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Physio U4 > Regulation of GI Function > Flashcards

Regulation of GI Function Flashcards

1
Q

Main GI function

A

provide H2O, electrolytes, and nutrients

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2
Q

GIT must be able to

A

secrete, motility, digest, circulate blood, and regulate via ANS

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3
Q

GI tube begins with

A

striated muscle of the pharynx, upper esophageal sphincter, and upper 1/3 of the esophageal body

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4
Q

GI tube ends with

A

striated muscle of EAS

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5
Q

swallowing and defecation are

A

voluntary (to some degree) striated muscle

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6
Q

mid-esophageal body to Internal EAS are

A

visceral smooth muscle controled by the ANS: enteric, PS, and S

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7
Q

GIT receives about ______% of CO

A

25

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8
Q

Postprandial hyperemia

A

after eating, enhanced metabolism leads to local vasodilation of the mesenteric arterioles

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9
Q

What is the basis for postprandial hyperemia

A

maintain the concentration gradient for nutrients to promote their diffusion into capillaries

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10
Q

Mobilization of blood from splanchnic circulation

A

splanchnic circulation has the largest reservoir of blood, blood is mobilized (70%) from splanchnic to maintain MAP

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11
Q

How could mobilization from splanchnic circulation to maintain systemic MAP be bad for the gut?

A

the gut could become ischemic since mobilization of blood into systemic circulation comes 70% from the splanchnic vascular bed

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12
Q

What receptor subtype is on the resistance vessels of smooth muscle of splanchnic circulation?

A

alpha-1 adrenergic receptors

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13
Q

alpha-1 adrenergic receptors

A

NT: EPI, NE
action: vasoconstriction of resistance vessels

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14
Q

What system causes vasoconstriction and mobilization of blood?

A

sympathetic

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15
Q

Sympathetic regulation

A

direct innervation of smooth muscle of arterioles; vasoconstriction decreases blood flow into splanchnic circulation

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16
Q

Autoregulatory escape

A

during vasoconstriction, metabolic vasodilatory substances accumulate and override the sympathetic system’s ability tp continue constricting the vessels

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17
Q

Functional Hyperemia

A

PS system increases GI motility and an elevation in metabolism will INDIRECTLY cause and increase in blood flow

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18
Q

Sympathetic system ________ innervates smooth muscle of the arterioles and Parasympathetic system _________ innervates smooth muscle

A

DIRECTLY; INDIRECTLY

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19
Q

Parallel splanchnic blood flow

A

3 major arteries (Celiac, Superior Mesenteric, and Inferior Mesenteric) allow blood flow to be regulated independently to the individual GI segments or accessory organs

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20
Q

Series splanchnic blood flow

A

PORTAL V; requires that all venous drainage from the gut is delivered to the liver before entering the general systemic circulation

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21
Q

What is the reason for the series type of blood flow?

A

so all ingested nutrients, bacteria, toxins, and viruses go the liver before entering systemic circulation

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22
Q

Where might colon cancer first metastasize?

A

liver due to the portal drainage system

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23
Q

Mucosal capillary characteristics

A

high capillary density (large SA for nutrient absorption and efficient O2 delivery), fenestrated capillaries (high pore SA for H2O and solute exchange) fenestra are permeable to small solutes, NOT macromolecules

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24
Q

Layers of the GIT

A

Muscularis externa, submucosa and mucosa

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25
Q

muscularis externa is composed of

A

CIRCULAR muscle that determines circumference and LONGITUDINAL muscle that determines length

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26
Q

Mucosa is composed of

A

enterocytes: that absorb and secrete electrolytes
endocrine cells: that secrete hormones and paracrines
lamina propria: basement membrane
Muscularis mucosa: folding of mucosa

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27
Q

Submucosa is composed of

A

mucosal capillaries: provide mucosa and visceral SM with nutrients, O2
Lymph vessels: absorb some nutrients
Submucosal nerve plexus: controls secretion and absorption of electrolytes and secretion of some peptides by endocrine cells

