Metabolism and Regulation of Body Temperature. Subtopics: ENERGY BALANCE AND METABOLIC RATE.

Energy Balance 1st Law of Thermodynamic: Energy is neither created nor destroyed, but can be transferred and converted from one form to another. Energy balance between caloric intake and energy output: a) If caloric content in the food ingested < energy output (balance is negative), endogenous stores are utilized. Glycogen, body protein, and fat are catabolized, and the individuals loses weight.

b) If caloric value of the food intake exceeds energy loss due to heat & work, and the food is properly digested & absorbed (balance is positive), then energy is stored and the individual gains weight.

Metabolic Rate Animal organisms oxidizes carbohydrates, proteins, and fats; producing principally CO2, H2O and energy necessary for life processes. The complex, slow, stepwise oxidation process are called catabolism (metabolism). Catabolism function – liberates energy in small, usable amount.

Uses of energy (produced from catabolism): i) Maintaining body functions. ii) Digesting and metabolizing food. iii) Thermoregulation. iv) Physical activity. Energy storage: a) in the form of special energy-rich phosphate compounds (ATP). b) in the form of proteins. c) in the form of fats. d) in the form of glycogen.

Energy liberated appears as: Energy output = External work + Energy storage + Heat. What is metabolic rate.? The sum of all the energy-requiring biochemical reactions over a given time interval.

Factors affecting the metabolic rate :- :: muscular exertion during or just before measurement. :: recent ingestion of food. :: high or low environmental temperature. :: height, weight, and surface area. :: sex. :: age. :: growth.

:: reproduction. :: lactation. :: emotional state. :: body temperature. :: circulating levels of thyroid hormone. :: circulating epinephrine and norepinephrine levels.

Basal Metabolic Rate (BMR): a) Determined at rest in a room at a comfortable temperature in the thermoneutral zone, 12 to 14 hours after the last meal.

b) Value falls about 10% during sleep and up to 40% during prolonged starvation. c) Rate during normal daytime higher than BMR (because of muscular activity and food intake). d) Large animals have higher absolute BMRs, but the ratio of BMR to body weight in small animals is much greater (variable: body surface area).