Skin & Temperature control

Question 1

• what is core body temp
• what does it vary with?
• what happens above 41°C
• what happens below 30°C

Answer 1

• CBT is normally 37 +/- 0.5°C
• varies with
• external temperature
• activity
• menstrual cycle
• circadian rhythm
• above 41°C, proteins denature
• below 30°C, lose consciousness

Question 2

how is core body temp maintained?

Answer 2

by balacing heat loss and heat gain

Question 3

What are the 4 factors that affect thermal balance and explain them

Answer 3

• evaporation
• respiration + sweating
• radiation
• radiation of heat, both into body ie through sun and out ie after exercise
• accounts for 60% of heat loss
• conduction
• heat transfer direct between touching objects
• convection
• heat transfer due to bulk movement of molecules within gases and liquids
• blood causes convection as it transfers heat from core to periphery ie skin

Question 4

how do we detect body temperature?

Answer 4

• cold and warm receptors
• some receptors that fire when cold and others when warm
• Range in middle when cold and warm fire at same rate

Question 5

How can you tell warm and cold receptors apart?

Answer 5

via their dynamic response to change in temp: diagram

Question 6

What are the different classes of thermoreceptors & where are they located?

Answer 6

• peripheral thermoreceptors

located in skin, especially in face, scrotum as sperm needs to be kept cool

• central thermoreceptors

located in spinal cord, abdominal organs, hypothalamus

Question 7

In response to cold stress, how is heat generation within the body increased?

Answer 7

• increased metabolism & background metabolic rate
• Voluntary muscular activity
• Shivering thermogenesis
• involuntary muscle activity: use skeletal muscle, make it contract to produce heat as by-product
• Non-shivering thermogenesis
• only significant in infants, due to brown adipose tissue

Question 8

in response to cold stress, how is heat loss from the body reduced?

Answer 8

• sympathetic arterial constriction
• behavioural responses ie adding clothing, moving to warmer environment
• hypothermia- body temp reduced to 35°C

Question 9

who are those at risk with the cold?

Answer 9

• neonates
• elderly
• homeless

Question 10

why are neonates at risk in the cold?

Answer 10

• not much fat
• don’t shiver well

Question 11

why are the elderly at risk in the cold?

Answer 11

• don’t detect temp change so well
• less shivering capacity
• more immobile

Question 12

what is the treatment of cold stress?

Answer 12

• 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 13

what is a condition which arises as a response to cold stress?

Answer 13

frost bite

Question 14

in frost bite, why may tissue damage occur?

Answer 14

may result from

• direct cellular damage

or

• secondary effects of vascular damage

Question 15

how does vascular damage contirbute to frostbite?

Answer 15

1. vasoconstriction
2. increase in blood viscosity
3. increase chance of clot
4. thrombosis –> anoxia

Question 16

how does cellular damage contribute to frostbite?

Answer 16

1. ice crystals form in ECF
2. increases extracellular osmolality
3. draws fluid out of cells, they get dehydrated
4. cell death

Question 17

what does cold stress cause?

Answer 17

increase in mortality

Question 18

in response to heat stress, heat production is minimised by what?

Answer 18

• reduced food intake
• decreased physical activity

Question 19

in response to heat stress, heat loss from the body is increased by?

Answer 19

• arteriolar dilation
• sweating - sympathetic cholinergic fibres increase evaporative heat loss
• behavioural responses

-removing clothing, moving to shaded area

Question 20

what are some consequences of heat stress?

Answer 20

• heat exhaustion
• heat stroke

Question 21

what is heat exhaustion?

Answer 21

• body temp raised in range 37.5- 40 degrees celsius
• 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 22

what are symptoms of heat exhaustion?

Answer 22

• headache
• confusion
• nausea
• clammy skin/profuse sweating
• tachycardia
• hypotension
• fainting & collapse

Question 23

what is heat stroke?

Answer 23

• body temperature raised to above 40degrees Celsius
• body’s temp control mechanisms fail

Question 24

what are symptoms of heat stroke?

Answer 24

hot dry skin & circulatory collapse

Question 25

who are the most at risk in heat?

Answer 25

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

Question 26

treatment of heat stress?

Answer 26

• move to cool environment
• remove clothing
• fan
• sponge with tepid water
• give fluids

Question 27

• what is fever?
• what is it caused by?

Answer 27

• part of body’s mechanism for fighting infection
• caused by endogenous pyrogens ie IL-1, IL-6

Question 28

how does fever occur?

Answer 28

• endogenous pyrogens shift set point
• caused by local production of prostaglandins by cyclo-oxygenase in hypothalamus

Question 29

how do anti-pyretics such as aspirin and paracetamol reduce fever ?

Answer 29

by inhibiting enzyme cyclo-oxygenase & reducing levels of prostaglandins

Question 30

what is fever’s effect?

Answer 30

to increase set point so to regulate it around 39, so start doing things to increase core temperature to reach that ie shivering