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Flashcards in GI I Deck (84):
1

What are the three systems that innervate the GI tract?

Symp
Parasymp
Enteric nervous system

2

What is the enteric nervous system? What is it regulated by?

Nervous system located entirely within the GI tract, regulated by the PNS and SNS

3

What are the intrinsic neurons to the GI tract from?

Enteric

4

What are the four types of ENS neurons?

1. Motor neurons
2. Sensory
3. Associative neurons
4. Intestinofugal neurons

5

What are the three functions of the sensory neurons in the ENS? Which type of stimulation is the most important?

Nocioceptive
**Mechanoreceptive**
Chemoreceptive

6

What do the motor neurons of the ENS regulate? (4)

Smooth muscle contraction
Vasodilation (promotes)
Water and electrolytes
Hormones

7

Symp promotes or inhibits GI function?

Inhibits

8

Parasymp promotes or inhibits GI function?

Promotes

9

What is the function of associative neurons of the GI system?

Interneurons between one group of neurons to the next

10

True or false: the GI tract can function independently of the CNS

True, but it functions better with para and symp innervation

11

What are the ways that the PNS and SNS can regulate GI tract function?

Direct synapse with smooth muscle

Synapse with ENS

12

What PNS ganglion terminates on the ENS: pre or postganglionic? What about for SNS?

Preganglionic for PNS

Postganglionic for SNS

13

What is the function of Ach on the PNS/SNS/ENS of the GI system? (3)

Vasodilation
Increased secretions
Smooth muscle contraction

14

What are the function of NE on the PNS/SNS of the GI system? (3)

Vasoconstriction
Inhibit smooth muscle contraction
Decreased secretions

(excitatory)

15

What is the function of 5HT on the ENS in the GI system?

Induces vasodilation
Induces smooth muscle contraction
Stimulate secretion

(excitatory)

16

What is the function of dopamine on the ENS in the GI system?

Inhibit ENS neuronal firing (inhibitory)

17

What is the function of NO on the ENS of the GI system?

Smooth muscle relaxation (inhibitory)

18

What is the function of VIP on the ENS in the GI system?

Smooth muscle relaxation (inhibitory)

19

What are the three key regulators of GI smooth muscles? Which stimulate, and which inhibit GI contractions?

1. Ach (stimulate)
2. VIP (inhibit)
3. NO (inhibit)

20

What is the defining characteristic of the smooth muscle electrical potential?

has a BER (slow wave)

21

What are the four types of GI motor activities?

1. Segmental (mixing)
2. Peristaltic (moving)
3. Reverse peristaltic (Storing)
4. Migrating motor complex

22

What are segmental contractions?

Squishing back and forth (like a toothpaste tube). Used for mixing

23

What is peristaltic contraction?

Wave of contractions that moves in a direction

24

What are the neurotransmitters that are needed in peristaltic contractions (upstream and downstream of the bolus)?

Ach upstream of bolus

NO
VIP downstream

25

What is the migrating motor complex?

The wave of activity to move food down the GI tube that occurs about every 90 minutes

26

What happens to the migrating motor complex when a meal is introduced?

Disrupted

27

Where is the GI tract under voluntary control? (3)

Upper 1/3 of the esophagus is striated muscle

Upper esophageal sphincter

External anal sphincter

28

What are the six sphincter sites in the GI tube?

1. Upper esophageal
2. Lower esophageal
3. Pyloric
4. Ileocecal
5. Internal anal
6. External anal

29

Blood from the GI tract is absorbed via what vein to carry it to the liver?

Hepatic portal vein

30

How is the blood supply set up in the GI tract villus? What is the consequence of this if blood supply to the villi is compromised?

Counter-current--necrosis is thus easier

31

What is postprandial hyperemia?

Increased blood flow following a meal that occurs in a stepwise fashion

32

The flow of blood through the GI system is regulated by what?

Muscularis layers and through the villi and submucosal

33

How long is vasodilation maintained following a meal?

2-4 hours

34

What is the neurotransmitter used to decreased blood flow? Receptor?

NE
alpha adrenergic receptor

35

Non-bilious emesis =?

Not yet reached bile duct

36

Patient's with pyloric stenosis are deficient of what neurotransmitter at that site?

NO

37

What are the four major factors that increase blood flow to the GI tract?

1. PNS
2. Neurotransmitters (e.g. VIP)
3. Hypoxia
4. Hyperosmolarity

38

What is the outermost layer of the GI tract, made up primarily of CT and covered by squamous epithelial cells?

Serosa

39

What is the just beneath the serosa, and is composed of longitudinal and circular smooth muscle layers?

Muscularis

40

Neurons the innervate the muscularis regulate what action?

