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digestive regulation Flashcards

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1
Q

regulation of GI function; describe intrinsic system

A
  • In the GI wall
  • Enteric nervous system
  • Endocrine control
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2
Q

regulation of GI function; describe extrinsic system

A
  • Outside wall of GI tract
  • Influence intrinsic system
  • Central nervous system
  • Endocrine control
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3
Q

enteric nervous system is connected to, communicated w and receives feedback from the ___ and ____

A

SNS and PNS

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4
Q

is enteric nervous system capable of independent function from the remainder of the nervous system

A

yes; local reflex activity

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5
Q

what is enteric nervous system involved with in the regulation of digestive processes

A

 Controls secretions of the GI organs
 Controls peristalsis and some other movements

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6
Q

instrinsic system nerves and endocrine secretion

A
  • nerves; enteric nervous system (ENS)
  • endocrine secretions; secretin, gastrin, CCK, GIP, and Motilin
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7
Q

extrinisc system nerves and endocrine secretions

A
  • nerves; vagus and splanchnic nerves
  • endocrine secretions; aldosterone
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8
Q

what 3 neurons are included in the enteric nervous system (ENS)

A

1) sensory (afferent) neurons
2) interneurons
3) motor (efferent) neurons

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9
Q

in ENS, the sensory (afferent) neurons detect

A

chemical and mechanical conditions in the gut

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10
Q

in the ENS, motor (efferent) neurons control

A

peristalsis

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11
Q

in the ENS, interneurons

A

make the enteric nervous system capable of reflexes, and able to act as an integrating centre when there’s no CNS input

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12
Q

sensory neurons include mechanoreceptors; where are they and what do they do

A
  • Within muscle layers
  • sense Distension of gut (stretch, pressure)
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13
Q

sensory neurons include chemoreceptors; where are they and what do they do

A
  • Mucosa
  • sense chemical conditions in gut lumen (peptides, pH, etc)
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14
Q

ENS; where do interneurons travel within

A

travel long distances within the myenteric plexus (auerbach’s) and connect the myenteric and submucosal plexus (meissner’s)

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15
Q

Submucous plexus (Meissner plexus): where and what does it regulate

A

in submucosa → regulates fluid and electrolyte movement across the intestinal mucosa

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16
Q

Myenteric plexus (Auerbach plexus): where and what does it regulate

A

in muscularis propria between the longitudinal and circular layers of the smooth muscle in walls of the GI tract →
coordinates smooth muscle contractions involved in peristalsis

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17
Q

motor (efferent) neurons innervate what

A

smooth muscle within the gut wall and within arteries

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18
Q

Regulation of smooth muscle contractions occurs via

A

interneuronal connections.

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19
Q

The signal that efferent neurons that signal glands within the gut can be either

A

excitatory – stimulating movement or release of substances from glands ‐ or inhibitory

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20
Q

describe axon terminals in the ANS (what are they called, what do they allow for and what do they secrete)

A

often in bead‐like strings,
called varicosities

allow for a bigger, more wide‐spread activation of the target tissue, and allow more neurotransmitter to be released across that range of tissue

secrete neurotransmitters aka neurocrines, can be excitatory or inhibitory

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21
Q

Excitatory neurocrine transmitters are mainly _____, meaning they secrete ______

A

cholinergic
acetylcholine

  • although also neuropeptides such as substance P which are also excitatory
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22
Q

inhibitory neurocrine transmitters are mainly

A

peptides

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23
Q

Vasoactive intestinal
peptide can be either excitatory or inhibitory, depending on the receptor on the target tissue. When it is released in the gut muscle, it has an ______ effect. However, when it’s released in the mucosal glands, it has an _____ effect.

