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Phys4 GI Lect2
Phys4 Neural control of GI function
| Question | Answer |
|---|---|
| Which nervous system is responsible for carrying the visceral afferents back to the brain? | PNS |
| 3 possible pathways of a sympatheic efferent signal | 1.Synapse at its same spinal level on the sympathetic chain. 2.Travel up & down the chain and synapse. 3.Bypass the chain and synapse elsewhere (this is the case for GI SNS). |
| Where do the SNS GI Preganglionic neurons synapse? | Synapse on either the: 1.Celiac Ganglia. 2.Superior Messenteric Ganglia. 3.Inferior Messenteric Ganglia. **Also sometimes directly on the target organ itself. |
| What do sympathetic afferents carry back to the brain? | PAIN |
| PNS affect on GI | 1.Relaxes sphincters. 2.Inc motility & tone. 3.Inc secretion. **Via ACh->M3 |
| SNS affect on GI | 1.Contract sphincters (a1). 2.Dec tone & motility. 3.Dec secretions. **Use NE on B2/A2 and A1 |
| Where will NE acting on A2 occur in the GI? | they will be on the PREsynaptic nerve, serve an inhibitory function. |
| Can Vagal nerve stimulation cause muscle relaxation of the GI muscle? | YES, they sometimes synapse onto INHIBITORY neurons. |
| Layers of the Duodenum | 1.Intestinal Villi w/ epithelial lining. 2.Lamina propria (will find glands & vessels here). 3.Muscularis Mucosa ( 4.Submucosa. 5.Muscularis Externa (Very important for motility. 6.Serosa. |
| How are the muscle fiber arranged in the muscularis externa | 1.Outer longitudinal muscle layer (along the length of the tube). 2.Inner circular muscle layer(along the circumfrence). |
| Names and locations of the 2 main Enteric NS ganglion w/in the gut tube | 1.Myenteric (Aurbach's) Plexus: Located b/w the longitudinal & Circular muscle layers, runs from proximal esophagus to rectum. 2.Submucosal Plexus: Located b/w the submucosa & circular muscle layers, only in large & small intestine. |
| Primary function of Myenteric Plexus | Movement & Motility. |
| Primary function of Submucosal Plexus | Blood flow and Secretion |
| How would you classify the neuronal signals leaving the enteric nerves? | POST-ganglionic: 1.Post-gang PNS. 2.Post-Post-gang SNS. 3.Post Enteric |
| Do they PNS and SNS synapse primarily on the Enteric ganglia within the GI walls? | Yes, SNS can also synapse directly onto target organs. **Just remember it is Pre-gang PNS and Post-gang SNS synapsing on the enteric ganglia |
| Potential synapses of afferent GI sensory neurons | 1.Synapse on enteric plexus (short pathway). 2.Travel to prevertebral ganglia (long pathway SNS). 3.Travel to brain & spinal cord (long pathway). |
| Example of a hormone that is also a neurotransmitter | CCK |
| Classic GI excitatory neurotransmitters are | 1.ACh. 2.Sustance P family (neurokinins or tachykinins). |
| Classic Inhibitory GI neurotransmitters are | 1.VIP (found exclusively w/in the nerves, inhibits smooth mucle). 2.NO. |
| Long reflexes of the ANS | Reflexes with: (typically VAGO-VAGAL reflex). 1.an afferent arm traveling to CNS. 2.an efferent arm travelling back to the gut from the CNS. |
| Short reflexes of the ANS | (local or intramural reflexes) take place ENTIRELY within the gut wall. **No travel to and from CNS, Efferent info comes directly from Enteric NS. |