FR3-Energy balance

Question 1

Prolonged exposure to temperature extremes in either direction can overtax the body’s thermoregulatory mechanisms, leading to disorders and even death: Cold-Related Disorders-Frostbite

Answer 1

Frostbite involves excessive cooling of a particular part of the body to the point where tissue in that area is damaged. If exposed tissues actually freeze, tissue damage results from disruption of the cells by formation of ice crystals or by lack of liquid water

Question 2

Prolonged exposure to temperature extremes in either direction can overtax the body’s thermoregulatory mechanisms, leading to disorders and even death: Cold-Related Disorders-Hypothermia

Answer 2

• Hypothermia, a fall in body temperature, occurs when generalized cooling of the body exceeds the ability of the normal heatproducing and heat-conserving regulatory mechanisms to match the excessive heat loss.
• As hypothermia sets in, the rate of all metabolic processes slows because of the declining temperature. Higher cerebral functions are the first affected by body cooling, leading to loss of judgment, apathy, disorientation, and tiredness, all of which diminish the cold victim’s ability to initiate voluntary mechanisms to reverse the falling body temperature.
• As body temperature continues to plummet, depression of the respiratory center occurs, reducing the ventilatory drive so that breathing becomes slow and weak.
• Activity of the cardiovascular system also is gradually reduced. The heart is slowed and cardiac output decreased
• . Cardiac rhythm is disturbed, eventually leading to ventricular fibrillation and death

Question 3

Prolonged exposure to temperature extremes in either direction can overtax the body’s thermoregulatory mechanisms, leading to disorders and even death: Heat related disorders- Heat exhastion

Answer 3

• Heat exhaustion is a state of collapse, usually manifested by fainting, that is caused by reduced blood pressure brought about as a result of overtaxing the heat-loss mechanisms.
• Extensive sweating reduces cardiac output by depleting the plasma volume, and pronounced skin vasodilation causes a drop in total peripheral resistance.
• Because blood pressure is determined by cardiac output times total peripheral resistance, blood pressure falls, an insufficient amount of blood is delivered to the brain, and fainting takes place.
• Thus, heat exhaustion is a consequence of overactivity of the heat-loss mechanisms rather than a breakdown of these mechanisms.
• Because the heat-loss mechanisms have been very active, body temperature is only mildly elevated in heat exhaustion.
• By forcing cessation of activity when the heat-loss mechanisms are no longer able to cope with heat gain through exercise or a hot environment, heat exhaustion serves as a safety valve to help prevent the more serious consequences of heat stroke.

Question 4

Prolonged exposure to temperature extremes in either direction can overtax the body’s thermoregulatory mechanisms, leading to disorders and even death: Heat related disorders- Heat stroke

Answer 4

• Heat stroke is an extremely dangerous situation that arises from the complete breakdown of the hypothalamic thermoregulatory systems.
• Heat exhaustion may progress into heat stroke if the heat-loss mechanisms continue to be overtaxed. Heat stroke is more likely to occur on overexertion during a prolonged exposure to a hot, humid environment.
• The elderly, in whom thermoregulatory responses are generally slower and less efficient, are particularly vulnerable to heat stroke during prolonged, stifling heat waves
• the hypothalamic temperature-control centers are damaged by the heat, the body temperature rapidly rises even higher because of the complete shutdown of heat-loss mechanisms.
• Furthermore, as the body temperature increases, the rate of metabolism increases correspondingly because higher temperatures speed up the rate of all chemical reactions; the result is even greater heat production.
• This positive-feedback state sends the temperature spiraling upward.
• Heat stroke is a very dangerous situation that is rapidly fatal if untreated

Question 5

Why is the difference between hyperthermia and fever?

Answer 5

• Hyperthermia denotes any elevation in body temperature above the normally accepted range.
• The term fever is usually reserved for an elevation in temperature caused by endogenous pyrogen resetting the hypothalamic set point during infection or inflammation; hyperthermia refers to all other imbalances between heat gain and heat loss that increase body temperature.
• Hyperthermia has a variety of causes, some of which are normal and harmless, others pathologic and fatal

Question 6

What is the most common cause of hyperthermia?

Answer 6

sustained exercise.

• As a physical consequence of the tremendous heat load generated by exercising muscles, body temperature rises during the initial stage of exercise
• The elevation in core temperature reflexly triggers heat-loss mechanisms (skin vasodilation and sweating), which eliminate the discrepancy between heat production and heat loss.
• As soon as the heat-loss mechanisms are stepped up sufficiently to counterbalance the increased heat production, the core temperature stabilizes at a level slightly above the set point despite continued heat-producing exercise.
• Thus, during sustained exercise, body temperature initially rises, then is maintained at the higher level as long as the exercise continues

Question 7

In the face of insufficient energy input in the form of ingested food during prolonged starvation, what does the body resorts to?

Answer 7

breaking down muscle protein to meet its needs for energy

Question 8

Explain Pathological Hyperthermia

Hyperthermia can also be brought about in a completely different way:

Answer 8

• excessive heat production in connection with abnormally high circulating levels of thyroid hormone or epinephrine that result from dysfunctions of the thyroid gland or adrenal medulla, respectively.
• Both these hormones elevate the core temperature by increasing the overall rate of metabolic activity and heat production.
• Hyperthermia can also result from malfunction of the hypothalamic control centers. Certain brain lesions, for example, destroy the normal regulatory capacity of the hypothalamic thermostat.
• When the thermoregulatory mechanisms are not functional, lethal hyperthermia may occur very rapidly.
• Normal metabolism produces enough heat to kill a person in less than 5 hours if the heat-loss mechanisms are completely shut down