Peristalsis

41

What is the layer beneath the mucosa? What does it contain?

Submucosa, composed of blood vessels, glands, and CT

42

What are the components of the mucosa?

Lamina propria and lamina muscularis

43

What is the lamina propria composed of?

capillaries, neurons, and immune cells

44

What is the lamina muscularis composed of?

layer of smooth muscle that helps coordinate GI motility

45

In general, the SNS (BLANKS) GI activity

Inhibits

46

In general, the PNS (BLANKS) GI activity

Activates

47

What are the two ways the the SNS affects the GI tract?

1. Indirectly by innervating ENS neurons
2. DIrectly innervate GI smooth muscle,endocrine, and secretory cells

48

What are the two ways the the PNS affects the GI tract?

1. Indirectly modulate GI function via ENS
2. Directly innervate specific cells of the GI tract with postganglionic fibers

49

What are associative neurons (interneurons) of the ENS?

specialized neurons that are used to communicate information between ENS neurons

50

What do the extrinsic neurons of the ENS sense?

Nocioception
Mechanoception
Chemoception

51

What are the three paracrine regulators of the GI tract?

1. Prostaglandins
2. Histamine
3. Somatostatin

52

What is the source and target of prostaglandins in the GI tract?

Source: Stomach and intestines/immune cells

Target: same

53

What is the action of prostaglandins on the GI tract? (blood flow? Acid? Mucus? Motility? Fluids?)

Increase blood flow
Decreased acid
Increase mucus
Increase motility
Increase fluid secretion

54

What is the source and target of histamine in the GI tract?

Source: Stomach and intestines/immune cells

Target: same

55

What is the action of histamine on the GI tract? (acid? Fluid?)

Increase acid secretion
Increased fluid secretion

56

What is the target and source of somatostatin in the GI tract?

Source: stomach, duodenum, pancreatic cells

Target: Stomach and intestines

57

What is the action of somatostatin on the Gi tract? (Acid? Fluid absorption? Smooth muscle contraction?)

Decrease acid secretion
Increase fluid absorption
Decrease smooth muscle contraction

58

Blood flow to and from the GI tract is known as what?

Splanchnic circulation

59

What is the vein that delivers blood from the liver to the body?

Hepatic vein

60

What are the key molecules that increase blood flow?

Ach
CO2
Hyperosmolarity
VIP

61

What is the major vasoconstrictor of the GI tract?

NE

62

What is the effect of NE on the action potential wave of GI muscles?

Hyperpolarizes membranes, making

63

What are the three general GI movements?

Mixing
Moving
Storing

64

What are reverse peristaltic contractions?

Storing contractions seen in the stomach and colon that permit retrograde movement of material

65

What is the migrating motor complex?

is a wave of contractility that sweeps over the GI tract that is regulated by multiple stimuli, and occurs even in the absence of food

66

What hormone has been shown to play a role in regulating and initiating the MMC?

Motlin

67

What are the two stimuli that stimulate contractions in the GI tract?

Ach
Stretch

68

What two sphincters of the GI tract are under voluntary control?

Upper esophageal
Lower rectal

69

The key regulators which relax sphincter smooth muscle, resulting in a dilated sphincter, are what?

NO and VIP

70

What does the upper esophageal sphincter separate?

Pharynx and upper esophagus

71

What does the lower esophageal sphincter separate?

Esophagus and stomach

72

What does the pyloric sphincter separate?

Stomach and duodenum

73

What does the ileocecal sphincter separate? What causes it to open/close?

Ilium and the cecum
Opens with distension of the ileum

Ascending colon distention causes contraction

74

Both the ENS stimulatory pathways and inhibitory pathways are within the same branch of the ANS. Which branch (parasymp or symp)?

Parasympathetic

75

What allows the External anal sphincter to open?

Voluntary and involuntary relaxation of the sphincter

76

What keeps the External anal sphincter to closed usually?

Involuntary reflex

77

What does peptide YY come from, and what does it do?

from the ileum, and decreases enzyme and fluid secretion from the pancreas

78

Where does secretin come from, and what does it do?

from the duodenum, and causes the stomach and pancreas to:
1. Increase HCO3
2. Decrease acid secretion
3. Delay gastric empyting

79

Where does somatostatin come from, and what is its target?

From the stomach, duodenum, and pancreas

Target = Stomach, intestines, liver

80

What is the effect of somatostatin on acid secretion?

Decreases

81

What is the effect of somatostatin on fluid absorption?

Increases

82

What is the effect of somatostatin on smooth muscle contraction?

Decreases

83

What is the effect of somatostatin on secretions in general?

Decreases

84

What is the effect of somatostatin on bile flow?

Decreases