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28
Q

Auerbach’s plexus:

A

nerves of the enteric system that control motility of visceral SM

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29
Q

Meissner’s plexus:

A

nerves of the enteric system that control secretion of some peptides by endocrine cells and secretion/absorption of electrolytes by enterocytes

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30
Q

4 major ganglion for SYMPATHETIC neurons (postganglion originate) to splanchnic vessels (postganglionic efferents originate here)

A

superior cervical, celiac, superior mesenteric, inferior mesenteric

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31
Q

Postganglionic SYMPATHETIC terminate on:

A

salivary glands, visceral smooth muscle sphincters, enteric neurons, splanchnic arterioles, mucosa

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32
Q

Sympathetics effect on salivary glands

A

increase salivation

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33
Q

Sympathetics effect on visceral smooth muscles sphincters

A

constrict

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34
Q

Sympathetics effect on enteric neurons

A

inhibit neuronal activity

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35
Q

Sympathetics effect on splanchnic arterioles

A

vasoconstriction

36
Q

Sympathetics effect on mucosa

A

inhibit secretions

37
Q

Parasympathetics of the head originate in

A

facial, glossopharyngeal, and vagus

38
Q

Sacral parasympathetics originate in

A

pelvic nerve

39
Q

Parasympathetic nerves terminate on

A

submandibular and otic ganglion –> increased salivation

striated muscle of pharynx, UES, upper 1/3 esophagus -> swallowing

40
Q

Postganglionic parasympathetic nerves innervating abdominal accessory organs

A

increase secretion of digestive and buffering juices

41
Q

Enteric neurons function to

A

modulate activity, act like postganglionic parasympathetic

42
Q

Afferent fibers within the Sympathetic and Parasympathetic systems function to

A

bring input from GIT to brain, spinal cord, prevertebral ganglion to alter the efferent autonomic output to the GIT

43
Q

Enteric neurons originate in

A

myenteric plexus and submucosal plexus

44
Q

myenteric plexus neurons function to

A

control motility of visceral smooth muscle and secretions from accessory organs

45
Q

Submucosal plexus neurons function to

A

control enterocyte secretion and absorption of electrolytes,

endocrine secretion of hormones and paracrines

46
Q

Enteric neurons terminate on

A

enteric neurons, visceral smooth muscles, sphincters, enterocytes, endocrine cells, prevertebral neurons

47
Q

Enteric neurons modulate activity by

A

either increasing or decreasing digestion (can act to stimulate OR inhibit)

48
Q

Enteric neurons act primarily as

A

postganglionic parasympathetic

49
Q

4 functional types of neurons in the ENS

A

Intrinsic primary afferent neurons (IPANs), Interneurons, Motor neurons, Intestinofugal afferent neurons (IFANs)

50
Q

Intrinsic primary afferent neurons (IPANs) function to

A

act as the SENSORY portion; chemosensitive (sense nutrient content) and mechanosensitive neurons (tension of smooth muscle distention)

51
Q

Motor Neurons if ENS function to

A

Act as EXCITATORY or INHIBITORY

52
Q

EXCITATORY motor neurons of ENS release

A

ACh, neurokinins, substance P and K

53
Q

INHIBITORY motor neurons of ENS release

A

NO, Vasoactive intestinal peptide (VIP), ATP

54
Q

Motor neurons function to

A

contract or relax visceral smooth muscle, constrict of relax sphincters, cause secretion of absorption of electrolytes and modulation of hormone release

55
Q

Intestinofugal afferent neurons (IFANs) function to

A

modulate SYMPATHETIC neurons activity to GIT

56
Q

Intestinofugal afferent neurons originate ____________ and terminate ___________

A

myenteric plexus and project to the prevertebral sympathetic ganglion

57
Q

Striated muscle of the pharynx, UES, upper 1/3 of esophagus, and EAS is controlled by

