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GI Final > 2 Motility Of The GI Tract > Flashcards

2 Motility Of The GI Tract Flashcards

1
Q

Digestive process

A

GI motility

Ingestion

Propulsion

Mechanical digestion

Chemical digestion

Absorption

Defecation

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2
Q

Lines the lumen of the GI tract

A

Mucosa

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3
Q

Fx of submucosa

A

Relays info to and away from the mucosa

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4
Q

Fx of muscularis external

A

Motility of the GI tract

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5
Q

What do parietal cells secrete?

A

HCl

Intrinsic factor

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6
Q

Chief cells secrete ______.

A

Pepsinogen

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7
Q

Gastrin is secreted by ________.

A

Enteroendocrine cells

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8
Q

Specialized group of cells in the intestinal wall

Involved in transmission of info from enteric neurons to smooth m.

A

Interstitial cells of Cajal (ICCs)

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9
Q

What are the pacemaker cells in the intestinal wall?

What do they generate?

A

ICCs

Generate the basic electrical rhythm (slow-wave activity) of GI smooth m.

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10
Q

What changes do the ICC cells undergo?

Why?

A

Cyclic changes in the membrane potential

Due to unique ion channels that periodically open and produce inward (pacemaker) currents that generate the slow wave activity

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11
Q

Two basic electrical waves in the smooth m of the GI tract

A

Slow waves

Spike potentials

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12
Q

Slow waves make it possible for contractions to be stimulated more _________ by raising the RMP ________ to threshold and less _________.

A

Easily

Closer

Negative

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13
Q

Where is the rate of slow waves lowest?

Highest?

A

Stomach (3/min)

Duodenum (12/min)

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14
Q

T/F: slow waves are true action potentials.

A

FALSE

Not AP, instead they are slow changes in the RMP

Not sufficient to completely depolarize the membrane and stimulate contractions

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15
Q

Spike waves are true_____.

A

Action potentials

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16
Q

What stimulates spike waves (depolarization)?

A

Stretching of the muscle

ACh

Parasympathetics

Several specific GI hormones

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17
Q

When do spike waves occur?

A

Automatically when the RMP of the GI smooth m is more positive than about -40 millivolts

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18
Q

The spike potentials last ____ to ____ times as long in GI muscle as the AP in large nerve fibers.

A

10 to 40 times longer

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19
Q

Hyperpolarization is stimulated by _____.

A

NE or epinephrine on the fiber membrane

Sympathetic nerves that secrete NE at their endings

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20
Q

What is the RMP in the gut?

A

-56 millivolts

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21
Q

Depolarization in the GI tract is stimulated by _____.

How is this released?
What receptors does it act through?
What does it do?

A

ACh

Released by postganglionic axons

Acts through muscarinic receptors

Increases the amplitude and duration of the slow waves

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22
Q

T/F: slow waves cause Ca to enter the smooth m fiber.

A

FALSE

Slow waves cause Na to enter the smooth m

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23
Q

What ion causes the contraction of smooth m in the GI tract?

A

Calcium

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24
Q

When are spike potentials generated?

Why?

A

At the peak of slow waves

To allow enough Ca ions to enter the fibers and cause a contraction

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25
Q

Name the two effects of Calcium

A

The rising phase of an AP

Triggers a Contractile response

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26
Q

What happens at threshold?

A

Voltage-gated Ca channels are activated

Ca influx into smooth m

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27
Q

What determines the intensity/strength of the contractions?

A

The number of AP that occur when the slow-wave potential reaches threshold

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28
Q

Describe phasic contractions and their location

A

Cyclic contractions that permit mixing and propelling

Pylorus, distal 2/3 of corpus, antrum (distal stomach)

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29
Q

Describe tonic contractions and their location

A

Continuous contractions that relax under neural stimulation

Cardia, fundus, first 1/3 of corpus (proximal stomach) and sphincters that control the flow of GI contents from one region of the GI tract to another

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30
Q

Where and what is the ENS?

Function?

