Heat

What is heat?

The kinetic energy of molecules.

Normal Core Temperature

The normal core temperature of the human body is 37 degrees C.

What temperature is a medical emergency?

A core temperature of 42 degrees C (107.6 F) is a medical emergency.

What happens at 35 degrees C?

Core temperature of 35 degrees C (95 F) begins hypothermia.

What is hypothermia's main cause of death?

Cardiac arrest is the main cause of death by hypothermia.

What is the thermal gradient between body core and skin surface?

A typical thermal gradient is approximately 4 degrees C.

What is voluntary heat production?

During exercise, 70-80% of energy is released as heat.

What is the role of shivering in heat production?

Shivering increases heat production by approximately 5 times.

What hormones are involved in non-shivering thermogenesis?

Thyroxine and catecholamines are involved in non-shivering thermogenesis.

Where is body temperature primarily regulated?

Body temperature is primarily regulated by the preoptic anterior hypothalamus (POAH).

What is the response to increased core temperature?

Stimulation of sweat glands for evaporative heat loss and cutaneous vasodilation.

What happens in response to decreased core temperature?

Shivering occurs and increases norepinephrine release, leading to increased heat production.

What causes a fever?

A fever is caused by an increase in body temperature above normal due to pyrogens.

How is deep-body temperature measured?

Deep-body temperature is measured rectally, in the ear, or in the esophagus.

What are the four major ways to lose body heat?

Radiation, evaporation, convection, and conduction.

What is the primary method of heat loss at rest?

Radiation accounts for 60% of heat loss at rest.

How does evaporation help during exercise?

Evaporation becomes the most important method of heat loss during exercise.

What factors affect evaporation rate?

Evaporation rate depends on temperature, relative humidity, convection currents, and the amount of skin surface exposed.

What is the result of exercising in a hot environment?

It results in a reduced ability to lose body heat, leading to higher core temperatures and heart rates.

What can sweat rates reach during high exercise intensity?

Sweat rates can reach as high as 4-5 L/hr during intense exercise.