enteric nervous system

Question 1

define ENS

Answer 1

network of cell bodies, processes, axons in the wall of GI tract
can work independently of brain

Question 2

more cell bodies: s.c. or ENS?

Answer 2

ens

Question 3

what neurons are included in ENS?

Answer 3

neurons within wall of gi tract, axons & terminals of parasymp, symp & visceral sensory neurons that innervate GI tract

Question 4

myenteric plexus

Answer 4

main neural supply of gut

Question 5

submucosal plexus (2 functions)

Answer 5

regulate secretion into lumen of GI tract
arterioles for blood flow to mucosa

Question 6

primary vs secondary vs tertiary plexus (ens)

Answer 6

1: connective nerve trunks between myenteric ganglia
2: nerve trunks that run into circular muscles
3: supply longitudinal muscles

Question 7

where does ganglionated plexus begin? (submucosal vs myenteric)

Answer 7

sub: pylorus
my: upper oesophageal sphincter (and all the way to anus)

Question 8

which ens ganglia is bigger?

Answer 8

myenteric (bigger than submucosal)

Question 9

efferent nerve supply
2 different paths, where do they innervate

Answer 9

sympathetic: entire
parasympathetic: upper & lower

Question 10

afferent nerve supply
2 different paths, where do they run?, what do they innervate

Answer 10

innervate entire GI tract
vagal: cell bodies in nodose ganglia
dorsal root: run in splanchnic & pelvic nerves

Question 11

functions of ENS

Answer 11

1. movement of intestinal content
2. regulation of water & electrolyte transport across mucosa
3. control of acid secretion, mucus secretion, bicarbonate secretion

Question 12

movement of salts and water for homeostasis (2 types)

Answer 12

absorption: lumen -> body
secretion: body -> lumen

Question 13

describe intestinal movements

Answer 13

when nutrients present in lumen:
localised contractions - then propagate = peristalsis

Question 14

blockers of intestinal movement (what and how)

Answer 14

1. tetrodotoxin: blocks a.p.
2. antagonist muscarinic & nicotinic receptors

Question 15

intrinsic sensory neurons (ens)
sensitive to what

Answer 15

distension, mucosal deformation, presence of nutrients

Question 16

excitatory motor neurons & inhibitory motor neurons (ens)
what nt’s

Answer 16

to circular & longitudinal muscles (2 types)
e: contract (Ach, SP) i: relax (NOS)

Question 17

interneurons in ENS (2 types)

Answer 17

Orally: ascending
Anally: descending

Question 18

secretomotor neurons (ens)

Answer 18

secretion control

Question 19

vasodilator neurons (ENS)

Answer 19

control diam of art

Question 20

intestinofugal neurons (ens)

Answer 20

coordinate activities throughout entire ens

Question 21

interplexus interneurons

Answer 21

communication between 2 plexus

Question 22

law of the intestine
(what was the experiment, what does this mean?)

Answer 22

contraction ABOVE, relaxation BELOW stimulus
ASCENDING, ORALLY: excitation
DESCENDING, ANALLY: inhibition

Question 23

top-down approach (ens)

Answer 23

properties neurons must have for behaviours

Question 24

immunohistochemistry

Answer 24

label for specific neurochemical markers
ganglion = 20 diff neurons

Question 25

transcriptomics

Answer 25

see what neurons have similar mRNA

Question 26

how are functions of ens neurons defined?

Answer 26

physiology, projections

Question 27

properties of ISNs

Answer 27

Properties: primary responders to physiological stimuli, mult. axons to span large areas, chemosensitive to detect nutrients, mechanosensitive channels

Question 28

do motor neurons allow propagation of motor patterns?

Answer 28

NO

Question 29

ISN -> local interneurons & motor neurons = _____ projections

Answer 29

polarised projections

Question 30

how does propagation occur?

Answer 30

descending interneurons connected to ascending interneurons & excitatory motor neurons therefore anally directed constriction follows relaxation = propagation

Question 31

local disruption in neural circuit (ens) -> propagation

Answer 31

produce stationary contractions on either side of disruption

Question 32

factors altering gut behaviour

Answer 32

chemical composition of contents, volume of contents, viscosity and texture of contents

Question 33

what does high nutrient content favour in the gut?

Answer 33

segmentation (over propulsion)

Question 34

large volume of contents triggers?

Answer 34

propulsive contractile patterns and receptive relaxation = increase speed

Question 35

low vs high viscosity contents in gut

Answer 35

low: move quick, no deformation of mucosa high: move slow, mechanical stimulation of mucosa

Question 36

EE cells

Answer 36

1% of enterocytes -> produce hormones in response to nutrient presence apical membrane exposed lumen basal membrane exposed to lamina propria

Question 37

EC cells

Answer 37

syn, store, release SEROTONIN respond to chemical and mechno stim (via taste rec or mechanorec)

Question 38

neuropods *present on what cells, what do they do?*

Answer 38

on EE and EC cells contact terminals of sensory neurons have proteins involved in transmitter release

Question 39

blocking serotonin uptake

Answer 39

increasing segmenting motor activity in jejunum

Question 40

blocking serotonin receptors in mucosa

Answer 40

reduces nutrient induced segmenting motor activity

Question 41

releasing serotonin from mucosa with cholera tocin

Answer 41

increases propulsive motor activity (rapidly)

Question 42

can serotonin cross blood brain barrier?

Answer 42

no

Question 43

Amino Acid Application (onto mucosa)

Answer 43

initiates local reflexes via serotonin and or atp

Question 44

Amino Acid Application (onto mucosa)

Answer 44

initiates local reflexes via serotonin and or atp

Question 45

cholinergic secretomotor neuron *process of how it works*

Answer 45

Ach -> M3 -> increase Cl- grad

Question 46

non-cholinergic secretomotor neurons *process*

Answer 46

Vip -> AC -> cAMP -> CFTR open

Question 47

secretion process (ens)

Answer 47

Cl- influx via cftr (tops of villi) -> water and Na+ follow passively

Question 48

absorption process (ens)

Answer 48

Electroneutral (no direct neural control), constituently active Na+ transported from lumen into enterocytes (@ tips of villi & mucosal surface of colon) Via NHE3 sodium hydrogen exchanger (in apical membrane) Newly differentiated enterocytes -> CFTR Older enterocytes -> NHE3 Increased speed = Less absorption

Question 49

diarrhoea from cholera

Answer 49

Diarrhoea results Activates AC, releases 5-HT from EC cells Increased propulsive contractions & hypersecretions Increases excitability of myenteric ISNs = hyperactive