Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 26 Lecture Outline 26-1 Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stable with equal energy intake and output around a homeostatic set point Determined by combination of environmental and hereditary factors 26-2 30-50% of variation between individuals due to heredity rest due to eating and exercise habits Appetite regulators short term effects last minutes to hours long term effects last weeks to years 26-3 Hunger – Ghrelin Satiety Peptide YY Cholecystokinin (CCK) Satiety Leptin Insulin Ghrelin – hunger from parietal cells of empty stomach Peptide YY (PPY) – satiety from enteroendocrine cells in ileum and colon secreted in proportion to calories consumed acts as ileal break (slows stomach emptying) Cholecystokinin (CCK) – satiety 26-4 from enteroendocrine cells of duodenum and jejunum appetite-suppressing effect on brain Leptin – secreted by adipocytes in proportion to body fat stores Insulin – pancreatic beta cells 26-5 effect similar to leptin (but weaker) 26-6 One calorie - amount of heat required to raise temperature of 1 g of water 1 °C Fats contain about 9 kcal/g Carbohydrates and proteins, about 4 kcal/g 1000 calories is a kilocalorie or Calorie sugar and alcohol are “empty” calories -- few nutrients Substance used for fuel is oxidized primarily to make ATP 26-7 Definition - Ingested chemical used for growth, repair or maintenance Macronutrients consumed in large amounts Micronutrients needed in small amounts Recommended daily allowances (RDA) safe estimate of daily intake for standard needs Essential nutrients can not be synthesized 26-8 proteins, fats and carbohydrates minerals, vitamins, 8 amino acids and 1-3 fatty acids must be consumed in the diet 26-9 Nearly all dietary carbohydrates come from plants The RDA for carbohydrates is greater than for any other nutrient Carbohydrates are found/stored in 3 places in body Most carbohydrate serves as fuel 26-10 neurons and RBCs depend on glucose Sugars do serve as structural components muscle and liver glycogen; blood glucose nucleic acids, glycoproteins and glycolipids, ATP Blood glucose carefully regulated by insulin and glucagon Fibrous material that resists digestion Fiber is important to diet (RDA is 30 g/day) Water-soluble fiber (pectin) blood cholesterol and LDL levels Water-insoluble fiber (cellulose, lignin) 26-11 excess interferes with mineral absorption - iron absorbs water in intestines, softens stool, gives it bulk, speeds transit time Most of the body’s stored energy Fat-soluble vitamins (A,D,E,K) absorbed with dietary fat hydrophobic, contains 2X energy/g, compact storage glucose and protein sparing (no protein utilized for energy) ingest less than 20 g/day risks deficiency Chemical precursors (cholesterol and fatty acids) Structural 26-12 phospholipids and cholesterol are components of plasma membranes and myelin Should be less than 30% of daily calorie intake Most fatty acids synthesized by body animal origin -- meat, egg yolks and dairy products found in nuts, seeds and most vegetable oils Cholesterol 26-13 Coconut and palm oil Unsaturated fats essential fatty acids must be consumed Saturated fats typical American gets 40-50% found in egg yolks, cream, shellfish, organ meats and other meats Lipids transported in blood as lipoproteins 26-14 protein and phospholipid coat around a hydrophobic cholesterol and triglyceride core Categorized into 4 groups by density more protein means higher density 26-15 Form in absorptive cells of small intestine 26-16 enter lymphatic system, then blood transports ingested fat to cells VLDL produced by liver to transport lipids to adipose tissue for storage when triglycerides removed become LDLs (mostly cholesterol) LDL 26-17 absorbed by cells in need of cholesterol for membrane repair or steroid synthesis Production and function 26-18 liver produces an empty protein shell travels through blood, picks up cholesterol delivers cholesterol to liver, for elimination in bile Desirable to maintain total cholesterol concentration of < 200 mg/dL most cholesterol is endogenous dietary restrictions lower blood cholesterol levels by 5% with restriction of dietary cholesterol by 15 to 20% with restriction of certain saturated fats 26-19 vigorous exercise lowers blood cholesterol 12-15% of body mass mostly in skeletal muscles Functions muscle contraction movement of body, cells, cell structures cell membranes (receptors, cell identity, pumps) fibrous proteins (collagen, keratin) structural globular proteins (antibodies, myoglobin, enzymes) functional 26-20 plasma proteins: blood osmolarity and viscosity RDA - 44-60 g/day for meat eaters RDA - 60-100 g/day for vegans Nutritional value depends on proportions of amino acids 8 essential amino acids can not be synthesized isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine 26-21 Cells do not store surplus protein Animal proteins (meat, eggs, dairy) are “complete proteins” Plant sources must be combined in the right proportions beans – have very little tryptophan or cysteine rice – is deficient in isoleucine and lysine Examples of protein combinations Beans with a corn tortilla Lentils with rice Peanut butter on toast Soy protein is complete on its own 26-22 Positive nitrogen balance occurs in children; they ingest more than they excrete promoted by growth and sex hormones Negative nitrogen balance 26-23 body proteins being broken down for fuel (muscle atrophy) glucocorticoids promote protein catabolism in states of stress Calcium and phosphorus Phosphorus cofactors for enzymes Iron - essential for hemoglobin and myoglobin Chlorine - component of stomach acid (HCl) Mineral salts 26-24 phospholipids, ATP, CP, buffers, nucleic acids Calcium, iron, magnesium and manganese bones and teeth electrolytes; govern function of nerve and muscle cells; regulate distribution of body water Vegetables, legumes, milk, eggs, fish and shellfish Animal tissues contain large amounts of salt 26-25 carnivores rarely lack salt in their diets herbivores often supplement by ingesting soils Recommended sodium intake is 1.1 g/day Typical American diet contains 4.5 g/day Body synthesizes some vitamins from precursors niacin, vitamin A and D vitamin K, pantothenic acid, biotin, folic acid produced by intestinal bacteria Water-soluble vitamins (C, B) Fat-soluble vitamins (A, D, E, K) 26-26 absorbed with water in small intestine; not stored absorbed with dietary lipids; stored Dietary carbohydrate burned as fuel within hours of absorption (glucose catabolism) C6H12O6 + 6O2 6CO2 + 6H2O 26-28 Transfers energy from sugar to ATP Series of small steps to efficiently transfer energy to ATP (reduces energy lost as heat) Glycolysis (yields 2 ATP) Aerobic respiration (yields 34-36 ATP) completely oxidizes pyruvic acid to CO2 and H2O Anaerobic fermentation (if no O2 available) 26-29 glucose (6C) split into 2 pyruvic acid molecules (3C) pyruvic acid reduced to lactic acid Capture energetic electrons from glucose during its catabolism NAD (nicotinamide adenine dinucleotide) FAD (flavin adenine dinucleotide) 26-30 derived from niacin (Vitamin B3) derived from riboflavin (Vitamin B2) Aerobic 38 ATP 10 NADH Anaerobic 2 ATP 8 NADH Yes No Which need oxygen? Yes 26-34 Without oxygen, your muscles switch to lactic acid fermentation. Only 2 ATP are made (the glycolysis portion of the pathway) Fate of pyruvic acid depends on oxygen availability In an exercising muscle, demand for ATP is greater than oxygen supply; ATP produced by glycolysis Lactic acid travels to liver to be oxidized back to pyruvic acid when O2 is available (oxygen debt) then stored as glycogen or released as glucose Fermentation is inefficient, not favored by brain or heart 26-37 Without oxygen, yeast fermentation produces CO2 and ethanol as waste products. Only 2 ATP are made (the glycolysis portion of the pathway) Read this section from pg 1029 Hepatic cirrhosis 25-39 Patient presentation Malnutrition Ascites Gynecomastia Patient presentation vomiting blood Patient presentation confusion confabulation Thiamine deficiency Alcohol interferes with absorption Patient presentation confusion agitation termors fever hallucinations paranoia Delirium tremens “the DTs” caused by acute alcohol withdrawal may be fatal 1 out every 10 American men between 18 and 29 is an alcoholic Antabuse (Disulfiram) is used to treat alcoholism Causes an “instant hangover” if patient drinks alcohol Notify doctor attending to patient ATP is quickly used after it is formed - it is not a storage molecule Glycogenesis -- synthesis of glycogen stimulate by insulin Glycogenolysis -- glycogen glucose extra glucose will be stored stimulated by glucagon and epinephrine only liver cells can release glucose back into blood Gluconeogenesis -- synthesis of glucose from noncarbohydrates, such as fats and amino acids 26-46 Triglycerides are stored in adipocytes constant turnover of molecules every 3 weeks released into blood, transported and either oxidized or redeposited in other fat cells Lipogenesis = synthesizing fat from other sources amino acids and sugars used to make fatty acids and glycerol Lipolysis = breaking down fat for fuel 26-47 glycerol is converted to PGAL and enters glycolysis fatty acids are broken down 2 carbons at a time to produce acetyl-CoA (beta oxidation) Amino acid pool Dietary amino acids plus 100 g of tissue protein broken down each day into free amino acids As fuel - first must be deaminated (removal of NH2)--what remains enters the citric acid cycle 26-48 the NH2 becomes ammonia (NH3) which is toxic and which the liver converts to urea (excreted in urine) Liver converts ammonia (NH3) to urea which is removed from blood by kidneys This is called the ornithine cycle. 