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LSS : Alimentary system > regulation of the gut : > Flashcards

regulation of the gut : Flashcards

1
Q

what is the enteric system?

A

this is the control of the gut

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2
Q

how many neurones does the wall of the gut contain?

A

10 - 100 million

contains a rich plexus of ganglia interconnected by tracts of mine unmyelinated nerve fibres

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3
Q

what is the function of the enetric nervous system?

A

enteric system integrates the motor and secretory activities of the GI system.

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4
Q

is the enteric nervous system independent or dependent?

A
  • can function independently

- if the sympathetic and parasympathetic nerves to the gut are cut then many motor and secretory activities carry on

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5
Q

what does the enteric nervous system regulate?

A 
Motility
Blood flow
Water and electrolyte transport
Secretion
Absorption
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6
Q

what are the three types of neurones in the enteric system?

A
  • sensory
    respond to mechanical, thermal, osmotic and chemical stimuli
  • motor
    axons terminate on smooth muscle cells of the circular or longitudinal layers, secretory cells of the gastrointestinal tract
  • interneurones
    integrate the sensory input and effector output
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7
Q

what is the myenteric plexus?

A

located between the circular and longitudinal smooth muscle layers
- controls the activity of the muscularis externa

function to control the gut motor function

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8
Q

what is the Submucosal plexus ?

A
  • Sensing environment within lumen
function : 
- Blood flow, epithelial and endocrine cell function.
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9
Q

what are the minor plexuses?

A

including deep muscular plexus (inside circular muscle), and the ganglia supplying biliary system and pancreas

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10
Q

what sympathetic nerves carry innervation to the midgut?

A
  • thoracic splanchnic nerves
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11
Q

what nerves carry sympathetic innervation to the remainder of the gut?

A

Lumbar splanchnic nerves

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12
Q

what is the main sympathetic neurotransmitter?

A

noradrenaline

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13
Q

what does the sympathetic nervous system do to the gut?

A

Activation of the sympathetic nerves usually inhibit the activities of the GI system.

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14
Q

what parasympathetic nerves innervate the GI tract?

A

vagus nerve

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15
Q

what parasympathetic nerves innervate the rest of the gut?

A

pelvic nerves

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16
Q

what is the main parasympathetic neurotransmitter?

A

acetyl choline

17
Q

where do most sympathetic fibres innervate?

A

Majority sympathetic fibres do not directly innervate structures in the GI tract- terminate on neurons in the intramural plexuses.

except Vasoconstrictor sympathetic fibers do directly innervate the blood vessels of the GI tract

18
Q

what is the interinsic and extrinsic innervation of the GI tract?

A
  • Intrinsic innervation:
    Neurons of the enteric nervous system
  • Extrinsic innervation:
    Afferents (pain, nausea, fullness)
    Efferents (coordination - sympathetic and parasympathetic nervous systems).
19
Q

**how is the central nervous system involved?

A
20
Q

what are the overall actions of the parasympathetic

A

The parasympathetic nervous system innervates the gut via long preganglionic neurones (mostly via the vagus nerve) and short postganglionic neurones to promote gut motility, secretion and digestion

21
Q

what are the overall actions of the sympathetic

A

The sympathetic nervous system innervates the gut via short preganglionic and long post ganglionic fibres to inhibit gut motility and secretion, and cause constriction of blood vessels and contraction of sphincters

22
Q

**what is the main gut hormones?

A
23
Q

what cells in the gut sense nutrients?

A
  • enteroendocrine
24
Q

what is the function of the gastrointestinal endocrine system.

?

A
  • Regulation of the mechanical processes of digestion
  • Regulation of the chemical and enzymatic processes of digestion
  • Control of post absorptive processes involved in the assimilation of digested food and CNS feedback regulating intake
  • Effects on the growth and development of the GI tract
25
Q

what are the paracrine roles?

A
  • acting on near by cells
  • Somatostatin from the stomach can inhibit acid secretion by paracrine mechanisms.

but also somatostatin can also work in otger ways

26
Q

what does gastrin do?

where is it synthesised?

what is release stimulated by?

A

Gastrin stimulates gastric acid secretion
- Synthesised in gastric antrum and upper small intestine

  • Release stimulated by:
    Amino acids and peptides in the lumen of the stomach.
    Gastric distension.
    Vagus nerve directly
27
Q

what does somatostatin do?

A
  • universal inhibitor
    causes inhibition of gastric secretion, motility, intestinal and pancreatic secretions, release of gut hormones, intestinal nutrient and electrolyte transport, growth and proliferation.
28
Q

where is somatostatin synthesised?

A

Synthesized in endocrine D cells of the gastric and duodenal mucosa, pancreas

29
Q

where is secretin secreted?

A

by the S cells of the upper duodenum and jejunum

30
Q

what is the stimulus of secretin?

A

Major stimulus is the presence of acid in the duodenum

31
Q

what does secretin do?

A

Stimulates pancreatic bicarbonate secretion

High concentrations: inhibition of gastric acid and gastric emptying.

32
Q

where is CCK secreted?

A

Secreted by cells most densely located in the small intestine.

33
Q

what stimulates release of CCK?

A

stimulated by fat and peptides in the upper small intestine.

34
Q

what does CCK do?

A

stimulates pancreatic enzyme release

  • delays gastric emptying
  • stimulates gallbladder contraction.
  • decreases food intake and meal size.
35
Q

where is GIP secreted from?

A

Secreted by mucosal K cells

36
Q

when is GIP released?

A

GIP released following ingestion of a mixed meal

37
Q

what does GIP do?

A

stimulates release of insulin

38
Q

what cells secrete peptide YY?

A
  • Cells found throughout the mucosa of the terminal ileum, colon and rectum
  • released from L cells
39
Q

what does PYY do?

A

PYY reduces intestinal motility, gallbladder contraction and pancreatic exocrine secretion.

  • Inhibitor of intestinal fluid and electrolyte secretion.

LSS : Alimentary system (13 decks)

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