Gi motility and Regulation [3] Flashcards Preview

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

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

A

Segmentation
-mixing w/o propulsion

Peristalsis

  • propulsive: contraction of adjacent segments occuring in coordinated manner
  • contractile ring moves toward food bolus
2
Q

Basic electrical rhythm (BER)

  • describe
  • would depolarization of BER alone cause contraction?
A

cyclic change in membrane polarization of sm cells

  • slow waves → pulsatile
  • consists of upstroke depolarization, partial repolar, and plateau potential
3
Q

Would depolarization of BER alone cause contraction?

Which is lower in freq, stomach BER or duodenal BER?

A
  • 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
Q

3 stages of swallowing

- voluntary or involuntary?

A
  1. Voluntary
    - oral cavity → tongue push bolus → oropharynx
  2. Pharyngeal phase
    - involuntary: glottis over trachea
    - UES relax
  3. Esophageal phase
    - involuntary: esophageal peristalsis
5
Q

Mech of esophageal motility

A
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
Q

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

A

Achalasia → dysphagia

7
Q

describe how the stomach stores food

- what about P concerns?

A

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
Q

Motility roles of stomach

A

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
Q

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

A

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
Q

Key hormones secreted by Small intestines

A

CCK
Secretin
GIP (gastrointestinal peptide)

11
Q

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

A

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
Q

Main fxn of large intestines

- how many types of motility?

A

reabsorb water and ions

  • two types of motility
    1. haustration
    2. mass movements
13
Q
  1. haustration vs
  2. mass movements

of Large intestines

A
  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
Q

Gastroileal reflex

- mediated by which nerves?

A

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

15
Q

Gastrocolic reflex

- mediated by which nerves?

A

Food in stomach stimulates mass movement in colon

- mediated by enteric nerves

16
Q

defecation sequence

A

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