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Gastrointestinal System > Physiology of Deglutition > Flashcards

Physiology of Deglutition Flashcards

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1
Q

What is gastrointestinal motility?

A

The movement of food and liquids through the GI tract via coordinated muscle contractions

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1
Q

Why can certain organs like the intestine and the heart produce action potential even outside of the body?

A

They have their own pacemaker

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2
Q

What is the importance of GI motility?

A

Digestion
Nutrient Absorption
Waste elimination

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3
Q

What are the 5 different types of movement?

A

Peristalsis
Segmentation
Tonic Contractions
Migrating Motor Complex
Mass Movements

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4
Q

Which organ is only supported by peristalsis?

A

Esophagus

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5
Q

What happens during segmentation?

A

Mixing of the food, can commonly be seen in the stomach

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6
Q

What are tonic contractions?

A

Sustained contractions, usually seen with sphincters

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7
Q

When does Migrating Movement Complex occur?

A

During fasting, its advantage is that it pushes out the residual of the digestive system

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8
Q

What is mass movement?

A

Happens in the large intestine, movement of large amounts of substances, usually feaces.

Happens 2 to 3 times a day

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9
Q

What is the enteric nervous system made up of?

A

Myenteric: between inner circular and outer longitudinal: function is contraction

Submucous: found in the submucosa, close to glands function is secretion

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10
Q

Where are voluntary skeletal muscles found?

A

Mouth
Pharynx
External anal sphincter

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11
Q

What is the difference between the external anal sphincter and the internal?

A

Internal anal sphincter is smooth muscle

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12
Q

Which kind of muscle is responsible for weak and graded contractions?

A

Longitudinal Muscle

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13
Q

What happens to the longitudinal muscle when contracting?

A

The radius increases

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14
Q

What happens to the circular muscle when contracting?

A

The radius decreases

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15
Q

What is the process of peristalsis?

A

Contraction of both the circular (before food) and the longitudinal (after food) muscles

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16
Q

Longitudinal Muscles:

A
  1. Thin Muscle Coat
  2. Contractions shorten intestine length, radius increases
  3. Activated by excitatory motor neurons
  4. Few gap junctions
  5. Extracellular Ca2+ influx is important in excitation-contraction coupling
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17
Q

Circular Muscles:

A
  1. Thick Muscle Coat
  2. Contraction increases length of intestines, radius decreases
  3. Activated by myogenic pacemakers and excitatory motor neurons
  4. Many gap junctions
  5. Intracellular Ca2+ release is important fro excitation-contraction coupling
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18
Q

What is an example of myogenic contraction?

A

Interstitial Cells of Cajal: Origin of Phasic and Tonic Contraction

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19
Q

What are examples of neurogenic contraction?

A

Intrinsic (Enteric NS)
Extrinsic (SNS & PNS)
Endocrine
Pancrine

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20
Q

What is the difference between pharmaco-mechanical and electro-mechanical coupling

A

Electro-mechanical coupling requires a change in action potential in order for Ca2+ to open

Pharmaco-mechanical coupling requires a signal, and the sarcoplasmic reticulum then releases the Ca2+

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21
Q

What are examples of signals that activate pharmacy-mechanical coupling?

A

Neurocrine
Paracrine
Endocrine

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22
Q

What do interstitial cells of Cajal serve as in GI muscles?

A

Pacemakers

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23
Q

What is the process of contraction for GI muscles?

