Gut L2

Question 1

what is gut motility

Answer 1

controlled movement of food from mouth to anus

mixing of food with digestive system enzymes and exposure to absorbtive surfaces

Question 2

describe the motility in food reaching the stomach and once in the stomach

Answer 2

• muscular contraction of oesophagus cause relaxation of LOWER OESOPHAGAL SPHINCTER
• top of stomach relaxed O inc stomach vol
• pressure in the bottom of stomach O food sits at the top, liquid goes straight down
• movement to MAIN part of stomach triggers MECHANORECEPTORS and distension which triggers MOTILITY

Question 3

what is responsible for the electrical rhythm in the stomach

Answer 3

interstitial cells of Cajal

Question 4

what can cause vagus nerve damage

what is the effect of having a not inact vagus nerve on the stomach

Answer 4

• a long term effect of diabetes or from BARIATRIC surgery

food won’t sit at the top of stomach, it is forced into the main body immediately O causes high pressure

Question 5

if you have a healthy vagus nerve how does the stomach respond to food

Answer 5

1) FUNDUS (top part of stomach) relaxes
2) vago vagal reflex
3) receptive relaxation
4) inc in volume w/out inc in pressure
5) adaptive relaxation (stomach dilates in response to gastric filling)

Question 6

where do contractions in the stomach originate

Answer 6

pacemaker zone

Question 7

what is the antrum of the stomach

Answer 7

thick muscular wall, stimulates contractions from the BOTTOM

Question 8

what is a tonic contraction of GI muscle

Answer 8

sustained contratcion eg muscle sphincter are naturally closed

Question 9

what is a phasic contraction of GI muscle

where do slow waves originate, how do they pass to smooth muscle

Answer 9

contraction-relaxation cycles
dependent on SLOW WAVE potentials( spontaneous depolarisation and repolarisation using volt gated Ca2+ channels)
- originate in INTERSTITIAL CELLS OF CAJAL, pass to smooth muscle via GAP JUNCTIONS

Question 10

in the stomach what is PROPULSION (pt 1)

Answer 10

bolus PROPELLED towards the CLOSED PYLORUS

Question 11

in the stomach what is GRINDING (pt 2)

Answer 11

in the antrum, the trapped material is churned

Question 12

in the stomach what is RETROPULSION (pt 3)

Answer 12

the bolus is PUSHED BACK to the proximal stomach, continues until all residues have been reduced in size

Question 13

what is the function of the ANS in the gut

what is the effect of sympathetic and parasympathetic on ANS

Answer 13

forms neural connections with ENTERIC NS
SYMPATHETIC: inhibits SECRETION and motility
PARA: stimulates

Question 14

what is a short reflex in the gut wall

Answer 14

• the ENTIRE process is cont in the gut wall (eg mechanoreceptor in gut wall, myenteric nerve plexux)

Question 15

what is a long reflex in the gut wall

Answer 15

• part of the process is in the CNS ( eg smell of food, triggers submucosal plexus - saliva and gastric acid production)

Question 16

what are the 2 things that regulate gastric motility?

Answer 16

• neural enterogastric reflex (gives you feeling of needing to defacate)
• hormonal mechanisms

Question 17

when food reaches the s.int how is yhe action of the stomach switched off

Answer 17

1) ENDOCRINE CELLS- food residue in s.int triggers hormone release
2) CHEMORECEPTORS- change in pH triggers chemoreceptors to feedback to the stomach and inhibit motility in the stomach
3) MECHANORECEPTORS- cause DISTENSION of s.int which feedbacks to stomach

Question 18

what is the role of chemoreceptors in the s.int

Answer 18

detect changes in OSMOLALITY, absorbption of nutrients raises blood hormone level O feedbacks on stomach to INHIBIT motility and secretion

Question 19

what is the primary stimulus for s.int motility

Answer 19

DISTENSION - via enteric NS

Question 20

what are the 2 type sof movement in the s.int

Answer 20

1) PERISTALSIS-movement of food down the gut

2) SEGMENTATION- food being mixed

Question 21

what is segmentation in the s.in

what is it altered by

Answer 21

• food moved back and forth
• contractions of CIRCULAR MUSCLE, ALTERNATE CONTRACTION and RELAXATION of segments
• mixes CHYME w/ digestive secretions
• electrical activity generated by PACEMAKER cells
• altered by: HORMONES, ENTERIC NS, AUTONOMIC NS

Question 22

what is peristalsis in the l.in

what is it altered by

Answer 22

• circular muscles contract just behind the mass
• pushes into receiving section
• bolus moves between 2 and 25cm
• altered by: hormones & NS

Question 23

what is the gastro colonic reflex

Answer 23

contraction of the stomach causes contraction of the stomach which causes contraction of the COLON

Question 24

how does food move through the colon

Answer 24

in thirds, then mixing, then moves another third

Question 25

what influences defaecation

Answer 25

• once rectal pressure reaches a certain point, it causes the EXTERNAL ANAL SPHINCTER to relax

Question 26

what is the stimulation for defecation

what is the response

Answer 26

distension of rectum

response: contraction of rectum, RELAXATION of internal anal sphincter, contraction of EXTERNAL ANAL SPHINCTER

Question 27

what is the MMC what is its role

Answer 27

MIGRATING MOTOR COMPLEX

• for removing indigestible
• ALL sphincters open, allows indigestible content to move through from gut to faeces

Question 28

what is receptive relaxation

Answer 28

increasing the volume of an area but not increasing the pressure eg fundus relaxes

Question 29

what is adaptive relaxation

Answer 29

when the stomach relaxes as it fills