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Block 1 - GI > Phys 1-2 > Flashcards

Phys 1-2 Flashcards

1
Q

7 sphincters of the GI tract

A 
UES
LES
Pyloric
Sphincter of Oddi
Ileocecal
Internal anal
External anal
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2
Q

Contraction of the muscularis externa is primarily responsible for ___

A

Mixing and propulsion of luminal contents

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3
Q

Collection of neurons in the GI tract

  • brain of the gut
  • can exert much of its function independent of the CNS
A

Enteric nervous system

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4
Q

Examples of things the Enteric Nervous System controls

A
  1. Motility
  2. Exocrine/endocrine secretions
  3. Microcirculation
  4. Regulating immune and inflammatory responses
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5
Q

Parasympathetic innervation to the GI tract is supplied by nerve fibers from ___

A
  1. Vagus (above and including the transverse colon)

2. Pelvic sacral nerves (below and the distal end of the transverse colon)

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6
Q

Preganglionic parasympathetic fibers terminate on ____, and the postganglionic neurons are shared with __
Mostly cholinergic

A
  • Ganglia of the intramural plexuses

- ENS

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7
Q

Activation of parasympathetic nerves (vagus) is most often (inhibitory/excitatory), (decreasing/increasing) GI motility or secretion

A

Excitatory

Increasing

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8
Q

Vagovagal reflexes

A
  • have both afferent and efferent limbs
  • ACh and Substance P released from postganglionic neurons excites contraction
  • release of VIP and NO inhibit contraction
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9
Q

Sympathetic innervation:

Post ganglionic adrenergic fibers arise from ___

A

Prevertebral and paravertebral ganglia

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10
Q

Activation of sympathetic nerves is most often (inhibitory/excitatory), (decreasing/increasing) GI motility or secretion

A

Inhibitory

Decreasing

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11
Q

Most sympathetic fibers synapse on cells of the ___ plexuses where the ___ released inhibits _____ release by activating ____ receptors.

A
  • Intramural (submucosal and myenteric)
  • norepinephrine
  • parasympathetic acetylcholine
  • alpha 2 presynaptic
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12
Q

Factors which influence the _____ (inhibitory) and the ____ (stimulating) act through the intramural plexuses

A

Muscularis externa

Muscularis mucosae

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13
Q

Sympathetic fibers innervate ____ in the gut directly causing ____
What type of receptor?

A

Blood vessels
Vasoconstriction
Alpha 1

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14
Q

True or false: GI smooth muscle is multi unit

A

False: single unit

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15
Q

BER

A

Basal electrical rhythm (rate of slow waves)

  • stomach=3/min
  • duodenum=12/min
  • slows from duodenum to ileum
  • colon does not have BER
  • BER is set by pacemaker cells
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16
Q

True or false: The frequency and amplitude of slow waves can be modified

A

False. Frequency cannot, amplitude can

  • sympathetic decreases
  • parasympathetic increases
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17
Q

More action potentials =

A

Greater force of contraction

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18
Q

Initial rising phase of the AP is due primarily to Ca entry into the cell through ___ channels. Depolarization occurs coincident with ___

A

L-type Ca

⬆️Gk+

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19
Q

Initial APs occur where on the slow wave?

A

Near the peak on the rising phase

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20
Q

True or false: the intestine can contract in the absence of APs

A

False. The stomach can

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21
Q

Two functional types of movements of the GI tract

A
  1. Mixing-local constrictive contractions (segmentation) and peristaltic contractions
  2. Propulsive-peristalsis moves contents down through the GI tract. Distension is the stimulus for peristalsis
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22
Q

Peristaltic reflex or “law of the gut”

A

Muscles toward the mouth contract first, then moves downward.
-simultaneous relaxation of the smooth muscle in front of the distension that is mediated through ENS

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23
Q

Migrating Motor Complex

A

Strong wave of contractile activity that spreads down through the GI tract between meals

  • once every two hours during fasted period (interdigestive period)
  • function is to sweep clean the lumen between meals
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24
Q

Control of contractile activities of the GI system involves 4 things:

A
  1. CNS
  2. ENS
  3. Electrical coupling between cells
  4. Humoral factors

*motile activity of the gut is the NET result of the integration of these 4 influences

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25
Q

Circular layer of muscularis externa tends to make sections ___ while the longitudinal layer tends to make sections ___

