Card Set Information

2014-04-10 22:06:25

Show Answers:

  1. What is not a function of the liver?
    Insulin release
  2. Where does the majority of nutrients get absorbed in the GI tract?
    small intestine
  3. How is it possible that the GI tract absorbs more liquid per day than the amount that we ingest?
    the body reabsorbs its own secretions
  4. what is the function of bile?
    acid neutralization
  5. how are GI processes regulated?
    • control mechanisms of the GI tract are governed by volume and composition of the contents
    • rather than the nutritional state of the body
    • body is designed to absorb all nutrients, whether it needs them or not
  6. basic principles of neural regulation
    • through the enteric and central nervous systems
    • the ens releases and is regulated by hormones 
    • cns contributes through SNS and PSNS
    • SNS is anti-bowel and anti-secretion
    • PSNS is pro-bowel and pro-secretion
  7. hormonal regulation of the gi tract
    • hormones are released into the GI blood supply allowing communication from one portion to another
    • hormones interact with other organ systems 
    • major purpose of hormones is to regulate acid, bicarbonate, mucus, and enzyme secretions to aid digestion and absorption
  8. neural and hormonal regulation of the GI tract can be divided into three phases
    • cephalic-CNS senses sight, smell, taste, and chewing of food activates PSNS to increase gut secretions and motility
    • gastric-stomach phase responds to digestion, acidity, and peptides
    • gastrin is the critical hormone in this phase
    • intestinal-inititaed by distension, acidity, osmolarity, and digested nutrients
    • secretin and and CCK are major hormones released by the small intestine
  9. pH throughout the GI tract
    • stomach 1-5
    • small intestine 6-7
    • terminal ileum 7-8
    • large intestine, rectum 6-7
  10. which drug action is most likely to reduce bowel motility and secretions
    anticholinergic activity
  11. gastric gland
    • many in the stomach
    • contain major functional cells
  12. mucous cells
    produce mucus and bicarbonate for protection from acid
  13. parietal cells
    produce acid
  14. enteroendocrine cells
    produce gastrin to trigger more acid release from parietal cells
  15. regulation of HCl production in the stomach
    • cephalic phase-PSNS to ENS produce acetylcholine, increasing HCl production
    • gastric phase-long and short neural reflexes and direct stimulation of gastrin secretion, increasing HCl production
    • Intestinal phase-long and short neural reflexes; secretin, CCK, and other hormones decrease HCl production
  16. an increase in H+ in the small intestine affects secretin production in the SI and acid production in the stomach in what ways?
    • secretin secretion increases in the SI
    • gastric acid secretion is reduced in stomach
  17. enterochromaffin-like cells
    • release histamine onto parietal cells
    • stimulated by:
    • ACh-innervation from vagus nerve; seeing, smelling, thinking about food
    • Gastrin-contraluminal secretion from G cells induced by proteins released from ingested foods; induced by distension of stomach 
    • inhibited by:
    • somatostatin-released contraluminally from D cells in the antrum 
    • when pH<3, results in decreased histamine and gastrin secretion
  18. parietal cells
    • only cells to release gastric acid
    • located in body and fundus of stomachwithin gastric glands
    • stimulated by:
    • ACh-released from cholinergic neurons innervating the parietal cells 
    • Histamine-released by ECL cells; most potent signal for acid production
    • Gastrin-released from G cells in the antrum
  19. three primary defenses against acid stimulated by prostaglandins E2 and I2
    • increased mucus secretion creates a thick and viscous physical barrier 
    • increased bicarbonate secretion neutralizes acid near mucosal cells
    • PGE2 and I2 inhibit acid secretion from parietal cells
  20. gastric emptying
    refers to emptying of the stomach contents into the small intestine
  21. NSAIDS inhibit prostoglandin production, if NSAIDs act on the stomach this way, what would be their expected effect?
    • decrease mucus production
    • decrease bicarbonate secretion
  22. the enteric nervous system in the SI
    • appx 100 million neurons in the gut
    • some are connected to ANS, but many can function independent of the ANS
    • these are intrinsic neurons
    • afferent (sensory) and efferent (motor) project to and from the CNS and ENS
  23. intrinsic enteric nervous system innervation of the SI
    • myenteric plexus innervates the longitudinal and circular muscle and some mucosal glands
    • muscularis mucosae-vibrates for enhanced absorption
    • mucosal glandular epithelium secretes various substances
    • enteric blood vessels can change hemodynamics 
    • intestinal endocrine cells release chemical signals to blood
  24. intrinsic enteric nervous system innervation of the SI
    • -intrinsic afferent and efferent nerve fibers function regardless of autonomic input
    • -serotonin is most important in afferent pathway secretion
    • -released from enterochromaffin cells when nutrients stretch or interact chemically with these cells
  25. myenteric plexus triggers peristalsis
    • via efferent innervation of the circular muscle 
    • contraction behind bolus
    • relaxation in front of bolus occurs simultaneously
    • propels bolus in anal direction
    • 5-HT3 receptor antagonists decrease motility and increase water absorption
  26. what may be considered one of the most bothersome nuisance side effects of opiate drugs like oxycontin, morphine, hydrocodone, and codeine?
