Body Temperature Regulation

Normal Body Temperature

• Normal body temperature is around 37.8°C (100°F) and remains relatively constant, except when a person has a febrile illness.
• The normal oral temperature is 37°C (98.6°F), which can vary between 35.8°C and 37.3°C (96.4°F and 99.1°F).
• The skin temperature, on the other hand, rises and falls with the temperature of the surroundings.

Physiological Variations of Body Temperature

• In infants, body temperature varies according to environmental temperature for the first few days after birth due to an underdeveloped temperature regulating system.
• In children, body temperature is slightly higher (0.5°C) than in adults due to increased physical activity.
• In old age, body temperature decreases slightly due to reduced heat production.
• In females, body temperature is lower due to a lower basal metabolic rate compared to males.
• Body temperature follows a diurnal variation, with a 1°C decrease in the early morning and a 1°C increase in the afternoon.
• Body temperature also fluctuates after meals, exercise, sleep, emotional conditions, and during the menstrual cycle.

Heat Balance

• Heat balance is crucial for maintaining a constant body temperature, which depends on the balance between heat produced in the body and heat lost from the body.
• Heat production in the body occurs through metabolic activities, muscular activity, hormonal regulations (thyroxin and adrenaline), and radiation from the environment.
• Heat loss from the body occurs through the skin (maximum heat loss), respiratory system, kidney, and gastrointestinal tract.

Mechanisms of Heat Gain and Loss

• Conduction: A small amount of heat is lost from the body through direct contact with solid objects, while a larger proportion of heat is lost through conduction to air.
• Insulation beneath the skin helps maintain a normal internal core temperature despite temperature fluctuations in the surroundings.
• Blood flow to the skin from the body core provides an effective means of heat transfer.
• The skin acts as a controlled "heat radiator" system, with blood flow regulating heat transfer from the body core to the skin.

Detection of Temperature

• Temperature receptors in the skin and deep body tissues play a crucial role in temperature regulation.
• The skin has more cold receptors than warmth receptors, making it more sensitive to detecting cool and cold temperatures.
• Deep body temperature receptors are found in the spinal cord, abdominal viscera, and great veins in the upper abdomen and thorax.

Heat Gain Center and Heat Loss Center

• The posterior hypothalamus acts as the heat gain center, stimulating heat production through shivering and metabolic reactions.
• The preoptic area in the hypothalamus acts as the heat loss center, promoting heat loss through vasodilation and sweat secretion.

Mechanisms that Decrease or Increase Body Temperature

• When the body temperature increases, the heat loss center in the preoptic area is stimulated, promoting heat loss through vasodilation and sweat secretion.
• When the body temperature decreases, the heat gain center in the posterior hypothalamus is stimulated, promoting heat production through shivering and metabolic reactions.

Temperature-Increasing Mechanisms

• Prevention of heat loss through skin vasoconstriction
• Increase in thermogenesis (heat production) through shivering and increased metabolic reactions

This quiz covers the concept of body temperature, its regulation, and differences between core and skin temperatures. It also discusses normal body temperature ranges in humans.