Thermoregulation

WHAT IS THERMOREGULATION?

The process by which the body maintains its core internal temperature.  It is an example of homeostasis.

HEAT GAIN & LOSS

There are three ways by which the body gains or loses heat...

• Radiation: heat energy is transferred from one place to another in the form of electromagnetic waves
• Conduction: heat energy is transferred by the collisions of molecules
• Convection: heat energy is transferred by currents in air or water

THE HYPOTHALAMUS

Human body temperature is controlled by the hypothalamus in the brain.  Thermoreceptors in the hypothalamus monitor the temperature of the blood flowing through it.  This is the core body temperature.  (There are also thermoreceptors in the skin which monitor skin temperature and environmental temperature.  These send nerve impulses to the hypothalamus.)

If the thermoreceptors in the hypothalamus detect a change in body temperature away from the normal level, the hypothalamus brings about corrective mechanisms to return the body temperature back to the normal level.  This process works by negative feedback.

HEAT LOSS RESPONSES 

• Vasodilation
  • The hypothalamus sends impulses along the parasympathetic nerves to the skin arterioles, causing smooth muscle in the walls of these arterioles to relax.  The shunt vessel constricts, forcing more blood to flow through the surface capillaries, thus increasing the amount of heat energy lost by radiation.
• Increased rate of sweating
  • More sweat is secreted onto the surface of the skin.  As the water in the sweat evaporates it removes heat from the body.
• Pilorelaxation
  • The parasympathetic nerves going to the erector pili muscles at the…