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A Physiology > 6.2. Motor functions of the gastrointestinal tract and their control > Flashcards

6.2. Motor functions of the gastrointestinal tract and their control Flashcards

1
Q

I. Slow waves
1. What are the features of SMCs in the GI tract?

A

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

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2
Q

I. Slow waves
2. What are the features of slow waves?

A
  • 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
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3
Q

I. Slow waves
3. Origin of slow waves

A
  • Slow waves originate from interstitial cells of Cajal in the myenteric plexus which have spontaneous, cyclic depolarizations/repolarizations that spread to adjacent cells
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4
Q

I. Slow waves
4. What are the 2 thresholds in SMC slow wave potential?

A

a) Threshold for contraction (w/o having an AP spike)
b) Electrical threshold (AP is generated)

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5
Q

I. Slow waves
5A. How are different types of contractions made?

A

Depending on the degree of depolarization, different types of contractions are made

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6
Q

I. Slow waves
5B. Depending on the degree of depolarization, What are the 2 types of contractions?

A

1) Depolarization does not peak beyond electrical threshold
=> tonic contraction (basal activity)

2) Depolarization reaches above electrical threshold
=> phasic contractions (↑AP
frequency => ↑ contraction force)

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7
Q

I. Slow waves
6. What are the 4 steps in development of SMC AP?

A
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8
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1A. What are the 5 mechanical functions of GI motility?

A
  1. Grinding
  2. Mixing
  3. Storage
  4. Propulsion
  5. Reflex inhibition
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9
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1B. One of mechanical functions is
“Grinding”
=> Explain this function

A

mechanical preparation, ↑surface area helps digestion (↑ contact with enzymes) and movement of food

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10
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1C. One of mechanical functions is
“Mixing”
=> Explain this function

A

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

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11
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1D. One of mechanical functions is
“Storage”
=> Explain this function

A
  • Storage: optimized digestion + absorption
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12
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1E. One of mechanical functions is
“Propulsion”
=> Explain this function

A
  • Propulsion: in predefined portions as appropriate
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13
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY
1F. One of mechanical functions is
“Reflex inhibition”
=> Explain this function

A

Reflex inhibition: inhibits the food/chyme to move in the orad direction (except proximal colon)

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14
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
2. What are the components of GI-upper tract?

A

the oral cavity and oropharynx

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15
Q

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?

A

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)

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16
Q

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

A

Vocalization = not able to speak w/o saliva
=> dry mouth (xerostomia = loss of speech)

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17
Q

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

A
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18
Q

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?

A
  1. Oral phase (voluntary)
  2. Pharyngeal phase (involuntary)
  3. Esophageal phase (involuntary)
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19
Q

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)?

A

When tongue forces bolus back toward the pharynx, which has many somatosensory receptors that initiate involuntary swallowing

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20
Q

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)?

A
  • 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
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21
Q

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)?

A
  • 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
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22
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
4. Describe the structure of esophagus?

A

Composed of UES (upper esophageal sphincter), corpus
(body), LES (lesser esophageal sphincter)

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23
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
5. What is the mechanism of operation of esophagus?

A

Composed of UES (upper esophageal sphincter), corpus
(body), LES (lesser esophageal sphincter)

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24
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of the upper GI-tract
6. What happens if vagal N (PARA-autonomous N) is cut?

A
25
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
7. What are the main functions of the stomach

A

STORAGE + GRINDINIG/MIXING

26
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
8. What is the main function of proximal stomach?

A

storage function

27
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
9. What is the mechanism of proximal stomach?

A
  • Membrane potential around this region is stable, therefore, no phasic contraction occurs
  • Receptive relaxation occurs before receiving the food, and adaptive relaxation occurs when it is being filled with food => relaxation due to NO
28
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
10. What are the main functions of distal stomach?

A

grinding, mixing and propulsive functions

29
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
11A. What is the mechanism of distal stomach?

A
30
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
11B. What is the role of Interstitial cells of Cajal in distal stomach?

A

Interstitial cells of Cajal (pacemaker cells) initiate slow waves

31
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
11C. What cause the peristaltic constrictor waves in distal stomach?

A
  • Slow waves eventually become stronger, causing peristaltic constrictor waves (mixing waves)
32
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility
11D. How can constrictor rings mix the distal stomach?

A
33
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12A. What are 2 types of regulation of stomach emptying?

A
  1. Gastric factors that promote emptying (open pylorus)
  2. Duodenal factors that inhibit gastric emptying
34
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12B. How do gastric factors promote emptying?