A
  1. Spontaneous genesis of slow waves (Cajal cells)
  2. Slow waves conduction and transmission to smooth muscle
  3. Depolarisation, opening of calcium channels, A.P genesis
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24
What happens in the case that there is ICC loss?
Human motility disorders
25
What is Hirschprung's disease?
Congenital condition that prevents newborns and young children from passing stool.
26
What do slow wave potentials cause?
Spontaneous generation of action potentials, do not result in muscle contraction
26
What causes smooth muscle contraction of the gut?
Waves of action potentials moving along via gap junctions, muscle tension + slow wave simultaneously
27
Why are the slow waves in the stomach so slow?
Because the main function of the stomach is storage and mixing.
28
Where are the fastest slow waves found?
In the small intestine
29
What is the frequency of slow waves in different segments?
Stomach = 3/min Duodenum = 11 to 12/min Distal Ileum & colon = 6 to 7/min
30
What is peristalsis?
Wave-like contractions that move the food through the esophagus, stomach and intestines
31
What is the mechanism of peristalsis?
Coordinated contractions and relaxation of circular and longitudinal muscles
32
What is the function of peristalsis?
Propels the bolus forward, ensuring it moves along the digestive path
33
What is responsible for the contraction of propulsive segment during peristalsis?
Acetylcholine
34
What is responsible for the relaxation in the receiving segment during peristalsis?
Nitrogen Oxide
35
What is segmentation used for?
Mixing of food with digestive enzymes
36
What is the mechanism of segmentation?
Involves alternating contractions of intestinal segments without net movement forward
37
What is the function of segmentation?
Mixing of chyme with digestive juice, facilitating nutrient absorption
38
What are tonic contractions?
Sustained contraction, that occur in certain GI sphincters
39
In which GI sphincters can you see tonic contractions?
Lower oesophageal, Pyloric, Ileocecal
40
What is the mechanism of the tonic contractions?
Maintains a barrier function, controlling the passage of food between different section of the GI tract.
41
What is the function of tonic contractions?
Prevent backflow
42
What is mass movement?
Strong, wave-like contraction in the large intestine
43
What is the function of mass movement?
Moves fecal matter towards rectum
44
What is the function of mass movement?
Facilitates defecation and ensures efficient waste elimination
45
When does Migrating Motor Complex occur?
During fasting
46
What is migrating motor complex?
Cyclic, recurring motility occurring during fasting
47
What is the mechanism of MMC?
Sweeps residual undigested material through digestive tract
48
What is the function of MMC?
Prevents bacterial overgrowth and prepares GI tract for next meal
49
How many stages of MMC are there?
4
50
What happens in stage 1 of MMC?
Basal phase, no contractions
51
What happens in stage 2 of MMC?
Pre-burst phase, irregular contractions
52
What happens in stage 3 of MMC?
The good food material migrates distally due to regular contraction
53
What happens during stage 4 of MMC?
Transition period between phases 3 and 1
54
What are the neural mechanisms that control the movements of material along the digestive tract?
Parasympathetic --> Acetylcholine and local reflexes Sympathetic --> Norepinephrine (Inhibitory)
55
What is the function of acetylcholine?
Increases gut motility and absorption
56
What hormonal mechanisms control the movements of material along the digestive tract?
Secretin --> Secretion & Relaxation Gatsrin --> Contraction Cholecystokinin --> Contraction
57
What local mechanisms control the movements of material along the digestive tract?
Changes in the pH, chemical stimulus, and stretching
58
Where does the enteric nervous system begin?
Beginning in the esophagus and extends all the way to the anus
59
What is the function of the myenteric nervous system?
GI motility control
60
What are the stimulatory influences of the myenteric NS?
Increase in tonic contraction Increase in contraction frequency
61
What are the inhibitory influences of the myenteric NS?
Decreased sphincter tone
62
What is the function of submucosal NS?
Local Control: 1. Secretion 2. Absorption 3. Contraction of muscularis mucosa
63
What are the functions of saliva?
Break down Mixing Hydration
64
What is the daily volume of saliva?
1 to 1.5 liters
65
What signals for salivation?
Food stimulates receptors that signal salivary nuclei in the medulla & pons
66
What is parasympathetic salivation like?
Thin saliva, rich in enzymes
67
What is the sympathetic satiation like?
Thicken saliva, more mucous
68
What is the significance of chewing?
Breaks food into little pieces to eb easily swallowed Expose food to salivary enzymes Help digestion of all types of food, especially cellulose
69
What are the three stages of swallowing?
Voluntary swallowing process Pharyngeal Involuntary Process Oesophageal Involuntary Process
70
What happens during Voluntary Swallowing Process?
The tongue moves the bolus of food into the back of the mouth
71
What happens during the Pharyngeal Involuntary Process?
The food enters the upper throat area, Soft palate elevates Epiglottis closes off the trachea Force food downward to esophagus Breathing reinitiated
72
How long does the Pharyngeal Involuntary Process take?
About 1 second
73
What happens during the Oesophageal Involuntary Process?
Food bolus moves dow the esophagus through peristalsis
74
How many sphincters guard the esophagus?
2 1. Upper Oesophageal Sphincter 2. Lower Oesophageal Sphincter
75
What is the function of the Upper Oesophageal Sphincter?
Prevents air from entering the GIT
76
What is the function of the Lower Oesophageal Sphincter?
Prevents gastric contents from re-entering the esophagus
77
What is the location of the LES?
Between the oesophageal body and the gastric fungus
78
Why is there high pressure in LES?
Limits reflux of gastric contents into oesophageal body, sphincter remains closed
79
What factors control LES pressure?
Myogenic properties (circular SM of sphincter) Inhibitory neural influence (Nitric oxide) Excitatory neural influence (Acetylcholine)
80
What is achalasia?
An oesophageal motility disorder of the lower oesophageal body and LES, preventing relaxation
81
What problems does achalasia cause?
Degeneration of oesophageal muscles, and nerves controlling the muscles
82
What is a hiatus hernia?
Part of the stomach extends through an opening of the diaphragm into the chest
83
What is GERD?
Long term condition in which stomach contents rise up into the oesophagus
84
What is usually associated with hiatus hernia?
GERD
85
What is the gastric motility like?
Very slow movement
86
What are the proximal functions of the stomach?
Accommodation and storage
87
What is the motor pattern of the proximal part of the stomach?
Tonic
88
What is the detail function of the stomach?
Grinding of food, emptying duodenum
89
What is the motor pattern like in the distal part of the stomach?
Phasic
90
What is the process of gastric motility?
1. Relaxation of funds (vasovagal reflex) 2. Contraction of body and antrum 3. Pylorus contracts 4. Mixing by retropulsion
91
What are the motility types that exist in the small intestine?
Segmentation and peristalsis
92
What are the 3 functions of the small intestine motility?
Mixing contents with enzymes --> helps digestion Maximising exposure of the contents to membranes of intestinal cells --> helps absorption and digestion Propulsion of contents into large intestine
93
Motility of the large intestine or colon: Mass Movement
Propels the contents of one segment of the large intestine into the next downstream segment
94
Motility of the large intestine or colon: Segmentation
Causes contents to be continuously mixed
95
Motility of the large intestine or colon: Defecation
Involuntary reflexes and voluntary reflexes --> evacuation of colonic content through anal canal

Gastrointestinal System (29 decks)

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