6.2. Motor functions of the gastrointestinal tract and their control Flashcards
(58 cards)
I. Slow waves
1. What are the features of SMCs in the GI tract?
The SMCs in the GI-tract are single-unit SM that are electrically coupled together via gap junctions, that allow a spread of APs for coordination
I. Slow waves
2. What are the features of slow waves?
- The SMC of the GI-tract experience a characteristic fluctuation of depolarization and repolarization, known as slow waves
- Slow waves are not APs, but described as membrane potential that cyclically gets less negative and then more negative
- They can be considered the pacemaker cells of the GI smooth muscle and they drive the frequency in different areas of the GI
I. Slow waves
3. Origin of slow waves
- Slow waves originate from interstitial cells of Cajal in the myenteric plexus which have spontaneous, cyclic depolarizations/repolarizations that spread to adjacent cells
I. Slow waves
4. What are the 2 thresholds in SMC slow wave potential?
a) Threshold for contraction (w/o having an AP spike)
b) Electrical threshold (AP is generated)
I. Slow waves
5A. How are different types of contractions made?
Depending on the degree of depolarization, different types of contractions are made
I. Slow waves
5B. Depending on the degree of depolarization, What are the 2 types of contractions?
1) Depolarization does not peak beyond electrical threshold
=> tonic contraction (basal activity)
2) Depolarization reaches above electrical threshold
=> phasic contractions (↑AP
frequency => ↑ contraction force)
I. Slow waves
6. What are the 4 steps in development of SMC AP?
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1A. What are the 5 mechanical functions of GI motility?
- Grinding
- Mixing
- Storage
- Propulsion
- Reflex inhibition
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1B. One of mechanical functions is
“Grinding”
=> Explain this function
mechanical preparation, ↑surface area helps digestion (↑ contact with enzymes) and movement of food
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1C. One of mechanical functions is
“Mixing”
=> Explain this function
Mixing: aids in digestion + ‘’renewal’’ of surface, since chyme/food near the walls of intestine is absorbed
=> new material can get close to wall and get absorbed
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1D. One of mechanical functions is
“Storage”
=> Explain this function
- Storage: optimized digestion + absorption
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1E. One of mechanical functions is
“Propulsion”
=> Explain this function
- Propulsion: in predefined portions as appropriate
II. MECHANICAL FUNCTIONS OF GI MOTILITY
1F. One of mechanical functions is
“Reflex inhibition”
=> Explain this function
Reflex inhibition: inhibits the food/chyme to move in the orad direction (except proximal colon)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
2. What are the components of GI-upper tract?
the oral cavity and oropharynx
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3A. What are the 7 main functions of the oral cavity and oropharynx?
1) Immunological sampling of food for pathogens (Waldeyer’s lymphatic ring)
2) Lubricationoffood
3) Tasting of food (taste buds)
4) Teeth protection
5) Vocalization = not able to speak w/o saliva => dry mouth (xerostomia = loss of speech)
6) Mastication
7) Swallowing (3 phases)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3B. One of the main functions of the oral cavity and oropharynx is
“Vocalization”
=> Explain
Vocalization = not able to speak w/o saliva
=> dry mouth (xerostomia = loss of speech)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3C. One of the main functions of the oral cavity and oropharynx is
“Mastication”
=> Explain
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3D1. One of the main functions of the oral cavity and oropharynx is
“Swallowing”
=> What are the 3 phases of swallowing?
- Oral phase (voluntary)
- Pharyngeal phase (involuntary)
- Esophageal phase (involuntary)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3D2. One of the main functions of the oral cavity and oropharynx is
“Swallowing”
=> What happen in phase 1 - Oral phase (voluntary)?
When tongue forces bolus back toward the pharynx, which has many somatosensory receptors that initiate involuntary swallowing
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3D3. One of the main functions of the oral cavity and oropharynx is
“Swallowing”
=> What happen in phase 2 - Pharyngeal phase (involuntary)?
- Soft palate pulled up so that food cannot go into the nasal cavity.
- UES relaxes, allowing food to move to esophagus and a peristaltic wave of contraction propels food through the open sphincter
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
3D4. One of the main functions of the oral cavity and oropharynx is
“Swallowing”
=> What happen in phase 3 - Esophageal phase (involuntary)?
- Food is propelled through esophagus by a primary peristaltic wave.
- If that wave is not enough, a secondary wave is initiated due to the distension of the esophagus
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
4. Describe the structure of esophagus?
Composed of UES (upper esophageal sphincter), corpus
(body), LES (lesser esophageal sphincter)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
5. What is the mechanism of operation of esophagus?
Composed of UES (upper esophageal sphincter), corpus
(body), LES (lesser esophageal sphincter)
II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
6. What happens if vagal N (PARA-autonomous N) is cut?
