lecture 16-GI secretory functions, digestion, absorption

Question 1

what are the functions of saliva

Answer 1

initial starch digestion and initial triglyceride digestion. lubrication of food and protection of mouth and esophagus

Question 2

describe the composition of saliva at lowest flow rates

Answer 2

lowest osmolarity. lowest sodium, chloride and bicarbonate ion concentrations, highest potassium ion concentrations

Question 3

describe the composition of saliva at high flow rates

Answer 3

composition closest to that of plasma

Question 4

describe the first stage of salivary secretion of ions

Answer 4

occurs in acini, secretion contains ptyalin (alpha-amylase), composition is isotonic with ionic concentration similar to plasma

Question 5

describe the second stage of salivary secretion of ions

Answer 5

occurs in salivary ducts, active reabsorption of sodium and secretion of potassium ions, active/passive secretion of bicarbonate ions

Question 6

what cranial nerves regulate salivary secretion

Answer 6

cranial nerves VII and IX

Question 7

what factors increase saliva production

Answer 7

food in mouth, smells, conditioned reflexes, nausea

Question 8

what factors decrease saliva production

Answer 8

sleep, dehydration, fear, anticholinergic drugs

Question 9

name secretory cell types in gastric glands

Answer 9

mucous neck cells, chief (peptic) cells, parietal (oxyntic) cells

Question 10

describe the direct way that vagal stimulation increases gastric secretions

Answer 10

CN X innervates parietal cells (stimulates H+ secretion directly), utilizes Ach and muscarinic receptor

Question 11

describe the indirect way that vagal stimulation increases gastric secretions

Answer 11

CNX innervates G cells, stimulates gastrin secretion, gastrin stimulates secretion of H+, neurotransmitter is GRP

Question 12

what is the second messenger for histamine stimulation

Answer 12

cAMP

Question 13

what is the second messenger for gastrin stimulation

Answer 13

on parietal cell: IP3/Ca++

Question 14

what does somatostatin inhibit

Answer 14

gastric H2 secretions

Question 15

describe the direct way that somatostatin inhibits gastric H secretions

Answer 15

somatostatin binds to receptors on parietal cell that are coupled to adenyl cyclase via a Gi protein (antagonistic to stimulatory action of histamine)

Question 16

describe the indirect way that somatostatin inhibits gastric H secretions

Answer 16

inhibits the release of histamine and gastrin

Question 17

describe the role of prostaglandins in gastric secretions

Answer 17

inhibits gastric H2 secretions by activating Gi protein, inhibiting adenyl cyclase

Question 18

describe the gastric phase of gastric secretion

Answer 18

local nervous secretory reflexes, vagal reflexes, gastrin-histamine stimulation

Question 19

describe the intestinal phase of gastric secretion

Answer 19

nervous and hormonal mechanisms

Question 20

what is the trypsin inhibitor secreted by

Answer 20

glandular cells

Question 21

what is the digest enzymes for carbohydrates

Answer 21

pancreatic amylase

Question 22

what is the digestive enzymes for fat

Answer 22

pancreatic lipase, cholesterol esterase, phospholipase

Question 23

decrease pancreatic secretions at low flow rates

Answer 23

isotonic fluid composed mostly of sodium and chloride ions

Question 24

describe pancreatic secretions at high flow rates

Answer 24

isotonic fluid composed mostly of sodium and bicarbonate ions

Question 25

describe acinar cells

Answer 25

produce small volume of pancreatic secretion composed mainly of sodium and chloride ions

Question 26

describe ductal cells

Answer 26

secrete bicarbonate ion and reabsorb chloride ion via a chloride-bicarbonate exchange mechanism. ducts are permeable to water (so water moves into ducts to make secretion isotonic)

Question 27

how does acetylcholine effect pancreatic secretions

Answer 27

stimulates enzyme secretion by acinar cells and potentials effect of secretin

Question 28

what does CCK do in regulation of pancreatic secretions

Answer 28

causes dramatic increase in secretion of pancreatic enzymes. potentiates effect of secretin on ductal cells to stimulate bicarbonate secretion

Question 29

what does secretin do in regulation of pancreatic secretions

Answer 29

stimulates release of large amounts of sodium bicarbonate by ductal cells

Question 30

what causes the release of enzymes into acini

Answer 30

vagal stimulation

Question 31

what factor stimulates the release of bile from the gallbladder

Answer 31

presence of fatty food in duodenum

Question 32

what are bile acids conjugated with

Answer 32

glycine or taurine

Question 33

CCK in blood stream causes___

Answer 33

gallbladder contraction and relaxation of sphincter of Oddi

Question 34

what causes gallstones

Answer 34

too much absorption of water from bile, too much absorption of bile acids from bile, too much cholesterol in bile, inflammation of epithelium

Question 35

what are condensations reactions used for

Answer 35

to remove hydrogen ions and hydroxyl ions from building blocks in order to allow the bonding of monomers into polymers

Question 36

what is the role of hydrolysis reactions

Answer 36

incorporating water molecules in such a way that polymers are broken down into monomers

Question 37

how does absorption of fructose occur

Answer 37

entirely by facilitated diffusion in small intestine

Question 38

what does lactase break lactose down into

Answer 38

glucose and galactose