IB Option H Further Human Physiology PPT

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IB Option H Further Human Physiology PPT

  1. 1. Option H: Further Human Physiology<br />IB Biology<br />
  2. 2. H1 - Hormonal Control<br />Hormones = chemical messengers secreted by endocrine glands into the blood and transported to specific target cells. Example: insulin – produced by pancreas; target: liver cells <br />Hormones can be:<br />Steroids: progesterone, estrogen, testosterone <br />Peptide derivative: insulin; leptin (appetite control-metabolism regulation / target = hypothalamus)<br />Tyrosine derivatives: thyroxine (thyroid hormone) = regulates metabolism <br />
  3. 3. Hormone Absorption<br />Different hormones = difference in solubility<br />Steroid hormones = can cross plasma membrane/nuclear membrane – bind with receptor, affecting gene expression directly<br />Protein hormones = cannot cross the membrane = trigger a cascade reaction mediated my chemicals called second messengers. <br /> Ex: adrenalin = attaches to membrane receptor = stimulates transformation from glycogen to glucose<br />
  4. 4. Hypothalamus/Pituitary <br />- Hypothalamus:Links nervous and endocrine systems(Pituitary: double lobed gland below hypothalamus)<br /> Hypothalamus controls each lobe differently:<br />Hypothalamus neurons produce hormones that are transported and stored in vesicles in the axon located in the posterior pituitary. Nerve impulses cause the release of the vesicles into blood stream. <br />Hypothalamus also produces GnRH (gonadotropin releasing hormone) = transported to anterior pituitary by portal vein = GnRH stimulates production of FSH (follicle stimulating hormone) and LH (luteinizing hormone) by anterior pituitary (target tissue)<br />
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  6. 6. Integration between pituitary and hypothalamus:ADH<br />hypothalamus neurosecretory cells produce ADH (anti-diuretic hormone or vasopressin = promotes osmoregulation) <br />ADH is transported through nerve impulses by to the posterior pituitary where it is stored <br />Osmoregulatory sensitive cells in the hypothalamus sense changes in solute concentration<br />ADH is released from its storage region and secreted into the blood<br />target tissue = collecting ducts of kidney = makes it more permeable to H20 = the body reabsorbs more H20, diluting blood solutes = OSMOREGULATION<br />
  7. 7. H2 - Digestion<br />Digestive juices are secreted into the alimentary canal (lumen of gut) by GLANDS. <br />Exocrine Glands + juice content: <br />salivary glands = saliva: amylase, lipase, mucus, slightly alkaline solution that moistens the food, <br />gastric glands in stomach wall = gastric juice: pepsin, hydrochloric acid, salt, water, mucus<br />pancreas = pancreatic juice: amylases, trypsin, chymotrypsin, lipase, carboxipeptidase, bicarbonate ion<br />small intestine = enteric juice: carbohydrases, dipeptidases, enterokinases (enteropeptidases)<br />
  8. 8. Pancreas – An exocrine and endocrine gland<br />
  9. 9. Exocrine Glands<br />release secretion into ducts which open onto cavities like skin, mouth, alimentary canal<br />acini (acinus = singular – “berry”) = cluster of secretory cells<br />2 portions: glandular + duct <br />Exocrine cells have: rough endoplasmic reticulum (b) well developed next to nucleus (c) and Golgi apparatus (d), more secretory vesicles with protein, more mitochondria (a)<br />
  10. 10. Gastric Juice Regulation<br /><ul><li>sight/smell of food = reflex = gastric juices released
  11. 11. How?</li></ul>presence of food in stomach = secretion of gastrin by endocrine cells within the stomach wall -> target tissue: gastric juice cells in stomach<br /><ul><li>gastrin: polypeptide hormone produced by mucous lining of stomach</li></ul>stimulates HCl production (parietal cells) and pepsinogen production (chief cells)<br />when pH in stomach drops = gastrin secretion is inhibited by secretin (duodenum secretion)<br />Membrane-bound enzymes in the gut epithelium<br />enzyme is attached to fixed surface = more efficient = not removed/plays other roles too<br />examples of membrane bound enzymes = enterokinase, maltase, lactase, sucrase<br />
  12. 12. Cellulose<br />humans lack cellulase<br />cellulose remains undigested/released in feces<br />cows/sheep = symbiotic relationship with cellulose digesting bacteria (termites/protozoan too)<br />cellulose = fiber = creates bulk (mass) = stimulates peristalsis/satiety <br />
  13. 13. Digestive Enzymes<br />Pepsin/Trypsin = proteases<br />Pepsinogen (stomach) + Trypsinogen (pancreas) = zymogens = inactive enzyme precursor chemically altered after secretion to become active (this prevents self digestion of the cell)<br />
  14. 14. Ulcers/Cancer in the stomach<br />acidic environment = barrier to infections<br />mucus protects stomach wall<br />Helicobacter pylori (bacterium) cause stomach infection leading to ulcers -> can lead to cancer<br />Lipid Digestion<br />Lipase – water soluble enzyme – acts on water-insoluble lipids (tend to coalesce into larger droplets) = PROBLEM<br />Triglycerides turn into fatty acids and glycerol<br />Bile acts as “detergent” = breaks fat into tiny droplets (emulsion), increasing surface area exposed to lipase<br />
  15. 15. H3 - Absorption of Digested Food<br />Structure of ileum:<br />villi = fingerlike projections that increase surface area of small intestine<br />crypts = contain secretory cells of intestinal secretion<br />mucosa = mucus secreting membrane<br />muscles = create contractions – promote movement of chyme along alimentary canal<br />serosa = tough outer membrane composed of collagen<br />Unabsorbed material / eliminated with feces (egested) = cellulose, lignin, bile pigments, bacteria and intestinal cells<br />
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  17. 17. Absorption in the small intestine<br />absorption happens through epithelial cells covering each villus<br />nutrients must cross epithelial cells (not enough space to go between cells = tight junctions)<br />cell membrane = microvilli = increase surface area even more<br />cell uses ATP to make endocytosis happen (cell needs many mitochondria for that)<br />Transport in the intestine can involve:<br />Simple diffusion (molecules follow concentration gradient, crossing the membrane through channel proteins – “pore”)<br />Facilitated diffusion (ex. Fructose)<br />Active transport (ex. Glucose = pumps use energy to move nutrient against concentration gradient)<br />Endocytosis (pynocytosis = cells uses energy = vesicles carry substances)<br />
  18. 18. Absorption of fatty acids<br />monoglycerides, bile salts, fatty acids = combine forming micelles -> diffuse across membrane -> inside cell they reassemble into triglycerides <br />protein is added to lipid -> vesicles called chylomicrons<br />exocytosis -> release lipoprotein from cell -> enter lacteals vessels (lymphatic system) -> converge into lymph vessels that carry them to circulatory system<br />

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