A

Gastric factors that promote emptying (open pylorus):
- Increased food volume stretches stomach wall => stretch activates myenteric reflexes
- Gastrin released from G-cells of antral mucosa => stimulates motor functions in the body of the stomach

35
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12C1. What are the 2 main effects of Duodenal factors?

A

Duodenal factors that inhibit gastric emptying
1. Effects of enterogastric nervous reflexes
2. Hormonal feedback

36
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12C2. How can Duodenal factors lead to Effects of enterogastric nervous reflexes?

A
  • When food enters the duodenum, nervous reflexes are initiated
  • These reflexes pass back to stomach to slow down (stop gastric emptying if there is too much chyme in the duodenum)
37
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12C3. How can Duodenal factors lead to Hormonal feedback?

A
  • Fat stimulates inhibitory hormone release
  • CCK blocks increased stomach motility
  • Secretin and GIP decreases GI motility
38
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Gastric motility - Regulation of stomach emptying
12D. Make the schematic diagram of Regulation of stomach emptying

A
39
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines
13. What are the main functions of small intestine?

A
40
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14A. What are the 2 main movements in the small intestine?

A
  1. Segmentation
  2. Peristalsis
41
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14B. The first movement of small intestine is SEGMENTATION
=> Describe

A
42
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14C1. The second movement of small intestine is PERISTALSIS
=> Describe

A
43
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14C2. The second movement of small intestine is PERISTALSIS
=> What is Propulsive movement?

A

Propulsive movements (peristaltic waves 1cm/sec) which propel chyme through the intestine

44
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14C3. The second movement of small intestine is PERISTALSIS
=> How does Peristaltic contractions begin?

A
  • Peristaltic contractions begin by contraction behind the bolus, while muscle in front relaxes
    => this propels the chyme forward
45
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - MOVEMENTS IN THE SMALL INTESTINE

14C4. The second movement of small intestine is PERISTALSIS
=> How is Peristalsis regulated?

A

Regulated by gastroenteric reflexes (myenteric plexus) and hormones:
- ↑ gastrin, CCK, insulin, serotonin
- ↓ secretin, glucagon

46
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - Law of intestine
15. State the law of intestine?

A

Peristalsis occurs when the enterochromaffin cells in the mucosa detect the bolus and release serotonin (5-hydroxytryptamine) which activates the peristaltic reflex.

47
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - Law of intestine
16. What happen in orad side?

A

Orad side: contraction
- Excitatory transmitters are released (ACh, substance P)
- Circular muscles contract, while longitudinal muscles relaxes

48
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of small intestines - Law of intestine
17. What happen in Caudad side?

A

Caudad side: receptive relaxation
- Inhibitory transmitters are released (NO, ATP, VIP)
- Circular muscles relax, while longitudinal muscles contract
=> Drugs for mood disorder usually effect serotonin, so one of the side effects can be constipation

49
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of large intestines
18. What are the main functions of large intestine?

A
50
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of large intestines
19. What are the functions of the ileocecal valve and sphincter?

A
  • Valve is protruded into the lumen of the cecum, preventing backflow of content
  • Gastroileal reflex and gastrin induce opening of the sphincter
  • Distension/irritation of the cecum closes the sphincter
51
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of large intestines
20. What are the features of Motility of large intestines?

A
52
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Motility of large intestines
21. Describe Defecation reflex (stretch)

A
53
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
1. Explain Vomiting

A
54
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
2. What is the neural mechanism of vomiting?

A
  • Vagus N and SYM afferent fibers transmit signal to vomiting
    center in the brainstem
55
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
3. What happen in the early stages of vomiting?

A
  • In the early stages of vomiting, the patient starts to feel nauseous and autonomic symptoms are seen (nausea, ↑HR, pale skin, sweating)
  • Such events are followed by anti-peristalsis (backward peristalsis up the GI-tract)
56
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
4. What does vomiting result from?

A

Vomiting results from a squeezing action of the abdominal muscles (inhalation with mouth + nostrils closed) associated with simultaneous gastric contraction and opening of the esophageal sphincters

57
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
5. What is the purpose of vomiting?

A
  • A way by which the upper GI-tracts get rid of its content when they become irritated, overdistended
58
Q

II. MECHANICAL FUNCTIONS OF GI MOTILITY - Special motility patterns
6. Make a schematic diagram of diarrhea

A

A Physiology (88 decks)

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