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Physiology GI > Physiology 12.28.13 Intro to GI > Flashcards

Physiology 12.28.13 Intro to GI Flashcards

1
Q

What is GI motility largely controlled by?

A

intrinsic regulation

enteric nervous sytem

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2
Q

describe the enteric NS

A

contains as many neurons as spinal cord and can function independently of outside innervations

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3
Q

What are the two most important components of the enteric system

A
  1. Submucosal (Meissner’s) Plexus

2) Myenteric (Auerbach’s) Plexus

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4
Q

What is the role of the submucsoal (Meissner’s Plexus)

A

gives rise to MUCOSAL plexus (within individual villi) that regulates SECRETORY activity

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5
Q

What is the role of the Myenteric (Auerbach’s) Plexus

A

gives rise to DEEP MUSCULAR PLEXUS that innervates the circular and longitudinal muscle layers which are responsible for intestinal MOTILITY

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6
Q

What else is the Enteric NS regulated by

A

Autonomic NS (both PS and SYMP)

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7
Q

What are the transmitters of the enteric nervous system

A

Myenteric Plexus- controls Motility

Submucosal plexus- controls secretion

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8
Q

What are the excitatory transmitters ofr teh Myenteric Plexus (controls motility) -2

A
  1. Ach

2. Substance P

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9
Q

What happens to KO mice that lack Substance P receptor

A

insensitive to opiates

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10
Q

what are INHIBITORY transmitters of the myenteric plexus (relaxes smooth muscle) 2

A
  1. VIP (Vasoactive intestinal polypeptide)

2. NO (nitric oxide)

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11
Q

What are the Excitatory Transmitters of the Submucosal Plexu (promotes secretion)

A
  1. ACh

2. VIP

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12
Q

Are there inhibitory transmitters for the submucosal plexus?

A

no?

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13
Q

What are the excitatory transmitters for the external autonomic control of the GI system?

A

1.ACh (PS via the vagus)

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14
Q

What does ACh (PS via the vagus) do to GI system (3)

A
  1. Increases peristalsis (stimulates SM)
  2. Increases Mucosal secretions
  3. Relaxes Sphincters
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15
Q

What are Inhibitory Transmitters that are external autonomic control of GI sytem

A

Epinephrine, NE (sympathetic)

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16
Q

What does sympathetic innervation with Epi/NE do to GI system

A

ihibits!

  1. Blocks SM contractions
  2. Decreases mucosal secretions, but increases small intestinal absorption
  3. Contracts Sphincters
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17
Q

What does PS (cholinergic/vagus do)

A

increases motility/secretion

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18
Q

What doees Symp system do

A

Decreases motility

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19
Q

Does circular and longitudinal muscle layers consist of GI?

A

YES!

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20
Q

Describe SM of GI

A
  1. electically coupled to neighboring cells to form bundels of cells taht function as an effective unit
  2. Cytoskeleton anchors the actin filaments
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21
Q

What are dense bodies in SM of GI?

A

1 they are equivalent to Z disks (in sk muscle)

  1. serve as attachment points for the THIN FILAMENTS
  2. Intermediate filametns link teh dense bodies intoa cytoskeletal network that allows teh contractile force of individual cells to be transferred to the muscle as a whole
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22
Q

What anchors the actin filaments in SM cells?

A

the Cystoskeleton

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23
Q

Describe the Electrical Acitivity

A

Following an AP, contraction of GI (visceral) SM is elicted by Calcium either crossing teh PM or being released from SR

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24
Q

Describe the role of Ca in SM contraction/electrical activity

A

Ca binds to calmodulin –> activates calmodulin-dependent myosin light chain kinases –> catalyzes phosphorylation of myosin, a necessary step in contraction of visceral SM

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25
Q

Do SM have troponin C?

A

NO!

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26
Q

What si the viscarl smooth musle latch bridge mechanism

A

allows maintained TONIC contractions even after dephosphorylation

This allows sustained contractin of intestinal sphincters with very little energy expenditure

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27
Q

When does the final relaxation ocur in SM

A

after dissociation of Ca-calmodulin complex

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28
Q

What determines the resting potential of GI SM

A

combined Na and K permeability of hte membrane as well as electrogenic contribution form Na/ K ATPase

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29
Q

What cells generate the rhythm of the GI system

A

INterstitial cells

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30
Q

where are the interstitital cells located? What kind of characteristics do they have?

A

between teh ciruclar and longitudinal muscle cells.

Characteristics of both SM and fibroblasts

Function as pacemakers (set frequency of slow waves)of the gut, and establish electrical rhythm for GI motility

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31
Q

What modulates the contracile force of contraction

A
  1. Myenteric plexus fo the enteric NS

2. Autonomic and hormonal input (outside enteric NS)

32
Q

Characteristic of circular and longitudinal muscle layers of the upper 1/3 esophagus

33
Q

Lower 1/3 of esophagus is…

34
Q

Mid-esophagus is….

A

progression from skeletal to smooth

35
Q

The rest of the GI tract until teh external anal sphincter is…..

36
Q

The external anal sphcincter is….

A

Striated!

and under voluntary control!

37
Q

What are the two importnat sphincter that control esophageal motlity

A
  1. Upper esophageal sphincter

2. Lower esophageal sphincter

37
Q

What forms the upper esophageal sphincter

A

formed by thickening of circular layer of striated muscle.

During swallowing , upper esophageal sphincter relaxes to receive bolus of food

37
Q

Describe the role of the UES in swallowing

A
  1. During swallowing, UES relaxes to receive the bolus of food.
  2. Muscles in pharynx contract and force food into region of sphincter
  3. Initiates peristaltic wave which propels food down the esopahgus
  4. all of this is coordinated by a swallowing center in medualla
38
Q

During swallowing, does the UES relax or contract?

