Thermoregulation

Thermoregulation

Maintenance of a relatively constant core body temp. to maintain optimum enzyme activity

Ways of losing heat

• Evaporation of water

  • latent heat lost from surface (mouth /sweat)

• Radiation to surroundings

  • IR from skin → surroundings absorb it

• Convection to surroundings

  • Convection currents form from skin (warm air rises, cooler air sinks)

• Conduction to surroundings

  • Passes thermal energy between particles as they vibrate more 

Ectotherms

• Use surroundings to warm bodies 

• Coe body temp. heavily dependent on environment 

• Invertebrate animals 

  • Those in water don’t need to thermoregulate 

Why do ectotherms in water not need to thermoregulate 

Water has high heat capacity, temp doesn’t change much 

Endotherms

• Mammals and birds

• Rely on metabolic processes to warm up, usually maintain v. stable core 

• Use heat produced internally to maintain body temperature

Endo and Ecto metabolic rates

Endo metabolic rate 5x higher than ecto

• Endo need to consume more food to meet metabolic needs

• Ecto use less of their food in resp. , need to find less food, can last long w.out food

Ectotherm behavioural responses (increase temp.)

• Bask in sun

• Orientate / Change bodies so that max. SA exposed to sun

• Press bodies against warm ground 

• Exothermic metabolic reactions (vibrate wings, contract muscles & vibrate)

Ectotherm behavioural response (decrease temp)

• Shelter from sun

• Press bodies against cool, shady surfaces

  • Move into water or mud

• Orientate bodies so minimum SA exposed to sun

• Minimise movement to reduce metabolic heat generated 

Ectotherm physiological 

darker colours tend to live in colder areas (absorb more radiation)

Alter heart rate to increase or decrease metabolic rate and to affect warming or cooling across body surfaces 

Endotherms thermoregulation

Hypothalamus and body temp

1. Receives info about temp from thermoreceptors

2. Thermoreceptors send impulses along sensory neurones to hypothalamus, sending impulses along motor neurones to effectors

   1. E.g. skeletal muscles, sweat glands, erector pili muscles, smooth muscles of shunt vessels