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Physiology 2 Test 2 AH > Lecture 10 Intro GI > Flashcards

Lecture 10 Intro GI Flashcards

0
Q

what kind of cells is the serosa?

A

outer layer of CT, simple squamous epithelium

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1
Q

Layers of the Gut Tract Wall (Outer to Inner)

A
  1. Serosa
  2. Longitudinal smooth muscle
  3. Myenteric (Auerbach)
    4) Circular smooth muscle
    5) Meissner’s plexus
    6) Mucosa
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2
Q

where is the serosa missing?

A

esophagus

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3
Q

what forms the enteric nervous system?

A

Myenteric (Auerbach) and Meissner’s plexus

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4
Q

how are the neurons supported in the enteric nervous system?

A

by intrinsic glial cells

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5
Q

Is the myenteric plexus excitatory or inhibitory?

What hormones does it use?

A

excitatory

Ach and NO

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6
Q

what kind of neurons does the myenteric plexus consist of?

what does it control?

A

linear chain of interconnecting neurons

controls intestinal smooth muscle, participates in tonic and rhythmic contractions

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7
Q

What are the effects of the myenteric plexus?

A

Increases VITR

velocity (of excitatory waves), intensity, tonicity, rate

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8
Q

What does meissner’s plexus control?

A

GI secretion, absorption, local blood flow
also helps control local contraction of submucosal muscle

aka submucosal plexus

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9
Q

What are the layers of the gut tract wall?

A

submucosa - thicker than lamina propria, has blood vessels

mucosa - single cell layer, continuous sheet lining G.I. tract

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10
Q

what does the mucosa include?

A

lamina propria - loose CT with nerves, blood vessels, glands

muscularis mucosa - thin layer of smooth m., makes folds

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11
Q

what is characteristic of propulsive movements?

A

contractile ring
stimulus is distension, STRONG parasymp. signals, irritation
requires Myenteric (Auerbach) plexus
travels any direction

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12
Q

what are the characteristics of mixing movements?

A

may be caused by peristaltic contractions

local, intermittent contractions in gut wall

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13
Q

slow waves are not ____ ______.

what is the average intensity and frequency?

A

action potentials

I: 5-15mv Freq: 3-12 (increases from stomach to duodenum)

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14
Q

What kind of cells are the smooth muscle cell electrical pacemakers and what do they generate?

A

Cells of Cajal generate slow waves

slow wave –> spike potential –> muscle contraction

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15
Q

what are spike potentials? what is their threshold potential? how long do they last?

A

true action potentials
-40mv
10-20ms or 10-40x as long as normal AP

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16
Q

what kind of channels do spike potentials open?

A

Calcium

17
Q

True or False

Calcium channels open rapidly and close slowly

A

FALSE

open slowly
close rapidly

18
Q

What factors cause depolarization?

A

stretching of muscle
Ach (PS)
GI hormones

19
Q

what causes hyperpolarization

A

NE and Epi

Sympathetic nerve stim

20
Q

what causes tonic contractions

A

repetitive spike potentials
hormones
continuous entry of calcium ions

21
Q

What g.i. reflexes result from the gut to prevertebral symp. ganglia and then back to g.i.?

A

gastrocolic - colon evacuation
enterogastric - inhibit stomach motility and secretion
colonoileal - empty ileum to colon

22
Q

What g.i. reflexes result from gut to spinal cord/brain stem and back?

A

pain reflex - inhibits entire g.i. tract
defecation - from colon/rectum to spinal cord and back
stomach/duodenum reflex - to brain stem and back control gastric motor and secretory activity

23
Q

Gastrin stimulus and site

A

protein, distension, nerve action

G cells of antrum, D, J

24
Q

CCK stimulus and site

A

protein, fat, acid

I cells of DJI

25
Q

Secretin stimulus and site

A

fat, acid

S cells of DJI

26
Q

GIP stimulus and site

A

protein, fat, carbs

K cells of DJ

27
Q

Motilin stimulus and site

A

fat, acid, nerve action…we are all FANs of motilin

M cells of DJ

28
Q

Gastrin action

A

stimulates gastrin secretion and mucosal growth

29
Q

CCK action

A 
stimulates pancreatic enzyme secretion
stimulates pancreatic bicarb secretion
stimulates growth of exocrine pancreas
inhibits appetite
inhibits gastric emptying
30
Q

Secretin action

A 
stimulates pepsin secretion
stimulates pancreatic bicarb secretion
stimulates biliary bicarb secretion
stimulates growth of exocrine pancreas
inhibits gastric acid secretion
31
Q

GIP action

A

stimulates insulin release

inhibits gastric acid secretion

32
Q

Motilin actions

A

stimulates gastric and intestinal motility

secreted during fasting

33
Q

what are the motor functions of the stomach

A

storage of food
mixing of food with gastric secretions
slow emptying of chyme into the small intestine

34
Q

what 3 routes mediate the enterogastric nervous reflexes?

A
  1. directly from duodenum to stomach through enteric nervous system in gut wall
  2. extrinsic nerves going to prevertebral ganglia, then back inhibitory symp nerve fibers to stomach
  3. vagus nerves to brainstem
35
Q

what factors are continually monitored in the duodenum that can initiate these reflexes?

A
  1. degree of distension in duodenum
  2. irritation of duodenal mucosa
  3. acidity of duodenal chyme
  4. breakdown products (protein) in chyme
36
Q

what hormones control feedback from duodenum?

A

CCK - most potent

GIP and secretin a little

37
Q

what are the 2 types of movements in the small intestine?

A

mixing and propulsive contractions

38
Q

what controls intestinal movement?

A
  1. gastroenteric reflex initiated by distension via myenteric
  2. gastrin, CCK, insulin, motilin, serotonin
  3. irritation of intestinal mucosa
  4. gastroileal reflexes
39
Q

what are the principal functions of the colon

A

water and electrolyte absorption from chyme

fecal storage

40
Q

what are produced by large circulare constrictions plus contractions of the teniae coli?

A

haustrations

Physiology 2 Test 2 AH (6 decks)

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