L23 - 24 ENS

Question 1

Are there more neuron cell bodies in ENS or spinal cord

Answer 1

ENS

Question 2

6 Layers of ENS (Superficial to Deep)

Answer 2

1) Muscosal layer - vili, site of secretion and absorption
2) Muscularis mucosae - thin layer of muscle
3) Submucosal plexis - Regulation of secretion of water and salts, 20% of neurons in ENS
4) Circular muscle - Mechanical work moving material in GIT
5) Myenteric plexus - Regulation of GIT motility, 80% of neurons in ENS
6) Longitutidinal muscle - Mechanical work moving material in GIT

Question 3

Two ganglionated plexuses and what do they do?

Answer 3

1) Myenteric (Auerbach’s) plexus provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input. It is in between the longitudinal and circular layers of muscularis externa.
2) Submucosal (Meissner’s) plexus – in between mucosa and muscle layer, has only parasympathetic fibres and provides secretomotor innervation to the mucosa nearest the lumen of the gut. q

Question 4

Submucousal begins at stomach but is ganglionated at? Myenteric is ganglionated at

Answer 4

Pylorus

Upper Oesophageal Sphnicter

Question 5

Lack of secretion leads to

Answer 5

Constipation and cystic fibrosis

Question 6

Too much secretion (overactivity of submucosal plexus) leads to

Answer 6

Diarrhoea

Question 7

Several non-ganglionated plexuses innervate?

Answer 7

Muscle, mucosa, blood vessela

Question 8

EXTRINSIC NERVE SUPPLY

• Symp: innervates?
• Para: innervates?

Answer 8

Symp innervates whole length of GIT

Para innervates most but less prominent in Jeujunem and ileum

Question 9

__% of vagal afferents are primary afferents

Answer 9

90

Question 10

Dorsal root ganglion cell afferents run in ____ and ____ nerves and are often thought to be ____

Answer 10

Splanchnic and pelvic, nociceptive

Question 11

Secretion is an active/passive process when water and salt moves from ___ into ___

Answer 11

Active, Body into lumen

Question 12

ENS contributes to control of acid secretion in _____, mucus secretion along ______and bicarbonate secretion in _____

Answer 12

Stomach, gut, duodenum

Question 13

Contractions abolished by ______, which blocks neural action potentials (by inhibiting __ channels), but not those of smooth muscle because ____

Answer 13

Tetrodotoxin, voltage gated Na+ channels, Smooth muscle AP are Ca2+ dependent not Na+ dependent

Question 14

•Jejunum contains entire circuit for generation of a complex behaviour
–Circuit involves two types of cholinergic neurons (Ach onto neurons – nicotinic muscles and Ach on the muscle –muscarinic receptors)

Answer 14

•Jejunum contains entire circuit for generation of a complex behaviour
–Circuit involves two types of cholinergic neurons (Ach onto neurons – nicotinic muscles and Ach on the muscle –muscarinic receptors)

Question 15

Intrinsic sensory neurons - What are they sensitive to?

Answer 15

Distention, mucosal deformation, nutrients

Question 16

Interneurons - what directions do they run in?

Answer 16

–Running orally, ascending

–Running anally, descending

Question 17

Secretomotor neurons - what do they aid with?

Answer 17

-2 classes, neurons that drive the movement of water and salt across the intestinal mucosa

Question 18

Latch effect of smooth muscle

Answer 18

When it contracts, it doesn’t relax without an active intervention. Actin-myosin crossbridges don’t break when Ca2+ is removed – hence inhibitory motor neurons are needed.

Question 19

NOS - inhibitory or excitatory?

Answer 19

Inhibitory

Question 20

NOS neurons make vasoactive intestinal peptide, but vasoactive intestinal peptide neurons in submuscousal plexus not found in NOS

Answer 20

NOS neurons make vasoactive intestinal peptide, but vasoactive intestinal peptide neurons in submuscousal plexus not found in NOS

Question 21

Main secretatory motor neurons in the ENS

Answer 21

Vaso-active intestinal peptide

Question 22

When have not eaten for 3 – 4 hours have the fasted state or interdigestive motor pattern is known as

Answer 22

MMC, begins at upper duodenum, last for 90 mins

Question 23

Interstitial cells of Cajal (ICC)

Answer 23

• In addition to neural pattern generators have pacemakers intrinsic to muscle layers – ICC
• ICC near myenteric plexus are electrically coupled via gap junctions to each other & to smooth muscle cells
• ICC generate rhythmic membrane potential changes (slow waves) in muscle
• Neural activity has little effect on slow wave frequency, but alters probability of slow waves generating action potentials and hence contractions

Question 24

Segementation circuit has 2 rhythmic pattern generators. There is a band of active excitatory motor neurons at site of contraction and 2 inhibitory bands on each side

Answer 24

Segementation circuit has 2 rhythmic pattern generators. There is a band of active excitatory motor neurons at site of contraction and 2 inhibitory bands on each side

Question 25

Key logic point – if neuron responds to sensory stimulus without synaptic transmission it must have a sensory function, in addition to any other functions

Answer 25

Key logic point – if neuron responds to sensory stimulus without synaptic transmission it must have a sensory function, in addition to any other functions