56 - Regulation of body temperature. Body temperature and isothermia. Heat production and loss. Neurophysiology of temperature regulation. Hyperthermia and Hypothermia. Acclimatization. Regulation of body temperature during exercise.

sections

body temperature

isothermia

heat production and heat loss

evaporation

radiation

conduction

convection

vasodilation

neurophysiological regulation of body temperature

hyper thermia

hypothermia

regulation of body temp during exercise

body temperature

• Normal body temp 37oC

• Heat regulation is generally controlled by cutaneous blood flow via the hypothalamus

• The rich network of blood vessels in the skin provide a good mechanism for heat exchange.

• The core temperature stays consistent most of the time, expect in people diseases.

• However the skin temperature will change due to the exposure of a very hot or a very cold environment.

• The body temperature increases during exercise and varies with temperature extremes of the surroundings because the temperature regulatory mechanisms are not perfect.

isothermia

Isothermia—the temperature remains constant

heat production and heat loss

• Heat production is a principal by-product of metabolism

• Vasoconstriction- decrease the flow of blood to the skin, shivering in muscles

• Secretion of noradrenaline, adrenaline and thyroxine- t4 to increase heat production and erection of hair to increase insulation

• The rate depends on:

  • rate heat be conducted from where it is produced in the body core to the skin

  • rate heat can be transferred from the skin to the surroundin

evaporation

when you sweat, cooling effect

radiation

The heat generated from within the body is given off to the surrounding atmosphere

conduction

(transfer of heat between objects in contact ) Conductive heat loss occurs when the skin is subjected to either cold air or water,

convection

– is the process of air or water flowing by the skin carrying away body heat

vasodilation

to increase the flow of heat to the skin

neurophysiological regulation of body temperature

• Feedback Circuit of temperature regulation. Regulation center of thermoregulation in hypothalamus.

• Skin has thermoreceptors, sends signals to hypothalamus

• Leads to shivering or sweating, vasoconstriction or vasodialaiton- via sympathetic fibres

hyperthermia

• Hyperthermia is elevated body temperature due to failed thermoregulation that occurs when a body produces or absorbs more heat than it dissipates.

  • Heavy sweating can lead to dehydration, increased heart rate, decreased blood volume and pressure.

  • Exercise can cause hyperthermia- due to generation of heat as a bi-product of muscle contraction.

  • Fever is the elevation of body temperature following the invasion of microorganism in the body. It causes a change in the hypothalamus. Body temp and metabolic rate increase.

hypothermia

• a body temperature of less than 35-36°C which is also due to an imbalance of heat production and loss of heat from the body.

  • At first negative feedback response to increase temp but does not work

  • Acclimatization - the ability of the human body to adapt to warmth/ heat and coldness.

regulation of body temp during exercise

• During exercise the body's heat production increases.

• Some of the heat produced is stored, raising body core temperature by a few degrees.

• Rises in body temperature are sensed by central and skin thermoreceptors and this sensory information is processed by the hypothalamus to trigger appropriate effector responses.

• Evaporation of sweat and increased skin blood flow (vasodilation)