Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GI Exam > Neural Control of GI Motility & Funtion > Flashcards

Neural Control of GI Motility & Funtion Flashcards

1
Q

2 reservoirs of the GI tract

A

*stomach (reservoir for ingested food)
*left colon/rectum (reservoir for feces)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

function of sphincters in the GI tract

A

*control direction and rate of movement between functional zones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

important sphincters (valves) in the GI tract

A

*lower esophageal sphincter
*pyloric valve
*ileocecal valve
*internal & external anal sphincters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

voluntary vs. automatic elements of the GI tract

A

*entry to and exit from GI tract = voluntary control
*movement of contents through most of GI tract = automatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

layers of the GI tract

A

1) mucosa (enzymes, absorption, secretion)
-epithelium
-basement membrane
-lamina propria
-muscularis mucosa

2) submucosa (vascular, transport)

3) muscularis propria (motility, structural)
-circular smooth muscle layer
-longitudinal smooth muscle layer
-muscle fibers electrically connected

4) nerve plexes (secretion/motility control)
-submucosal (Meissner’s)
-myenteric (Auerbach’s) [b/w circular and longitudinal muscle layers]

5) serosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

enteric nervous system

A

*largest network of nerve cells outside CNS
*controls and regulates all GI functions (motility, secretion, absorption, blood flow)
*functions SEMI-AUTONOMOUSLY
*modulated by SYMP/PARASYMP balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

myenteric plexus

A

*aka Auerbach’s plexus
*controls MOTOR function
*velocity and intensity of smooth muscle contraction
*sphincter tone (pylorus, IC valve)
*located between the circular and longitudinal muscle layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

submucosal plexus

A

*aka Meissner’s plexus
*controls EPITHELIAL function
*secretion and absorption
*mucosal blood flow
*located below the submucosal layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

sensory neurons of the enteric nervous system

A

*provides FEEDBACK to the CNS
*endings in epithelium, gut wall
*communicates with enteric plexi, spinal cord, and CNS via vagus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

parasympathetic actions in the GI tract

A

*cholinergic
*ACTIVATES GI tract
*increases gut motility
*relaxes sphincters
*increases secretion
*gallbladder contraction
*increases blood flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

sympathetic actions in the GI tract

A

*adrenergic
*INHIBITS GI tract
*decreases gut motility
*contracts sphincters
*decreases secretions
*gallbladder relaxation
*decreases blood flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

patterns of gut motility

A

1) isolated contractions
2) segmentation
3) peristalsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

isolated contractions (pattern of gut motility)

A

*no net movement
*stimulated by radial stretching of gut wall by chyme (lumenal contents)
*mediated by myenteric plexus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

segmentation (pattern of gut motility)

A

*no net movement
*chyme simultaneously pushed anterograde and retrograde
*facilitates MIXING of chyme & secretions, and absorption of nutrients and water (aids in digestion, not movement)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

peristalsis (pattern of gut motility)

A

*propulsive movement
*propels chyme in oral to caudal direction (at a rate of 2-25 cm/sec)
*peristaltic wave begins on oral side of a gut segment and proceeds distally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

gastrointestinal blood flow - overview

A

*arterial blood provided by: celiac artery, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA) [except upper 2/3 of esophagus & rectum]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

regulation of GI blood flow

A

*splanchnic circulation is the most highly regulated blood flow in the body (5-10% of cardiac output when asleep; up to 25% after a meal)
*controlled by sympathetic nervous system and release of gut hormones (ex. somatostatin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

venous blood flow from GI tract

A

*venous blood flows from GI tract to the liver via portal venous system and subsequently into superior vena cava
*blood passes through hepatic sinusoids to hepatic veins to vena cava to right atrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

3 phases of swallowing

A

1) oral phase
2) pharyngeal phase
3) esophageal phase

20
Q

oral phase of swallowing

A

*voluntary
*mediated by CNs V, VII, IX, and XII
*mastication physically breaks up food, leading to increased surface area accessible to enzymes
*enzyme secretion: amylase (salivary glands) and lingual lipase (tongue)
*tongue propels bolus from oral cavity to pharynx

21
Q

pharyngeal phase of swallowing

A

*involuntary
*mediated by swallowing center, CN IX, and vagus
*soft palate elevation; closure of epiglottis
*food bolus passes pharynx into esophagus

22
Q

esophageal phase of swallowing

A

*automatic
*mediated by myenteric plexus and vagus
*primary peristalsis: continuous movement from pharynx to stomach
*secondary peristalsis: initiated by local distension
*LES relaxation

23
Q

lower esophageal sphincter (LES) - overview

A

*3cm band of circular muscle at the gastroesophageal junction
*tonically contracted
*resting pressure modulated by vagal tone and GI hormones
*function: prevents retrograde reflux of gastric contents into esophagus
*primary peristaltic waves trigger LES relaxation

24
Q

gastroesophageal reflux disease (GERD) - simplified

A

*can be caused by reduced LES tone
*drugs that reduce LES tone worsen GERD (anticholinergics, xanthines, etc)

