R1iii: Additional – Explain the role of skin in maintaining normal body temperature

Definition: Skin = the outer covering of the body. The largest organ in the body and interface SA with the external environment

Skin has an important role in thermoregulation as it is both a sensor & effector, co-ordinated by the Hypothalamus

Sensor

  • Detects ambient temperature
  • Warm Receptors = unmyelinated C fibres, increase firing > 30C
  • Cold Receptors = Ad fibres
  • Increase firing <25C

Effectors

  • Controls heat loss via Radiation, Conduction, Convection, Evaporation & Behaviour!
  • Basal skin circulation = 12ml/100g/min
    • Increases x30 w heat
    • Decreases x10 w cold

Control of Peripheral Capillary Tone

  • T <25 = increased sensitivity to catecholamines via a1 rec = VC = decreased heat loss
  • Deep veins run alongside large arteries → sets up a countercurrent exchange 00> warms blood returning to Heart, conserving core temp
  • T>30 = activation of sweating

Sweating

  • Latent Heat of Evaporation of H2O = 2.4kJ/ml
  • Lost as heat energy
  • Not as effective in humid conditions

Physical Barrier to Heat Loss

  • Increased heat loss when barrier penetrated (ie burns)

Behaviour

  • Seek warmth, increase clothing in cold, minimise radiation & convection heat loss
  • In heat; increase fluid intake, decrease clothing, seek shade