7.GI - GI tract physiology 1 Functions of the...

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GI tract physiology HKin 191 1 1) Functions of the gastrointestinal (GI) tract 2) Digestion: function and regulation 1) mouth 2) esophagus 3) stomach 4) small intestine and accessory organs 5) large intestine 3) Exercise and digestion 1) gastric emptying 2) mouth-to-cecum transit
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GI tract physiology HKin 191 2 Key concepts appetite is neuro-hormonally regulated sensor b response systems digestion is a sequential process that is highly monitored and cross-regulated digestion requires multiple enzymes and chemicals from a variety of organs the movement if food through the system is regulated and coordinated with intake with rate of digestion with contents of GI tract various factors can effect the rate of food movement through the system activity nature of ingested food/drink
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GI tract physiology HKin 191 3 •processing of food and extracting nutrients •storage of food •elimination of wastes 1) Functions of the GI tract: general
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GI tract physiology HKin 191 4 Ingestion Secretion Mixing and propulsion Digestion (break down) Absorption Storage/use Elimination 1) Functions of the GI tract: general Digestive processes
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GI tract physiology HKin 191 5 Regulation of hunger • higher fat levels are detected by sensors in adipocytes • adipocytes release the hormone leptin into the circulation • leptin binds to leptin receptors in the hypothalamus • blocks effects of appetite stimulants • neuropeptide Y and anandamide • desire to eat drops, reducing food intake and fat storage feedback 1) Functions of the GI tract: ingestion - uptake of food and liquids
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GI tract physiology HKin 191 6 2) Digestion Three phases 1) cephalic: 2) gastric: 3) intestinal: linked and co-regulated
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GI tract physiology HKin 191 7 Mechanical chewing (mastication) Chemical saliva: functions 2) Digestion: the mouth (cephalic phase)
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GI tract physiology HKin 191 8 Regulation of saliva production 1) Chemosensors in the mouth afferent signal to brain stem b efferent signal to salivary glands (facial and glossopharyngeal nerves) • increase parasympathetic activity stimulates saliva production 2) Cognitive stimulus (anticipatory response) •smell of food… •sound of a bell? 2) Digestion: the mouth (cephalic phase)
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GI tract physiology HKin 191 9 Swallowing • voluntary initiation: • involuntary swallowing: 2) Digestion: the mouth (cephalic phase)
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GI tract physiology HKin 191 10 2) Digestion: the mouth (cephalic phase) Swallowing •peristaltic action moves food “bolus” down the esophagus
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GI tract physiology HKin 191 11 Mechanical and chemical digestion • stomach is primary site of digestion 1) Mechanical digestion in the stomach 2) Digestion: the stomach (cephalic and gastric phases) longitudinal layer circular layer muscle layers oblique layer
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GI tract physiology HKin 191 12 2) Chemical digestion in the stomach salivary amylases: hydrochloric acid (HCl): b
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7.GI - GI tract physiology 1 Functions of the...

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