Gut L2 Flashcards
what is gut motility
controlled movement of food from mouth to anus
mixing of food with digestive system enzymes and exposure to absorbtive surfaces
describe the motility in food reaching the stomach and once in the stomach
- 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
what is responsible for the electrical rhythm in the stomach
interstitial cells of Cajal
what can cause vagus nerve damage
what is the effect of having a not inact vagus nerve on the stomach
- 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
if you have a healthy vagus nerve how does the stomach respond to food
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)
where do contractions in the stomach originate
pacemaker zone
what is the antrum of the stomach
thick muscular wall, stimulates contractions from the BOTTOM
what is a tonic contraction of GI muscle
sustained contratcion eg muscle sphincter are naturally closed
what is a phasic contraction of GI muscle
where do slow waves originate, how do they pass to smooth muscle
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
in the stomach what is PROPULSION (pt 1)
bolus PROPELLED towards the CLOSED PYLORUS
in the stomach what is GRINDING (pt 2)
in the antrum, the trapped material is churned
in the stomach what is RETROPULSION (pt 3)
the bolus is PUSHED BACK to the proximal stomach, continues until all residues have been reduced in size
what is the function of the ANS in the gut
what is the effect of sympathetic and parasympathetic on ANS
forms neural connections with ENTERIC NS
SYMPATHETIC: inhibits SECRETION and motility
PARA: stimulates
what is a short reflex in the gut wall
- the ENTIRE process is cont in the gut wall (eg mechanoreceptor in gut wall, myenteric nerve plexux)
what is a long reflex in the gut wall
- part of the process is in the CNS ( eg smell of food, triggers submucosal plexus - saliva and gastric acid production)
what are the 2 things that regulate gastric motility?
- neural enterogastric reflex (gives you feeling of needing to defacate)
- hormonal mechanisms
when food reaches the s.int how is yhe action of the stomach switched off
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
what is the role of chemoreceptors in the s.int
detect changes in OSMOLALITY, absorbption of nutrients raises blood hormone level O feedbacks on stomach to INHIBIT motility and secretion
what is the primary stimulus for s.int motility
DISTENSION - via enteric NS
what are the 2 type sof movement in the s.int
1) PERISTALSIS-movement of food down the gut
2) SEGMENTATION- food being mixed
what is segmentation in the s.in
what is it altered by
- 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
what is peristalsis in the l.in
what is it altered by
- circular muscles contract just behind the mass
- pushes into receiving section
- bolus moves between 2 and 25cm
- altered by: hormones & NS
what is the gastro colonic reflex
contraction of the stomach causes contraction of the stomach which causes contraction of the COLON
how does food move through the colon
in thirds, then mixing, then moves another third
what influences defaecation
- once rectal pressure reaches a certain point, it causes the EXTERNAL ANAL SPHINCTER to relax
what is the stimulation for defecation
what is the response
distension of rectum
response: contraction of rectum, RELAXATION of internal anal sphincter, contraction of EXTERNAL ANAL SPHINCTER
what is the MMC what is its role
MIGRATING MOTOR COMPLEX
- for removing indigestible
- ALL sphincters open, allows indigestible content to move through from gut to faeces
what is receptive relaxation
increasing the volume of an area but not increasing the pressure eg fundus relaxes
what is adaptive relaxation
when the stomach relaxes as it fills
