TEMPERATURE REGULATION

INCREASE IN BODY TEMPERATURE

• An increase in body temperature, for example due to vigorous exercise or being in a warm place, causes the blood and the skin temperature to increase (stimulus).
• The temperature receptors in the skin detect this increase.
• A signal in the form of nerve impulse is then transmitted to the hypothalamus in the brain.
• When the hypothalamus is stimulated, it then transmits nerve impulses to the relevant body parts.
• The arterioles in the skin dilate. More blood is transported to the blood capillaries and this removes more heat.
• Sweat glands become active and more sweating occurs and hence more heat removed.
• The hair erector muscles in the skin relax causing the hair to lie flat. Therefore less heat is trapped by the hair.
• Metabolic rate decreases and hence heat production decreases.
• Breathing rate increases so as to remove more heat in exhaled air.
  
• All these mechanisms lower down the blood temperature (Negative feedback) and eventually the temperature will return to normal.
  

DECREASE IN BODY TEMPERATURE

• A decrease in body temperature, for example due to starvation, fasting or being in cold places, causes the blood and the skin temperature to decrease (stimulus).
• The temperature receptors in the skin detect this decrease.
• A signal in the form of nerve impulse is then transmitted to the hypothalamus in the brain.
• When the hypothalamus is stimulated, it then transmits nerve impulses to the relevant body parts.
• The arterioles in the skin constrict. Less blood is transported to the blood capillaries and hence less heat is removed.
• Sweat glands become inactive and no sweating occurs. Therefore no heat is removed.
  
• The hair erector muscles in the skin contract causing the hair to stand erect. Therefore more heat is trapped by the hair. (Remember: still air trapped in between the hairs acts as an insulator, therefore less heat is removed)
• Metabolic rate increases and hence heat production increases.
• Breathing rate decreases so as to conserve more heat.
• Shivering due to muscle contractions occurs if very cold to produce more heat.
  
• All these mechanisms increases the blood temperature (Negative feedback) and eventually the temperature will return to normal.