lecture 24

Question 1

receptors in the wall of the GI tract respond to what?

Answer 1

they respond to stretch from food in the lumen.
change in lumenal composition
and chemical factors like PH osmolarity, sugars and what not

Question 2

what are the effectors for receptors in the lumen what can we say from this

Answer 2

smooth muscle and glands, reflexes from receptors stimulate smooth muscle contraction and gland secretion. we can thus say there is nervous and hormonal regulation of GI function

Question 3

describe CNS regulation of GI function

Answer 3

co-ordination over long distances.
PNS- rest and digest stimulates motility and secretion
SNS- inhibits those things
but there is no direct innervation to GI, just modulation of the ENS

Question 4

describe ENS regulation of GI function

Answer 4

local reflexes, things like the submucosal plexus helping control secretions. myenteric plexus controlling contraction of the muscularis

Question 5

what are the 4 critical hormones in GI activity regulation

Answer 5

CCK, gastrin, secretin, GIP

Question 6

properties of GI smooth muscle that is involved in motility

Answer 6

contracts without external input, has own pacemaker cells, the strength of contractions is regulated by nervous and hormonal input

Question 7

frequencies of contraction in the stomach duodenum and ileum

Answer 7

stomch 3 per min
duodenum is 12 per min
ileum is 9 per min

Question 8

describe the migrating motor complex and what are its 3 stages

Answer 8

this occurs in fasting, 4 hours after a meal and then every 2 hours until our next meal. it is coordinated contractions of stomach, SI,LI in that order to shift along luminal contents. functions for house keeping.
three stages are inactive intermittent and intense activity

Question 9

what are the generalised motility patterns of each GI tract part during feeding

Answer 9

storage in the stomach and colon.
Propulsion / Movement in Esophagus, stomach, small and large intestine by Peristalsis
mixing in the stomach by retropulsion and SI by segmentation

Question 10

whats the feeding state motility pattern in the mouth and describe

Answer 10

it reduces the size of food to allow ingestion by esophagus, its a voluntary action by skeletal muscle, but the frequency and strength of chewing is reflex controlled. also allows mixing with saliva for taste

Question 11

whats the feeding state motility pattern in the esophagus and describe

Answer 11

swallowing is voluntary response with the top skeletal muscle third of the esophagus, it allows for transport of food to the stomach

Question 12

whats the gastric fasting state motility and function

Answer 12

after 4 hours from a meal continues till eating, 2 hours of inactivity 50 min uncoordinated activity, 10 min coordinated activity
House keeping
 Removes residual secretions
 Removes undigested material
 Promotes epithelial cell turnover

Question 13

describe stomach storage motility in the fed state

Answer 13

this comes from nervous regulation via the vagus nerve. its done by receptive regulation as food presence in the stomach causes expansion of body and fundus, increasing V with minimal P change

Question 14

describe the peristaltic motility of the stomach

Answer 14

its initiated in the greater curvature and spreads. it does 3 contractions per minute. with the first 60mins of activity following meal being gentle
the 60-300 being intense

Question 15

describe the digestive motility in the stomach fed state

Answer 15

this is retropulsion. its due to the peristalsis of the stomach and the pyloric sphincter being closed. this moves the stomach chyme back and forward. resulting in mechanical digestion

Question 16

what causes gastric emptying

Answer 16

combination of peristalsis and periodic relaxation of the pyloric sphincter

Question 17

what factors affect the rate of gastric emptying

Answer 17

the capacity of the digestive enzymes, the acid composition, the level of fat in the chyme, the meal composition- fluids faster than solids

Question 18

functions and motility patterns of the large intestine

Answer 18

it functions to absorb water and ions, also to store faeces.
large intestine does large periods of inactivity. it does segmentation for Exposure to absorptive surfaces and Absorption of fluid and salt from faeces, also does mass peristalsis 1-2 times a day do defecate