Body temperature and the thermoregulatory centre

• Homeostasis is the regulation of internal conditions inside cells or organisms to create the optimum conditions for biological function
• Nervous system and hormones are responsible for controlling homeostasis
• Body control systems involve both nervous and chemical responses
• Important parts of body control systems include:

  • Receptors: detect a stimulus
  • Coordination centres: receive information from receptors, process it, and instigate a response
  • Effectors: create a response
• Body temperature is controlled during homeostasis to maintain the temperature at which enzymes work best, around 37°C
• Thermoregulatory centre in the hypothalamus in the brain controls body temperature by receiving information from temperature receptors in the skin and sending nervous impulses
• When too hot:

  • Sweat glands release more sweat for evaporative cooling
  • Blood vessels leading to skin capillaries dilate for increased heat loss
• When too cold:

  • Skeletal muscles contract and shiver to generate heat
  • Blood vessels leading to skin capillaries constrict to conserve core body temperature
  • Hairs on the skin lie flat when warm and rise when cold to control body temperature
• Control of body temperature is a negative feedback mechanism that regulates shivering, sweating, and blood flow in skin capillaries
• Vasoconstriction and vasodilation alter the amount of blood flowing through skin capillaries:

  • Vasoconstriction: arterioles narrow, blood flow decreases, and heat loss decreases
  • Vasodilation: arterioles widen, blood flow increases, and heat loss increases