GI Motility Flashcards
Slow Wave Electrical Activity
- Fluctuations in what generate these waves?
- What modulates this activity?
- Are these action potentials?
- What is the frequency of these waves in the stomach? In the duodenum?
- The frequency of these waves is not controlled by […]
- The amplitude of these waves can be controlled by […]
What are the gastrocolic and duodenocolic reflexes?
She didn’t elaborate on these, but just said that it’s basically communication between the duodenum and the colon telling the colon to empty itself for the incoming contents from the small intestine.
Which snack empties fastest?
- Apple
- Orange
- Unsalted peanuts
- French fries
Apple
Let’s say I eat a bunch of french fries that are high in fat and salt. This is going to slow the gastric emptying of my stomach as discussed due to the contents that is sensed by the duodenum. Describe how the GI system will respond to slow gastric emptying with regards to:
- GI hormone secretion
- Short reflexes
- Long reflexes
What is the sequence of actions in the pharyngeal stage of swallowing?
Tongue pushes bolus up and back to reach back of mouth / pharynx. Bolus reaching back of mouth stimulates stretch receptors which send signals to brainstem via CN 9 and 10. CNs respond by mediating closing off of nasopharynx (elevate soft palate), elevating larynx to close off airway (epiglottis covering trachea), and opening of the upper esophageal sphincter. Pharynx contracts to push bolus into esophagus.
Describe the motor function of the small intestine during the fasting state.
Describe how the stomach functions as storage for contents from esophagus.
Describe the motility, control and innervation of the large intestine?
Cholinergic agonists promote defecation by:
- Increasing rectal contractility
- Decreasing rectal contractility
- Relaxing the external sphincter
1
What two types of movements will be seen in the small intestine during the fed state?
Regulation of neural and hormonal stimuli is achieved by modulation of […]
Ca2+
Describe the process of mixing and propulsion of food that occurs in stomach.
What are the different types of smooth muscle contraction in the GI tract?
What signals cause the smooth muscle cells of the GI tract to depolarize?
- Stretch
- Ach
- GI hormones
- Gastrin (stomach)
- Motilin, CCK, secretin, GIP (intestines)
What is important to know about the oral phase of swallowing?
What is the defecation reflex?
- Feces filling rectum activates stretch receptors in GI tract wall. Receptors transmit signal to spinal cord.
- Involuntary reflex –> efferent signal from gut synapses on neuron in ventral horn of spinal cord that carries afferent involuntary signal to internal anal sphincter causing relaxation.
- Efferent signal from gut also talks to neurons that communicate with the cerebral cortex. This lets the brain know that the body thinks its time to poop, but the brain can either agree and if so relax the external anal sphincter or it can disagree and keep the external anal sphincter contracted preventing defecation.
- What condition may be seen if a person has poor LES tone?
- What if they have too much LES tone?
- Gatric reflux (risk for barrett’s esophagus)
- Achalasia (may present as atypical chest pain)
What signals modulate hyperpolarization of the GI tract?
NE
SNS
Spike Potentials
- When are these generated?
- What is the result of these potentials?
- What is happening during the depolarization phase of these potentials?
- What is happening during the repolarization phase of these potentials?
What controls stomach emptying?
The contents of the food when it reaches the duodenum. Carbs, low osmolality, and high pH food empties fastest.
- Carbs>>proteins>>fats
- Low osm >> high osm
- Basic >> low pH
- The […] NS mediates the oral phase of swallowing.
- The […] NS mediates the pharyneal phase of swallowing.
- The […] NS mediates the esophageal phase of swallowing.
- Somatic
- Autonomic
- Autonomic / enteric
What are the 3 functions of the stomach?
Storage
Mixing
Emptying
What are the effects of Glucose-dependent Insulinotropic Peptide (GIP) on the GI tract?
Decrease gastric motility
Increase intestinal motility
The upper esophagus is controlled by […] nervous system while the lower esophagus is controlled by […] nervous system
Autonomic (CN 9, 10)
Autonomic (CN 10) and enteric
When in the fed state, which hormone controls GI motility?
Gastrin
- Increase gastric motility
What are the two types of electrical activity observed in the gut?
What type of movement is seen in the proximal colon vs. the transverse colon and onwards?
- Describe the events that happen in the esophageal phase of swallowing.
- What is the distinction between primary and secondary esophageal peristalsis?
- Bolus passes through upper esophageal sphincter –> beginning of this phase. Autonomic NS continues action potential down esophagus so that there is contraction behind the bolus to push it along. UES closes, LES opens, contraction pushes bolus into stomach.
- After primary peristalsis, if there is still distension of the esophagus, then secondary peristalsis will also occur where the pressure from remaining esophageal contents causes esophageal distension and activates the myenteric reflexes to propel the remaining contents down the GI tract to clear the esophagus.
What are the primary functions of the large intestine?
Absorption
Storage/elimination
What is the function of the lower esophageal sphincter?
- Coordination of movement of food into the stomach
- Prevents reflux of gastric contents
What are the 3 major categories of regulation of the GI motor function?
- Neural (enteric NS and autonomic NS)
- Autonomous smooth muscle function
- GI hormones
When does the LES relax?
In response to swallowing/esophageal distension. This is mediated by PSNS vagal preganglionic neural input to enteric neurons that secrete NO and VIP to realx.
What signals cause the smooth muscle cells of the GI tract to become hyperpolarized?
- NO and VIP
- NE (SNS)
- GI Hormones
- Gastrin (intestines)
- CCK, Secretin, GIP (stomatch)
- Somatostatin
- What is the swallowing reflex?
- What are the 3 stages?
- Sequence of events that result in propulsion of food from mouth to stomach
- Oral, pharyngeal, esophageal
What signals modulate the spike of gastric activity associated with eating?
Stretch
Ach
PSNS
The LES is […] contracted
Constantly –> under tonic contraction from vagus input (ach)
Migrating motor complexes
- What are they?
- When do these occur?
- What is their purpose?
- What stimulates their occurrence? What ends their occurrence?
- 5-10 minute bursts of electrical and contractile activity that propogate from stomach to terminal ileum and repeat ever 75-90 mins
- Fasting
- Clean up gut between meals
- Motilin / feeding
What are the effects of Somatostatin on the GI tract?
Decrease gastric motility
What are the effects of Colecystokinin (CCK) on the GI tract?
Decrease gastric motility
Increase intestinal motility
Increase gallbladder contraction
What is chyme?
Mixture of food and stomach secretions that passes into small intestine
The mixing and propulsion functions of the stomach are under the control of the […] NS
Enteric
- What are cells of cajal?
- Where are they located?
- How do the slow waves they generate propogate?
- Why are these structures of clinical importance?
- Pacemaker cells with the ability to generate spontaneous cyclic depolarizations and repolarizations that results in slow wave activity
- Between circular and longitudinal muscle layers of muscularis externa
- Propogate through gap junctions
- See image
When in the fasting state, which hormone controls GI motility?
Motilin
- Increase gastric motility
- Increase intestinal motility
What are the effects of secretin on the GI tract?
Decrease gastric motility
Increase intestinal motility
