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VETS1003 > digestive regulation > Flashcards

digestive regulation Flashcards

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
Q

enteric nervous system accomplishes synaptic transmission by using more than ____ neurotransmitters including :

A

30
acetylcholine, dopamine, nitric oxide and serotonin

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26
Q

visceral reflexes
stimulus and response

A

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

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27
Q

where are endocrine cells found

A

in the epithelium of the GI tract

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28
Q

endocrine cells have a narrow apex; what does it do

A

samples lumen contents

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29
Q

endocrine cells have a broad base that secretes

A

regulatory peptides (true enodcrines, paracirnes, autocrines and neurocrines)

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30
Q

endocrine cells secrete regulatory peptides: some of these secreted peptides are true endocrine hormones

where do they travel and what are 2 examples

A

They travel through the
blood stream to affect other regions of the gut.

examples of this include gastrin and somatostatin.

31
Q

endocrine cells secrete regulatory peptides: some of these secreted peptides are paracrines

where do they travel and what are 2 examples

A
  • Diffuse locally through extracellular fluid
    (ECF)
  • Somatostatin, peptide YY
32
Q

endocrine cells secrete regulatory peptides: some of these secreted peptides are autocrines

A

modify or regulate functions of same cell

33
Q

endocrine cells secrete regulatory peptides: some of these secreted peptides are neurocrines

what are these released by

A

enteric neurons

34
Q

GASTRIN

production
actions
release stimulus

A

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
Q

SECRETIN

production
actions
release stimulus

A

production: duodenum

actions:
primary: stimulates pancreatic HCO3- secretions
secondary: stimulates billary HCO3- secretion

release stimulus
H+ in duodenum

36
Q

cholecystokinin (CCK)

production
actions
release stimulus

A

production: SI, most in duodenum

actions:
primary; stimulates pancreatic enzyme secretion
secondary: inhibits gastric emptying

release stimulus: proteins and fats in SI

37
Q

gastric inhibitory polypeptide (GIP)

production
actions
release stimulus

A

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
Q

motilin

production
actions
release stimulus

A

production: duodenum, jejunum

actions
primary: increases gut motility between meals
secondary: regulate tone lower esophageal sphincter

release stimulus: ACh

39
Q

major gastrointestinal hormones (5)

A
  • gastrin
  • secretin
  • cholecystokinin (CCK)
  • gastric inhibitory polypeptide (GIP)
  • motilin
40
Q

gastrin feedback loop

A
  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
Q

Intrinsic system (Enteric Nervous System) influenced by

A

extrinsic system

42
Q

autonomic nervous system includes

A
  • Parasympathetic (stimulates)
  • Sympathetic (inhibitory)
43
Q

Parasympathetic Nervous System: ganglion location

A

Ganglion is close to target organ

44
Q

Parasympathetic Nervous System: Preganglionic fibres synapse on

A

cell bodies of enteric nervous system

45
Q

Parasympathetic Nervous System: postganlionic fiber is short or long

A

short
(so long myelinated preganglionic nerve)

46
Q

sympathetic nervous ganglia location

A

close to spinal cord in thorax and abdomen

47
Q

autonomic nervous system: brief recap

A

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
Q

symapthetic nervous system: is postganglionic fibre long or short

A

long

(short preganglionic fibre, which is myelinated, with the cell body in the spinal cord.)

49
Q

sympathetic nervous system recap

A

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
Q

sympathetic action on smooth muscle walls

parasympathetic

A

relaxes

contracts

51
Q

sympathetic action on smooth muscle sphincters

parasympathetic

A

contracts

relaxes

52
Q

sympathetic and parasympathetic saliva secretion

A

increase
increase

53
Q

parasympathetic action on gastric acid secretion

A

increases

54
Q

parasympathetic action on pancreatic secretion

A

increase

55
Q

extrinsic: endocrine effects:

aldosterone secreted in response to

A
  • Low BP
  • Low sodium
  • High potassium
  • Factors occurring outside of GI tract
56
Q

main effects or aldosterone are in _____ but also has effects in GIT

A

kidney

57
Q

______ is the main
mineralocorticoid steroid hormone produced by the adrenal gland

A

aldosterone

58
Q

what does aldosterone stimulate

A

sodium and water reabsorption from the gut and salivary glands in exchange for potassium ions

59
Q

gut-associated lymphoid tissue: GI tract has many immune cells such as

A

phagocytes and lymphocytes

60
Q

gut-associated lymphoid tissue: Mucosa exposed to numerous

A

microorganisms and antigens

61
Q

normmal immune response

A
  • Production of antibodies
  • Recruitment of killer cells
  • Sensitised lymphocytes can secrete cytokines
62
Q

cytokines influence intrinsic nervous and endocrine systems, give examples

A
  • Increase motility and secretions
  • Diarrhoea
  • Dilute offending antigen
  • “Flush” toxins from lumen
63
Q

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?

A

the amount of food that can be digested and absorbed increases

64
Q

in summary: GIT has its own independent intrinsic enteric nervous system that contains

A

receptors, sensory neurons, interneurons and motor neurons

65
Q

GIT has intrinsic endocrine system and main hormones include

A

gastrin, secretin, CCK, GIP and motilin

66
Q

gastrin, secretin, CCK, GIP and motilin, these hormones are part of what system

A

intrinsic endocrine system of GIT

67
Q

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.

A

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
Q

Interneurons in the enteric nervous system travel within the myenteric plexus. What does the myenteric plexus co-ordinate?

A

Peristalsis

69
Q

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

A

D. Vagus nerve

70
Q

Which of the following cell types found in the epithelium of the GI tract are part of the intrisic endocrine system?

A

Enterochromaffin cells

71
Q

Which of the following hormones stimulates the parietal cells in the stomach to release hydrochloric acid?

A

Gastrin

72
Q

Which of the following hormones stimulates pancreatic enzyme secretion, and is released when proteins and fats are present in the small intestine?

A

Cholecystokinin

73
Q

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?

A

Acetylcholine

74
Q

Which of the following hormones is involved in the extrinsic endocrine control of the GI tract?

A

Aldosterone

VETS1003 (23 decks)

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