Skin & Temperature control Flashcards
- what is core body temp
- what does it vary with?
- what happens above 41°C
- what happens below 30°C
- 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
how is core body temp maintained?
by balacing heat loss and heat gain
What are the 4 factors that affect thermal balance and explain them
- 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
how do we detect body temperature?
- 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
How can you tell warm and cold receptors apart?
via their dynamic response to change in temp: diagram
What are the different classes of thermoreceptors & where are they located?
- 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
In response to cold stress, how is heat generation within the body increased?
- 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
in response to cold stress, how is heat loss from the body reduced?
- sympathetic arterial constriction
- behavioural responses ie adding clothing, moving to warmer environment
- hypothermia- body temp reduced to 35°C
who are those at risk with the cold?
- neonates
- elderly
- homeless
why are neonates at risk in the cold?
- not much fat
- don’t shiver well
why are the elderly at risk in the cold?
- don’t detect temp change so well
- less shivering capacity
- more immobile
what is the treatment of cold stress?
- 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
what is a condition which arises as a response to cold stress?
frost bite
in frost bite, why may tissue damage occur?
may result from
- direct cellular damage
or
- secondary effects of vascular damage
how does vascular damage contirbute to frostbite?
- vasoconstriction
- increase in blood viscosity
- increase chance of clot
- thrombosis –> anoxia
how does cellular damage contribute to frostbite?
- ice crystals form in ECF
- increases extracellular osmolality
- draws fluid out of cells, they get dehydrated
- cell death
what does cold stress cause?
increase in mortality
in response to heat stress, heat production is minimised by what?
- reduced food intake
- decreased physical activity
in response to heat stress, heat loss from the body is increased by?
- arteriolar dilation
- sweating - sympathetic cholinergic fibres increase evaporative heat loss
- behavioural responses
-removing clothing, moving to shaded area
what are some consequences of heat stress?
- heat exhaustion
- heat stroke
what is heat exhaustion?
- 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
what are symptoms of heat exhaustion?
- headache
- confusion
- nausea
- clammy skin/profuse sweating
- tachycardia
- hypotension
- fainting & collapse
what is heat stroke?
- body temperature raised to above 40degrees Celsius
- body’s temp control mechanisms fail
what are symptoms of heat stroke?
hot dry skin & circulatory collapse