A

Walls of the intestines

Aggregates of neurons and glia (enteric ganglia) interconnected to form plexuses (myenteric and submucosal)

Controls the activities of the GI tract

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31
Q

What two hormones are produced by gut bacteria?

A

Dopamine and serotonin

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32
Q

How are the intrinsic nerves of the GI system arranged?

A

Two main plexuses: myenteric and submucosal

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33
Q

Where is the myenteric plexus and what does it contain?

A

Between the circular and longitudinal muscle layers of the GI tract

Inhibitory and excitatory nerves that control the function to the muscle layers and controlling movement

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34
Q

Location and containts of the submucosal plexus

A

Submucosa

Secretomotor neurons that promote vasodilation, regulate the secretion of fluid and electrolytes, and contractions of the muscularis mucosa

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35
Q

Functions and contents of saliva

A

Hydrolysis of starch

Buffers neutralize acids

Antibacterial agents kill some bacteria ingested with food

Water, electrolytes, mucin, IgA, lysozyme, salivary amylase

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36
Q

Chewing, voluntary and involuntary grinding, ripping, and tearing of food

A

Mastication

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37
Q

Moving bonus towards the pharynx

A

Deglutition

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38
Q

Functions of salivary amylase

A

Starts the breakdown of carbs

Lubricates and cleanses oral cavity

Dissolves chemicals

Suppresses bacterial growth

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39
Q

Muscles of chewing and chewing process are innervated by what nerves?

A

Motor branch of the 5th CN

Chewing process regulated by brain stem nuclei

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40
Q

Three functions of chewing

A

Reduces size of ingested particles to help swallowing

Mixes food with saliva and exposes it to enzymes and lubrication

Increases the surface area of ingested material therefore increases digestion rate

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41
Q

Three phases of swallowing

A

Voluntary oral phase

Involuntary pharyngeal phase

Esophageal phase

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42
Q

Sensory signals use what nerves during swallowing?

A

Glossopharyngeal

Vagal

Trigeminal

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43
Q

Motor impulses pass through _____ to control a _____ process that directs food into the ______ and away from the airway.

A

CN

Involuntary

Esophagus

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44
Q

Describe the oral phase of swallowing

A

Voluntary

Chewing completed

Swallowing begins by the tongue moving up and back against the palate

Tongue pushes the bolts to the back of the oral cavity into the oropharynx

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45
Q

When does swallowing change from voluntary to involuntary?

A

After the oral phase

Beginning of the pharyngeal phase

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46
Q

Describe the pharyngeal phase of swallowing

A

Involuntary

Soft palate pulled up and pharyngeal folds move inward to make a passage for food

Larynx moves forward and up against epiglottis to block trachea and open UES

UES relaxes to receive bonus

Constrictor muscles of pharynx contract to force bonus through UES

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47
Q

The pharyngeal phase of swallowing stimulates ______ receptors in the pharynx

A

Touch

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48
Q

What forces the bolus through the UES?

A

Middle pharyngeal constrictor m.

Inferior pharyngeal constrictor m.

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49
Q

What action prevents the bolus from entering the trachea during swallowing?

A

Larynx moves forward and upward against the epiglottis

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50
Q

When does the esophageal phase of swallowing begin?

A

When the bolus passes through the UES

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51
Q

The bolus passing through the UES initiates ________.

A

Peristaltic wave along the esophagus (primary peristalsis)

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52
Q

Primary peristalsis reaches the LES, it relaxes and allows the bolus into the stomach. Distention of the stomach my the bolus initiates _______.

A

A second wave of contraction (secondary peristalsis)

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53
Q

T/F: if the vagus N was cut (vagotomy), secondary peristaltic waves would still exist

A

TRUE

Primary peristaltic waves would be affected

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54
Q

What is primary peristalsis and when does it occur?

How long does it last?

A

Continuation of the peristaltic wave that begins in the pharynx and spreads to the esophagus

Pharyngeal phase

8-10 seconds

55
Q

Primary peristalsis is regulated by______.

