Thermoregulation

• define thermoregulation?

  use of homeostatic mechanisms to maintain balance between heat production and heat loss

  • heat loss = heat gain
• why is 37c the normal body temp?

  most cellular reactions occur at optimal level
• where's heat produced from on body?

  most energy from cellular respiration release in form of heat
• function of thermoreceptors?

  detect change in internal/external temp
• peripheral thermoreceptors?

  skin & mucus membrane

  cold & heat receptors

  when stimulated, hypothalamus receives info and initiates either:

  • heat conservation and production mechanism OR
  • mechanism to decrease heat production, increase heat loss
• central thermoreceptors?

  main temp regulating centre:

  • hypothalamus
  • spinal cord
  • abdominal organ

  Nerve impulse sent by hypothalamus to increase/decrease temp
• hows heat lost?

  conduction

  convection

  evaporation

  radiation
• what happens when body is too cold?

  Cold receptors alert hypothalamus; initiates mechanism to conserve & produce heat:

  • vasoconstriction
  • shiver
  • Increase thyroxine production- Increase metabolic rate
  • Adrenal Medulla - Increase cellular respiration
  • piloerection
  • behavioural: turn on heater etc.
• describe vasoconstriction?

  Body temp too COLD

  • Sympathetic nerves constrict blood vessels
  • Decrease blood flow thru capillary near skin surface
  • Thus, prevents excess heat loss by body surface -> skin cools
• why does skin cool when we feel cold?

  vasoconstriction: decrease blood flow thru capillary near skin surface.
• what constricts blood vessels?

  sympathetic nerves
• Role of adrenal medulla?

  Hypothalamus stimulates sympathetic nerves to cause adrenal medulla -> release adrenaline and noradrenaline

  • increase cellular respiration = increase heat production = maintain internal body temp
• what stimulates adrenal medulla?

  hypothalamus stimulates sympathetic nerves to stimulate adrenal medulla
• what does adrenal medulla release?

  adrenaline

  noradrenaline
• Shivering?

  Hypothalamus stimulates parts of brain:

  • Increase skeletal muscle tone -> rhythmic contraction of muscle (shivering)
  • Stimulates metabolic activity
  • None of energy needed for external work, all released as heat
• Piloerection?

  muscles at bottom of hair follicles contract- hair strands erect-> creates insulating layer which prevents heat loss
• vasodilation?

  occurs when body temp too hot

  • capillary near skin surface dilates; allow more blood flow to skin
  • thus increase heat leaving body by radiation and convection
• sweat is only effective in ?

  low humidity
• sweat?

  effective: low humidity

  • active secretion of fluid by sweat glands and periodic contraction of cells surrounding ducts to pump swear to skin surface
• sweat is the active secretion of what ?

  fluid by sweat glands and periodic contraction of cells surrounding ducts to pump sweat to skin surface
• what helps pump sweat to skin surface?

  periodic contraction of cells surrounding ducts
• decreased thyroxine production?

  slow/long lasting solution

  • Thyroid decrease amount of thyroxine secreted = decrease metabolic rate
• pilorelaxation?

  relax muscles at base of hair follicles-> lie flat; trap less heat
• body temp TOO HOT?

  vasodilation

  sweat

  decrease thyroxine production

  pilorelaxation

  behavioural
• why is it uncomfy to run in a humid day?

  sweat cools body by evaporation

  • humidity prevents evaporation so less cooling