Chapter 3 - Chapter 3 Basics of Digestion Hunger and thirst...

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Chapter 3 Basics of Digestion Hunger and thirst : physical needs which drive how much and how often we eat, physiological response (hypothalamus triggers hunger) Appetite : another powerful drive, but unreliable Influenced by food preferences and psychological stimulation May eat without being hungry or needing nourishment Taste: 5 basic categories Sweet: tip of tongue Salty: sides of tongue Sour: sides of tongue Bitter: back of tongue Savory (umami): throughout mouth; not all people are sensitive to this taste sensation Humans share an innate preference for sweet (pleasure), salty (electrolytes), and fatty (rich textures and aromas) foods Sometimes food preferences and nutritional needs conflict and make changing food choices challenging Brain recognizes taste: food dissolves in saliva, contacts the tongue surge, taste cells send nerve impulses to the brain Both mouth and nose contribute to tasting of foods Aromas detected by olfactory cells in nasal cavity as food odors enter both nose and mouth Flavor refers to both taste and aroma Digestion : a multi-step process of breaking down foods into absorbable components using mechanical and chemical means it the gastrointestinal (GI) tract. Involves both mechanical and chemical processes. GI tract consists of: o Mouth o Esophagus o Stomach o Small and large intestines o Other organs Main roles of GI tract: o Break down food o Absorb nutrients
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o Prevent microorganism or other harmful compounds in food from entering tissues of the body GI tract is about 23 feet long with extensive surface area for nutrient absorption o Cells lining GI tract are replaces every three to five days Mechanical digestion : chewing, grinding food to aid swallowing Peristalsis : the forward, rhythmic muscular contracting that moves food through GI tract Chemical digestion
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  • Spring '08
  • Quintana
  • GI Tract, chemical digestion, o Stomach

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