Effects Of Exposure To Cold And Heat Human

Effects Of Exposure To Cold And Heat

Effects Of Exposure To Cold

During exposure to cold, the body temperature h maintained by two mechanisms.

1. Heat production
2. Prevention of heat loss.

Heat Production: When the body is exposed to cold, heat is produced by the following activities:

By Increased Metabolic Activities:

• The heat gain center in the hypothalamus is stimulated during exposure to cold.
• It activates the sympathetic centers, which cause the secretion of adrenaline and noradrenaline.

Read And Learn More: Medical Physiology Notes

• These hormones, especially adrenaline increase heat production by accelerating cellular metabolic activities.

By Shivering:

• Shivering is the increased involuntary muscular activity with a slight vibration of the body in response to fear, onset of fever, or exposure to cold.
• Shivering occurs when the body temperature falls to about 25°C (77°F).
• The primary motor center for shivering is situated in the posterior hypothalamus near the wall of the III ventricle.
• During exposure to cold, the heat production center activates the motor center, and shivering occurs. Enormous heat is produced during shivering due to severe muscular activities.

Prevention Of Heat Loss:

• When the body is exposed to cold, the heat gain center in the posterior nucleus of the hypothalamus is stimulated.
• It activates the sympathetic centers in the posterior hypothalamus resulting in cutaneous vasoconstriction and a decrease in blood flow.
• Due to a decrease in cutaneous blood flow, sweat secretion is decreased and heat loss is prevented.

Effects Of Exposure To Severe Cold

• Exposure of the body to severe cold leads to death if quick remedy is not provided.
• The survival time depends upon the temperature of the environment.
• If a person is exposed to ice cold water, i.e. 0°C for 20-30 minutes, the body temperature falls below 25°C (77°F) and the person can survive if he is placed immediately in a hot water tub with a temperature of 43°C (110°F).
• The survival time at 9°C (28°F) is about 1 hour and the survival time at 15.5°C (60°F) is about 5 hours.

The effects of exposure of the body to extreme cold are:

1. Loss of temperature-regulating capacity
2.  Frostbite

Loss Of Temperature Regulating Capacity:

• The capacity of the hypothalamus in regulating the body temperature is affected when the body temperature reduces to about 34.4°C (94°F).
• The hypothalamus totally loses the power of temperature regulation when body temperature falls below 25°C (77°F). Shivering does not occur.
• In addition to the loss of hypothalamic function, metabolic activities are also suppressed.
• Sleep or coma develops due to depression of the central nervous system.

Effects Of Exposure Frostbite:

• Frostbite is the freezing of the surface of the body when it is exposed to cold.
• It occurs due to sluggishness of blood flow.
• Most commonly the exposed areas such as ear lobes and digits of hands and feet are affected.
• Frostbite is common in mountaineers.
• Prolonged exposure will lead to permanent damage of the cells followed by thawing and gangrene (death and decay of tissues) formation.

Effects Of Exposure To Heat

1. Heat exhaustion
2. Dehydration exhaustion
3. Heat cramps
4. Heatstroke.

1. Heat Exhaustion:

• Heat exhaustion is the body’s response to excess loss of water and salt through sweat caused by exposure to hot environmental conditions.
• In fact, it is a warning that the body is getting too hot.
• Heat exhaustion results in loss of consciousness and collapse. Before the loss of consciousness.

The following warning signs appear in the body:

• Increased heart rate
• Increased cardiac output
• Dilatation of cutaneous blood vessels
• Increased moisture in the body
• Fall in blood pressure
• Weakness and uneasiness
• Mild dyspnea.

2. Dehydration Exhaustion:

• Prolonged exposure to heat results in dehydration. It is due to excessive sweating.
• Dehydration leads to a fall in cardiac output and blood pressure.
• Collapse occurs if treatment is not given immediately.

3.  Heat Cramps:

Severe painful cramps occur due to a reduction in the quantity of salts and water as a result of increased sweating during continuous exposure to heat.

4. Heatstroke-Sunstroke:

Heatstroke:

• Heatstroke is an abnormal type of hyperthermia that occurs during exposure to extreme heat.
• It is characterized by an increase in body temperature above 41°C (106°F) accompanied by some physical and neurological symptoms.
• Compared to other effects of exposure to heat such as heat exhaustion and heat cramps, heatstroke is very severe and often becomes fatal if not treated immediately.
• The hypothalamus loses the power of regulating body temperature.

Sunstroke:

Sunstroke is hyperthermia caused by prolonged exposure to the sun during summer in a desert or tropical area.

Persons Susceptible to Heatstroke or Sunstroke: People more susceptible to heatstroke or sunstroke are:

1. Infants
2. Old people with renal, cardiac, or pulmonary disorders
3. People doing physical labor under the sun
4. Sportsmen are involved in continuous sports activities without breaks.

Heatstroke Features:

• The common features of heatstroke or sunstroke are nausea, vomiting, dizziness, headache, abdominal pain, difficulty in breathing, vertigo, confusion, muscle cramps, convulsions, paralysis, and unconsciousness.
• If immediate and vigorous treatment is not given, damage of brain tissues occurs, resulting in coma and death.

Heatstroke and Humidity:

• The development of heatstroke depends upon the humidity of the environment.
• If the environmental air is completely dry, exposure of body for several hours even to a temperature of 54.4°C (130°F) does not cause heat stroke.
• If air is 100% humid, even a temperature of 41 °C (106.8°F) causes heatstroke.

Heatstroke Prevention:

• Heatstroke or sunstroke can be avoided by the following measures.
• Avoiding dehydration by taking plenty of fluids such as water or sports drinks
• Taking frequent breaks during work or sports activity
• Wearing light clothes with a hat.

Heatstroke Treatment:

• The person affected by heatstroke or sunstroke must be treated before the damage of organs.
• And the subject should be immediately moved from a hot environment and hospitalized as soon as possible.
• Immediate cooling of the body is the usual treatment. The person must be immersed in cold water or cold water may be sprayed on the skin.
• If water supply is not sufficient, cooling the head and neck of the subject should be done first.
• Ice cubes can be rubbed on the head and neck. Ice packs must be kept under the armpits and groin. The cooling efforts should be continued till the body temperature falls to about 35°C.