A

inhibitory
stimulatory

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24
Q

how is the ENS an exception to the 2-neuron efferent innervation rule of the ANS

A

It might have 3 or more neurons

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25
enteric nervous system accomplishes synaptic transmission by using more than ____ neurotransmitters including :
30 acetylcholine, dopamine, nitric oxide and serotonin
26
visceral reflexes stimulus and response
stimulus * Change in temperature * Stretch of the GI tract * Pain (irritation) in the viscera * Change in blood gas composition response * Shivering, hair erection, sweating * Sneezing, coughing * Contraction of the GI tract * Change in breathing pattern
27
where are endocrine cells found
in the epithelium of the GI tract
28
endocrine cells have a narrow apex; what does it do
samples lumen contents
29
endocrine cells have a broad base that secretes
regulatory peptides (true enodcrines, paracirnes, autocrines and neurocrines)
30
endocrine cells secrete regulatory peptides: some of these secreted peptides are true endocrine hormones where do they travel and what are 2 examples
They travel through the blood stream to affect other regions of the gut. examples of this include gastrin and somatostatin.
31
endocrine cells secrete regulatory peptides: some of these secreted peptides are paracrines where do they travel and what are 2 examples
* Diffuse locally through extracellular fluid (ECF) * Somatostatin, peptide YY
32
endocrine cells secrete regulatory peptides: some of these secreted peptides are autocrines
modify or regulate functions of same cell
33
endocrine cells secrete regulatory peptides: some of these secreted peptides are neurocrines what are these released by
enteric neurons
34
GASTRIN production actions release stimulus
production: distal stomach actions: primary: stimulates stomach HCl secondary: stomach motility, trophic effect on stomach epithelium release stimulus: - Distension of stomach antrum - Vagal stimulation - Protein in stomach - High gastric pH
35
SECRETIN production actions release stimulus
production: duodenum actions: primary: stimulates pancreatic HCO3- secretions secondary: stimulates billary HCO3- secretion release stimulus H+ in duodenum
36
cholecystokinin (CCK) production actions release stimulus
production: SI, most in duodenum actions: primary; stimulates pancreatic enzyme secretion secondary: inhibits gastric emptying release stimulus: proteins and fats in SI
37
gastric inhibitory polypeptide (GIP) production actions release stimulus
production: duodenum, upper jejunum actions: primary: inhibits gastric motility and secretions secondary: stimulates insulin (if sufficient glucose present) release stimulus CHO and fat in SI
38
motilin production actions release stimulus
production: duodenum, jejunum actions primary: increases gut motility between meals secondary: regulate tone lower esophageal sphincter release stimulus: ACh
39
major gastrointestinal hormones (5)
- gastrin - secretin - cholecystokinin (CCK) - gastric inhibitory polypeptide (GIP) - motilin
40
gastrin feedback loop
1. Stomach fills with food 2. Buffering occurs → increase pH + Protein in stomach 3. Gastrin released 4. Increased HCl production 5. Decrease pH → decreases Gastrin release
41
Intrinsic system (Enteric Nervous System) influenced by
extrinsic system
42
autonomic nervous system includes
- Parasympathetic (stimulates) - Sympathetic (inhibitory)
43
Parasympathetic Nervous System: ganglion location
Ganglion is close to target organ
44
Parasympathetic Nervous System: Preganglionic fibres synapse on
cell bodies of enteric nervous system
45
Parasympathetic Nervous System: postganlionic fiber is short or long
short (so long myelinated preganglionic nerve)
46
sympathetic nervous ganglia location
close to spinal cord in thorax and abdomen
47
autonomic nervous system: brief recap
The efferent nerves are a 2 nerve system. They have a pre‐ and a post‐ganglionic nerve, which synapse in a ganglion. In the parasympathetic nervous system, this ganglion is close to the target organ. In fact, they synapse on the cell bodies of the enteric nervous system, in the myenteric or submucosal plexus. So it has a long myelinated preganglionic nerve, with the ganglion sitting close to the target organ. This preganglionic nerve releases acetylcholine. The acetylcholine goes across the synaptic cleft and binds to a nicotinic type 2 receptor. From here, that stimulates the post‐ganglionic nerve, which is also cholinergic. So this postganglionic nerve also releases acetylcholine into the synaptic cleft. Now, this acetylcholine can bind to a number of different types of muscarinic receptors, types 1, 2 and 3. This are G‐protein coupled receptors. So when they get stimulated, they stimulate a signal transduction pathway
48
symapthetic nervous system: is postganglionic fibre long or short
long (short preganglionic fibre, which is myelinated, with the cell body in the spinal cord.)
49
sympathetic nervous system recap
