Sanders: Enteric Nervous System Flashcards
These cells lie within the gut mucosa and transduce luminal mechanical and/or chemical stimuli into the release of signaling molecules.
Enteroendocrine cells
These cells contain and secrete serotonin, are the largest population of enteroendocrine cells, and have the most widespread distribution.
Enterochromaffin cells
Enterochromaffin cells have both (blank) and (blank) capabilities.
chemosensitive; mechanosensitive
Describe the distribution of enterochromaffin cells in each crypt.
There are very few enterochromaffin cells in each crypt.
Primary sensory organ affecting GI motility.
EC cells
Enterochromaffin cells contain 90% of the body’s (blank).
5-HT (serotonin)
How do epithelial cells “mop up” 5-HT following its release?
They have seratonin reuptake transporters (SERTs)
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
5-HT
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.
Type II neurons
Describe the action potentials of AH/Type II neurons.
Fire an AP, which is followed by a long0lasting hyperpolarizing after-potential. Cannot fire subsequent APs right away.
What is the ionic mechanism for the after-hyperpolarizations in Type II neurons?
Ca+ channel activation
In AH neurons, a meal can cause excitatory post-synaptic potentials. Why is this important?
After a meal, it is important for your gut to “awaken” and amplify sensory input
Why is it difficult to localize pain in the gut?
AH neurons are all connected, so the sensory network is vastly distributed.
AH neurons synapse with each other by releasing (blank), which forms a self-reinforcing network.
tachykinins
These cells are characterised by the presence of short lamellar dendrites and a single long axon
Type I neurons
These cells have distinct electrical behavior: They fire action potentials throughout the duration of a long lasting depolarization
S/Type 1 cells
Compare the “spike” or action potential in S cells to that of AH cells.
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.
Nerves with cell bodies within the gut
enteric nervous system
What do sympathetic nerves mainly do in the gut?
Regulate blood flow
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?
myenteric and submucosal; myenteric; submucosal
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
IPAN (AH neuron); interneuron; motor neuron; contraction
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
IPAN; interneuron; motor neuron; relaxation
Produces excitation above the site of stimulation and relaxation below site of stimulation
Peristaltic reflex
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
after-hyperpolarization
