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PHGY 210 > Gastro V > Flashcards

Gastro V Flashcards

1
Q

How does the duodenum use hormones to control antral peristalsis? What hormones does it use?

A

It uses secretin, CCK, GIP, VIP, and neurotensin to slow the movement of gastrointestinal contents and the release of acid. This works in the opposite direction of stomach peristalsis

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2
Q

What is the enterogastric reflex?

A

The cells in the duodenum can detect stretch and send signals to inhibit emptying. This is called the enterogastric reflex.

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3
Q

What is vomiting? What parts of the GIT does it involve?

A

It is the emptying of the contents of the upper GIT (involves the duodenum and stomach contents)

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4
Q

What is the cause of vomiting? What is the role of the GIT?

A

Results from an increase in intraabdominal pressure due to the action of the diaphragm and abdominal muscles - the GIT is mostly passive.

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5
Q

What are the 5 main events that lead to vomiting?

A
  1. The proximal stomach and esophagus are relaxed
  2. The upper duodenum and distal stomach contract
  3. Creates a gradient of pressure because we also get contraction of abs.
  4. The lowering of the diaphragm will move the LES outside of its abdominal cavity.
  5. All of these things together allow intraabdominal pressure to overcome LES.
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6
Q

Regulation of vomiting occurs in what part of the brain? Where is it relative to other brain structures?

A

The Vomiting Center, which is near the fourth ventricle.

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7
Q

Name 6 ways in which the Vomiting Center can be activated.

A
  • Pharyngeal stimulation
  • GIT or urogenital distension
  • Pain, cardiac ischemia
  • Biochemical disequilibrium
  • Vestibular signals
  • Psychoganic factors
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8
Q

What is the response of the vomiting center when stimulated? What is the physiological consequence of this response?

A

It will trigger a widespread autonomic dischange, leading to an imbalance between parasympathetic and sympathetic activities. This will lead to sweating, vasoconstriction, salivation, irregular heart rate, etc.

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9
Q

After the vomiting center has been activated, name the 4 events that follow between that and vomiting.

A
  1. Widespread autonomic discharge
    +
  2. Nausea
  3. Retching
  4. Emesis
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10
Q

When emesis begins, what are the 2 main physiological changes observed? What is their overall impact?

A
  1. Relaxation of upper GI tract + spasm of pyloric antrum and duodenum
  2. Contraction of abdominal muscles and diaphragm
    This will reverse the pressure gradient down the GIT and allow for GIT contents to flow towards the mouth.
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11
Q

What is the function of the chemoreceptor trigger zone (CTZ)?

A

It sends signals to the Vomiting Center based on the presence of emetic agents circulating in the bloodstream.

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12
Q

Where is the CTZ located?

A

It is located in the brainsteam outside the blood-brain barrier.

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13
Q

What are the three stages of vomiting? Describe what each one is.

A

Nausea - a psychic experience
Retching - abrupt, uncoordinated respiratory movements with glottis closed
Emesis - actual expulsion of contents of upper GIT

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14
Q

Describe the process by which emesis is completed.

A

Emesis is completed with the reversal of thoracic pressures from negative to positive, as the diaphragm is displaced upwards, forcing esophageal contents to be expelled through the mouth.

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15
Q

What is the main function of the small intestine?

A

Most digestion and ALL absorption of nutrients occur in the SI.

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16
Q

What are the three regions of the SI? Name them from top to bottom of the SI.

A

Duodenum, jejunum, ileum

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17
Q

Name 4 functions of the upper small intestine.

A
  1. Neutralization of chyme
  2. Osmotic equilibration of chyme
  3. Digestion
  4. Absorption
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18
Q

What are the major motor activities of the small intestine? Explain their importance.

A
  1. Effective mixing of chyme with digestive juices to bring it in contact with absorptive cells
  2. Slow propulsion (2-6 hours)
19
Q

What determines the frequency of intestinal contractions?

A

Governed by BER (ECA).

20
Q

What determines the amplitude of intestinal contractions?

A

Related to the numbers of spikes of ERA

21
Q

Is BER uniform throughout the intestine? Explain why or why not.

