Human Bio - Thermoregulation

• Increase Heat Production:

  • shivering
  • thyroxine
  • adrenaline + noradrenaline
  • increase in voluntary activity
• Shivering:

  • hypothalamus send stimuli to brain regions controlling skeletal muscle tone
  • increase muscle tone = shiver
• Thyroxine:

  • hypothalamus - anterior lobe to secrete TSH
  • thyroid stimulated to secrete thyroxine
  • increase metabolic rate
• Adrenaline + Noradrenaline:

  • sympathetic nerves stimulate adrenal medulla to secrete
  • increase cellular metabolism
• Decrease Heat Loss:

  • vasoconstriction
  • sweating reduction
  • conscious behaviour
  • reduction of SA
• Vasoconstriction:

  hypothalamus stimulates sympathetic nerves to contract skin BVs

  decrease flow of blood to skin + transfer of heat

  skin cooler = less blood flowing through + less heat loss
• Increase Heat Loss:

  • vasodilation
  • sweating
  • conscious behaviour
  • increase SA
• Vasodilation:

  • increase blood flow to skin
  • greater heat loss through radiation + convection
• Sweating:

  • sweat evaporates from skin = cooling effect
• Decrease Heat Production:

  • decrease in metabolic rate (thyroxine secretion)
  • decrease in voluntary activity
• Peripheral Thermoreceptors

  • skin + mucous membrane
  • provide hypothalamus w/ info about external environment
• Central Thermoreceptors

  • hypothalamus
  • detect temperature of internal environment
• 2 types of Thermoreceptors:

  1. Cold: stimulated by low temps, hypothalamus then initiates heat conservation + production
  2. Heat: stimulated by high temps, hypothalamus then increase heat loss + reduces heat production
• Heat Loss by:

  • Conduction: direct contact of particles
  • Convection: movement of liquid/gas
  • Radiation: infrared radiation emitted
  • Evaporation: liquid form gas (absorbs heat energy)