A

Longer and thinner

Shorter and wider

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26
Q

Known transmitters which excite smooth muscle contraction:

A

ACh

Substance P

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27
Q

Known transmitters which relax GI smooth muscle

A

NO

VIP

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28
Q

Transmitter released by enteric interneurons

A

Serotonin (5-HT)

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29
Q

___ increases Force of stomach contractions and ____ is responsible for the MMC

A

Gastrin

Motilin

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30
Q

___ is secreted in the small intestine. It tends to decrease gastric motility and increases gall bladder contractility

A

Cholecystokinin (CCK)

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31
Q

___ decreases motility of most of the GI tract

A

Secretin

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32
Q

____ mildly decreases gastric motility

A

Gastric inhibitory peptide (GIP)

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33
Q

3 phases of swallowing

A
  1. Oral/voluntary
  2. Pharyngeal
  3. Esophageal
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34
Q

In which phase of swallowing:
The soft palate move upward, superior constrictor muscles and palatopharyngeal fold move toward one another thus preventing reflux of rod into the nasopharynx

A

Pharyngeal

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35
Q

In which phase of swallowing:

Tactile receptors initiate swallowing reflex at pharynx level

A

Oral or Voluntary phase

36
Q

In which phase of swallowing does:

Primary and secondary peristalsis

A

Esophageal phase

37
Q

In which phase of swallowing do:
Vocal cords pull together
Larynx moves against the epiglottis (prevent food from entering trachea)
Respiration is reflexively inhibited

A

Pharyngeal phase

38
Q

In which phase of swallowing does:
UES relax
UES constricts

A

Pharyngeal

Esophageal

39
Q

In which phase of swallowing is:

Modulated and coordinated by a medullary “swallowing center”

A

Pharyngeal

Continues to esophageal

40
Q

The muscle layer of the upper third of the esophagus is ___. The lower third is ___. The central region is ____. Innervation of the 3 regions?

A

Skeletal/striated
Smooth
Mixed
Vagus

41
Q

Pressure at UES

A

Resting : 40mmHg
Upon swallowing the pressure rapidly drops then rapidly increases immediately after the bolus passes to prevent entry of air

42
Q

Pressure at LES

In a normal person the pressure at the LES is always higher than ___ except ___

A

Resting: 30mmHg

Gastric pressure except during swallowing

43
Q

What type of nerve stimulation causes contraction of LES?

A

Both parasympathetic and sympathetic
(Parasympathetic inhibitory fibers also exist)
*The ENS alone can maintain construction when extrinsic nerves are cut

44
Q

The LES is tonically contracted by ___

A

Extrinsic and intrinsic nerves, hormones; and neuromodulators

45
Q

LES relaxation is primarily mediated by ___

A

Vagovagal reflex that causes relaxation of the circular muscle layer

46
Q

A condition where the LES does not relax fully during swallowing.

A

Achalasia

*associated w/ degeneration of nerve ganglion cells within the myenteric nerve plexus, often as a result of an autoimmune attack

47
Q

LES incompetence causes ___

A

Gastric reflux

48
Q

A hiatal hernia occurs when ___

A

Part of the stomach moves upward into the thoracic cavity.

49
Q

Achalasia (and Hirschsprung’s disease) are due to __

A

Absence of ENS ganglion cells at the LES (and internal anal sphincter) which prevents relaxation and thus passage of material through the sphincter

50
Q

This part of the stomach is more muscular and controls the rate of chyme efflux

A

Antrum

51
Q

This sphincter separates the stomach and small intestine

A

Pyloric

52
Q

Reflex of relaxation of the orad portion of the stomach is mediated by ____. What are the transmitters?

A

Vagal efferents

VIP and NO

53
Q

Amount of food that can be stored in the stomach without a substantial increase in intragastric pressure

A

1 L

54
Q

As pressure builds in the antrum, some chyme is forced into the ___ while most is forced ___

A

Into the duodenum

Back in the body of the stomach by retropulsion

55
Q

Gastric emptying is regulated by ___ mechanisms

A

Neural and hormonal

56
Q

Receptors in the small intestine can sense and respond to :

A

Acidity
Far content
Osmotic pressure

57
Q

__ is released in response to food in the stomach and increases stomach motility and thereby promotes gastric emptying

A

Gastrin

58
Q

Acid, fats, and hyoertonicity all tend to ___ gastric motility and ___ stomach emptying