A

Medulla

56
Q

When and why does the secondary peristaltic wave occur?

A

When the food crosses the LES and until all the food is emptied into the stomach

If the primary peristaltic wave doesn’t move all the food into the stomach

57
Q

Regulation of the secondary peristaltic wave

A

Medulla and myenteric NS

58
Q

Resting pressures are ______ at the UES and LES.

Why?

A

High

Because both sphincters have continuous resting smooth m tone

59
Q

Receptive relaxation is a ______ reflex that causes what?

A

Vagovagal reflex

Causes the muscles of the proximal stomach to relax

Opens the LES allowing the bolus to enter the stomach

Allows the stomach to expand without increasing intragastric pressure

60
Q

Esophageal pressure drops to match the low pressure in the proximal stomach during ______.

A

Receptive relaxation

61
Q

What mediates the vagovagal reflex?

A

Mediated by myenteric neurons releasing vasoactive intestinal peptide and nitric oxide

62
Q

Components of the UES

A

Instinct striated circular muscle

63
Q

Components of the LES

A

Smooth muscle

64
Q

UES and LES are _______ between swallows.

Why?

A

Closed

Prevents air and gastric acid back flowing into the esophagus

65
Q

LES controls and prevents what?

A

Controls the passage of bolus into the stomach

Prevents the reflux of gastric contents into the esophagus so can’t damage mucosa

66
Q

What controls the contraction of the LES between swallows?

A

Vagal cholinergic mechanisms

67
Q

What allows the LES to relax during swallowing?

A

Vagal inhibitory fibers

68
Q

What neurotransmitters cause the Vagal inhibitory fibers to allow the LES to relax?

A

Nitric oxide and vasoactive intestinal peptide (VIP)

69
Q

Factors that increase LES tone (5)

A

ACh

Increase intraabdominal and intragastric pressure

Gastrin

Motilin

Protein-rich food

70
Q

Factors that decrease LES tone (9)

A 
Nitric oxide
VIP
CCK
GIP
Beta adrenergic receptor agonists
Secretin
Progesterone
Prostaglandin E
Fat-rich food
71
Q

Inappropriate relaxation of the LES

A

GERD

72
Q

GERD can be caused by_______. (5)

A

Loss of LES tone

Increased frequency of transient relaxations

Loss of secondary peristalsis after transient relaxation

Increased stomach volume or pressure

Increased production of acid

73
Q

LES does not open fully with the peristaltic wave, food becomes retained at the level of the LES

A

Achalasia

74
Q

Achalasia is caused from a degeneration of ________.

A

Neurons in the myenteric plexuses

Specifically a loss of inhibitory neurons in the wall of the esophagus

75
Q

Symptoms and treatment of achalasia

A

Regurgitation of food, CP, difficulty swallowing, cough, weight loss

Drugs to reduce the tone of the LES

76
Q

Pts with achalasia lack what enzyme and neurotransmitters?

A

Nitric oxide synthase

Other inhibitory neurotransmitters VIP and nitric oxide

77
Q

Loss of inhibitory neurons in achalasia prevents _______.

A

Relaxation of the LES after swallowing

propagation of the esophageal peristaltic wave

78
Q

Two sphincters of the stomach

A

LES and pyloric sphincter

79
Q

Function of orad region of stomach

A

Reservoir and move gastric contents to the distal stomach

Little mixing of ingested contents

80
Q

Function of caudad region of stomach

A

Grind, mix, and propel gastric contents

81
Q

The musculature of the orad stomach is ______ and contractions are ________.

Include what type of contractions?

A

Think

Weak

Tonic contractions

82
Q

Hormone that decrease contractions and increases gastric distensibility in the orad stomach

A

CCK

83
Q

Peristaltic waves ______ in velocity as they approach the gastroduodenal junction.

What does this cause?

A

Increase

Retropulsion

84
Q

What is retropulsion of the stomach?

What does it cause?

