homeostasis and body temperature

• Homeostasis


  The regulation of the internal conditions of a cell or organism in response to internal and external changes
• Importance of Homeostasis


  • It keeps conditions constant for enzyme action and cell functions
  • It includes the control of blood glucose concentration, body temperature, and water and ion levels
• Control Systems


  • Involve responses using nerves and chemical responses using hormones
  • Include receptors that detect stimuli, coordination centres that receive and process information from receptors, and effectors that bring about responses to restore optimum levels
• Control Mechanism (Negative Feedback)

  1. Receptor detects a change in a stimulus

  2. Coordinating centre compares the stimulus to a set point

  3. Effector produces a response to correct any difference from the set point
• Human body temperature


  Should be kept at around 37°C to provide an optimum temperature for enzymes to work
• Thermoregulatory Centre in the Brain


  • Monitors and controls body temperature
  • Has receptors that monitor the temperature of the blood flowing through the brain
  • Receives information (impulses) from temperature receptors in the skin
• When body temperature is too high


  1. Blood vessels widen, directing more blood to the surface of the skin (vasodilation)

  2. More sweat is produced from the sweat glands and evaporates

  3. Both mechanisms cause a transfer of energy from the skin to the environment
• When body temperature is too low

  1. Blood vessels narrow, directing blood away from the surface of the skin (vasoconstriction)

  2. Sweating stops

  3. Skeletal muscles uncontrollably contract and relax quickly (shiver), which transfers more heat to the blood
• Blood vessels in the skin cannot move, so narrowing or widening is the only way that they can adjust how much energy is transferred to the outside
• The temperature receptors in the skin give the brain an early warning of changes in the external temperature, allowing behaviour to be adjusted to stop the body temperature changing