Physiology 7: Body temp Flashcards
What happens if body temp is too low?
Too low
- Slow metabolism
Inadequate O2 supply (molecules have less kinetic energy, lower O2 affinity)
Freezing of cells
What happens if body temp is too high?
Too high
Proteins denature
Inadequate O2 supply (metabolic rate increases, tissue O2 requirement increases)
Membrane structure alterations
= geographical ranges of animals would be restricted to temp favourable regions
What are the 4 heat exchange processes?
Radiation
Convection
Conduction
Evaporation
Describe radiation
Without direct contact
In humans, 60% heat loss
E.g from the sun
Describe convection
Air/fluid across body surface
15% heat loss
Describe conduction
With direct contact
In humans, 3% heat loss
Describe evaporation
Water from body surface
22% heat loss
How to minimise heat loss through radiation in a cold environ
Decreasing SA:V
Layers of clothing
How to minimise heat loss through convection in a cold environ
Layers of clothing
Sheltered from wind
How to minimise heat loss through evaporation in a cold environ
Little exposed skin
Dry
How to minimise heat loss through respiration in a cold environ
Cover mouth and nose, stops cold air from entering lungs
larger animals have ______ SA:V so lose heat less quickly
smaller
Describe ectotherms
Body temp fluctuates with environ
Temp conformers
Heat is derived from environ
E.g reptiles, amphibians
What are ectotherms also known as
poikilotherms
Give an example of an ecotherm
Reptiles, amphibians
Describe endotherms
Constant body temp
Regulators
Heat derived from metabolism
What are endotherms also known as
homeotherms
Give an example of an endotherm
humans
What are the benefits for ectotherms?
Metabolic rate is 5x slower than endo
Less energy = less food = less h20
Can devote large proportion of energy budget to reproduction
Good colonisers of poor arid environs
What are the disadvantages for ectotherms?
No nocturnal environ niches (unless in tropical and summer temperate areas)
Cannot sustain high activity bursts as risks O2 debt
Anaerobic = lactate accumulation = fatigue
*
What are the benefits for endotherms?
Can sustain high activity burst
Nocturnal activity
Able to exploit cooler environs
Forage widely and migrate over long distances
What are the disadvantages for endotherms?
Require larger body sixes with lower SA:V
Metabolic rate 5x faster than ecto
*
What are the 3 mechanisms for insulation?
Brown fat
Blubber
Fur/hair/feathers
Describe brown fat
Brown fat (adipose tissue)
Specialised for rapid heat production
Describe blubber
Thick vascularized adipose tissue under skin of sea mammals
Low thermal conductivity of skin, low metabolic activity
What is the function of fur/hair/feathers
Reduces convection by trapping layer of warm air close to skin surface
Effect is lost if air is replaced by water
Describe countercurrent heat exchanges
Blood in hot artery flows by colder veins and exchanges heat, so cold blood does not return to the heart
Where are countercurrent heat exchanges found?
birds, tongues of whales, dolphins fins
Describe the thermal neutral zone
→ above upper critical limit, body must expend energy to decrease body temp
→ lower critical ***
Hypothalamus = control centre for this
What are the thermoregulatory processes below the lower critical limit?
Vasoconstriction
Shivering
Hormones
Brown adipose tissue
Describe vasoconstriction
Diameter of blood vessels decreases
Blood flow to skin decreases
Skin cools
Less heat loss to environ through radiation, conduction and convection
Heat trapped in body core
What is shivering?
Rapid contriction of skeletal muscles
What are the hormones involved in the thermoregulatory processes below the lower critical limit?
Adrenaline
Thyroxine
Describe how the brown adipose tissue is involved in the thermoregulatory processes below the lower critical limit
Rich in mitochondria = breakdown fuel into heat only
Usually broken down into energy and heat
Rich blood supply
Found in newborn mammals, hibernating mammals and the necks of human adults
Non-shivering thermogenesis
What are the thermoregulatory processes below the upper critical limit?
Vasodilation
Perspiration
Panting
Describe vasodilation
Diameter increases
Blood flow to skin increases
Skin heats up
***
Describe hypothermia
if metabolic heat production cannot compensate for heat loss
Describe hyperthermia
if evaporative cooling cannot counteract heat gain