A

The gastric contents are propelled back into the body of the stomach and remain until the next contraction

Causes a thorough mixing of gastric contents and mechanically reduces the size of solid particles

85
Q

Stomach contractions go from _______region to ________region and ________ in force and velocity.

A

Orad

Caudad

Increase

86
Q

How long do stomach contractions last?

A

2-20 seconds

3 contractions per minute

87
Q

What happens when the chyme that was being propelled forward hits the closed pyloric sphincter?

What is this process called?

When does it happen?

A

The chyme is tossed back into the antrum for more mixing

Retropulsion

During each peristaltic contraction

88
Q

What three things INCREASE the number and force of contractions?

A

Vagal N, gastrin, motilin

89
Q

What three things depress/inhibit contractions?

A

Sympathetic N, secretin, gastrin inhibitory peptide (GIP)

90
Q

What causes changes in gastric emptying? (3)

A

Alterations in motility of the stomach, gastroduodenal junction, and duodenum

91
Q

Three factors that increase gastric emptying?

A

Decrease in distention of orad stomach

Increase in force of peristaltic contractions of caudad stomach

Increase diameter and inhibit segmenting contractions of proximal duodenum

92
Q

Four factors that inhibit gastric emptying

A

Relaxation of orad stomach

Decrease number and force of contractions of caudad stomach

Contractions of pylorus

Increase segmenting contractions of duodenum

93
Q

Acidic chyme in the duodenum stimulates the release of _______ which ______.

A

Secretin

Reduces gastric motility and increases tone of pyloric sphincter

94
Q

Products of lipid digestion stimulate the release of what hormones?

A

CCK, GIP

Also reduce gastric motility

95
Q

Protein digestion stimulates the release of what hormones?

A

Gastrin, CCK, GIP

Slow gastric emptying

96
Q

Factors in duodenum that inhibit further emptying are part of _______ reflex.

A

Entero-gastric reflex

97
Q

Housekeeper of the stomach

A

Migrating motor complex (MMC)

98
Q

During fasting state, stomach had regular contractions every ______ minutes called _______.

A

90-120 minutes

Migration motor complex (MMC)

99
Q

MMC increases from _______ region of stomach to _______.

Function?

A

Proximal stomach to antrum and duodenum

Removes large non digestible solids left behind in stomach and SI

Removes mucus, sloughed cells, bacteria from SI

100
Q

Collection of disorders that delay gastric emptying (no evidence of obstruction)

A

Gastroparesis

101
Q

Causes of gastroparesis

A

Idiopathic

Systemic disease with abnormalities of neuromuscular fx like diabetes or scleroderma

Injury of vagus N (extrinsic input to stomach) impairs gastric emptying

102
Q

Part of the digestive tract that does most of the chemical and mechanical digestion

A

small intestine

103
Q

_______ is stored then released slowly in a controlled fashion in the ______ part of the SI.

A

Chyme

Duodenum

104
Q

This is in the lining of the SI and absorbs digested food into capillaries

A

Villi

105
Q

Most food absorption occurs where in the SI?

A

Jejunum and ileum

106
Q

Fx of the small intestine

What does it degrade?

A

Digestion of proteins into peptides and AA (mostly in stomach but some in SI)

Peptides degraded into AA

Lipids degraded into fatty acids and glycerol

Carbs degraded into simple sugars

107
Q

Chyme is propelled through the SI by ______.

How long does it take chyme to pass from the pylorus to ileocecal valve?

A

Peristaltic waves

3-5 hours

108
Q

Peristalsis is faster in the _______ SI than black SI

A

Proximal

Terminal

109
Q

Two types of movement in the small intestine

A

Peristaltic waves

Segmentation contractions

110
Q

______ contraction in the SI occurs at regularly spaced intervals along the SI

Alternate segments of contraction and relaxation give the appearance of _______.

They chop the chyme many times.

A

Segmentation

Rings

111
Q

Stretch or distention of the SI releases _______ which activates IPANS and then stimulates the _______causing peristalsis.

