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regulation Flashcards

1
Q

summarise the enteric nervous system

A

intrinsic
10-100million neurons
rich plexus of ganglia (nerve and glial cells) - interconnected by unmyelinated nerve fibres

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2
Q

how many neurones does the CNS have

A

100billion

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3
Q

why are the neurons not myelinated

A

Speed not as important

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4
Q

role of the enteric nervous system

A

integrate the motor and secretory functions of the GI tract

independent of CNS

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5
Q

secretion controlled by the GI tract

A

panc, enzymes juice

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6
Q

conditions where the ENS is degenerated/dysfunctional

A

inflammation - ulcerative colitis -degeneration off enteric ns – not regulated

post-op

IBS – some problems associated with enteric Ns

Aging – constipation - motility, degeneration of ens with age

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7
Q

what fucntions does the ENS regulate

A

Motility
Blood flow

Water and electrolyte - Absorb ions that power water absorption

transport
Secretion
Absorption

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8
Q

describe the neurons in the ENS

A

sensory - respond to mech, thermal, osmotic and chemical stimuli eg CCK respond to the FA in the duodenum -> stim panc juice release

motor - axons end on sm - circular/longitudinal, secretory cells or bv

interneurons - between neurons, integration, coordinate stimuli

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9
Q

describe the myenteric plexus

A

between longitudinal and circular muscle

contral activity of muscularis externa - gut motor func

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10
Q

describe the submucosal plexus

A

Under epi layer – sense what going on in the lumen, change blood flow, endo and epi func – help digestion

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11
Q

plexuses down the gut

A

Sub and myenteric are continuous down the gut

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12
Q

describe minor plexuses

A

include deep musclualr plexus - inside the circular muscle

and ganglia supplying the biliary system and pancreas

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13
Q

describe the role of the ANS

A

automatic
sm, cardic, glands

symp and parasymp

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14
Q

describe the organisation of the sympathetic nervous system

A

cell bodies of preganglionic in thoracic and lumbar spinal cord - short
cell bodies of post are in the pre and para-vertebral ganglia
long postganglionic neurons

thoracic splanchnic nerves carry innervation to the fore and midgut - first 2/3 transverse colon
lumbar splanchnic to hindgut

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15
Q

role of the sympathetic nervous system

A

when don’t need to think about digestion too much – move blood flow to different areas
Evacuate bowels when scared – evolutionary because of shut down of symp

contraction of sphincters and vasoconstriction

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16
Q

neurotransmitter of the sympathetic ns

A

norepinephrine or noradrenaline (same thing)

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17
Q

describe the organisation of the PNS

A

cell bodies of preganglionic in brainstem and sacral spinal cord
cell body of post - close to target organs
preganglionic neurons synapse on ganglia close to gut wall/directly with enteric plexi
long pre and short postganglionic

most from vagus - to the transverse colon
remainder - pelvic nerves

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18
Q

role of the PNS

A

Digestive regulation
Stuff in stomach and duodenum – digestion complex

can cause excitation – sometimes turn something on and switch something else off

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19
Q

NT of PNS

A

Ach

20
Q

relkationship between sympathetic NS and bv

A

regulate bv via the ENS

also reserves right to also control gut function directly – SNS canstop flow to gut - vasoconstrictor sympathetic fibres from coeliac, superior and inferior mesenteric arteries

21
Q

ANS relationship with ENS

A

ANS neurons synapse on the ENS myenteric and submucosal plexi
interact and regulate the ENS function

22
Q

how are afferent signals interperated

A

ENS receives local afferents - chemo and mechanoreceptors – effects downstream – don’t need to go back to brain

Some can go back to CN S – integrate func – output to modulate enteric ns

23
Q

describe the innervation of the GI tract

A

intrinsic - neurons of enteric
extrinsic - afferents: pain, nausea (toxins), full
efferents: coordination

24
Q

where are hormones of the GI endocrine system produced

A

endocrine cells in mucosa/submucosa of stomach, intestine and panc

25
Q

what ‘type’ of endocrine

A

paracrine, neurocrine - hormone released from neurone – eg hypothalamic releasing factors

in gut – neurons release hormones rather than nT

26
Q

summarise the GI tract as an endocrine system

A

Diffuse endocrine system – most cells not endocrine but there are endocrine cells within it – 15 epi layer are endo
All the way down gut

