Thermoregulation Flashcards
Describe normal variation on core body temperature
Normal body temperature is 36.5-37.5 degrees C
Normal temperature: Tsetpoint - Tcore
Changes to T set point lead to changes in Tcore
Circadian rhythms varies temperature by 1 degree for sleep due to endogenous rhythms
What is core temperature?
Temperature of abdominal, thoracic and intracranial regions. It is regulated by heat transfer with shell and maintained within a couple of degrees of set point
What is set point?
Regulated by prostaglandins. The target temperature to be maintained, baseline temperature which physiological mechanisms work to regulate. Monitored by hypothalamus.
What is the shell temperature? How is it regulated?
Temperature of skin, subcutaneous fat and limb.
Regulated through changes in perfusion - vasodilation to increase blood flow, vasoconstriction to decrease blood flow, increase or decrease sweating
How to measure temperature? Worst to best
Axilla
Tympanic/skin
Oral
Rectal
Esophageal
Mixed venous blood
Explain the thermoregulatory mechanisms of heat loss
Evaporation
Radiation
Conduction
Convection
Explain the thermoregulatory mechanisms of sweating
Regulated by the autonomic nervous system.
Cholinergic sympathetic nerve fibres release acetylcholine.
Acetylcholine binds to muscarinic receptors on eccrine sweat glands.
Stimulates sweat production in response to internal (core body temperature) and external factors
Explain the thermoregulatory mechanisms of vasoconstriction
What is conduction
Direct transfer of heat between objects in contact
What is convection?
Transfer of thermal energy to moving fluid and gas
What is radiation
Transfer of thermal energy via electromagnetic radiation
What is evaporation?
Transfer of thermal energy as latent heat of evaporation
What is relative humidity?
Percentage of water vapour present in air compared to max possible at that temperature
Explain the thermoregulatory mechanisms of heat gain
Environmental
Thyroid hormones (increased basal metabolic rate)
Catabolism of food
Postural changes
Convection
Conduction
Radiation
Shivering
Basal metabolic activity
What factors affect heat exchange?
Vapour/temperature pressure gradient - skin and environment
Surface area:volume
Wind speed
Insulation
Pilo-erection
Shivering
Skin blood flow
Behaviour
Explain the thermoregulatory mechanisms of shivering
Explain the thermoregulatory mechanisms of vasodilation
Explain heat balance
Core temperature is regulated by compensatory body temperature changes ie heat gain to compensate for heat loss to increase in body temperature aim is for heat loss to equal heat gain
What is basal metabolic rate?
Rate at which body uses energy while at rest at maintain vital function
Explain the normal physiological response of fever
Explain the normal physiological response of hypothermia
Explain why adrenaline isn’t given at TB < 30 degrees
Explain why only defib 3 times in hypothermia
What is body temperature?
Due to biochemical processes which are constantly taking place, requiring energy
What is temperature regulation?
Ability of an organism to regulate its internal temperature to a particular level that provides optimal conditions for metabolic processes to occur
What are thermoreceptors?
Temperature sensitive receptors that inform the hypothalamus about change in temperature at the surface of the skin and at the core
What is neural control of temperature
- Detection of temperature - peripheral thermoreceptors monitor skin temperature, and central thermoreceptors monitor core temperature
- Transmission to the brain - information from the thermorecpetors is sent to the hypothalamic thermoregulatory integrating centre, it is also sent to the cerebral cortexr allowing for conscious perception of temperature
- The hypothalamic thermoregulatory integrating centre processes the temerature data and initiates appropriate responses
- Effector responses - sweat glands (activated to produce sweat for cooling down), smooth muscles in blood vessels (control vasodilation to release head or vasoconstriction to conserve heat) or skeletal muscles (activated to produce shivering for heat generation)
What is the thermoneutral zone (TNZ)?
Range of environmental temperatures where vasodilation/constriction controls thermoregulation.
For a clothed adult ranges in 21-26 degree weather are between 26 (lower critical temperature) and 29 degrees (upper critical temperature) ambient temperatures
What happens if the ambient temperature is outside the TNZ?
Above 29 degrees: increased metabolic rate for vasodilatin and sweating
Below 26 degrees: increased metabolic rate for shivering and vasoconstriction
What is
