GI Phys 1: Intro to GI System

Question 1

Endocrine

Answer 1

regulation that utilizes the blood to send widespread signals throughout the body

Question 2

Paracrine

Answer 2

regulation that targets cells in close proximity (neighboring cells) and results in a more localized effect

Question 3

Neurocrine

Answer 3

regulation that occurs when neurons innervate endocrine, vascular, or muscle cells and modulate their function

Question 4

localized communication and signaling occurs with which regulators

Answer 4

paracrine regulators

Question 5

4 key features of the ENS

Answer 5

1) branch of ANS
2) 100 million neurons (= to SC)
3) located entirely in GI
4) regulated by local stimuli and PNS/SNS

Question 6

ENS stands for

Answer 6

enteric nervous system

Question 7

all cell bodies of the ENS are where?

Answer 7

all cell bodies of the ENS are within the GI tract.

Question 8

define gut-brain axis

Answer 8

communication between ENS and CNS

Question 9

PNS efferents 3 functions

Answer 9

stimulate motility
stimulate secretions
vasodilation

Question 10

SNS efferents 3 functions

Answer 10

inhibit motility
inhibit secretions
vasoconstriction

Question 11

ENS functions 5

Answer 11

motility regulation
secretory regulation
mechanical sensation
chemical sensation 
pain sensation

Question 12

neuronal innervation of the GI tract:

Answer 12

PNS and SNS can regulate the GI tract directly or indirectly. The ENS can function by itself. It can also be targeted indirectly via pre-ganglionic fiber of PNS that innervates ENS neurons. unique!

Question 13

ACh: Primary NT of what?

Answer 13

Ach is the primary NT of the PNS. Ach is released by the pre and post ganglionic fibers of the PNS!

Question 14

NT’s of the PNS and SNS (2)

Answer 14

Ach and NE (norepi)

Question 15

Key NT’s of the ENS (5)

Answer 15

Ach
Serotonin
Dopamine
Nitric Oxide
Vasoactive Intestinal Peptide (VIP)

Question 16

functions of Ach

Answer 16

vasodilation, smooth mm contraction, stimulate secretion

Question 17

function of serotonin

Answer 17

vasodilation, increase smooth mm contraction ,stimulate secretion

Question 18

key NT for interneurons =

Answer 18

serotonin!

Question 19

functions of dopamine

Answer 19

inhibit ENS neuronal firing

Question 20

functions of NO

Answer 20

smooth mm relxation (vasodilator of GI and cardiac/smooth mm)

Question 21

functions of VIP (vasoactive intestinal peptide)

Answer 21

smooth muscle relxation (vascular and GI)

Question 22

Dopamine: how does it inhibit ENS neuronal firing?

Answer 22

dopamine inhbitis ens firing via dop2 receptors that are expressed pre-synaptically. when dopamine binds to dop2 receptors, it decreases neuronal firing and the release of NT

Question 23

BER = ?

Answer 23

basal electrical rhythm or slow waves

Question 24

define BER

Answer 24

a spontaneous oscillating depolarization and repolarization wave that does not elicit a contraction. the cell is at rest, but will get closer to threshold during depolarization.

Question 25

BER rhythmic pattern is initated bywhat

Answer 25

Interstitial cells of Cajal - these are pace maker cells and lie between the longitudinal and circular msucle

Question 26

define spike potentials

Answer 26

rapid depolarization events that occur at the peak of the slow wave and elicit a contraction

Question 27

3 primary regulators of GI smooth muscle

Answer 27

1) Ach (stimulates contraction) 2) VIP (inhibits contraction) 3) NO (inhibits contraction)

Question 28

4 types of GI motor activity

Answer 28

1) segmental contractions (mixing) 2) peristaltic contractions (moving) 3) reverse peristaltic contractions (storing and keeping empty) 4) migrating motor complex MMC

Question 29

Segmental contractions

Answer 29

- think of sqeezuing tube of toothpaste in various areas - gives you basic mixing - segments alternate contractive state

Question 30

peristaltic contractions

Answer 30

coordinated contraction and relaxation

Question 31

GI motility

Answer 31

upstream contraction (Ach) and downstream relxation (NO, VIP) allow for coordinated mvmt through the GI system

Question 32

define MMC

Answer 32

migrating motor complex is a rhythmic motility patern that occurs during the interdigestive period (btwn meals) about every 90 minutes

Question 33

purpose of MMC

Answer 33

to maintain directional movement of undigested contents

Question 34

strongest contractions of MMC

Answer 34

in upper GI tract (stomach, duodenum, jejunum) and fade in inensity in the ileum and colon

Question 35

loss of MMC can lead to what

Answer 35

colonization of bacteria in the upper GI tract. can lead to overgrowth of bacteria

Question 36

striated mm locations (3)

Answer 36

1) upper esophageal sphincter 2) upper 1/3 of esophagus 3) EAS (external anal sphincter)

Question 37

sphincter fxn

Answer 37

sphincter mm's are located between each organ to control emptying and are common sites of pathology

Question 38

Splanchnic circulation

Answer 38

receives 30% of cardiac output at rest

Question 39

blood is delivered via which two arteries

Answer 39

celiac and superior mesenteric arterities. the GI organs drain into the portal vein

Question 40

Blood flow from GI organs to the liver via which vein

Answer 40

portal vein. contents absorbed via GI tract must pass through the liver