1 physiology of feedimg, appetite & hunger


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  • Sareen Gropper, Jack Smith and James Groff, Advanced Nutrition and Human Metabolism, fifth ed. WADSWORTH
  • Ellie Whitney and Sharon RadyRolfes; Under standing Nutrition, Twelfth Edition. 2011, 2008 Wadsworth, Cengage Learning
  • Ellie Whitney and Sharon RadyRolfes; Under standing Nutrition, Twelfth Edition. 2011, 2008 Wadsworth, Cengage Learning
  • 1 physiology of feedimg, appetite & hunger

    1. 1. 1-Physiology of feedings,appetite & hungerPreparedBy;Dr. Siham M.O. Gritly1Dr. Siham Gritly
    2. 2. Pleasure of eating2Dr. Siham Gritly
    3. 3. Hypothalamus and other glands3Dr. Siham Gritly
    4. 4. glossary• appetite: the integrated response to the sight,smell, thought, or taste of food that initiates ordelays eating.• hunger: the painful sensation caused by a lackof food that initiates food-seeking behavior• hypothalamus: a brain center that controlsactivities such as maintenance of water balance,regulation of body temperature, and control ofappetite.4Dr. Siham Gritly
    5. 5. • satiation: the feeling of satisfaction; andfullness that occurs during a meal and stopeating. Satiation determines how much food isconsumed during a meal.• satiety: the feeling of fullness andsatisfaction that occurs after a meal andinhibits eating until the next meal. Satietydetermines how much time passes betweenmeals.5Dr. Siham Gritly
    6. 6. • binge-eating disorder: an eating disorder withcriteria similar to those of bulimia nervosa,excluding purging or other compensatorybehaviors.• Bulimia nervosa: an eating disordercharacterized by repeated episodes of binge eatingusually followed by self induced vomiting, misuseof laxatives or diuretics, fasting, or excessiveexercise.6Dr. Siham Gritly
    7. 7. Physiology of feeding• Feeding - the placement of food in the mouth,and the treatment of food in the oral cavity• mastication• Swallowing –• The swallowing process is commonly dividedinto oral, pharyngeal, and esophageal stagesaccording to the location of the bolus.• Deglutition - process of swallowingDr. Siham Gritly 7
    8. 8. 8Dr. Siham Gritly
    9. 9. Physiology of appetite and hungerRegulation of food intake• Ingestion of food is determined by the intrinsicdesire of the person for food, this is calledhunger• hunger is the physiological response to a need forfood caused by nerve signals and chemicalmessengers originating and acting in the brain,primarily in the hypothalamus.• Hormones of hypothalamus promotes thoughts ofeating• The type of food the person preferred isdetermined by appetite9Dr. Siham Gritly
    10. 10. • when there are no food for many hours, thestomach undergo intense rhythmic contractioncalled hunger contractions• These contraction cause a tight feeling in thestomach and cause pain known as hungerpangs• Hungry person also become more tense andrestless and often has a strange feeling in hisentire body10Dr. Siham Gritly
    11. 11. • After a meal Satiety is developed; thismeans the feeling of fullness and satisfactionthat occurs after a meal and inhibits eatinguntil the next meal. Satiety determines howmuch time passes between meals• the feeling of satiety continues to suppresshunger and allows a person to not eat again fora while.11Dr. Siham Gritly
    12. 12. • During the course of a meal, as food enters theGI tract and hunger diminishes, satiationdevelops “stop eating,” .• As receptors in the stomach stretch andhormones such as cholecystokinin becomeactive, the person begins to feel full. Theresponse: satiation occurs and the personstops eating12Dr. Siham Gritly
    13. 13. Factors influences hunger• 1-Physiological influences of hunger• Empty stomach• Gastric contractions• Absence of nutrients in small intestine GI• Hormones such as Ghrelin that produced byfundus of the human stomach and cells of thepancreas and Leptin release from adiposetissue13Dr. Siham Gritly
    14. 14. • Endorphins (the brain’s pleasure chemicals)• Endorphins are neurotransmitters produced bypituitary gland and hypothalamus• enhancing the desire for food by the smell,sight, or taste of foods,• Dopamine is classified as a catecholamine (aclass of molecules that serve asneurotransmitters and hormones).14Dr. Siham Gritly
