EFFECTS OF EXPOSURE TO COLD

EFFECTS OF EXPOSURE TO COLD

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

1. Heat production

2. Prevention of heat loss.

HEAT PRODUCTION

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

1. By Accelerating Metabolic Activities

Heat gain center in hypothalamus is stimulated during exposure to cold. It activates the sympathetic centers, which cause secretion of adrenaline and noradrenaline. These hormones, especially adrenaline increase heat production by accelerating cellular metabolic activities.

2. By Shivering

Shivering is the increased involuntary muscular activity with 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). Primary motor center for shivering is situated in posterior hypothalamus near the wall of the III ventricle. During exposure to cold, heat gain 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, heat gain center in the posterior nucleus of hypothalamus is stimulated. It activates the sympathetic centers in posterior hypothalamus, resulting in cutaneous vasoconstriction and decrease in blood flow. Due to decrease in cutaneous blood flow, sweat secretion is decreased and heat loss is prevented.

EFFECTS OF EXPOSURE TO SEVERE COLD

Exposure of body to severe cold leads to death, if quick remedy is not provided. The survival time depends upon environmental temperature. If a person is exposed to ice cold water, i.e. 0°C for 20 to 30 minutes, the body temperature falls below 25°C (77°F) and the person can survive if he is placed

immediately in hot water tub with a temperature of 43°C (110°F). Survival time at 9°C (28°F) is about 1 hour and at 15.5°C (60°F) it is about 5 hours.

Effects of exposure of body to extreme cold are:

1. Loss of temperature regulating capacity

2. Frostbite.

LOSS OF TEMPERATURE REGULATING CAPACITY

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

FROSTBITE

Frostbite is the freezing of 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.

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