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Fasting physiology
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Fasting physiology






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    Fasting physiology Fasting physiology Presentation Transcript

    • FASTINGPHYSIOLOGY Sriloy Mohanty, B.N.Y.S
    • Contents… Introduction Biochemical cycles in fasting Stages of fasting and their physiology Physiology according to the systems  Liver in fasting  Adipose tissue in fasting  Skeletal muscles in fasting  Brain in fasting  Kidney in fasting  Endocrine system in fasting  Cardiovascular system in fasting  Respiratory system in fasting  Sleep in fasting  Urinary system in fasting
    • Introduction Fasting is a complete voluntaryabstinence from taking any kind of food for a definite period of timeDuring a fasting body lives in reserve. (Dr.Herbert M.Shelton)
    • What is fasting ??? Abstinence from food For a limited period of time Only water Plasma levels of glucose, amino acid, TAG falls Decline in Insulin secretion Increased glucagon secretion
    • Fuel storeFuel storage in a normal adult of 70 kg male  Fat:15.0kg =135,000kcal  Protien:06.0kg =24,000kcal  Glucose 0.2kg =800kcalThe fat storage is sufficient to meet energy needs for about three month
    • Stages of fasting Stage 1:-gestrointestinal phage  CHO depleated Stage 2:-  Glycolysis  Gluconeogenesis  Fat oxidation  Ketogenesis Stage 3:-  Does not occurs in fasting
    • Enzymatic changes in fasting The flow of intermediates through the pathway of energy metabolism is controlled by four mechanisms  Availability of the substrate  Allosstatic regulation of enzyme  Covalent modification of enzymes Induction-repression of enzyme synthesis
    • Liver in fasting Carbohydrate metabolism  1st glycogen degradation  1st glucose is used till glucose level goes down  Rapid mobilization of liver glycogenstores  Then gluconeogenesis  From muscle-glucogenic amino acid and lactate  From adipose tissue-glycerol
    • Cont… Fat metabolism  Increased fatty acid oxidation  Obtained from TAG hydrolysis in adipose tissue  It provides NADH and ATP required for gluconeogenesis  Increased synthesis of ketone bodies  When the concentration of acetyl CoA exceeds the oxidative capacity  Starts during 1-2 days of fasting  Can be used by most of the tissue including brain
    • Adipose tissue in fasting Carbohydrate metabolism Fat metabolism  Increased degradation of TAG  Causeddue to increased catecholamines (nor- epinephrine)  Increased release of fatty acid  Hydrolysis of stored TAG  Bound to albumin  Glycerol produced from TAG degradation is used as a precursor for gluconeogenesis by liver  Decreased uptake of fatty acid  Lipoprotien lipase activity of adipose tissue is low
    • Resting skeletal system in fasting Fuel source i. Glucose ii. Glycogen stores iii. Fatty acid Carbohydrate metabolism  Glucose to skeletal muscle by GLUT-4 protien  Glucose metabolism is reduced because of depressed circulating insulin
    • Cont… Lipid metabolism  1st two weeks fatty acid from adipose tissue and ketone bodies from liver  3rd week ketone bodies level increases Protein metabolism  1st few days-rapid break down of muscle protein  Later the proteolysis decreases as brain start using the ketone bodies as a fuel
    • Brain in fasting Day 1  Glucose as a fuel  (blood glucose maintained by hepatic gluconeogenesis) 2-3 week  Increased plasma ketone bodies  Replaces glucose as a primary fuel
    • Endocrine system in fasting Increased growth hormone levels  Mobilizes the fats from adipose tissue Decreased thyroid hormones  Decreased basal metabolic rate  Decreased erythropoisis rate  Decreased heart and respiratory rate  Increased drowzyness
    • Cont… Decreased insulin  Caused due to low blood sugar and Increased glucagon levels Increased glucagon  Increased glycolysis  Increased gluconeogenesis  Increased transport of amino acid  Increased lypolytic and ketogenic action  Increased free fatty acid in blood  Increased ketogenesis
    • Cont… Increased aldosteron Decreased sodium levels in body Increased aldosteron Increased retention of water and sodium Increased ECF Increased arterial blood pressure Increased ANP, BNP, CNP Excretion of water and sodium
    • Cont… Increased cortisol Increased adrenaline and nor-adrenaine  Increased urination  Increased brain activity  Quick fatique  Increased sweating  Increased blood pressure(systolic)  Increased general vasoconstriction  Decreased blood coagulation But in later stages all the functions alter,there is less sweating, urination,etc.
    • Cardio-pulmonary system infastin Increased heart rate Increased contractibility Increased conductivity Increased secretion of  Arterial natriuretic polypeptide  Brain natriuretic polypeptide  C-type natriuretic polypeptide Broncho dilatation Increased oxygenation
    • Blood Blood volume Increased RBC count remains same Blood becomes thin Decreased blood sugar, amino acid, TAG Decreased blood coagulation Decreased blood pressure General vasoconstriction Destruction of lymphocytes and basophils
    • GIT in fasting Increased secretion of GIT hormones Increased peristaltic movement Increased gherilin secretion Increased elimination
    • Sleep in fasting More sleep occures Drowzyness is Increased (Increased thyroid)
    • Urinary system in fasting Increased urine formation Increased ketouria (later stages) Increased sodium excretion Increased secretion of erythropoietin
    • Thank you…