Metabolic Rate for Medical Engineering PDF
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Summary
This document provides a comprehensive overview of metabolic rate, encompassing definitions, measurements, factors influencing it, and specific dynamic action. It delves into basal metabolic rate and the effects of various factors like age and climate on metabolic processes. This information is relevant to understanding human physiology and its application in medical contexts.
Full Transcript
Metabolic Rate Definition: It is the amount of energy (heat ) production per hour Measurement: Direct: In which the heat produced by the person during a specified time is actually measured by apparatus called calorimeter. Indirect: In which the heat is calculated as follow:...
Metabolic Rate Definition: It is the amount of energy (heat ) production per hour Measurement: Direct: In which the heat produced by the person during a specified time is actually measured by apparatus called calorimeter. Indirect: In which the heat is calculated as follow: ***If the amount of heat resulting from oxidation of a mixed food ( CHO + Fat + Proteins ) using 1 liter of O2 is 4.8 Kcal/ lit ***If normal resting and fasting individual consumes O2 at a rate of 250 ml / min ***Rate of O2 consumption / h = 250 × 60 = 15.6 L / h ***Metabolic rate = 15.6 × 4.8 = 75 Kcal / hr Factors affecting M.R: Exercise: most marked increase Eating: especially proteins. Exposure to cold: shivering Endocrinal: catecholamine & thyroxin Emotional state: anxiety (increase catecholamine & muscle tone) Starvation: decrease MR (decrease sympathetic and thyroxine) Specific Dynamic Action (S.D.A.) -It is the power of food to increase the metabolic rate. -Metabolic rate starts to increase 1 hour after taking food. Reaches its maximum in 3 – 4 hours. Decreases to basal level in 12 – 18 hours Causes: It is due to the metabolic processes of the absorbed food in the liver. S.D.A. depends on: -The type of food ingested: 30% of caloric value of proteins 6% of caloric value of CHO & 4%of caloric value of fats 1 -Quantity of food ingested: The more the amount of food the more the S.D.A. -The external temperature: S.D.A. is maximum at 33°C S.D.A. is absent at 3°C Basal Metabolic Rate B.M.R. is the energy production in unit time ( one hour ) (MR)under basal conditions which are: 1-Complete physical and mental rest. Comfortable - Not sleep- No emotion 2-In post-absorptive state 12 – 14 hours after the last meal 3-Comfortable external temperature: The person should not feel cold or hot, neither shivering nor sweating. Comfortable temperature is 20 – 25 for dressed persons and 28 – 31 when naked How B.M.R. is expressed? Amount of heat in calories given by the body per hour per square meter surface area under basal conditions: Complete physical Post-absorptive Comfortable and mental rest state external temperature O2 consumption / Liter / hour 4.8 = 40 cal / m2 / h B.M.R = in normal adult male Body surface area / m2 2 Factors affecting B.M.R. Physiological factors: Pathological factors: 1- Age 5- Climate Increase BMR decrease BMR 1- Hyperthyroidism 1- Hypothyroidism 2- Hyperpitutrism 2- Hypopitutrism 2- Sex 6- Race 3- Hyper function 3-Hypofunction of of adrenalmedulla suprarenal cortex 3- Physical 7- Sleep 4-Fever 4-hypothermia habits 5- Heart failure 5-Prolonged 6-blood diseases starvation and 4- Dietetic 8- Pregnancy malnutrition habits 7- Diabetes insipidus Effect of age on B.M.R. Newly born infants : 25 Kcal /h/m2 2 – 5 years : 60 Kcal /h/m2 Puberty : 55 Kcal /h/m2 20 years : 40 Kcal /h/m2 After 20 years : 1 cal. Decreases for every 10 years. Effect of sex on B.M.R. B.M.R. is lower in females than males due to: a-Lack of androgens. b-Presence of greater fat stores Effect of physical habits: Athletes have B.M.R. 10% higher than sedentary individuals due to a- Greater muscle bulk b- Lesser amount of fat Effect of dietetic habits: Prolonged ingestion of proteins increases the B.M.R. about 10% more than if a mixed diet or CHO only were ingested. 3 Effect of Climate: -B.M.R. is higher in persons living in cold countries. -B.M.R. is lower in persons living in hot countries. Effect of Race: Pure and dark races have lower B.M.R. than mixed races. Effect of pregnancy : It increases during pregnancy due to: -Increased thyroid activity -Additional metabolic activity of the fetus Sleep It decreases B.M.R. due to: -Decrease muscle tone -Decrease sympathetic activity 4