25
Q

achalasia

A

*failure of the LES to relax with swallowing
*can be primary or acquired
*presents with dysphagia
*can be treated with LES botox injections, interventional endoscopy, or surgery

26
Q

physiologic functions of the stomach

A

*food reservoir (2-4 L)
*grinding and mixing
-pacemaker drive 3 cycle/min contraction (body to antrum, mixing food and gastric juice)
-pylorus remains tonically contracted
*regulated emptying
-at end of each contraction wave, the pylorus opens to allow 10 ml of chyme into duodenum
-gastric emptying half-life about 1-2 hours

27
Q

factors that modulate the emptying rate of the stomach

A

*increase: food volume, increased vagal tone, and gastrin
*decrease: duodenal distension, high chyme osmolality, duodenal pH < 3.5, protein & fats

28
Q

dumping syndrome

A

*pylorus bypassed/removed during surgery
*leads to rapid, unregulated entry of chyme into small bowel, leading to acute osmotic load
*sx: bloating, nausea, vomiting, abdominal pain, diarrhea, hypotension, hypoglycemia
*rx: diet modification (multiple small meals)

29
Q

gastroparesis

A

*reduced or absent gastric motility caused by diabetes, vagal disruption, or idiopathic
*sx: early satiety, nausea, vomiting, weight loss, abdominal pain, malnutrition
*dx: gastric emptying scan
*rx: improve DM control; diet modification; metoclopramide (D2 receptor antagonist)

30
Q

regulation of peristalsis in small intestine

A

1) cephalic phase of digestion (sight, smell, taste of food leads to increased vagal tone and increased peristalsis)
2) gastroenteric phase (food distension of the stomach and duodenum lead to increased peristalsis)
3) GI hormones (stimulation or inhibition)

31
Q

migrating motor (myoelectric) complex (MMC)

A

*purpose = clean out gut bacteria in preparation for next meal
*appears between meals and during the night
*single waves start in stomach, sweep along small bowel to distal ileum every 90 min
*clears residual lumen contents

32
Q

ileus

A

*absent or impaired small bowel peristalsis caused by surgery, drugs (opioids), or critical illness
*compromises nutrition
*can prolong hospital stays

33
Q

intestinal pseudo-obstruction

A

*clinical picture of small bowel obstruction in absence of any physical or anatomical blockage
*absent peristalsis caused by neuromuscular disorders (scleroderma) or vasculitis

34
Q

functions of ileocecal valve

A

*one-way valve: prevents backflow of colonic contents into small intestine lumen
-IC valve is tonically constricted
-helps reduce SB bacterial colonization

35
Q

ileocecal valve reflexes

A

*mediated by cecal myenteric plexus and ANS
*gastroileal: gastric distension relaxes the ICV and stimulates ileal peristalsis, promoting movement of chyme into cecum
*cecal stretch: cecal back-pressure contracts the ICV and inhibits ileal peristalsis, stopping movement of chyme into cecum

36
Q

resection of ileocecal valve

A

*commonly resected in cancer, Crohn’s disease, etc
*uncontrolled diarrhea (loss of ileal brake)
*small intestine bacterial overgrowth

37
Q

colon has 2 functional organs

A

*right colon = electrolytes and H2O absorption
*left colon = storage of fecal matter

38
Q

colonic motility patterns

A

*haustrations (non-propulsive: local circular contractions facilitate electrolytes and water absorption)
*mass movements (propulsive: longitudinal contractions transport feces from right to left colon)
*gastrocolic reflex (distension of stomach and duodenum initiates colonic mass movements via ANS)

39
Q

constipation

A

*impaired motility leads to excess water absorption and hard feces

40
Q

diarrhea

A

*increased motility or unabsorbable osmoles leads to reduced water absorption and liquid stools

41
Q

internal anal sphincter

A

*circular smooth muscle
*autonomic control

42
Q

external anal sphincter

A

*striated skeletal muscle
*voluntary control

43
Q

recto-anal inhibitory reflex (RAIR)

A

*rectal distension leads to RELAXATION of internal anal sphincter
*mediated by enteric nervous system

44
Q

defecation reflex

A

*rectal distension leads to increased sigmoid peristalsis
*mediated by enteric nervous system and parasympathetic spinal circuit

45
Q

voluntary defecation

A

*mediated by skeletal motor nerves
*external anal sphincter relaxation
*increased abdominal wall pressure

46
Q

Hirshsprung’s Disease

A

*absent myenteric plexus in distal colon leads to failure of internal anal sphincter relaxation, leading to severe constipation and colonic dilation
*diagnosed by absence of recto-anal inhibitory reflex on anorectal manometry
*treated by surgical resection of the aganglionic section of distal colon

47
Q

impact of spinal cord injury or neuropathy on defecation

A

*disrupted pelvic motor and/or sensory nerve function, leading to loss of voluntary bowel control
*colonic myenteric reflexes are usually intact and can be used to re-train bowel function

GI Exam (54 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions