Lecture 10 Skin and Temperature Regulation

Question 1

Define homeothermic

Answer 1

maintains a stable internal body temperature regardless of external influence

Question 2

What happens when the body temperature is above 41 C

Answer 2

Proteins start the denature

Question 3

How is change in environmental temperature detected

Answer 3

Peripheral thermoreceptors in skin, face, scrotum

Question 4

How is change in core body temperature detected

Answer 4

Central thermoreceptors
spinal cord
abdominal organs
hypothalamus

Question 5

How is heat generated in the body in response to cold stress

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

Question 6

How is heat loss from the body reduced

Answer 6

– Vasomotor control- sympathetic arteriolar constriction reduced delivery of blood to the skin
– Behavioural responses- reducing surface area, adding clothing, moving to warmer environment

Question 7

Who are at ask of hypothermia

Answer 7

•	Hypothermia- below 35 C
•	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
–	cold store workers
–	outdoor pursuits
–	North Sea workers

Question 8

Treatment for hypothermia

Answer 8

• 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 9

How does frost bite occur vascular wise

Answer 9

• vasoconstriction
• increase in viscosity
• promotes thrombosis
• causes anoxia

Question 10

How does frost bite happen cellular wise

Answer 10

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

Question 11

What does cold stress increase the risk of

Answer 11

Heart attacks and strokes due to increased blood viscosity

Question 12

How is heat production minimised

Answer 12

• Decreased physical activity

* Decreased food intake

Question 13

How is heat loss from the body increased

Answer 13

• 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 14

What is heat exhaustion

Answer 14

• 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

Question 15

What are the symptoms of heat exhaustion

Answer 15

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

Question 16

What is heat stroke

Answer 16

• body temperature raised above 40ºC

* body’s temperature control mechanisms fail

Question 17

What are the symptoms of heat stroke

Answer 17

hot dry skin (sweating ceased) & circulatory collapse

Question 18

Who are most at risk of a heat stroke

Answer 18

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

Question 19

How is heat stroke treated

Answer 19

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

Question 20

What is the mechanism of a fever

Answer 20

• Part of the 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