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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
Do SM have troponin C?
NO!
26
What si the viscarl smooth musle latch bridge mechanism
allows maintained TONIC contractions even after dephosphorylation This allows sustained contractin of intestinal sphincters with very little energy expenditure
27
When does the final relaxation ocur in SM
after dissociation of Ca-calmodulin complex
28
What determines the resting potential of GI SM
combined Na and K permeability of hte membrane as well as electrogenic contribution form Na/ K ATPase
29
What cells generate the rhythm of the GI system
INterstitial cells
30
where are the interstitital cells located? What kind of characteristics do they have?
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
31
What modulates the contracile force of contraction
1. Myenteric plexus fo the enteric NS | 2. Autonomic and hormonal input (outside enteric NS)
32
Characteristic of circular and longitudinal muscle layers of the upper 1/3 esophagus
Striated!
33
Lower 1/3 of esophagus is...
SMOOTH!
34
Mid-esophagus is....
progression from skeletal to smooth
35
The rest of the GI tract until teh external anal sphincter is.....
SMOOTH!
36
The external anal sphcincter is....
Striated! and under voluntary control!
37
What are the two importnat sphincter that control esophageal motlity
1. Upper esophageal sphincter | 2. Lower esophageal sphincter
37
What forms the upper esophageal sphincter
formed by thickening of circular layer of striated muscle. During swallowing , upper esophageal sphincter relaxes to receive bolus of food
37
Describe the role of the UES in swallowing
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
During swallowing, does the UES relax or contract?
relaxes! it recieves teh bolus of food
38
What intiateis a peristalitc wave to propel food down esopahgus
muscles of pharynx contract and force food into region of sphincter
38
what coordiantes the swallowing?
swallowwing center in medulla
39
Is it possible to swallow food while standing on your head? How?
Yes! peristaltic waves!
39
WHere is the lower esophageal sphincter (LES) located?
lower 2 cm of esophagus LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves
39
Where does LES get its input from
1. tonically contracted via neural inputs from ENTERIC NS 2. Vagal CHOLINERGIC NERVES
40
What happens to LES as an esophageal persitaltic wave approaches it?
It relaxes (opens)
40
How does LES relax?
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
Receptive relaxation
filling of stomach causes relaxatin of the fundus and body of the stomach, enabling it to accommodate a large increase in volume
41
Intestinointestinal Reflex
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
What can happen if ther eis excessive stretch of distension of intestinal sements during surgery
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
Waht is the etnerogastric and ileogastric reflex
Distension of the duodenum or ileum decreases gastric motility
42
Gastroileal reflex
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
What mediates teh gastroileal reflex
Gastrin!
42
What is the Gastocolic Reflex
Fod in teh stomach increase colonic motility (probably mediated by PS fibers) Good idea to walk you dog after he eats!
43
What is the Colonocolic reflex
Distension of one part of the colon relaxes neighboring segments (probably sympathetic)
43
What is the Rectosphincteric reflex
Filling and contraction of the rectum relaxes teh internal Anal Sphincter
43
Is it possible to swallow food while standing on your head? How?
Yes! peristaltic waves!
44
WHere is the lower esophageal sphincter (LES) located?
lower 2 cm of esophagus LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves
44
WHere is the lower esophageal sphincter (LES) located?
lower 2 cm of esophagus LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves
44
WHere is the lower esophageal sphincter (LES) located?
lower 2 cm of esophagus LES is tonically contracted via neural inputs from both the enteric NS and the Vagal Cholinergic Nerves
45
Where does LES get its input from
1. tonically contracted via neural inputs from ENTERIC NS 2. Vagal CHOLINERGIC NERVES
45
Where does LES get its input from
1. tonically contracted via neural inputs from ENTERIC NS 2. Vagal CHOLINERGIC NERVES
45
Where does LES get its input from
1. tonically contracted via neural inputs from ENTERIC NS 2. Vagal CHOLINERGIC NERVES
46
What happens to LES as an esophageal persitaltic wave approaches it?
It relaxes (opens)
46
What happens to LES as an esophageal persitaltic wave approaches it?
It relaxes (opens)
46
What happens to LES as an esophageal persitaltic wave approaches it?
It relaxes (opens)
47
How does LES relax?
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
Receptive relaxation
filling of stomach causes relaxatin of the fundus and body of the stomach, enabling it to accommodate a large increase in volume
49
Intestinointestinal Reflex
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
What can happen if ther eis excessive stretch of distension of intestinal sements during surgery
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
Waht is the etnerogastric and ileogastric reflex
Distension of the duodenum or ileum decreases gastric motility
52
Gastroileal reflex
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
What mediates teh gastroileal reflex
Gastrin!
54
What is the Gastocolic Reflex
Fod in teh stomach increase colonic motility (probably mediated by PS fibers) Good idea to walk you dog after he eats!
55
What is the Colonocolic reflex
Distension of one part of the colon relaxes neighboring segments (probably sympathetic)
56
What is the Rectosphincteric reflex
Filling and contraction of the rectum relaxes teh internal Anal Sphincter

Physiology GI (4 decks)

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