    15. 15. Ellie Whitney and Sharon Rady Rolfes; Ref; Under standing Nutrition, Twelfth Edition. 2011, 2008Wadsworth, Cengage Learning• 2-Sensory influences• Seek food and start meal• Thought, sight, smell,sound, taste of foodEndorphins15Dr. Siham Gritly
    16. 16. • 3-Cognitive influences• Keep eating• Presence of others,social stimulation• Perception of hunger,awareness of fullness• Favorite foods, foods with special meanings• Time of day• Abundance of available food16Dr. Siham Gritly
    17. 17. • 4-Postingestive influences (after food enters thedigestive tract)• Satiation: End meal• Food in stomach activates stretch receptors• Nutrients in small intestine draw out hormones (forexample, fat draw out cholecystokinin CCK, whichslows gastric emptying)• cholecystokinin, receptor regulates satiety and therelease of beta-endorphin and dopamine.17Dr. Siham Gritly
    18. 18. • 5-Postabsorptive influences (after nutrientsenter the blood)• Satiety: Several hours later• Nutrients in the blood signal the brain (vianerves and hormones) about their availability,use, and storage• As nutrients decrease, satiety diminishes• Hunger develops18Dr. Siham Gritly
    19. 19. Neural Centers for regulation of food intakehypothalamus.• Most hormones are secreted from the glands thatproduce them under the influence of stimulatinghormones from the hypothalamus.• The hypothalamus is a part of the brain involvedin the control of involuntary activity in the body;contains many centers of neural control such astemperature, hunger, appetite and thirst• These hormones in turn are activated by releasinghormones from the pituitary gland.19Dr. Siham Gritly
    20. 20. Hypothalamus The part of the brain that lies below thethalamus. contains many centers of neural control suchas temperature, hunger, appetite and thirst20Dr. Siham Gritly
    21. 21. Lateral hypothalamus & Ventromedial nuclei ofthe hypothalamus• Hunger and satiety centers; hypothalamus glandresponsible of the hunger and satiety• Lateral hypothalamus stimulation cases a personto eat greedily or hungrily (hunger or feedingcenter neurotransmitters Endorphins )• Ventromedial nuclei of the hypothalamus causesthe sensation of food rejection or complete satiety(satiety center neurotransmitters )21Dr. Siham Gritly
    22. 22. • Destructive lesions or trauma of the Lateralhypothalamus causes complete lack of desirefor food• While destructive lesions of the Ventromedialnuclei of the hypothalamus cause; voraciousand the person continued eating until itbecome extremely obese (overactive)22Dr. Siham Gritly
    23. 23. Dr. Siham Gritly 23
    24. 24. Other Neural Center that enter into feeding• Another area of the hypothalamus Mammillarybodies activate feeding reflexes such as lickingthe lips and swallowing• another area higher centers than hypothalamuscontrol feeding mainly appetite includeamygdala and cortical areas of the limbicsystem which is coupled with thehypothalamus24Dr. Siham Gritly
    25. 25. Human brainamygdala25Dr. Siham Gritly
    26. 26. • Destructive lesions in the amygdala increasefeeding while other inhibit feeding (choice offood loses the mechanism of appetite control andquality of food• The cortical regions of the limbic system haveareas when stimulated can increase or decreasefeeding activities• It is believed that theses centers with amygdalaand hypothalamus responsible of the quality offood that is eaten26Dr. Siham Gritly
    27. 27. Limbic system27Dr. Siham Gritly
    28. 28. Factors that regulate food intake• Regulation of food intake can be divided into;• 1-nutritional regulation (metabolicregulation); concerned with the maintenanceof normal quantities of nutrient stores in thebody• Factors that control the degree of activity offeeding center of the hypothalamus are;28Dr. Siham Gritly
    29. 29. • A) Decrease in blood glucose concentration isassociated with the development of hunger(the glucostatic regulation theory of hungerand feeding regulation)29Dr. Siham Gritly
    30. 30. • B) the effect of blood amino acidconcentration on feeding; increaseconcentration of amino acid in the bloodreduces feeding activity30Dr. Siham Gritly
    31. 31. • C) effect of fat metabolism on feeding (longterm feeding); as the quantity of adipose tissueincreases the rate of feeding decrease this iscaused by a negative feedback regulation31Dr. Siham Gritly