  27. interneurons in the myenteric plexus influencing contractile stimulus
    • opiod releasing neurons inhibit ACh release and thus inhibit contraction
    • dopamine releasing neurons do the same
    • responds to serotonin afferent signaling by conducting an efferent signal to the glandular epithelial cells to secrete digestive substances
  28. afferent/sensory output to the CNS (serotonin)
    • serotonin stimulates intrinsic enteric neurons to initiate propulsion and further digestion of food in the intestines
    • excessive release can cause nausea and vomiting
    • irritant in intestine is treated with Substance P
  29. absorption in the small intestine
    • arrange for a large surface area which enhances nutrient absorption
    • villi increase SA and contain blood vessels and lacteal, which also absorb nutrients
    • microvilli increase SA and form the brush border
    • anything not digested in stomach is in the duodenum, which recieves enzymatic juices and detergents from the liver and pancreas
  30. major macronutrients are absorbed in the SI
    • carbs
    • proteins
    • fats
  31. carbohydrate digestion
    • most are consumed as di or polysaccharides which must be broken down into monosaccharides to be absrobed 
    • amylase breaks down polysaccharides
  32. protein digestion
    • broken down into peptide fragments by:
    • pepsin in the stomach
    • trypsin and chymotrypsin by the pancreas
    • further digested to free amin acids by carboxypeptidase from pancreas
    • and aminopeptidase on epithelial cells in SI membrane
    • free amino acids enter epithelial cells by secondary activbe transport coupled to Na
    • short chains of 2-3 amino acids absorbed by secondary active transport coupled to H+ ion gradient
  33. fat digestion
    • fat composed mostly of triglycerides 
    • fat globules formed in stomach 
    • in SI the globules are broken down and emulsified by bile salts 
    • lipids are broken down into individual molecules of fatty acids by pancreatic lipase in duodenal lumen 
    • individual fatty acids diffuse into intestinal epithelium cells and are re-conjugated to form triglycerides
    • used in SI to form chylomicrons, or major lipoproteins with cholesterol, phospholipids, and specific proteins
  34. fate of absorbed fat
    • cholymicrons enter lymphatic system then into the blood 
    • they are disassembled in the blood, and are used throughout the body for energy 
    • other lipoproteins or their precursors are synthesized in the liver
    • lipoproteins in the blood drop off cholesterol and fatty acids where they are needed
  35. what are apoproteins?
    • found in exterior shell of lipoproteins 
    • provide structural stability 
    • act as ligands for lipoprotein receptors
    • inhibit other lipoproteins from binding to receptors 
    • act as cofactors for lipid modulating enzymes
  36. cholesterol
    • synthesized in liver and intestine
    • important for steroid biosynthesis 
    • precursor of bile acids
    • critical for cell fluidity/rigidity 
    • major component of low density lipoprotein (LDL)
    • excess leads to atherosclerosis 
    • excretion of cholesterol occurs via bile as bile acids or cholesterol
  37. cholesterol ester
    • more hydrophobic than cholesterol 
    • necessary form for cholesterol transfer between lipoproteins 
    • synthesized from cholesterol by lecithin-cholesterol acyltransferase, an enzyme attached to lipoproteins
  38. triglycerides
    • storage form of fatty acids in liver, lipoproteins, and adipose tissue
    • made in intestine and liver from fatty acids and glycerol
    • elevation can lead to pancreatitis by releasing enzymes that will digest surrounding tissue
  39. free fatty acids
    • carbon chain with terminal carboxyilic acid
    • can be saturated or unsaturated
    • liberated from triglycerides by lipoprotein lipase
  40. pathways of lipoproteins: chylomicrons
    • produced exclusively in the intestine
    • formed from dietary free fatty acids and cholesterol, and apoB-48 synthesized in enterocytes
    • diacylglycerol (DAG) transferase forms triglycerides from FFA's before incorporation into cyhlomicrons
    • NPC1L1 transports cholesterol from lumen
  41. LDL clearance from the plasma
    • 75% of LDL plasma is mediated by the liver
    • ~1000 mutations in the LDL recpetor or apoB-100 are associated with poor LDL clearance and hypercholesterolemia
    • diets and meds that reduce cholesterol levels in cells trigger compensatory up-regulation of LDL receptors , increasing LDL plasma clearance
  42. LDL receptor response to low intracellular cholesterol
    • the sterol response element binding protein SREBP on the ER is cleaved more when cholesterol is low
    • freed protion of SREBP activates transcription of LDL-R mRNA in the nucleus 
    • LDL-R protein the increase via translation, resulting in uptake of cholesterol from blood
  43. what happens to mature HDL?
