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1.2 Lectures > Week 5 (Gut Motility) > Flashcards

Week 5 (Gut Motility) Flashcards

1
Q

What are Interstitial Cells of Cajal (ICC)?

A

Specialized interstitial cells in the GI tract that function as pacemaker cells, creating spontaneous slow action potentials leading to smooth muscle contraction.

Types based on location:
Myenteric plexus (ICC-MY)
Intramuscular layer (ICC-IM)
Deep muscular plexus (ICC-DMP)

Types based on location include ICC-MY (myenteric plexus), ICC-IM (intramuscular layer), and ICC-DMP (deep muscular plexus).

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2
Q

What is the slow wave potential?

A

The basic electric rhythm that, once reaching the slow wave threshold, initiates action potentials and contractions in the GI tract. (Spike Potentials)

This involves Ca/Na+ entry and K+ exit, leading to spike potentials and contractions.

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3
Q

What can changes in the number, structure, or function of ICC cause?

A

Motility disorders.

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4
Q

What is the gastro-colic reflex?

A

A reflex where food in the stomach increases colonic motility and colonic distension decreases gastric motility.

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5
Q

What is the function of the fundus, body/antrum, and pylorus of the stomach?

A

F: To store food.
B/A: Mix Food
P: mixing/empting

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6
Q

What occurs during each phase of stomach motility?

A

1) Cephalic phase: prior to eating, fundus receptic relaxation – VIP/NO/Adaptive relaxation- food in stomach
2) Gastric phase: when food enters the stomach
3) Intestinal phase: when chime enters small intestine

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7
Q

What are the parts of the small bowel?

A
  • Duodenum
  • Jejunum
  • Ileum

23 feet long and 1 inch diameter

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8
Q

What are the primary functions of small bowel motility?

A
  • Digestion
  • Absorption

Motility:
Mixing contractions
Peristalsis
Migratory motor complex

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9
Q

What are common disorders of small bowel motility?

A
  • Bloating
  • Pain
  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation
  • Small intestinal bacterial overgrowth
  • Adhesions
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10
Q

What is the primary reservoir for stool in the colon?

A

Cecum.

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11
Q

What hormones are involved in the control of GI motility?

A
  • Acetylcholine
  • Serotonin
  • Dopamine
  • VIP
  • Glucagon
  • Neurotensin
  • Somatostatin
  • Motilin
  • Substance P
  • CCK
  • Secretin
  • Gastrin
  • GLP-1
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12
Q

What is the role of the Auerbach or myenteric plexus?

A

Controls GI motility by coordinating muscular contractions.

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13
Q

What type of motility involves sustained contraction as in sphincters?

A

Tonic waves.

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14
Q

What are the phases of the migrating motor complex (MMC)?

A
  • Phase I: Quiescent phase
  • Phase II: Increasing action potential frequency
  • Phase III: Most active phase with strong rhythmic contractions
  • Phase IV: Declining activity
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15
Q

What characterizes Hirschsprung’s Disease?

A

Congenital absence of ganglion cells in the myenteric plexus, leading to failure to pass meconium within 24-48 hours.

Seen more often in males

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16
Q

What is the significance of the Valsalva maneuver in defecation?

A

Involves suitable environment, posture, deep breathing, and contraction of abdominal muscles to facilitate defecation.

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17
Q

What is the normal bowel movement frequency range and normal stool consistency?

A

3/day to 3/week.

Type 3,4,5

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18
Q

What are the characteristics of diarrhea?

A

Passage of loose mushy stool, often associated with urgency and worry about fecal incontinence.

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19
Q

What is the typical pathophysiology of Irritable Bowel Syndrome (IBS)?

A

Motility disorder with visceral hypersensitivity, inflammation, and altered intestinal microbiota
Can be due to diet, genetics
Brain-gut disorder

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20
Q

What triggers the gastro-colic reflex?

A

Food in the stomach/gastric distension-increases colonic motility
(Colonic distention will decrease gastric motility)

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21
Q

What are the symptoms of constipation?

A
  • Hard stool
  • Infrequent stool
  • Difficulty in passing stool
  • Excessive straining
  • Incomplete evacuation
  • Sensation of anal blockage
    *Bloating
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22
Q

What is the role of GLP-1 in GI motility?

A

Inhibits GI motility and gastric emptying.

23
Q

What is the primary role of the enteric nervous system?

A

Controls the gastrointestinal motility independently of the central nervous system.

24
Q

What is the function of the rectum in stool storage?

A

Secondary reservoir for stool.

25
What is the response of the colon to waking and meals?
Colon activity increases after waking and is inhibited during sleep; increases after meals (fat is most potent stimulus) (provoked by stimulant laxatives/irritation of colon)
26
What are haustrations in the colon?
Contractions that create sacs or segments in the colon for mixing and moving feces downward. Tenia coli contractions: make colon smaller (makes haustra) Haustration contraction are due to combined circular & longitudinal muscular contraction
27
What is the most common cause of opioid-induced gastrointestinal dysmotility?
Constipation. Can also cause Nausea, Vomiting, Gastro-esophageal reflux, Pain: Opioid-induced Hyperalgesia Acts primarily on mu (µ) receptors in the enteric nervous system (1) decreasing gastrointestinal transit 2) reducing intestinal secretion 3) increasing fluid absorption 4) increasing anal sphincter pressure 5) causing rectal hyposensitivity
28
What is the effect of fat on colon motility?
Fat is the most potent stimulus for increased colon motility.
29
What is GLP-1?
Hormone released from neuroendocrine L-cells in small intestine epithelium and colon; increase insulin release and inhibits glucagon release Released after food intake; Promotes satiety- reduce food intake, decreases appetite, reduces weight, improves insulin resistance
30
What are the main functions of GLP-1?
Increases insulin release; inhibits glucagon release
31
When is GLP-1 released?
After food intake
32
What effect does GLP-1 have on appetite?
Promotes satiety, reduces food intake, decreases appetite, reduces weight, improves insulin resistance
33
How does GLP-1 affect gastrointestinal motility?
Decreases gastric and small intestine motility, affects migrating motor complex (MMC)
34
What systems does GLP-1 act on?
Central nervous system, peripheral nervous system, and local enteric nervous system (ENS)
35
What are the indications for GLP-1 receptor agonists?
To treat obesity and diabetes mellitus
36
What are common gastrointestinal side effects of GLP-1 receptor agonists?
Nausea, vomiting, constipation, diarrhea
37
Fill in the blank: GLP-1 receptor agonists include _______.
semaglutide (ozempic), dulaglutide (trulicity), exenatide
38
What are the frequency of slow waves in the stomach, small intestine, and colon?
*Stomach: 3/min *Small intestine: 8-12/min Duodenum=11-12/min- most of segmentation takes place Ileum=8-10 *Colon: 3-6/min
39
What are the types of Motility in the GI tract?
1) Tonic waves: sustained contraction as in sphincters 2) Phasic waves-when there is food in intestine/distention a) Segmental (mixing) contractions of circular muscles: movement in forward and backward directions; mixes and break down food=forms chime-help absorption b) Peristaltic (propulsive) contractions: the forward movement of food or feces. Rhythmic contraction and relaxation of muscles- top contraction of circular and relaxation of longitudinal and below opposite
40
What is the Migratory Motor Complex?
Propulsive cyclic contraction: lasts 85-115 mins; mass movement of indigestible food/bacteria (sweeping role); controlled by CNS, ENS, hormones/motilin Reduced by: narcotics, stress, GLP-1 Stimulated by: erythromycin, ghrelin