26-49 Lasts about 4 hours during and after a meal Carbohydrates blood glucose is available to all cells for ATP synthesis excess is converted by liver to glycogen or fat Fats time of nutrient absorption and use for energy needs taken up by fat cells from chylomicrons in the blood primary energy substrate for liver, fat and muscle cells Amino acids 26-50 most pass through the liver and go onto other cells in liver cells, may be used for protein synthesis Regulated by insulin secreted in response to elevated blood glucose and amino acid levels and the hormones gastrin, secretin and cholecystokinin (CCK) Insulin increases the cellular uptake of glucose by 20-fold stimulates glucose oxidation, glycogenesis and lipogenesis but inhibits gluconeogenesis stimulates active transport of amino acids into cells and promotes protein synthesis 26-51 Homeostasis of blood glucose critical to brain Carbohydrates glucose is drawn from glycogen reserves for up to 4 hours and then synthesized from other compounds Fat when stomach and small intestine are empty- stored fuels are used adipocytes and liver cells convert glycerol to glucose free fatty acids are oxidized by liver to ketone bodies Protein metabolism 26-52 used as fuel when glycogen and fat reserves depleted wasting away occurs with cancer and other diseases from loss of appetite and altered metabolism By sympathetic nervous system and glucagon Blood glucose drops, glucagon secreted 26-53 glycogenolysis and gluconeogenesis raise glucose levels lipolysis raises free fatty acid levels Promotes glycogenolysis and lipolysis under conditions of injury, fear, anger and stress Adipose, liver cells and muscle cells respond to epinephrine Cortisol promotes increased blood glucose Fat and protein catabolism and gluconeogenesis More about this when we study the endocrine system 26-54 Amount of energy used in the body in a given period of time (kcal/hr or kcal/day) Basal metabolic rate (BMR) Factors affecting total MR 26-55 relaxed, awake, fasting, room comfortable temperature pregnancy, anxiety, fever, eating, thyroid hormones, and depression 26-56 Homeostasis requires heat loss to match heat gain Hypothermia - excessively low body temperature Hyperthermia - excessively high body temperature Thermoregulation - ability to balance heat production and heat loss “Normal” body temperature varies about 1.8 degrees F. in a 24-hour cycle Core body temperature is temperature of organs in cranial, thoracic and abdominal cavities low in morning and high in late afternoon rectal temperature is an estimate of core temperature adult varies normally from 99.0 - 99.7 degrees F. Shell temperature is temperature closer to the surface (oral cavity and skin) 26-57 adult varies normally from 97.9 - 98.6 degrees F. 26-58 Comes from energy-releasing chemical reactions such as nutrient oxidation and ATP use Exercise greatly increases heat production Radiation - loss of body heat to objects around us Conduction and convection - loss of body heat to the air which when warmed rises to be replaced by cooler air Evaporation - heat loss as sweat evaporates 26-59 caused by molecular motion producing infrared radiation extreme conditions as much as 2L of sweat lost per hour, dissipating heat by as much as 600 kcal/hour A part of your brain, the hypothalamis monitors the temperature of blood Too warm cutaneous vasodilation sweating Too cold cutaneous vasoconstriction arrector pili muscle contraction shivering thermogenesis (if needed) nonshivering thermogenesis - thyroid hormone and BMR (seasonal adjustment) Behavioral thermoregulation Examples? 26-60 Fever Hyperthermia - exposure to excessive heat protective mechanism that elevates BMR which produces more heat elevating the BMR, etc. heat cramps are muscle spasms due to electrolyte imbalance from excessive sweating heat exhaustion -- severe electrolyte imbalance producing fainting, dizziness, hypotension heat stroke -- body temperature > 104 °F, may cause delirium, convulsions, coma, and death Hypothermia - exposure to excess cold 26-61 as core body temperature , BMR causing a further body temperature decrease, etc. (fatal if body temperature 75 °F)