A

Intrinsic f of BER declines systematically from the proximal to distal intestine

22
Q

Name 3 differences between the muscle in the proximal vs distal intestine.

A
  1. f of BER is greater
  2. Excitability of smooth muscle is greater
  3. Thickness of smooth muscle is greater
    Therefore, both the frequency and the amplitude of contractions are greater in the proximal small intestine.
23
Q

How does pressure vary across the small intestine? What effect does this have on its functioning?

A

Because there are more contractions and more vigorous contractions proximally, there will be a low, net aboral PROPULSION of contents. A gradient of pressure has been generated.

24
Q

How does the frequency of the BER vary across the small intestine? Include specific numbers.

A

Aborally decreasing frequency gradient - the highest frequency is 12/min in duodenum and the lowest is 8/min in the terminal ileum.

25
Q

What is the most common type of contractile activity in the SI after a meal?

A

Segmentation

26
Q

What are the 3 factors involved in determining segmentation in the SI? Explain how.

A
  1. Myogenic response to distension
  2. ENS coordinates and organizes contraction in SI
  3. ANS and hormones modulate
27
Q

What are the main 2 functions of segmentation in the SI?

A

Segmentation is effective for (1) mixing contents with digestive enzymes and (2) bringing them in contact with absorptive cells via slow propulsion.

28
Q

Does peristalsis take place in the SI? Explain why or why not.

A

It does, but it is infrequent and irregular. Peristaltic waves are weak and only travel for short distances (a few centimeters). Segmentation is much more important for moving contents.

29
Q

In what situations is peristalsis in the SI significant?

A

In some pathologic conditions such as diarrhea, you can get more peristalsis than usual that will force contents out aborally.

30
Q

State the following about intestinal peristalsis:
a) Mediated by …
b) Muscles involved
c) Maximum frequency
d) Modulated by …

A

a) A series of local reflexes - the ENS
b) Interaction of longitudinal and circular muscle
c) Maximum frequency = frequency of BER
d) Modulated by the ANS and hormones

31
Q

What is the law of the intestine? Explain it.

A

It describes the forces that cause peristalsis in the small intestine. It occurs as follows:
1) Radial stretch due to bolus
2) Receptors get activated
3a) Ahead of bolus: contraction of longitudinal muscle and relaxation of circular muscle
b) Behind bolus: contraction of circular muscle and relaxation of longitudinal muscle
This sends the bolus into the colon.

32
Q

Name and locate the 6 main sections of the colon.

A

Starting at the terminal ileum:
1. Cecum
2. Ascending colon
3. Transverse colon
4. Descending colon
5. Sigmoid colon
6. Rectum

33
Q

The ileum and the colon are separated by the […]

A

ileocecal sphincter

34
Q

How much liquid enters and exits the colon per day?

A

1500 mL enters but only 200 mL leaves.

35
Q

What are the 3 functions of the colon?

A
  1. Mixing (promotes absorption of water and ions)
  2. Propulsion (slow - 50-60h for conversion of chyme of feces)
  3. Storage during the time from conversion from chyme to feces
36
Q

Where does the absorption of H2O and ions mainly take place in the GIT?

A

In the SI and to a lesser extent the colon

37
Q

What types of motility occur in the colon? How does this compare to elsewhere in the GIT?

A

Segmentation and peristalsis. It is different because the BER is irregular, so there is no fixed pattern unlike the rest of the GIT.

38
Q

How and when does the large intestine empty its contents?

A

2-3 times per day, corresponding with intake of a new meals

39
Q

What is the gastroileal reflex?

A

After intaking a meal, stretch in the stomach will lead to musclar activity at the distal part of the small intestine. This will push contents into the small intestine and open the ileocecal sphincter.

40
Q

What is the gastrocolic reflex?

A

Stretch in the stomach leads to forward movement in the colon. Contents in the distal part of the colon will be moved into the rectum.

41
Q

What is the ileocolic reflex?

A

Stretch in the ileum from a meal will activate muscular responses in the colon.

42
Q

Where does the migrating myoelectric motor complex take place?

A

It moves over the distal stomach and small intestine, up to the distal ileum.

43
Q

How often does the MMC occur?

A

It occurs regularly, at 90 minute intervals.

PHGY 210 (36 decks)

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