A

somatic and autonomic NS

58
Q

2/3 lower esophagus, GIT, and IAS is controlled by

A

Autonomic NS

59
Q

Sympathetic NS is inhibitory on

A

majority of GIT to reduce motility and slow digestion

60
Q

Sympathetic NS is excitatory on

A

salivary glands, sphincters (constrict), arterioles (vasoconstriction)

61
Q

Parasympathetic NS is excitatory on

A

enteric system, accessory organs, striated muscle (swallowing)

62
Q

The enteric NS can be excitatory or inhibitory depending on

A

initiating event, NT, and hardwired programs

63
Q

Enteric neurons involve

A

local, short reflex arc (IPAN>interneuron>Motor neuron (+ or -) OR long neural reflexes

64
Q

Local short reflexes of ENS

A

local, short reflex (IPAN>interneuron>Motor neuron (+ or -)

involve only enteric neurons and may be localized to segment or coordinate adjacent segments

65
Q

Long (CNS) neural reflex of ENS

A

MUST involve extrinsic Autonomic neurons and/or IFANs, serve to produce rapid, coordinated activity among many segments and accessory organs

66
Q

Which reflex arc overrides the other?

A

LONG neural reflex

67
Q

Parallel vagal pathways

A

inhibitory and excitatory depending on which part of the dorsal motor nucleus is activated

68
Q

Rostral dorsal motor nucleus

A

EXCITATORY; causes release of ACh from myenteric plexus and results in DEPOLARIZATION and contraction of smooth muscle

69
Q

Causal dorsal motor nucleus

A

INHIBITORY; synapses on nonadrenergic/noncholinergic motor neurons in the myenteric plexus to release NO resulting in HYPERPOLARIZATION of smooth muscle

70
Q

If the smooth muscle has intrinsic tone during caudal DMN inhibition then

A

hyperpolarization will slow the force production; when hyperpolarization is terminated the contraction will increase

71
Q

If smooth muscle did not intrinsic tone during caudal DMN inhibition then

A

hyperpolarization does not change the force production; when hyperpolarization is terminated the contraction will increase

72
Q

Off contraction

A

once the inhibitory hyperpolarization ceases then there will be an increase in contraction (force production)

73
Q

GI peptides function to

A

regulate GI function

74
Q

2 classes of GI peptides

A

Gastrin and CCK that work to INCREASE INTRACELLULAR Ca

Secretin-like peptides that work to STIMULATE cAMP SYNTHESIS

75
Q

Examples of secretin-like peptides

A

secretin, VIP, glucose-dependent insulinotropic polypeptide or gastrin inhibitory peptide (GIP), glucagon, glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2)

76
Q

examples of GI peptides that function as hormones

A

Gastrin, secretin, CCK, motilin, GLP-1, GIP

77
Q

GI peptide hormones function and site of release

A

released from GI mucosal endocrine cells into portal circulation; enter systemic circulation but only effect cells with receptors

78
Q

GI peptides that have paracrine function

A

somatostatin and histamine

79
Q

GI peptide paracrine function and site of release

A

released from GI mucosal endocrine cells and bind nearby receptors, local action, does not enter systemic circulation

80
Q

GI peptides that have neurocrine function

A

Substance P, VIP, GRP

81
Q

GI peptide neurocrine function and site of release

A

Released from nerve terminals to bind nearby receptors, do not circulate, local action only

82
Q

Other hormones not released by endocrine cells not located in the GIT

A

Aldosterone, thyroid hormones, vitamin D

83
Q

Aldosterone’s role

A

enhance sodium and water reabsorption

84
Q

Thyroid hormone’s role

A

normal GI motility

85
Q

Vitamin D’s role

A

enhance calcium absorption in small intestine

86
Q

3 main regulators of GI function

A

extrinsic nerves: (sympathetic (-) and parasympathetic (+)
intrinsic nerves: ENS (+ or -) minute to minute basis
Hormones, paracrines, and neurocrines

Physio U4 (9 decks)

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