    32. 32. • D) body temperature and food intakeinterrelationship; cold person tends to overeat• When exposed to heat tends to under eat• This relationship is due to interaction withinthe hypothalamus between the temperatureregulation system (hypothalamic thermostat)and the food regulating system (Lateralhypothalamus & Ventromedial nuclei of thehypothalamus)32Dr. Siham Gritly
    33. 33. • The temp of the body is regulated by nervousfeedback mechanisms these mechanismsoperate through temperature regulating centersin the hypothalamus33Dr. Siham Gritly
    34. 34. • 2-alimentray regulation, non-metabolicregulation; Habit, Gastrointestinal filling34Dr. Siham Gritly
    35. 35. Hormonal control of feeding, appetite andhunger• Hormones that play an important role in controllingfeeding pattern;• leptin (identified in 1994), Leptin release fromadipose tissue is enhanced by insulin• Obese persons are found with high circulating leptinlevels but without response to leptin in the arcuatenucleus (aggregation of neurons in the hypothalamus)• Neurons are nerve cells that receive and sendelectrical signals over long distances within the body35Dr. Siham Gritly
    36. 36. • Acts on hypothalamus to decrease foodintake and increase energy consumption• Abnormalities in leptin signaling appearto be correlated to overeating and obesity36Dr. Siham Gritly
    37. 37. • ghrelin (identified in 1999), called "hungerhormone," is produced in the stomach and brain,induces food intake, and operates through a brainregion that controls cravings for food and otherenergy sources• ghrelin is peptide hormone secreted by gastricmucosa, on an empty stomach and during fastingthis hormones increase, and level fall rapidly aftermeal• work together with leptin to balance the states ofhunger and satiety37Dr. Siham Gritly
    38. 38. • Insulin release from pancreatic islets cellsfollows intake of both carbohydrates andproteins.• Insulin increase appetite by inhibitingstimulatory neurons and by activatingreleasing neurons.• Resistance to insulin is very often associatedwith obesity and the loss of insulins regulationof metabolism as seen in diabetes type 2.Dr. Siham Gritly 38
    39. 39. • Insulin increase appetite by inhibitingstimulatory neurons and by activatingreleasing neurons.• Resistance to insulin is very often associatedwith obesity and the loss of insulins regulationof metabolism as seen in diabetes type 2.Dr. Siham Gritly 39
    40. 40. • orexin , Also called Hypocretins –neurotransmitter hormones that increase foodintake,• Synthesized in neurons located in the lateralHypothalamus• orexin are inhibited by leptin and activated byGhrelin and Hypoglycemia40Dr. Siham Gritly
    41. 41. The healthy eating cycle41Dr. Siham Gritly
    42. 42. Eating disorder• Both men and women are susceptible to eatingdisorders, although a greater percent of eatingdisorders are found in women.• The three most common eating disorders foundare:• 1-Anorexia Nervosa,• 2-Bulimia,• 3-Compulsive Exercise42Dr. Siham Gritly
    43. 43. Warning Signs of an Eating Disorder• Preoccupation (worry) with food and weight• Repeatedly expressed concerns about being fat• Increasing criticism of ones body• Frequent eating alone• Use of laxatives• Trips to the bathroom during or following meals• Continuous drinking of diet soda or water• Compulsive, excessive exercise• Complaining of always being cold43Dr. Siham Gritly
    44. 44. Anorexia nervosa• Anorexia nervosa: an eating disordercharacterized by a refusal to maintain aminimally normal body weight and a distortionin perception of bodyshape and weight( BMI ≤ 17.5)Excessive concernwith weight or weight gain44Dr. Siham Gritly
    45. 45. Health Complications from Anorexia• Anorexia poses life-threatening complicationsincluding:• malnutrition• Abnormal Heart Rhythms• low blood pressure• Dehydration• electrolyte imbalance• amenorrhea (interruption of the menstrual cycle)• osteoporosis (decreased bone mass)• sleep disorder45Dr. Siham Gritly
    46. 46. Signs and Symptoms of Anorexia• Excessive weight loss• Always thinking about food, calories, andbody weight• Wearing layered clothing• Mood swings or depression• Inappropriate use of laxatives, or diuretics inorder to lose weight• Avoiding activities that involve food46Dr. Siham Gritly
