What is dysbiosis?
microbial imbalances on or inside the body
Is there dysbiosis in a healthy status? What is there?
Normal behavior, emotion, nociception
Normal levels of inflammatory cells & mediators
Normal gut microbiota
Is there dysbiosis in a stressed state?
Changes in behavior, cognition, emotion, nociception
Altered levels of inflammatory cells & mediators
What is the effect of sympathetic stimulation on the gut?
decrease in secretions & peristalsis
blood redirected away from the gut & to other places like the brain
What is the effect of parasympathetic stimulation on the gut?
increase in secretions & peristalsis
What are some of the things that can affect the gut?
bacteria toxins/chemicals parasites hormones nutrients
What percentage of the vagus nerve is sensory?
Self-contained inside the gut are what neurons?
IPANs: intrinsic primary afferent neuron
What portions of the GI does the vagus innervate?
1/3 of colon
What are some afferent nerves that supply the GI that go thru the paravertebral/prevertebral ganglia to get there? Where are their cell bodies located?
Greater splanchnic nerve
Lumbar colonic nerve
Where are the cell bodies of the afferent vagal fibers?
Where are the cell bodies of the pelvic nerves found?
in the DRG of the sacral region of the spinal cord
What are the 3 pathways that connect the gut to the CNS?
- Vagal afferents–>upper GI
- Pelvic afferents–>colorectal (colon, rectum, internal anal sphincter)
- splanchnic afferents–>throughout GI tract, nociceptive
* *pudendal nerves
What percentage of the splanchnic nerve fibers are afferent? Where are their cell bodies found?
Cell bodies in the DRG
Some of the extrinsic afferent nerves are chemosensitive & some are not. What are these chemical agents that some are sensitive to?
ATP bradykinin capsaicin 5-HT histamine
What are the differences b/w a generator potential & an action potential?
Generator Potential: graded; larger stimulus-->larger potential-->large frequency of AP firing; but if doesn't meet threshold-->no AP **dependent on coupled transmitters doesn't propagate-->local phenomenon no refractory period AP: all or none refractory period propagation
What is the process of a spinal reflex?
Visceral Afferent Neuron Interneuron (in spinal cord) Pregang efferent Postgang efferent Effector
What counts as mechanical stimuli in the gut?
What counts as signaling molecules released from Peyer’s patches in the gut?
What types of luminal contents would signal enteroendocrine cells to release gut peptides?
What types of gut peptides would enteroendocrine cells release?
What areas of the brain are activated by the gut peptides released by enteroendocrine cells?
dostral vagal complex
What is the function of endocrine cells in the GI tract?
They are detectors that analyze luminal contents, survey mucosal status, & activate afferent neurons.
What are 5 examples of endocrine cells in the GI tract?
I cells in duodenum S cells in stomach & intestine EE cells in gut EC cells lymphoid tissue
What do the I cells in the duodenum release? When do they release it? What happens next?
released in response to fat & protein digestion
CCK causes satiation; increases gastric blood flow & mucous protection
CCK inhibits gastric motility & emptying
What do the S cells in the stomach & intestine release? When does it release it? What is the response?
in response to duodenal acidification
It enhances pancreatic exocrine secretion & bile flow.
What do the enteroendocrine cells in the gut do?
Release up to 20 different kinds of neuropeptides that can stimulate the vagal afferents in a paracrine fashion or the brain in an endocrine fashion
Where is most of the serotonin in the body stored?
90% of 5-HT stored in EC cells
What stimulates EC cells to release their stores? What do they store? What is the effect?
mechanical & chemical stimulation
Activates peristalsis (intrinsic)
Activates relaxation of the stomach (extrinsic afferent neurons)
Where is the lymphoid tissue found in the gut? What cell types are found here?
Peyer's patches antigen-sampling M cells macrophages eosinophils neutrophils mast cells
Of the gut nerves we have been talking about…which are sympathetic? Parasympathetic?
Sympathetic: Splanchnic nerves, Hypogastric nerves
Parasympathetic: Vagus, Pelvic nerves
What percentage of sympathetic nerves are afferent fibers?
What percentage of the vagus nerve?
Sympathetic: 20% afferent
Vagus: 80% afferent
Pelvic: 50% afferent
What do the vagal neurons sense?
pH & distention of the stomach
What do the pelvic neurons sense?
distention of the rectum & colon
Which set of visceral afferent nerve fibers senses pain in the gut?
Sympathetic nerves–splanchnic nerves
What does splanchnic stimulation elicit? Vagal stimulation?