Rabu, 11 Februari 2009

Body Temperature

Dr. Dedi Ardinata, M.Kes
Aim: Introduce Body Temperature

Objectives: At the end of this session students should be able to:

Discuss the reasons why thermal regulation is important

Describe the methods of heat gain and heat loss

Without thermoregulation to facilitate exercise the body would overheat and the effect would result in death. Our core body temperature can drop 10 degrees and the body can still survive, but a core increase of just 5 degrees is all we can tolerate.

Many athletes have died of heat stress for this reason. It is important to know how to cool off in hot weather by understanding thermoregulation and the best ways to make it work to your advantage.

Why is maintenance of body temperature important?

TEMPERATURE & METABOLSIM

Temperature affects metabolism (and Ps) of organisms by affecting the speeds of chemical reactions and the effectiveness of enzymes.

Thermal Conditions

Humans are homeothermic.

A constant internal temperature of 36.1 to 37.80C.

Body heat is transferred by conduction, evaporation, convection and radiation.

HEAT BALANCE RESEMBLES ENERGY BALANCE

INPUT - OUTPUT = + >>RISE IN TEMPERATURE

INPUT - OUTPUT = - >>FALL IN TEMPERATURE

INPUT - OUTPUT = 0 >>NO CHANGE IN TEMPERATURE

Factors That Affect Heat Gain

BMR, muscular activity, hormones, thermic effect of food, postural changes, and environment. (Total metabolic rate can increase 3 to 5 times from shivering and 20 to 25 times during sustained vigorous exercise in aerobically fit individuals.

Heat is conserved when blood is shunted into the cranial, thoracic and abdominal cavities and portions of muscle mass for insulation from the shell.

Factors That Affect Heat Loss

Radiation, conduction, convection, and evaporation, which is most important.

The body is cooled when internal heat buildup causes the blood vessels to dilate and direct warm blood to the shell.

Hypothalamic Regulation of
Core Temperature

The hypothalamus contains the central coordination center for temperature regulation. It initiates the responses that keep the body from overheating or overcooling

Heat-regulating mechanisms are activated by either:

Thermal receptors in the skin or,

Temperature changes in the blood

Free nerve endings in the skin respond to heat and cold and relay the senses to the hypothalamus and cerebral cortex.

Conduction

A direct transfer of heat through a liquid, solid or gas from one molecule to another.

Although most of the body heat is transported to the shell by circulation, a small amount continually moves by conduction through the deep tissues to the cooler surface

Radiation

Objects continually emit electromagnetic heat waves. Because our bodies are usually warmer than the environment, the net exchange of radiant heat energy is through the air to the solid, cooler objects in the environment.

Convection

The effectiveness of heat loss by conduction depends on how rapidly the air or (water) near the body is exchanged once it becomes warmed.

Evaporation

Heat is continually transferred to the environment as water is vaporised from the respiratory passage and skin surface.

For each litre of water that vaporises, 580 kcals are extracted from the body and transferred to the environment.

Various Sites to Measure Skin Temperature

Temperature Assessment Equipment:

·Electronic thermometer

·Tympanic membrane thermometer

·Glass thermometer

·Disposable single-use thermometer

·Temperature-sensitive patch or tape

·Automated monitoring devices

Body Temperatures: Core and Skin

If Skin Temperature Gets Hot:

If Skin Temperature Gets Cold:

Range of SKIN Temperature

Skin Temperature is Controlled by Blood Flow to Skin

Tidak ada komentar:

Poskan Komentar

kalau udah di baca beri komentar ya....