HEAT AND THE

HUMAN BODY

REPORTED BY

MARVIN B. GONZAGA

EFFECTS OF HEAT ON THE HUMAN BODY

Cell metabolism increases with increasing temperature

If body temperature rises above about 42○ C (108 ○ F), the body’s cooling mechanisms cannot keep up, and external intervention is necessary

BODY MECHANISMS TO GET RID OF EXCESS HEAT

Once heat reaches the surface, all 3 methodsof heat transfer remove heat, provided that theexternal temperature is lower than bodytemperature.

Convection – blood circulation;increased blood flow to the skin tohelp remove heat. When bodytemperature drops, blood flow tothe surface is reduced.

Perspiration - keeps temperaturefrom rising uncontrollably whensurrounding temperatures are high.

EXAMPLE

(a) Using data from Table 4.5, calculate the power in wasteheat put into a classroom by 30 students. (b) How manycalories of energy do the students put into the room duringa 50-min lecture?

Solution

(a.)Using the value of 210 W from Table 4.5, the power inwaste heat is simply

Pheat = (210 W/person)(30 persons)= 6300 W

Pheat = 6.3 kW

(b.) The number of calories can be calculated bymultiplying the power by time, or by using the value of 3.0kcal/min per person from Table 4.5

Q = 3.0 (kcal/min) (30 persons)(50 min)person

= (4500 kcal)(103 cal/kcal)

Q = 4.5 x 106 cal

= 3.0 (kcal/min) (30 persons)(50 min)person

= 30 kcal (50 min)min

Physical activity produces thermal energy since the body is not 100% efficient in converting food energy to work

Severe shivering results in little work and a lot of thermal energy

80 W

425 W

Diagnostics

DIAGNOSTIC AND THERAPEUTIC USESOF HEAT AND COLD

Temperature can indicate the presence and seriousness of an infection. Raising body temperature is one of the body’s defense mechanisms.

ThermographyGives an indication of blood supply. Depressed skin temperature means deficiency in blood flow.

Measures infrared radiation and maps body temperature. The picture is called a thermograph.

THERAPEUTIC USES OF HEAT

Applying heat to a part of the body brings relief through muscle relaxation and

increased blood flow

Conduction

Microwave Diathermy

Radiation

THERAPEUTIC USES OF COLD

Cryosurgery Organ freezing

Pain relief

If the temperature of the entire body is lowered, the metabolic rate drops and most

bodily functions are slowed.

THANK YOU!