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Option D: Human Physiology D.2 Digestion

Option D: Human Physiology D.2 Digestion. http://www.reflextouchtherapy.co.uk/wp-content/uploads/2016/03/human-digestive-system-chart.jpg. D.2. Essential idea: Digestion is controlled by nervous and hormonal mechanisms.

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Option D: Human Physiology D.2 Digestion

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  1. Option D: Human Physiology D.2 Digestion http://www.reflextouchtherapy.co.uk/wp-content/uploads/2016/03/human-digestive-system-chart.jpg

  2. D.2 • Essential idea: Digestion is controlled by nervous and hormonal mechanisms.

  3. D.2.U1 Nervous and hormonal mechanisms control the secretion of digestive juices. Typically there are gaps in between meals which means that digestive juices only need to be secreted at certain times. The nervous system and hormones work together to control the secretion of digestive juices. This helps to conserve energy! http://rbscan.com.au/wp-content/uploads/2015/10/Food-Clock-2.jpg

  4. D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut. There are two types of glands: Exocrine glands & Endocrine glands Examples of digestive exocrine glands: Salivary glands, pyloric glands (stomach), pancreas, goblet cells (small intestine) Some other examples: Sweat glands, Moll’s glands (eyes), mammary glands, sebaceous glands (skin)

  5. D.2.S1 Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs.

  6. D.2.U3 The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms. CEPHALIC PHASE 1) Thought, smell, sight or taste of food causes 2) Medulla sends message 3) Stomach begins producing Also stimulates production of (hormone) which is made in lower stomach and INTESTINAL PHASE 6) Sphincter opens to and a signal is sent to . Also stimulates production of (hormone) that . GASTRIC PHASE 5) Medulla sends message back to 4) After eating,

  7. D.2.U4 Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food. Secretion of the gastric pits include: Mucus protects the stomach cells from HCl

  8. D.2.U4 Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food. • Stomach acid has several purposes: • HCl + Protein = • Easier for enzymes to act on • HCl + Pepsinogen = • Pepsin + Large polypeptide chains = Smaller peptides • Smaller peptides get broken down further by other enzymes later • HCl that are consumed (stomach acid can have a pH as low as 2)

  9. D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers. Stomach ulcers: a paradigm shift in medicine A paradigm shift can be described as a huge change in scientific thought or consensus. The case of stomach ulcers is a rare example of how one discovery caused many experts to change their minds. It also led to the Nobel Prize for Medicine in 2005 for its discoverers. http://www.nobelprize.org/nobel_prizes/medicine/laureates/2005/press.html

  10. D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers. https://publichealth.arizona.edu/outreach/health-literacy-awareness/hpylori/transmission

  11. D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers. Helicobacter pylori

  12. D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs. Some people suffer from a condition called • Esophagus becomes irritated by HCl when the muscle at the top of the stomach does not function properly http://images.emedicinehealth.com/images/emedicinehealth/illustrations/gastroesophageal_reflux.jpg The acidic environment in the stomach is achieved by a called the H+, K+-ATPase. It uses one ATP to exchange two protons from the cytoplasm for two potassium ions in the lumen surrounding the parietal cell (cell that secretes HCl) http://d3qpq7e7yxjovl.cloudfront.net/content/ajpadvan/38/1/104/F3.large.jpg

  13. D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs. Late in the 20th century, researchers discovered a class of drugs that by cells in the gastric pits. These drugs are known as (PPIs). PPIs bind irreversibly to proton pump The effect is not permanent however, as the pumps are normally recycled and replaced with new pumps. http://www.nps.org.au/medicines/digestive-system/indigestion-reflux-and-stomach-ulcer-medicines/heartburn-and-reflux-medicines/for-health-professionals/pharmacology

  14. D.2.S1 Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs. Chyme from the stomach enters the small intestine for further digestion and absorption. The ileum is the section of the small intestine where most absorption occurs. The inner surface of the ileum has many folds, each covered in projections called villi. An electron micrograph at very high magnification: these are epithelial cells covering the villus; the microvilli on the surface of a single villus can be seen http://www.cals.ncsu.edu/course/zo250/brush_border.gif

  15. D.2.U5 The structure of cells of the epithelium of the villi is adapted to the absorption of food. 1 2 3 4 Infoldings (invagination) on side of epithelial cell closest to capillary bed increases surface area which increases absorption into capillary or lacteal

  16. D.2.U6 The rate of transit of materials through the large intestine is positively correlated with their fiber content. Fiber is composed mostly of cellulose and lignin in plant material. Both are components of the cell wall. • There is a positive correlation between the in one’s diet and the . • Fiber helps by • Muscles that push food along need to have a sufficient volume of material to apply pressure to High fiber diets can also help you manage your weight in part because it fills you up, giving a feeling of satiety without introducing excess energy. http://cdn.images.express.co.uk/img/dynamic/1/590x/secondary/186077.jpg

  17. D.2.U7 Materials not absorbed are egested. Some substances you consume do not get digested and therefore are not absorbed by the intestines. Instead they pass into the large intestine and become part of solid waste (feces).

  18. D.2.A2 Dehydration due to cholera toxin. is a disease caused by the bacterium Vibrio cholera Bacteria Binds to intestinal cell receptors and is taken into the cell by endocytosis Chain of reactions occurs that ultimately causes the efflux of Cl- (chlorine) and HCO3- (bicarbonate) ions from the cell into the intestine Water follows by osmosis leading to Water moves from blood to intestinal cells to replace water lost that can lead to death http://www.cdc.gov/cholera/general/ Cholera is spread by drinking water or eating food that is contaminated with the bacteria (often contaminated with feces).

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