Answer
#25
Metabolism comprises the processes involved in producing energy and heat in the body. Basal metabolic rate (BMR) is the rate at which the body at rest uses energy to support the vital processes such as breathing, essential cellular activities, and cardiovascular system functions, and muscle tone.
BMR is stated in terms of kilocalories used per square meter of body surface per hour; this is usually written kcal/mx^{2}/h. Thus for an average who weighs 70kg, the BMR has been calculated as 66kca/hr. One kilogram is roughly equivalent to 2.2 lbs. A rough estimation of one's BMR be obtained by multiplying one's weight in kilograms by 1.0 ( males), or 0.9 ( females).
Total metabolic rate (TMR) is the rate of consumption of kilocalories needed to support all ongoing body activities, both voluntary and involuntary. This is roughly BMR multiplied by a factor of 1.2-2.0, dependent on one's daily activity level
Several factors influence BMR and TMR.
Work Step by Step
Several factors affect the BMR and TMR.
The major factors that influence BMR are temperature, body surface area, stress( physical and emotional ) and thyroxine hormone; age and gender also have less dramatic effects
As the ratio between body volume, and body surface area increases, BMR increases.. A thin person of a given body weight, therefore, has a greater BMR than a fatter person of the same weight. As body temperature decrease out of the homeostatic range (97.7-99.5 deg F or adults) so does BMR: increased body temperature can raise BMR up to the point where proteins become denatured. Fever is a related condition that increases BMR. Stress, emotional and physical, also increases BMR. This influence is effected by release of catecholamines from the sympathetic nervous system, and from the adrenal medulla. Catecholamines ( epinephrine and norepinephrine) increase energy production by boosting fat catabolism. Another important influence on BMR is the hormone thyroxine. This thyroid hormone acts to raise cellular respiration by increasing oxygen consumption and ATP utilization. The increase in cellular respiration results in an increase in BMR
TMR
Skeletal muscle activity increases TMR dramatically, up to as high as twenty times (20X) during vigorous exercise by athletes.Another potent factor in raising TMR is food ingestion. The boosting of TMR by eating is also known as " food-induced thermogenesis, and is greatest when food is taken with alcohol. As might be expected fasting and low calorie intake have depressive effects on TMR.
Since rising body temperature, above the normal range ( euthermia), increases enzyme catalysis, it generates a rise in metabolic rate--about 10% increase in metabolic rate for every degree rise above the normal body temperature range. Above the temperature level where body proteins begin to be natured, this positive relationship between increasing temperature, and metabolic rate falls off..