A

relaxes!

it recieves teh bolus of food

38
Q

What intiateis a peristalitc wave to propel food down esopahgus

A

muscles of pharynx contract and force food into region of sphincter

38
Q

what coordiantes the swallowing?

A

swallowwing center in medulla

39
Q

Is it possible to swallow food while standing on your head? How?

A

Yes!

peristaltic waves!

39
Q

WHere is the lower esophageal sphincter (LES) located?

A

lower 2 cm of esophagus

LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves

39
Q

Where does LES get its input from

A
  1. tonically contracted via neural inputs from
    ENTERIC NS
  2. Vagal CHOLINERGIC NERVES
40
Q

What happens to LES as an esophageal persitaltic wave approaches it?

A

It relaxes (opens)

40
Q

How does LES relax?

A

proper relaxation of LES requires a

  1. decrease in firing rate of VAGAL EXCITATORY FIBERS (VEF)
  2. Increase in firing rate of VAGAL INHIBITROY FIBERS (VIF)
40
Q

Receptive relaxation

A

filling of stomach causes relaxatin of the fundus and body of the stomach, enabling it to accommodate a large increase in volume

41
Q

Intestinointestinal Reflex

A

Distension of one part of the intestine relaxes neighboring segments.

Pathologically, excessive stretch or distenstion of intestinal segments (during surgerY) can cause secretions fo the intestin to relax tot point that peristalsis is inhibited. This results in a functional obstructino of the intestine (paralytic ileus that can be fatal if not corrected

41
Q

What can happen if ther eis excessive stretch of distension of intestinal sements during surgery

A

Intestinointestinal reflex!

) can cause secretions fo the intestin to relax tot point that peristalsis is inhibited. This results in a functional obstructino of the intestine (paralytic ileus that can be fatal if not corrected

41
Q

Waht is the etnerogastric and ileogastric reflex

A

Distension of the duodenum or ileum decreases gastric motility

42
Q

Gastroileal reflex

A

Elevated secretion and motility in teh stomach increase motility of the ileum and relax the ileocecal sphincter (probably mediated by gastrin)- goes to colon?

42
Q

What mediates teh gastroileal reflex

42
Q

What is the Gastocolic Reflex

A

Fod in teh stomach increase colonic motility (probably mediated by PS fibers)

Good idea to walk you dog after he eats!

43
Q

What is the Colonocolic reflex

A

Distension of one part of the colon relaxes neighboring segments (probably sympathetic)

43
Q

What is the Rectosphincteric reflex

A

Filling and contraction of the rectum relaxes teh internal Anal Sphincter

43
Q

Is it possible to swallow food while standing on your head? How?

A

Yes!

peristaltic waves!

44
Q

WHere is the lower esophageal sphincter (LES) located?

A

lower 2 cm of esophagus

LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves

44
Q

WHere is the lower esophageal sphincter (LES) located?

A

lower 2 cm of esophagus

LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves

44
Q

WHere is the lower esophageal sphincter (LES) located?

A

lower 2 cm of esophagus

LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves

45
Q

Where does LES get its input from

A
  1. tonically contracted via neural inputs from
    ENTERIC NS
  2. Vagal CHOLINERGIC NERVES
45
Q

Where does LES get its input from

A
  1. tonically contracted via neural inputs from
    ENTERIC NS
  2. Vagal CHOLINERGIC NERVES
45
Q

Where does LES get its input from

A
  1. tonically contracted via neural inputs from
    ENTERIC NS
  2. Vagal CHOLINERGIC NERVES
46
Q

What happens to LES as an esophageal persitaltic wave approaches it?

A

It relaxes (opens)

46
Q

What happens to LES as an esophageal persitaltic wave approaches it?

A

It relaxes (opens)

46
Q

What happens to LES as an esophageal persitaltic wave approaches it?

A

It relaxes (opens)

47
Q

How does LES relax?

A

proper relaxation of LES requires a

  1. decrease in firing rate of VAGAL EXCITATORY FIBERS (VEF)
  2. Increase in firing rate of VAGAL INHIBITROY FIBERS (VIF)
48
Q

Receptive relaxation

A

filling of stomach causes relaxatin of the fundus and body of the stomach, enabling it to accommodate a large increase in volume

49
Q

Intestinointestinal Reflex

A

Distension of one part of the intestine relaxes neighboring segments.

Pathologically, excessive stretch or distenstion of intestinal segments (during surgerY) can cause secretions fo the intestin to relax tot point that peristalsis is inhibited. This results in a functional obstructino of the intestine (paralytic ileus that can be fatal if not corrected

50
Q

What can happen if ther eis excessive stretch of distension of intestinal sements during surgery

A

Intestinointestinal reflex!

) can cause secretions fo the intestin to relax tot point that peristalsis is inhibited. This results in a functional obstructino of the intestine (paralytic ileus that can be fatal if not corrected

51
Q

Waht is the etnerogastric and ileogastric reflex

A

Distension of the duodenum or ileum decreases gastric motility

52
Q

Gastroileal reflex

A

Elevated secretion and motility in teh stomach increase motility of the ileum and relax the ileocecal sphincter (probably mediated by gastrin)- goes to colon?

53
Q

What mediates teh gastroileal reflex

54
Q

What is the Gastocolic Reflex

A

Fod in teh stomach increase colonic motility (probably mediated by PS fibers)

Good idea to walk you dog after he eats!

55
Q

What is the Colonocolic reflex

A

Distension of one part of the colon relaxes neighboring segments (probably sympathetic)

56
Q

What is the Rectosphincteric reflex

A

Filling and contraction of the rectum relaxes teh internal Anal Sphincter

Physiology GI (4 decks)

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