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Gastrointestinal System > Physiology of Deglutition > Flashcards

Physiology of Deglutition Flashcards

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
Q

What happens in the case that there is ICC loss?

A

Human motility disorders

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25
Q

What is Hirschprung’s disease?

A

Congenital condition that prevents newborns and young children from passing stool.

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26
Q

What do slow wave potentials cause?

A

Spontaneous generation of action potentials, do not result in muscle contraction

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26
Q

What causes smooth muscle contraction of the gut?

A

Waves of action potentials moving along via gap junctions, muscle tension + slow wave simultaneously

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27
Q

Why are the slow waves in the stomach so slow?

A

Because the main function of the stomach is storage and mixing.

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28
Q

Where are the fastest slow waves found?

A

In the small intestine

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29
Q

What is the frequency of slow waves in different segments?

A

Stomach = 3/min
Duodenum = 11 to 12/min
Distal Ileum & colon = 6 to 7/min

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30
Q

What is peristalsis?

A

Wave-like contractions that move the food through the esophagus, stomach and intestines

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31
Q

What is the mechanism of peristalsis?

A

Coordinated contractions and relaxation of circular and longitudinal muscles

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32
Q

What is the function of peristalsis?

A

Propels the bolus forward, ensuring it moves along the digestive path

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33
Q

What is responsible for the contraction of propulsive segment during peristalsis?

A

Acetylcholine

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34
Q

What is responsible for the relaxation in the receiving segment during peristalsis?

A

Nitrogen Oxide

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35
Q

What is segmentation used for?

A

Mixing of food with digestive enzymes

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36
Q

What is the mechanism of segmentation?

A

Involves alternating contractions of intestinal segments without net movement forward

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37
Q

What is the function of segmentation?

A

Mixing of chyme with digestive juice, facilitating nutrient absorption

38
Q

What are tonic contractions?

A

Sustained contraction, that occur in certain GI sphincters

39
Q

In which GI sphincters can you see tonic contractions?

A

Lower oesophageal, Pyloric, Ileocecal

40
Q

What is the mechanism of the tonic contractions?

A

Maintains a barrier function, controlling the passage of food between different section of the GI tract.

41
Q

What is the function of tonic contractions?

A

Prevent backflow

42
Q

What is mass movement?

A

Strong, wave-like contraction in the large intestine

43
Q

What is the function of mass movement?

A

Moves fecal matter towards rectum

44
Q

What is the function of mass movement?

A

Facilitates defecation and ensures efficient waste elimination

45
Q

When does Migrating Motor Complex occur?

A

During fasting

46
Q

What is migrating motor complex?

A

Cyclic, recurring motility occurring during fasting

47
Q

What is the mechanism of MMC?

A

Sweeps residual undigested material through digestive tract

48
Q

What is the function of MMC?

A

Prevents bacterial overgrowth and prepares GI tract for next meal

49
Q

How many stages of MMC are there?

A

4

50
Q

What happens in stage 1 of MMC?

A

Basal phase, no contractions

51
Q

What happens in stage 2 of MMC?

A

Pre-burst phase, irregular contractions

52
Q

What happens in stage 3 of MMC?

A

The good food material migrates distally due to regular contraction

53
Q

What happens during stage 4 of MMC?

A

Transition period between phases 3 and 1

54
Q

What are the neural mechanisms that control the movements of material along the digestive tract?

A

Parasympathetic –> Acetylcholine and local reflexes
Sympathetic –> Norepinephrine (Inhibitory)

55
Q

What is the function of acetylcholine?

A

Increases gut motility and absorption

56
Q

What hormonal mechanisms control the movements of material along the digestive tract?

A

Secretin –> Secretion & Relaxation
Gatsrin –> Contraction
Cholecystokinin –> Contraction

57
Q

What local mechanisms control the movements of material along the digestive tract?

A

Changes in the pH, chemical stimulus, and stretching

58
Q

Where does the enteric nervous system begin?

A

Beginning in the esophagus and extends all the way to the anus

59
Q

What is the function of the myenteric nervous system?

A

GI motility control

60
Q

What are the stimulatory influences of the myenteric NS?