27
Q

why does the distribution of the endocrine cells change down the GI tract

A

you want differnet functions to occur

28
Q

what does L cell produce

A

Peptide YY and glucagone peptide 1

29
Q

describe a flask cell

A

finger of cytoplasm – detection mech- chemoreceptor signal down cell – hormone release – into circulatuon

30
Q

what cell produces CCK

A

I cells

31
Q

how are I cells stimulated

A

Different receptors at top
Cell can tell what is going in gut – hormone release appropriately – see hoe much glucose, what stage of digestion, contents

32
Q

what is the function of the GI tract endocrine system

A

regulation of mechanical processes - sm of GI, sphincter and gall bladder

and chemical and enzymatic processes of digestion - secretory cells, panc and liver

control of post absorbative processes involved in assimilation of digested food and CNS feedback regulating intake absorpative-= blood glucose level, appetite regulation

effects of growth and development of the GI - GLP2 – growth of intestine – target for drug for people with short bowel – need for normal gut func

33
Q

how is insulin controlled by GI endocrine system

A

GIP - stim insulin from B cells

Peptide YY3-36 acts on the cns to suppress appetite

34
Q

example of paracrine action sin the gut

A

histamine - from stomach wall - stimulus for parietal cells -> HCl

somatostatin - inhibit acid secretion by paracrine mechanisms

35
Q

describe gastrin

  • where
  • stimulated by
  • stimulates
  • inhibited
A

synthesised in gastric antrum and upper SI

stimulated by - aa and peptides in lumen of stomach, stretch, vagus - when think of food

stimulates - gastric acid secretion

inhibited when pH< 3 -be feedback

36
Q

describe somatostatin

A

syntheisised in D cells of gastric and duodenal mucosa, pancreas

universal inhibitor - gastric secretion, motility, intestinal and panc secretions, release hormones, nutrient and electrolyte transport, growth and proliferation

stimulated by mixed meal

37
Q

treatment of neuroendocrine tumour

A

somatostatin - Analogue – neuroendocrine tumour treatment, difficult to pick – non-specific symptoms – suppressed hormone and tumour growth

38
Q

why is a somatostatin analogue used - why cant we just use normal somatostatin

A

Peptide hormones have real;ly sshort half life – want to turn off gastrin – want to break it down quickly
Make analougue that has a longer half life so you don’t have to keep injecting blood

Different receptors – tweak molecule so it targets certain ones more – selectively

Need to inject – cant eat it because would just digest, maybe can encapsulate so can have oral treatment

39
Q

describe secretin

A

secreted by S cells
in upper duodenum and jejunum

stimulus - acid in duodenum pH<4.5

stimulates pancreatic bicarb secretion - potentiated by CCK

40
Q

secretin effects at high concentrations

A

If pH so low and really bhigh secretin need to stop gastrin – inhibit gastric acid and gastric emptying

41
Q

describe CCK

A

secreted by cells mainly in SI

stimulated by fat and peptides in upper SI

independent of the vagus

stimulates - pancreatic enzyme release, delays gastric acid emptying, stimulates gallbladder contraction, decrease food intake and meal size

42
Q

what does GIP stand for

A

gastric inhibitory polypeptide or glucose-dependant insulinotropic peptide

43
Q

action of GIP

A

secreted by mucoal K cells - duodenum and jejunum
follow mixed meal
stimulate insulin secretion

44
Q

effect of GIP receptor antagonists

A

reduce insulin release after a meal

45
Q

why does food injected into the blood trigger less insulin than that ingested

A

incretin effect - GIP regulate the level of insulin in the GI tract

46
Q

describe peptide YY

A

mucosa of terminal ileum, colon and rectum
released from L cells after eating

reduce motility, gall bladder contraction, pancreatic exocrine secretion, inhibit intestinal fluid and electrolyte secretion - PYY3-36 inhibits the food intake

ailmentary (15 decks)

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