A

Serotonin

Myenteric reflex

112
Q

Intestinal motility is enhanced by what hormonal control?

A

Gastric, CCK, 5-HT, thyroxine, insulin

113
Q

Intestinal motility is decreased by what hormonal control?

A

Secretin and glucagon

114
Q

What neural control increases intestinal motility and through what nerve?

A

Parasympathetic

Vagus N

115
Q

What neural control decreases intestinal movements?

A

Sympathetic

116
Q

What is the vomiting reflex?

A

Thoracic, diaphragmatic, and abdominal muscles contract

LES and diaphragm relaxes

High intraabdominal pressure forces the gastric contents into the esophagus

117
Q

What coordinates the synchronous contraction of inspiratory and expiratory muscles during the vomiting reflex?

What does this do to the thoracic pressure?

What happens to respiration?

A

Brain

The reversal of the thoracic pressure gradient

High positive thoracic pressure drives the expulsion of the vomit

Respiration is suppressed

118
Q

Two factors allowing the ileocecal junction to be a barrier between SI and LI

A

Valve like folds protruding from the ileum to the cecum

Smooth m at the end of the ideal wall is thickened, making a sphincter

119
Q

Muscle of the internal anal sphincter?

Muscle of the external anal sphincter?

A

Circular layer of muscle

Striated muscle

120
Q

Where are the cell bodies of the intrinsic nervous system in the colon?

A

Submucosal ganglia (Meissner’s plexus)

Myenteric ganglia (Auerbach’s plexus)

121
Q

Foregut and midgut innervated by______.

Hindgut innervated by_____.

Both are _______ innervation.

A

Vagus N (ends at splenic flexure)

Pelvic N (descending and sigmoid colon and anorectum)

Parasympathetic

122
Q

How does the fecal matter get though the LI and into the rectum?

When?

What controls it?

A

Mass movements (special type of peristaltic contractions)

3-4 times per day, after meals, contraction for 3 minutes

Parasympathetic innervation

123
Q

Mass movement is initiated by_____.

A

Gastronomic or duodenal reflexes

Intense stimulation of parasympathetic nerves

Overdistension of a segment of the colon

124
Q

What initiates the defecation reflex?

A

Rectal distension

125
Q

Contains water, inorganic salts, sloughed-off cells from the mucosa, bacteria, unabsorbed digested materials, indigestible parts of food

90% of water absorption is here

A

Feces

Large intestine

126
Q

Smooth m of the rectum and anal canal are controlled by parasympathetic nerves (S2-S4) especially the _______.

Stimulates your rectum and anal canal to _______ assisting in defecation.

A

Pelvic splanchnic N

Contract

127
Q

Smooth m of the rectum and anal canal is controlled by the _______ sympathetic nerve (T11-L2).

Stimulate rectum and anal canal to _______.

A

Hypogastic N

Relax

128
Q

Internal anal sphincter is controlled by the parasympathetic nerves (S2-S4).

Causes internal anal sphincter to _______ when the rectum and anal canal _______.

A

Relax

Contract

129
Q

Internal anal sphincter is controlled by sympathetic nerves (T11-L2).

Cause the internal anal sphincter to ______.

A

Contract

130
Q

External anal spinster is controlled by _______ spinal nerves.

A

S2-S4

131
Q

Short GI reflexes

A

Ileogastric reflex

Enterogastric reflex

Gastrocolic reflex

Colonoileal reflex

132
Q

Long GI reflexes

A

Vomiting reflex

Pain reflex

Vagovagal reflex

Defecation reflex

133
Q

Defecation reflex

Internal anal sphincter is _____.

External anal sphincter is ______.

A

When feces enters rectum, spinal cord reflex is triggered

Involuntary

Voluntary

134
Q

Urge to defecate occurs when renal pressure is _____.

Internal and external anal sphincters relax and there is reflex expulsion of the rectum contents when renal pressure is _____.

A

18 mmhg

55 mmhg

GI Final (11 decks)

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