Skin and Temperature Control

Question 1

what . is the normal body temperature and what happens when the body gets too hot and what happens when the body gets too cold?

Answer 1

• Man is homeothermic
• 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

• Varies with

• external temp
• activity
• circadian rhythm
• menstrual cycle

Question 3

Core temperature is maintained by balancing heat ____ and heat ____

Answer 3

loss

gain

Question 4

what is involvedi n thermal balance?

Answer 4

Question 5

what is responsible for the detection of body temperature?

Answer 5

“Cold” receptors and “warm receptors

Warm receptors fire when it is hotter when it should be and vice verse for cold receptors

Question 6

thermoreceptors are responsible for the detection of body temperature, where are they?

Answer 6

Peripheral thermoreceptors - located in the skin, especially in face, scrotum

Central thermoreceptors - located in spinal cord, abdominal organs, hypothalamus

Question 7

changes in the environmental temperature are detected by what?

changes in the core body temperature are detected by what?

and where deos this information go?

Answer 7

Question 8

one response to cold stress is increases the heat generated inside the body, how is this done?

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

one response to cold stress is decreasing tthe heat loss form the body, how is this done?

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

Hypothermia - a fall in deep body temperature to below 35ºC

who is at risk?

Answer 10

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 (homeless)

cold store workers

outdoor pursuits

North Sea workers

Question 11

what is the treatment of hypothermia or cold stress

Answer 11

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 12

what vascular changes happen in frost bite?

Answer 12

vasoconstriction

increase in viscosity

promotes thrombosis

causes anoxia

Question 13

what cellular changes happen in frost bite?

Answer 13

ice crystals form in extracellular space

increases extracellular osmolality

causes movement of water from intracellular space

cell dehydration and death

Question 14

describe the winter mortality in the UK?

Answer 14

40% excess mortality in winter in UK

partly due to increases in heart attacks and strokes following periods of cold weather

increased vasoconstriction and increased blood viscosity contribute

Question 15

is response ot heat sress, heat production is minimised by what?

Answer 15

Decreased physical activity

Decreased food intake

Question 16

is response ot heat sress, heat loss form the body is increased by what?

Answer 16

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 17

what is heat exhaustion (heat illness) and what does it cause?

Answer 17

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 18

what is heat stroke (heat injury) and what does it cause?

Answer 18

body temperature raised above 40ºC

body’s temperature control mechanisms fail

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

Question 19

who is most at risk of heat exhaustion or heat stroke?

Answer 19

neonates & the elderly

people doing physical work in hot humid environments

workers wearing non-breathable protective clothing

Question 20

what is the treatment of heat exhaustion or heat stroke?

Answer 20

move to cool environment

remove clothing

fan

sponge with tepid water

give fluids (oral, intravenous)

Question 21

what is a fever?

Answer 21

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
• explains why aspirin & paracetamol reduce fever

Analogy of a thermostat that has been reset

Body temperature regulates around a higher than normal body temperature

Mild fever is beneficial

Severe fever is dangerous

Question 22

why may you feel cold in a fever even though your body core temperautre is increased?

Answer 22

If in fever the set point is shifted up so for the period of set higher then core then you feel cold as your core temp is lower than the set point