41
What does the absence of Migratory Motor complex lead to?
gastroparesis intestinal pseudo-obstruction small bowel bacterial overgrowth
42
Describe the 4 phases of migratory motor complex.
Phase I- quiescent phase: slow waves, no action potential, no contraction (80 minutes) Phase II- increasing action potential frequency and activity-strong and irregular/ contractions (6 min) Phase III- most active, peak electrical/ mechanical activity: caused by intense (strong) rhythmic contractions of circular muscles (5-10 min), Phase IV= declining activity
43
What controls GI Motility?
1) Muscle control: Interstitial cells of Cajal /primitive smooth muscle cells 2) Nervous system *Central nervous system *Emotions/stress- possibly via autonomic nervous system and corticotropin releasing factor *Peripheral nervous system- cranial and spinal nerves *Autonomous Nervous System **Extrinsic innervation Parasympathetic nervous system (stimulatory) Sympathetic nervous system (inhibitory) **Intrinsic innervation (Enteric nervous system-LITTLE BRAIN) Auerbach or myenteric plexus: between longitudinal and circular muscles: controls GI motility (Ascending fibers=stimulatory, (Ach/Substance P) Descending fibers- relaxation- VIP/NO) Meissner plexus: outside submucosa helps mucosal blood flow, secretion and absorption 3) Hormonal control: Hormones/neuro-transmitters control 4) Gut microbiota
44
Review GI neurotransmitters/hormones.
45
What is the intra gut reflex?
for secretion and absorption, stimulation- causes peristalsis, secretion…
46
What is the gastro-ileal/Ileo-gastric reflex?
food in stomach increases ileal motility- relaxes IC valve-likely mediated by gastrin/vagus nerve. (ileal distension- decreases gastric motility)
47
What is the Vago-vagal reflex?
Defecation Reflex Distended colon causes contraction of colon- defecation
48
What are the functions of the colon
Absorption of fluids and electrolytes Storage of stool: *Primary reservoir: cecum, ascending colon *Secondary reservoir: rectum Propel stool : Transverse, descending, and sigmoid colon from primary to secondary reservoir Length of Large intestine: 5 feet Diameter: 3 Inch
49
Describe Colon motility.
Mass movement, Giant migrating contractions (GMC) or High amplitude propagating contractions (HAPC) 6-8/daily, Large amplitude (>100 mmHg), persist for 10-30 min major propulsive motor event- from cecum- rectum Causes urge to defecate
50
What makes up the Anal Canal?
Anal canal= from anorectal ring (puborectalis)-to anal verge/skin= 3-5 cm Dentate line divides anal canal-2/3 above and 1/3 below **Internal anal sphincter (IAS): involuntary, circular smooth muscle; 80% of resting pressure **External anal sphincter (EAS): voluntary, striated muscle, squeeze pressure, pudendal nerve) Dorsal curve-by vertebrae Ventral curve-puborectalis muscle
51
What are symptoms of Dys-motility?
Abdominal pain/ cramps/bloating Dyspepsia, heartburn, gastroesophageal reflux Irritable bowel syndrome Constipation Diarrhea Small bowel bacterial overgrowth /dysbiosis Chronic Intestinal pseudo-obstruction (Ogilvie syndrome) Hirschsprung’s disease
52
What causes Diarrhea?
1) osmotic diarrhea: unabsorbed solutes increase intra-luminal osmotic pressure, causing outpouring of water 2) secretory diarrhea: active water secretion. 3) Swift motility fast transit 4) Exudative diarrhea: Sloughing of mucosa: inflammation
53
What is Irritable Bowel Syndrome?
Abdominal pain with Alteration in bowel habits Constipation Diarrhea Alternating diarrhea and constipation Brain-gut disorder More common in women Green Flag(s): no weight loss, no night time symptoms, no blood in stool.. no risk of colon cancer or colitis.
53
What is the mechanism of constipation?
Slow transit: Slow movement of feces Evacuation disorder Combination More common in women

1.2 Lectures (9 decks)

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