GI motility

Question 1

enteric NS regulation of motility

Answer 1

mucosal layer detest chemicals or mechanical forces
receptor cell bodies are in the submucosal (meisnners) plexus
interneurones transmit signals to the myenteric plexus (auerbachs)
effector neurones in auerbachs modulate sensor activities in smooth muscle layers

Question 2

modulation of enteric with parasym

Answer 2

release ach onto excitatory enteric neurones

increases motility

Question 3

modulation of enteric with sym

Answer 3

noradrenaline acts on inhibitory enteric neurones (release VIP, NO)
decrease motility

Question 4

activity in stomach in fed state

Answer 4

• propulsion = propelled by peristalsis towards antrum, initiates pacemaker cells in the greater curvature, slow waves of depolarisation spread and may excite smooth muscle
• mixing in antrum: contents forced towards the antrum
• retropulsion: contraction of pylorus and antrum closes the sphincter, forces larger material back into antrum

Question 5

effects of continual cycles in stomach

Answer 5

contents become increasingly fluid over time 
creates chyme ( v. important)
more chyme = sphincter open for longer

Question 6

other important action of stomach

Answer 6

as a storage organ

Question 7

motility of stomach int he fasted state

Answer 7

MMCs (migrating motor complexes) spread from stomach to small intestine
slow waves of increased depolarisation and then decreases again
sweeps stomach contents into duodenum
motilin initiates in stomach
feeding terminates MMC

Question 8

motility of small intestine

Answer 8

exhibits slow waves of depolarisation, initiates contraction of circular smooth muscle
waves are a result of transient relief of enteric inhibition, frequency decreases along small intestine

Question 9

motility of small intestine in fed

Answer 9

isolated contraction of circular muscle causes segmentation or churning
peristalsis causes propulsion, propagate only over short distances

Question 10

motility of small intestine in fasted

Answer 10

MMC

Question 11

movement from small to large

Answer 11

ileo-caecal sphincter separates

distension of ileum promotes relaxation

Question 12

vomiting process

Answer 12

intitiated by vomiting centre in medulla

reverse peristalsis of small intestine, relax pyloric sphincter and stomach

Question 13

large intestine motility

Answer 13

longitudinal muscle creates taeniae coli that define folds
slow wave depolarisation induces contraction of circular smooth muscle to produce segmentation
waves increase frequency along large intestine
segmental contraction of haustra (folds) produces pendular movements contents
large peristaltic propulsions occur infrequently

Question 14

distal colon motility

Answer 14

non-propulsive segmentation which retards flow

Question 15

rectum motility

Answer 15

intermittently receives material and undergoes segmental contraction
distension causes internal sphincter to transiently relax
external sphincter can override this reflex and contract

Question 16

gall bladder motility controlled by

Answer 16

CCK
stimulates gallbladder smooth muscle contraction and relaxes sphincter of Oddi
allows bile to flow from duct into Pancreas

Question 17

bile components

Answer 17

bile salts
water and electrolytes
lecithin
cholesterol
pigments like bilirubin

Question 18

secretion of bile stages

Answer 18

• hepatocytes synthesise primary bile acids from cholesterol
• acids are conjugated to glycine or choline, ionise and exist as Na+ or K+ bile salts
• salts actively secreted into lumen by ATPase

Question 19

formation of secondary bile acids

Answer 19

• result from bacterial deconjugation, dehydroxylation of primary bile salts in the intestine
• some bile acids are reabsorbed in the ileum and returned to the liver bound to albumin
• can be taken back into hepatocytes
• enterohepatic circulation
• bile acids can be recirculated 3x before digestion is complete

Question 20

conjugated bile acids features

Answer 20

amphiphatic
form mixed micelles in aqueous environment
vehicle for lipid soluble substances int he aqueous environment of small intestine

Question 21

function of cells lining bile ducts

Answer 21

cholangiocytes
secrete watery NaHCO3, similar to mechanisms in pancreas
secretion stimulated by secretin, glucagon, VIP to increase cAMP and activate CFTR

Question 22

gall bladder function

Answer 22

stores bile

epithelial cells reabsorb NaCl to concentrate bile

Question 23

what is H pylori associated with?

Answer 23

peptic ulcers
also has been linked to some cancers
therefore can be treated with chemotherapy