    • HDL exchanges cholesterol esters for triglycerides from any triglyceride-containing lipoprotein by cholesterol ester transfer protein CETP
    • altered HDL can deposit new triglycerides and cholesterol esters into liver for metabolism
    • then returns to blood where it can get more cholesterol and triglycerides
    • HDL's protective effect related to ability to pull cholesterol from tissues, and facilitate excretion by the liver
  44. vitamin absorption
    • fat-soluble vitamins (A, D, E, K) are absorbed like lipids in SI 
    • by diffusion of mediated transport
    • B12 must first bind to a transport protein
    • intrinsic factor is secreted by the stomach's parietal cells 
    • Vit B12-intrinsic factor is absorbed in the ileum by endocytosis
  45. water and mineral absorption
    • absorbed by diffusion mostly within SI 
    • absorption of Na, K, Cl, Ca, and Fe are important to maintain physiological processes
  46. immune function of the SI
    • stomach resistant to organisms due to acidity
    • organisms in SI surveyed by Peyer's Patches, concentrated white blood cells 
    • Peyer's patches are considered Gut Associated Lymphoid Tissue (GALT)
  47. the pancreas functions
    • exocrine function-amylase, lipase, and bicarbonate secretion into the duodenum
    • responsible for digestion of polysaccharides and lipids in SI
    • bicarbonate neutralizes acid to make duodenum higher in pH so pancreatic enzymes are not destroyed 
    • endocrine- insulin secretion into blood
  48. the pancreas and hormones
    • communicates wtih SI
    • acid, peptides, fatty acids in SI trigger hormone release into the blood 
    • many reach pancreas through blood
  49. trypsin and chymotrypsin (proteases)
    • protein substrate
    • break peptide bonds in proteins to form peptide fragments
  50. carboxypeptidase
    • protein substrate 
    • splits off terminal amino acid from carboxyl end of protein
  51. lipase
    • fat substrate 
    • need bile activity to be exposed
    • splits off two fatty acids from triglycerides, forming free fatty acids and monoglycerides
  52. amylase
    • polysaccharide substrate 
    • splits polysaccharides into glucose and maltose
  53. ribonuclease and deoxyribonuclease
    • nucleic acid substrate
    • split nucleic acids into free mononucleotides
  54. the liver
    • serves as a secretory organ
    • secrete bile into bile duct before bile enters the duodenum to emulsify ingested fats
    • processes and stores nutrients
    • detoxifies chemicals 
    • removes red blood cells, leading to generation of bilirubin 
    • systhesizes plasma proteins such as albumin, clotting proteins, angiotensinogen, stored binding proteins
  55. liver exocrine (digestive) functions
    • sythesizes and secretes bile salts 
    • necessary for digestion and absorption of fats
    • secrets into the bile HCO3 which helps neutralize acid
  56. liver's clotting functions
    • produces plasma clotting fatctors such as prothrombin and fibrinogen
    • produces bile salts, which help absorb vitamin K in the GI tract, which is needed for clotting factor production
  57. liver's organic metabolism
    • converts plasma glucose into glycogen and triglycerides during absorption
    • converts plasma amino acids to fatty acids, which are incorporated into triglycerides in absorption
    • makes triglycerides and secretes them as lipoproteins during absorption
    • produces glucose from glycogen and other sources after absorption and relases it into blood 
    • converts fatty acids into ketones during fasting
    • produces urea and releases it into blood
  58. liver's cholesterol metabolism
    • makes cholesterol and puts it into blood
    • secretes plasma cholesterol into bile
    • converts plasma cholesterol into bile salts
  59. liver's excretory and degradative function
    • secretes bilirubin and other pigments into bile
    • excretes via bile endogenous and foreign organic molecules and trace metals 
    • transforms endogenous and foreign organic molecules
    • destroys old red blood cells
  60. the hepatic portal system
    • delivers absorbed nutrients to the liver for processing before they enter systemic circulation
    • nutrients and drugs absorbed from the SI are carried to the liver via the hepatic portal vein
  61. bile secretion and liver function
    • some drug molecules will fo through the liver to systemic circulation
    • others go back to the SI via bile duct
    • drugs are recycled through enterohepatic recirculation
    • SI-portal vein-liver-bile duct
  62. large intestine pathophysiology
    • ulcers
    • vomiting
    • gallstones
    • lactose intolerance
    • inflammatory bowel disease 
    • constipation/diarrhea