A

Increase in tonic contraction
Increase in contraction frequency

61
Q

What are the inhibitory influences of the myenteric NS?

A

Decreased sphincter tone

62
Q

What is the function of submucosal NS?

A

Local Control:
1. Secretion
2. Absorption
3. Contraction of muscularis mucosa

63
Q

What are the functions of saliva?

A

Break down
Mixing
Hydration

64
Q

What is the daily volume of saliva?

A

1 to 1.5 liters

65
Q

What signals for salivation?

A

Food stimulates receptors that signal salivary nuclei in the medulla & pons

66
Q

What is parasympathetic salivation like?

A

Thin saliva, rich in enzymes

67
Q

What is the sympathetic satiation like?

A

Thicken saliva, more mucous

68
Q

What is the significance of chewing?

A

Breaks food into little pieces to eb easily swallowed
Expose food to salivary enzymes
Help digestion of all types of food, especially cellulose

69
Q

What are the three stages of swallowing?

A

Voluntary swallowing process
Pharyngeal Involuntary Process
Oesophageal Involuntary Process

70
Q

What happens during Voluntary Swallowing Process?

A

The tongue moves the bolus of food into the back of the mouth

71
Q

What happens during the Pharyngeal Involuntary Process?

A

The food enters the upper throat area,
Soft palate elevates
Epiglottis closes off the trachea
Force food downward to esophagus
Breathing reinitiated

72
Q

How long does the Pharyngeal Involuntary Process take?

A

About 1 second

73
Q

What happens during the Oesophageal Involuntary Process?

A

Food bolus moves dow the esophagus through peristalsis

74
Q

How many sphincters guard the esophagus?

A

2
1. Upper Oesophageal Sphincter
2. Lower Oesophageal Sphincter

75
Q

What is the function of the Upper Oesophageal Sphincter?

A

Prevents air from entering the GIT

76
Q

What is the function of the Lower Oesophageal Sphincter?

A

Prevents gastric contents from re-entering the esophagus

77
Q

What is the location of the LES?

A

Between the oesophageal body and the gastric fungus

78
Q

Why is there high pressure in LES?

A

Limits reflux of gastric contents into oesophageal body, sphincter remains closed

79
Q

What factors control LES pressure?

A

Myogenic properties (circular SM of sphincter)
Inhibitory neural influence (Nitric oxide)
Excitatory neural influence (Acetylcholine)

80
Q

What is achalasia?

A

An oesophageal motility disorder of the lower oesophageal body and LES, preventing relaxation

81
Q

What problems does achalasia cause?

A

Degeneration of oesophageal muscles, and nerves controlling the muscles

82
Q

What is a hiatus hernia?

A

Part of the stomach extends through an opening of the diaphragm into the chest

83
Q

What is GERD?

A

Long term condition in which stomach contents rise up into the oesophagus

84
Q

What is usually associated with hiatus hernia?

A

GERD

85
Q

What is the gastric motility like?

A

Very slow movement

86
Q

What are the proximal functions of the stomach?

A

Accommodation and storage

87
Q

What is the motor pattern of the proximal part of the stomach?

A

Tonic

88
Q

What is the detail function of the stomach?

A

Grinding of food, emptying duodenum

89
Q

What is the motor pattern like in the distal part of the stomach?

A

Phasic

90
Q

What is the process of gastric motility?

A
  1. Relaxation of funds (vasovagal reflex)
  2. Contraction of body and antrum
  3. Pylorus contracts
  4. Mixing by retropulsion
91
Q

What are the motility types that exist in the small intestine?

A

Segmentation and peristalsis

92
Q

What are the 3 functions of the small intestine motility?

A

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
Q

Motility of the large intestine or colon: Mass Movement

A

Propels the contents of one segment of the large intestine into the next downstream segment

94
Q

Motility of the large intestine or colon: Segmentation

A

Causes contents to be continuously mixed

95
Q

Motility of the large intestine or colon: Defecation

A

Involuntary reflexes and voluntary reflexes –> evacuation of colonic content through anal canal

Gastrointestinal System (29 decks)

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