Body energy homeostasis
Humans=endotherms-produce their own heat source
Ectotherms-gain heat from the external environment
Core temperature is maintained by heat generation by metabolism and heat exchange with
the environment
All metabolic processes= heat production
Therefore, increase metabolic rate=increase heat production
Increase activity
ATP utilisation= heat as a by product
Further increase ATP production
Core temperature
Major thoracic, abdominal organs and brain
2/3rd body heat content
Maintained between 36.6-37.4 degrees
Tightly regulated
Peripheral temperature-
Wide temperature
Limbs,skin and subcutaneous tissue
30-32 degrees
1/3rd body heat content
5-7 degrees between core and peripheral maintained by vasoconstriction
Heat production:
Basal metabolism
Temperature rises 1 degree per hour
Skeletal muscle activity
Metabolic factors
Thyroid disease
Medications
Convulsions
Fever
Environmental heat
, Heat transfer:
Conduction:
Transfer of heat by direct contact
Minimal in air
More in water
Convection:
Transfer of heat via air circulation
Varies with wind velocity
Radiation:
Transfer of heat via electro-magnetic waves
Bidirectional
Result in heat gain in hot environments
Evaporation:
Transfer of heat via conversion of liquid to gas
Dominant mechanism of heat loss in hot environments
Neural circuits in the CNS regulate body temperature
Afferent neurones- peripheral and core thermoreceptors
Thermal afferent pathways within the CNS
Thermoregulatory integration centre in the preoptic anterior hypothalamus
(integrates sensation of core and peripheral body temperature)
Efferent pathways- autonomic and somatomotor inputs to effectors
Thermal effectors control heat transfer between body and environment
Central thermoregulatory network=active system
Regulates passive poikilothermic system- circulatory system and laws of physics determine
heat transfer between the body core and the environment
Acclimatization- Physiological adaptations that occur in response to repeated hot
environments
Increased sweat
Humans=endotherms-produce their own heat source
Ectotherms-gain heat from the external environment
Core temperature is maintained by heat generation by metabolism and heat exchange with
the environment
All metabolic processes= heat production
Therefore, increase metabolic rate=increase heat production
Increase activity
ATP utilisation= heat as a by product
Further increase ATP production
Core temperature
Major thoracic, abdominal organs and brain
2/3rd body heat content
Maintained between 36.6-37.4 degrees
Tightly regulated
Peripheral temperature-
Wide temperature
Limbs,skin and subcutaneous tissue
30-32 degrees
1/3rd body heat content
5-7 degrees between core and peripheral maintained by vasoconstriction
Heat production:
Basal metabolism
Temperature rises 1 degree per hour
Skeletal muscle activity
Metabolic factors
Thyroid disease
Medications
Convulsions
Fever
Environmental heat
, Heat transfer:
Conduction:
Transfer of heat by direct contact
Minimal in air
More in water
Convection:
Transfer of heat via air circulation
Varies with wind velocity
Radiation:
Transfer of heat via electro-magnetic waves
Bidirectional
Result in heat gain in hot environments
Evaporation:
Transfer of heat via conversion of liquid to gas
Dominant mechanism of heat loss in hot environments
Neural circuits in the CNS regulate body temperature
Afferent neurones- peripheral and core thermoreceptors
Thermal afferent pathways within the CNS
Thermoregulatory integration centre in the preoptic anterior hypothalamus
(integrates sensation of core and peripheral body temperature)
Efferent pathways- autonomic and somatomotor inputs to effectors
Thermal effectors control heat transfer between body and environment
Central thermoregulatory network=active system
Regulates passive poikilothermic system- circulatory system and laws of physics determine
heat transfer between the body core and the environment
Acclimatization- Physiological adaptations that occur in response to repeated hot
environments
Increased sweat
