BIOL 1140 1st Edition Lecture 22Outline of Last LectureI. The Brain and Spinal Cord Constitute the CNSII. The Spinal Cord Relays InfoIII. The Brain Processes and Acts on InfoIV. Receptors Receive and Convert StimuliV. Receptors are Classified According to StimulusVI. CNS Interprets Nerve Impulses Based on Origin and Frequency of ImpulsesVII. Some Receptors Adapt to Continuing StimuliVIII. Somatic Sensations and Special Senses Provide Sensory InfoIX. Thermoreceptors Detect TemperatureX. Mechanoreceptors Detect Limb Position, Muscle Length, and TensionXI. TasteXII. SmellXIII. HearingXIV. The Outer Ear Channels Sound WavesXV. Middle Ear Amplifies SoundOutline of Current LectureI. Digestive SystemII. Gastrointestinal TractIII. Digestive TractIV. Salvitory Glands of the MouthV. Digestive Tract ContinuedVI. Digestion and Absorption of NutrientsVII. OrgansVIII. Hormonal Control of Digestive SecretionsCurrent Lecture I. Digestive Systema. Mechanical breakdown and movement of foodb. Chemical breakdown of foodi. Starch -> glucoseii. Proteins -> amino acidsiii. Lipids -> glycerol + Fatty acids1. Chemical breakdown requires specific digestive enzymes to catalyze hydrolysis for each type of foodc. Absorption of nutrients from food into the bloodstreamd. Eliminating wasteII. Gastrointestinal (GI) Tract These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Includesi. Mouthii. Pharynxiii. Esophagusiv. Stomachv. Small intestinevi. Large intestinevii. Rectum and anusb. Accessory organs includei. Salvitory glands, pancreas, liver, gallbladderIII. The Digestive Tracta. Mouthi. Roof of mouth composed of two parts1. Anterior hard palate2. Posterior soft palateii. Tonsils help protect against infectioniii. Teach used to chew food into pieces small enough to swallowiv. Increases surface area of foodv. Tongue mixes chewed food with saliva and forms a bolus in preparation for swallowingIV. Salivary Glands of the Moutha. Three pairs of salivary glands send juices through ducts to the mouthi. Salivary amylase - begins starch digestionii. Bicarbonate- neutralizes acids 1. Amylase only works as a neutral pHiii. Lysozyme - inhibits bacteriaiv. Mucin - sticks food together to make it easier to swallowV. The Digestive Tract Continueda. Pharynxi. Receives air from the nasal cavities and food from the mouth1. Swallowing is a reflex action that occurs in the pharynx a. Soft palate/uvula moves to close off nasopharynx (leads to nasal cavity), and the trachea moves under the epiglottis to cover the glottis (leads to lungs)b. Esophagusi. Muscular tube that passes from the pharynx through the thoracic cavity and diaphragm into the abdominal cavity1. Rhythmic peristalsis pushes food along the digestive tract, alternating smooth muscle contractions2. Sphincters encircle tube and act as valvesc. Wall of digestive tract organs and structures has four layersi. Mucosa1. Mucous membrane layer that secretes protective mucus, has many folds for expansionii. Submucosa1. Contains blood vessels, lymph vessels and nervesiii. Muscluaris1. 2 smooth muscle layers that create peristaltic contractionsiv. Serosa1. Secretes fluid to keep outer surface slippery, attaches to body walld. Stomachi. Temporarily stores food and aids in digestion of proteins1. Walls of stomach have folds which expand and help churn and mix food with gastric juices 2. Lining contains gastric pits leading into gastric glands3. Cells of stomach lining secrete mucusa. Protect from self-digestion4. Produces hydrochloric acida. Acidity kills bacteria5. Products pepsinogen, which is converted in the enzyme pepsina. Partially digests proteinsb. Depends on exposure to HCL to make pepsinii. Stomach contractions push food into the small intestine through the pyloric sphincter1. Contractions are strongest when stomach is full2. Presence of food with high fat content causes secretion of hormones that slow peristalsisa. Fats take longer to digest3. Chime leaves the stomach and enters the small intestinee. Small intestinei. Primary site for digestion and nutrient absorption into bloodstream1. 3 segments: duodenum, jejunum, and ileuma. Folds of the walls contain villi and microvillib. Increase surface area and absorptive capability2. Receives secretions from pancreas, liver, and gallbladder to aid in chemical digestionf. Accessory Organsi. Pancreas exocrine functions:1. Makes and secretes digestive enzymes to break down fooda. Trypsin and chymotrypsin - digests proteinsb. Amylase - digests carbsc. Lipase - digests lipids2. Makes and secretes sodium bicarbonate to neutralize stomach acida. Enzymes would not work in an acidic environmentii. Liver1. Produces bile and urea2. Hepatic portal system: receives nutrient-rich blood directly from digestive organsa. Stores vitamins and iron, glycogen, and some lipidsb. Detoxifies chemicals, such as alcoholiii. Gallbladder1. Stores excess bile2. Bile is released into small intestine when fats are present3. Bile emulsifies fats to increase surface area and speed digestionVI. Digestion and Absorption of Nutrientsa. Where do nutrients go after they are absorbed in the small intestine?i. Glucose and amino acids are absorbed across the cells lining the small intestine by active transport, then transported by facilitated diffusion into the blood capillariesii. Fats are transported into lymphatic capillaries by diffusion and exocytosis1. Glucose and amino acids are polar molecules; fats are nonpolar2. Also fatty acids + glycerol reassemble into large lipid molecules after absorption, which are too big to enter blood capillariesVII. Organs a. The large intestinei. Absorbs water, salts, and some vitamins from food, and stores fecal material1. Compacts and solidifies feces2. Resident bacteria help digest some materialsii. Sections of the large intestine1. Cecum is pouch-like end of large intestine, appendix is attached 2. Colon is longest portion3. Rectum4. AnusVIII. Hormonal Control of Digestive Secretionsa. Secretion of digestive juices and motility is coordinated by the nervous system and hormonesi. Gastrin1. Released by stomach2. Triggered by presence of protein and stomach stretching3. Causes release of gastric juiceii. Secretin1. Released by small intestine2. Triggered by presence of acid3. Stimulates pancreas to release bicarbonateiii. Cholecystokinin1. Released by small intestine2. Triggered by presence of fat and protein3. Causes