Then we’ve got the sympathetic nervous system. You have your first, short preganglionic fibre, which is myelinated, with the cell body in the spinal cord. When it gets to the autonomic ganglia, there’s a synapse. This ganglia is sitting close to the spinal cord in the thorax and abdomen. This presynaptic nerve releases acetylcholine, which diffuses across the synaptic cleft and binds to a nicotinic type 2 receptor. These particular receptors also allow for ions to travel through and will stimulate the longer postganglionic nerve, which goes all the way to the effector tissue. In the GI tract, this postganglionic nerve releases noradrenaline, or norepinephrine. Some post‐ganglionic fibres synapse on the cell bodies of the enteric nervous system, other synapse directly on GI muscles and glands. Sympathetic stimulation in the GI tract usually has an inhibitory effect.
50
sympathetic action on smooth muscle walls parasympathetic
relaxes contracts
51
sympathetic action on smooth muscle sphincters parasympathetic
contracts relaxes
52
sympathetic and parasympathetic saliva secretion
increase increase
53
parasympathetic action on gastric acid secretion
increases
54
parasympathetic action on pancreatic secretion
increase
55
extrinsic: endocrine effects: aldosterone secreted in response to
* Low BP * Low sodium * High potassium * Factors occurring outside of GI tract
56
main effects or aldosterone are in _____ but also has effects in GIT
kidney
57
______ is the main mineralocorticoid steroid hormone produced by the adrenal gland
aldosterone
58
what does aldosterone stimulate
sodium and water reabsorption from the gut and salivary glands in exchange for potassium ions
59
gut-associated lymphoid tissue: GI tract has many immune cells such as
phagocytes and lymphocytes
60
gut-associated lymphoid tissue: Mucosa exposed to numerous
microorganisms and antigens
61
normmal immune response
* Production of antibodies * Recruitment of killer cells * Sensitised lymphocytes can secrete cytokines
62
cytokines influence intrinsic nervous and endocrine systems, give examples
- Increase motility and secretions - Diarrhoea - Dilute offending antigen - “Flush” toxins from lumen
63
regulatory peptides have a trophic effect : so when food intake increases, amount of regulatory proteins released in GI tract increases (like gastrin) this triggers hypertrophy of hut mucosa: what does this mean?
the amount of food that can be digested and absorbed increases
64
in summary: GIT has its own independent intrinsic enteric nervous system that contains
receptors, sensory neurons, interneurons and motor neurons
65
GIT has intrinsic endocrine system and main hormones include
gastrin, secretin, CCK, GIP and motilin
66
gastrin, secretin, CCK, GIP and motilin, these hormones are part of what system
intrinsic endocrine system of GIT
67
Which of the following statements regarding regulation of GI function is INCORRECT? A. The intrinsic system is comprised of 2 components, both of which are located within the wall of the GI tract. This system includes nerves, the enteric nervous system, as well as endocrine secretions such as secretin. B. The extrinsic system is comprised of 2 components, both of which are located outside the wall of the GI tract, and influence the intrinsic system. Extrinsic influence from the autonomic nervous system includes both afferent and efferent nerves. Extrinsic hormonal control is provided through the actions of gastrin. C. The extrinsic system is comprised of 2 components, both of which are located outside the wall of the GI tract, and influence the intrinsic system. Extrinsic influence from the autonomic nervous system includes both afferent and efferent nerves. Extrinsic hormonal control is provided through the actions of aldosterone. D. Gastrointestinal function is regulated by both intrinsic and extrinsic systems.
B. The extrinsic system is comprised of 2 components, both of which are located outside the wall of the GI tract, and influence the intrinsic system. Extrinsic influence from the autonomic nervous system includes both afferent and efferent nerves. Extrinsic hormonal control is provided through the actions of gastrin.
68
Interneurons in the enteric nervous system travel within the myenteric plexus. What does the myenteric plexus co-ordinate?
Peristalsis
69
Which of the following is NOT a component of the enteric nervous system? A. Submucosal plexus B. Myenteric plexus C. Chemoreceptors in the GI tract D. Vagus nerve
D. Vagus nerve
70
Which of the following cell types found in the epithelium of the GI tract are part of the intrisic endocrine system?
Enterochromaffin cells
71
Which of the following hormones stimulates the parietal cells in the stomach to release hydrochloric acid?
Gastrin
72
Which of the following hormones stimulates pancreatic enzyme secretion, and is released when proteins and fats are present in the small intestine?
Cholecystokinin
73
Which neurotransmitter is released by the preganglionic fibre of the parasympathetic nervous system, when it synapses on a cell body of the enteric nervous system, in the myenteric or submucosal plexus?
Acetylcholine
74
Which of the following hormones is involved in the extrinsic endocrine control of the GI tract?
Aldosterone

VETS1003 (23 decks)

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