A

Decrease

Reduce

59
Q

Peptides in the duodenum ___ gastric emptying

A

Decrease

*to enhance digestion in the stomach

60
Q

GI irritation causes paracrine release of ___ from ____ which stimulates vagal afferents to the vomiting center

A

Serotonin (5-HT)

Enterochromaffin

61
Q

A chemoreceptor ___ lies in the floor of the 4th ventricle. When stimulated directly by certain drugs (____) it causes vomiting. This is mediated by ____

A

“Emetic trigger zone”
Morphine, digitalis
Dopamine and serotonin receptors

62
Q

Vomiting due to psychic stimuli (odors, disquieting events, etc) probably only involves what?

A

The vomiting center

63
Q

That small intestine is the longest segment of the GI tract and it typically takes chyme between ___ to ___ hours to traverse it

A

2 to 4

64
Q

Most frequent type of movement in the small intestine

A

Mixing/chopping

65
Q

___ by chyme elicits localized contraction of the circular muscle layer at spaced intervals

A

Stretch/distension

66
Q

BER of:
Duodenum?
Ileum?

A

D: 12/min
I: 9/min

*frequency decreases along length

67
Q

The tissue of the small intestine is made more “excitable” by the distension of the stomach and the beginning of the entry of chyme into the duodenum

A

Gastroenteric reflex

68
Q

Muscles contract just behind the bolus of chyme while the muscle in front of the bolus relaxes

A

Law of the Gut

Myenteric Reflex

69
Q

Overdistension of one segment of the intestine will cause reflex relaxation in the rest of the intestine

A

Intestinointestinal reflex

70
Q

The stomach and terminal part of the ileum interact reflexively. Increased activity in the stomach will increase motility of the ileum and accelerate the movement of chyme through the ileocecal sphincter

A

Gastroileal reflex

71
Q

Gastric distension increases activity in the colon

A

Gastrocolic reflex

72
Q

MMC occurs in the ___ state about every ___ hours. It starts in the ___ and goes to the ___. It is inhibited by ___

A

Fasted
2
Stomach, ileocecal sphincter
Motilin

73
Q

Four phases of the MMC

A
  1. Quiescence; slow waves; little or no mechanical activity
  2. Irregular APs, contractions gradually increase in frequency and intensity
  3. Intense electrical and mechanical activity lasting 3-6 minutes
  4. Rapid decline in electrical and mechanical activity
74
Q

The ileocecal valve and sphincter are normally ___ to prevent ___

A

Closed

Efflux of colonic contents back into the small intestine

75
Q

Distension of the cecum causes ileocecal sphincter to ___

A

contract

76
Q

Distension of the terminal ileum causes ileocecal sphincter to ___

A

relax

77
Q

Gastrin and the gastroileal reflex ___ the ileocecal valve

A

Relax

78
Q

Haustrations of the colon

A

Similar to small intestine segmentation

79
Q

Taenia coli are present in the __

A

Colon (large intestine)

-3 strips of longitudinal smooth muscle

80
Q

The ___ and ___ reflexes increase mass movement activity (propulsive peristaltic waves that move contents analward/caudad)

A

Gastrocolic

Duodenocolic

81
Q

BER in the colon

A

No BER

-humans have irregular, intermittent slow waves in the colon

82
Q

Mass movement from the sigmoid colon fills the rectum while reflexively relaxing the internal anal sphincter and contracting the external anal sphincter

A

Rectosphincteric reflex

83
Q

The EAS is normally ___ at rest, and is a ___ muscle under ___ control via the ____ n.

A

Relaxed
Striated
Voluntary
Pudendal

84
Q

Other reflexes that act to reduce motility

A
  1. Peritoneointestinal (peritoneum irritatikn)
  2. Renointestinal (kidney irritation)
  3. Vesicointestinal (bladder irritation)
  4. Somatointestinal (irritation of skin over stomach)
85
Q

Gas in the GI tract has 3 sources:

A
  1. Swallowed air (stomach; belching)
  2. Bacteria (primarily large intestine; 90% reabsorbed, 10% flatulence)
  3. Diffusion from blood
86
Q

Noise made by movement of gas and chyme through the intestines due to peristalsis

A

Borborygmi

Block 1 - GI (15 decks)

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