Sanders: Enteric Nervous System

Question 1

These cells lie within the gut mucosa and transduce luminal mechanical and/or chemical stimuli into the release of signaling molecules.

Answer 1

Enteroendocrine cells

Question 2

These cells contain and secrete serotonin, are the largest population of enteroendocrine cells, and have the most widespread distribution.

Answer 2

Enterochromaffin cells

Question 3

Enterochromaffin cells have both (blank) and (blank) capabilities.

Answer 3

chemosensitive; mechanosensitive

Question 4

Describe the distribution of enterochromaffin cells in each crypt.

Answer 4

There are very few enterochromaffin cells in each crypt.

Question 5

Primary sensory organ affecting GI motility.

Answer 5

EC cells

Question 6

Enterochromaffin cells contain 90% of the body’s (blank).

Answer 6

5-HT (serotonin)

Question 7

How do epithelial cells “mop up” 5-HT following its release?

Answer 7

They have seratonin reuptake transporters (SERTs)

Question 8

Most of the intrinsic and extrinsic primary afferent neurons that innervate the gut extend processes into the lamina propria of the mucosal layer where they can become exposed to (blank) released by enterochromaffin cells

Answer 8

5-HT

Question 9

These cells characteristically have large oval or round cell bodies with several long axonal processes emanating from them. Make up 20-30% of all enteric neurons.

Answer 9

Type II neurons

Question 10

Describe the action potentials of AH/Type II neurons.

Answer 10

Fire an AP, which is followed by a long0lasting hyperpolarizing after-potential. Cannot fire subsequent APs right away.

Question 11

What is the ionic mechanism for the after-hyperpolarizations in Type II neurons?

Answer 11

Ca+ channel activation

Question 12

In AH neurons, a meal can cause excitatory post-synaptic potentials. Why is this important?

Answer 12

After a meal, it is important for your gut to “awaken” and amplify sensory input

Question 13

Why is it difficult to localize pain in the gut?

Answer 13

AH neurons are all connected, so the sensory network is vastly distributed.

Question 14

AH neurons synapse with each other by releasing (blank), which forms a self-reinforcing network.

Answer 14

tachykinins

Question 15

These cells are characterised by the presence of short lamellar dendrites and a single long axon

Answer 15

Type I neurons

Question 16

These cells have distinct electrical behavior: They fire action potentials throughout the duration of a long lasting depolarization

Answer 16

S/Type 1 cells

Question 17

Compare the “spike” or action potential in S cells to that of AH cells.

Answer 17

S cells fire repeatedly and do not have long after-hyperpolarizations. They have fast action potentials. AH cells have a “hump” on their falling phase due to an influx of Ca+ ions.

Question 18

Nerves with cell bodies within the gut

Answer 18

enteric nervous system

Question 19

What do sympathetic nerves mainly do in the gut?

Answer 19

Regulate blood flow

Question 20

The enteric nervous system contains two types of ganglia. What are they? Which one is mostly associated with motility? Which is mostly associated with regulation of blood flow, secretion, and absorption?

Answer 20

myenteric and submucosal; myenteric; submucosal

Question 21

Excitatory: EC cells in the mucosa activate a (blank) in the myenteric plexus, which carries a signal to an (blank) in the oral direction, which activates an excitatory (blank), which releases ACh or neurokinins to cause (blank) of the circular muscle in the oral direction

Answer 21

IPAN (AH neuron); interneuron; motor neuron; contraction

Question 22

Inhibitory: EC cells in the mucosa activate a (blank) in the myenteric plexus, which sends the signal through an (blank) in the anal direction to an inhibitory (blank), which releases NO or VIP to cause (blank) the circular muscle

Answer 22

IPAN; interneuron; motor neuron; relaxation

Question 23

Produces excitation above the site of stimulation and relaxation below site of stimulation

Answer 23

Peristaltic reflex

Question 24

AH neurons are appropriately named, because they filter action potentials coming in from the gut and send one strong AP followed by a period of (blank) in which no more APs are generated

Answer 24

after-hyperpolarization