstrual cycle

Question 4

where are peripheral thermoreceptors located?

Answer 4

skin, especially in face, scrotum

Question 5

heat generated within the body is increased by which mechanisms?

Answer 5

• general metabolism: oxidative phosphorylation and other chemical reactions are not 100% efficient
• voluntary muscular activity: ‘futile’ muscular activity
• shivering thermogenesis: involuntary muscular activity
• non-shivering thermogenesis: only significant in infants due to brown adipose tissue

Question 6

heat loss from the body is reduced by which mechanisms?

Answer 6

• vasomotor control: sympathetic arteriolar constriction reduces deliver of blood to the skin
• behavioural responses: adding clothing, moving to warmer environment, reducing surface area

Question 7

what is considered hypothermia?

Answer 7

a fall in deep body temperature to below 35 degrees celcius

Question 8

which groups are at risk of hypothermia?

Answer 8

• neonates (big SA:volume, not much fat, do not shiver well, but do have BAT)
• elderly
• homeless people
• cold store workers
• outdoor pursuits

Question 9

how do we treat cold stress?

Answer 9

• dry/insulate to prevent further heat loss
• slow re-warming with bag/blankets
• internal re-warming with hot drinks and/or warm air
• rapid re-warming by immersion in water, extracorpeal circulation

Question 10

what are the consequences of cold stress?

Answer 10

• frost bite
• vascular: vasoconstriction, increase in viscosity, promotes thrombosis, causes anoxia
• cellular: ice crystals form in EC space, increases ECF osmolality, causes movement of water from ICF, cell dehydration and death
• winter mortality: increases in MIs and strokes

Question 11

heat production is minimised by?

Answer 11

decreased physical activity
decreased food intake

Question 12

heat loss from the body is increased by

Answer 12

• vasomotor control: arteriolar dilation increases delivery of blood to the skin
• sweating: sympathetic cholinergic fibres increase evaporative heat loss
• behavioural responsed: removing clothing, moving to shaded area, increasing surface area

Question 13

what are the consequences of overheating?

Answer 13

• heat exhaustion (heat illness)
• heat stroke (heat injury)

Question 14

describe heat exhaustion

Answer 14

• heat illness with a body temperature raised in the range 37.5-30 C.
• results in vasodilation and drop in central blood volume.
• caused by a disturbance of the body’s fluid/salt balance due to excessive sweating/

Question 15

heat exhaustion/illness symptoms

Answer 15

• headache
• confusion
• nausea
• profuse sweating
• clammy skin
• tachycardia
• hypotension
• weak pulse
• fainting and collapse

Question 16

describe heat stroke

Answer 16

• heat injury when body temperature raised above 40 C
• body temperatures control mechanisms fail

Question 17

heat stroke/injury symptoms

Answer 17

• hot dry skin (sweating stops)
• circulatory collapse

Question 18

which groups are most at risk of heat stress?

Answer 18

• neonates and the elderly
• people doing physical work in hot, humid environments
• workers wearing non-breathable protective clothing

Question 19

heat stress treatment

Answer 19

• move to cool environment
• remove clothing
• fan
• sponge with tepid water
• give fluids (oral, IV)

Question 20

describe fever and what causes it

Answer 20

• part of body’s mechanism for fighting infection
• caused by endogenous pyrogens (IL-1, IL-6)
• concept of ‘set point’ controlled by the hypothalamus: endogenous pyrogens shift the set point, caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus