Gi motility and Regulation [3] Flashcards Preview

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Flashcards in Gi motility and Regulation [3] Deck (16):
1

what is the predominant motor activity in the intestine that ensures proper digestion and absorption?

What about movement that results in net propulsion of contents

Segmentation
-mixing w/o propulsion

Peristalsis
- propulsive: contraction of adjacent segments occuring in coordinated manner
- contractile ring moves toward food bolus

2

Basic electrical rhythm (BER)
- describe
- would depolarization of BER alone cause contraction?

cyclic change in membrane polarization of sm cells
- slow waves → pulsatile
- consists of upstroke depolarization, partial repolar, and plateau potential

3

Would depolarization of BER alone cause contraction?
Which is lower in freq, stomach BER or duodenal BER?

- no: ACh needs to be added to cause threshold ot be reached (due to Ca2+ influx)
- stomach BER is lower bc you want distal ends to be moving faster (or else back log)

4

3 stages of swallowing
- voluntary or involuntary?

1. Voluntary
- oral cavity → tongue push bolus → oropharynx
2. Pharyngeal phase
- involuntary: glottis over trachea
- UES relax
3. Esophageal phase
- involuntary: esophageal peristalsis

5

Mech of esophageal motility

UES: allows bolus to enter esophagus
Esophageal peristaltic waves:
- push bolus to LES in 5 sec.
- just before bolus arrives, LES relaxes
LES: relaxes so bolus → stomach
- prevents reflux into esophagus
- gatekeeper

6

Failure of LES to relax due to dmg/loss of enteric n. of LES

Achalasia → dysphagia

7

describe how the stomach stores food
- what about P concerns?

Accomodation
- regulated by vagus n.
Receptive relaxation

Allows fundus to accomodate/store fr. 1.5L → 3-4L w/o increase in intra-gastric P

8

Motility roles of stomach

mixing/churning with retropulsion and receptive relaxation
peristaltic spurts pushes sm amt of chyme pass pyloric sphincter
- another wave pushes rest of chyme back + break up food further into smaller pieces

9

Will the rate of gastric emptying increase or decrease with more food?

rate is increased due to gastric distension →
increase stretch →
peristalsis increase (vagal + myenteric reflexes)

Gastrin is also secreted in response to food → increase peristalsis and decrease pyloric tone

10

Key hormones secreted by Small intestines

CCK
Secretin
GIP (gastrointestinal peptide)

11

MMC occurs only during ____ and is terminated by ____.
It is initiated when____.
- phases?

fasting, eating
Activated when motilin is released by small intestine
- sweeping process every 90-100 min
- 40-60% of 90 min duration

Phase I: quiescence occurs for 40-60% of the 90 min

Phase II: motility ↑s, but w/ irregular contractions
- fails to propel content
- 20-30% of MMC duration

Phase III: from body → pylorus → duodenum → ileocecal valve
- 5-10 min of intense contractions

12

Main fxn of large intestines
- how many types of motility?

reabsorb water and ions
- two types of motility
1. haustration
2. mass movements

13

1. haustration vs
2. mass movements

of Large intestines

1. haustration: muscles of colon wall are contracted intermittently to divide colon into fxnal segments, "haustra"
- mix and dry chyme

2. mass movements: "giant migrating contractions"
unique to Lg intestines
- Slow intense + prolonged peristalsis contractions (propel chyme)
- strips area of LI clear of contents
- segmental activity stop temp, + loss of haustration

14

Gastroileal reflex
- mediated by which nerves?

stomach activity stimulates movement of chyme thru ileocecal sphincter → LI
- mediated by enteric nerves

15

Gastrocolic reflex
- mediated by which nerves?

Food in stomach stimulates mass movement in colon
- mediated by enteric nerves

16

defecation sequence

Colonic motility/contraction ↑s during meals due to ENS →
distention of colon as feces are moved to rectum →
rectum distention →
defecation reflex (spinal reflex due to pelvic n. which causes VIP + NP release) → relaxation of IAS) →
rectoanal inhibitory reflex (contraction of EAS) →
voluntary relaxation of EAS