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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
muscularis externa is composed of
CIRCULAR muscle that determines circumference and LONGITUDINAL muscle that determines length
26
Mucosa is composed of
enterocytes: that absorb and secrete electrolytes endocrine cells: that secrete hormones and paracrines lamina propria: basement membrane Muscularis mucosa: folding of mucosa
27
Submucosa is composed of
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
28
Auerbach's plexus:
nerves of the enteric system that control motility of visceral SM
29
Meissner's plexus:
nerves of the enteric system that control secretion of some peptides by endocrine cells and secretion/absorption of electrolytes by enterocytes
30
4 major ganglion for SYMPATHETIC neurons (postganglion originate) to splanchnic vessels (postganglionic efferents originate here)
superior cervical, celiac, superior mesenteric, inferior mesenteric
31
Postganglionic SYMPATHETIC terminate on:
salivary glands, visceral smooth muscle sphincters, enteric neurons, splanchnic arterioles, mucosa
32
Sympathetics effect on salivary glands
increase salivation
33
Sympathetics effect on visceral smooth muscles sphincters
constrict
34
Sympathetics effect on enteric neurons
inhibit neuronal activity
35
Sympathetics effect on splanchnic arterioles
vasoconstriction
36
Sympathetics effect on mucosa
inhibit secretions
37
Parasympathetics of the head originate in
facial, glossopharyngeal, and vagus
38
Sacral parasympathetics originate in
pelvic nerve
39
Parasympathetic nerves terminate on
submandibular and otic ganglion --> increased salivation | striated muscle of pharynx, UES, upper 1/3 esophagus -> swallowing
40
Postganglionic parasympathetic nerves innervating abdominal accessory organs
increase secretion of digestive and buffering juices
41
Enteric neurons function to
modulate activity, act like postganglionic parasympathetic
42
Afferent fibers within the Sympathetic and Parasympathetic systems function to
bring input from GIT to brain, spinal cord, prevertebral ganglion to alter the efferent autonomic output to the GIT
43
Enteric neurons originate in
myenteric plexus and submucosal plexus
44
myenteric plexus neurons function to
control motility of visceral smooth muscle and secretions from accessory organs
45
Submucosal plexus neurons function to
control enterocyte secretion and absorption of electrolytes, | endocrine secretion of hormones and paracrines
46
Enteric neurons terminate on
enteric neurons, visceral smooth muscles, sphincters, enterocytes, endocrine cells, prevertebral neurons
47
Enteric neurons modulate activity by
either increasing or decreasing digestion (can act to stimulate OR inhibit)
48
Enteric neurons act primarily as
postganglionic parasympathetic
49
4 functional types of neurons in the ENS
Intrinsic primary afferent neurons (IPANs), Interneurons, Motor neurons, Intestinofugal afferent neurons (IFANs)
50
Intrinsic primary afferent neurons (IPANs) function to
act as the SENSORY portion; chemosensitive (sense nutrient content) and mechanosensitive neurons (tension of smooth muscle distention)
51
Motor Neurons if ENS function to
Act as EXCITATORY or INHIBITORY
52
EXCITATORY motor neurons of ENS release
ACh, neurokinins, substance P and K
53
INHIBITORY motor neurons of ENS release
NO, Vasoactive intestinal peptide (VIP), ATP
54
Motor neurons function to
contract or relax visceral smooth muscle, constrict of relax sphincters, cause secretion of absorption of electrolytes and modulation of hormone release
55
Intestinofugal afferent neurons (IFANs) function to
modulate SYMPATHETIC neurons activity to GIT
56
Intestinofugal afferent neurons originate ____________ and terminate ___________
myenteric plexus and project to the prevertebral sympathetic ganglion
57
Striated muscle of the pharynx, UES, upper 1/3 of esophagus, and EAS is controlled by
somatic and autonomic NS
58
2/3 lower esophagus, GIT, and IAS is controlled by
Autonomic NS
59
Sympathetic NS is inhibitory on
majority of GIT to reduce motility and slow digestion
60
Sympathetic NS is excitatory on
salivary glands, sphincters (constrict), arterioles (vasoconstriction)
61
Parasympathetic NS is excitatory on
enteric system, accessory organs, striated muscle (swallowing)
62
The enteric NS can be excitatory or inhibitory depending on
initiating event, NT, and hardwired programs
63
Enteric neurons involve
local, short reflex arc (IPAN>interneuron>Motor neuron (+ or -) OR long neural reflexes
64
Local short reflexes of ENS
local, short reflex (IPAN>interneuron>Motor neuron (+ or -) | involve only enteric neurons and may be localized to segment or coordinate adjacent segments
65
Long (CNS) neural reflex of ENS
MUST involve extrinsic Autonomic neurons and/or IFANs, serve to produce rapid, coordinated activity among many segments and accessory organs
66
Which reflex arc overrides the other?
LONG neural reflex
67
Parallel vagal pathways
inhibitory and excitatory depending on which part of the dorsal motor nucleus is activated
68
Rostral dorsal motor nucleus
EXCITATORY; causes release of ACh from myenteric plexus and results in DEPOLARIZATION and contraction of smooth muscle
69
Causal dorsal motor nucleus
INHIBITORY; synapses on nonadrenergic/noncholinergic motor neurons in the myenteric plexus to release NO resulting in HYPERPOLARIZATION of smooth muscle
70
If the smooth muscle has intrinsic tone during caudal DMN inhibition then
hyperpolarization will slow the force production; when hyperpolarization is terminated the contraction will increase
71
If smooth muscle did not intrinsic tone during caudal DMN inhibition then
hyperpolarization does not change the force production; when hyperpolarization is terminated the contraction will increase
72
Off contraction
once the inhibitory hyperpolarization ceases then there will be an increase in contraction (force production)
73
GI peptides function to
regulate GI function
74
2 classes of GI peptides
Gastrin and CCK that work to INCREASE INTRACELLULAR Ca | Secretin-like peptides that work to STIMULATE cAMP SYNTHESIS
75
Examples of secretin-like peptides
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
examples of GI peptides that function as hormones
Gastrin, secretin, CCK, motilin, GLP-1, GIP
77
GI peptide hormones function and site of release
released from GI mucosal endocrine cells into portal circulation; enter systemic circulation but only effect cells with receptors
78
GI peptides that have paracrine function
somatostatin and histamine
79
GI peptide paracrine function and site of release
released from GI mucosal endocrine cells and bind nearby receptors, local action, does not enter systemic circulation
80
GI peptides that have neurocrine function
Substance P, VIP, GRP
81
GI peptide neurocrine function and site of release
Released from nerve terminals to bind nearby receptors, do not circulate, local action only
82
Other hormones not released by endocrine cells not located in the GIT
Aldosterone, thyroid hormones, vitamin D
83
Aldosterone's role
enhance sodium and water reabsorption
84
Thyroid hormone's role
normal GI motility
85
Vitamin D's role
enhance calcium absorption in small intestine
86
3 main regulators of GI function
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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