    47. 47. Diet Strategies for Anorexia nervosa• Appropriate diet is vital to recovery and mustbe according to each individual’s needs.• initial food intake may be only 1200 kcaloriesper day.• A variety of foods and foods with a higherenergy density help to ensure greater success.• As eating becomes more comfortable, aperson with aneroxia should gradually increaseenergy intake.47Dr. Siham Gritly
    48. 48. Bulimia• Bulimia is one such eating disorderthat describes a cycle of bingingand purging.• Bulimia can begin when restrictive diets fail, orthe feeling of hunger associated with reducedcalorie intake leads to reduce eating.• Like the person with anorexia nervosa, the personwith bulimia nervosa spends much time thinkingabout body weight and food48Dr. Siham Gritly
    49. 49. • Bulimia are multi-factorial, with psycho-developmental, socio-cultural, and geneticcontribution factors49Dr. Siham Gritly
    50. 50. Bulimia is of Two types:• 1-Purging type: The personregularly engages in self-inducedvomiting or the misuse of laxatives,diuretics.• 2-Nonpurging type: The person uses othercompensatory behaviors, such as fasting orexcessive exercise, but does not regularlyengage in self-induced vomiting or the misuseof laxatives, diuretics,50Dr. Siham Gritly
    51. 51. The Binge-Purge Cycle has no beginning or end, Bulimia isan addictive cycle on both physical and emotional levels.,this sequence involves a self-sustaining series of events andedictable response51Dr. Siham Gritly
    52. 52. Signs and Symptoms of Bulimia• Excessive weight loss• Visiting the bathroom after meals• Depression• Excessive dieting, followed by binge eating• Always criticizing ones body52Dr. Siham Gritly
    53. 53. Diet Strategies for CombatingBulimia Nervosa• Nutrition Principles• Eat a well-balanced diet and regularly timedmeals consisting of a variety of foods.• Include raw vegetables, salad, or raw fruit atmeals to prolong eating times.• Choose whole-grain, high-fiber breads, pasta,rice, and cereals to increase bulk.• Consume adequate fluid, particularly water53Dr. Siham Gritly
    54. 54. Compulsive Exerciser• Some athletes suffer from a slight form ofeating disorder that results in excessive andaddictive exercise in an attempt to control orlose weight.• Addictive exercisers may use extreme trainingas one way to expend calories and maintain orlose body weight in the attempt to improveperformance or achieve a desired body shapeor weight.54Dr. Siham Gritly
    55. 55. Warning Signs of a Compulsive Exerciser• suffer symptoms of overtraining syndrome.• Force to exercise even if you dont feel well.• almost never exercise for fun• Every time you exercise, you go as fast or hard asyou can.• experience severe stress and anxiety if he or shemiss a workout.• You miss family obligations because you have toexercise.55Dr. Siham Gritly
    56. 56. • Compulsive exercise is as dangerous as foodrestriction, binging and purging and the use ofdiet pills and laxatives.• Compulsive exercise can quickly lead to moreserious types of eating disorders includinganorexia and bulimia as well as a number ofserious physical dangers including kidneyfailure, heart attack and death.56Dr. Siham Gritly
    57. 57. Unspecified Eating Disorders,Binge-Eating Disorder• Binge-Eating Disorder• People with binge eating disorder consume lessduring a binge, rarely purge, and exert lessrestraint (self control) during times of dieting• Such an eating disorder does not meet the criteriafor either anorexia nervosa or bulimia nervosa• such compulsive overeating is a problem andoccurs in people of normal weight as well as thosewho are severely overweight.57Dr. Siham Gritly
    58. 58. • Obesity alone is not an eating disorder• There are also differences between obese bingeeaters and obese people who do not binge.Those with the binge-eating disorder reporthigher rates of, disgust about body size,depression, and anxiety.• Obese binge eaters tend to consume morekcalories and more dessert58Dr. Siham Gritly
    59. 59. • Sareen Gropper, Jack Smith and James Groff, Advanced Nutritionand Human Metabolism, fifth ed. WADSWORTH• Melvin H Williams 2010; Nutrition for Health, Fitness and Sport. 9thed, McGraw Hill• Heymsfield, SB.; Baumgartner N.; Richard and Sheau-Fang P. 1999.Modern Nutrition in Health and Disease; Shils E Maurice,Olson A. James, Shike Moshe and Ross A. Catharine eds. 9thedition• Guyton, C. Arthur. 1985. Textbook of Medical Physiology. 6thedition, W.B. Company59Dr. Siham Gritly