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regulation Flashcards

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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

20
Q

relkationship between sympathetic NS and bv

Study These Flashcards
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

Study These Flashcards
A

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

22
Q

how are afferent signals interperated

Study These Flashcards
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

Study These Flashcards
A

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

24
Q

where are hormones of the GI endocrine system produced

Study These Flashcards
A

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

25
what 'type' of endocrine
paracrine, neurocrine - hormone released from neurone – eg hypothalamic releasing factors in gut – neurons release hormones rather than nT
26
summarise the GI tract as an endocrine system
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
why does the distribution of the endocrine cells change down the GI tract
you want differnet functions to occur
28
what does L cell produce
Peptide YY and glucagone peptide 1
29
describe a flask cell
finger of cytoplasm – detection mech- chemoreceptor signal down cell – hormone release – into circulatuon
30
what cell produces CCK
I cells
31
how are I cells stimulated
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
what is the function of the GI tract endocrine system
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
how is insulin controlled by GI endocrine system
GIP - stim insulin from B cells Peptide YY3-36 acts on the cns to suppress appetite
34
example of paracrine action sin the gut
histamine - from stomach wall - stimulus for parietal cells -> HCl somatostatin - inhibit acid secretion by paracrine mechanisms
35
describe gastrin - where - stimulated by - stimulates - inhibited
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
describe somatostatin
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
treatment of neuroendocrine tumour
somatostatin - Analogue – neuroendocrine tumour treatment, difficult to pick – non-specific symptoms – suppressed hormone and tumour growth
38
why is a somatostatin analogue used - why cant we just use normal somatostatin
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
describe secretin
secreted by S cells in upper duodenum and jejunum stimulus - acid in duodenum pH<4.5 stimulates pancreatic bicarb secretion - potentiated by CCK
40
secretin effects at high concentrations
If pH so low and really bhigh secretin need to stop gastrin – inhibit gastric acid and gastric emptying
41
describe CCK
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
what does GIP stand for
gastric inhibitory polypeptide or glucose-dependant insulinotropic peptide
43
action of GIP
secreted by mucoal K cells - duodenum and jejunum follow mixed meal stimulate insulin secretion
44
effect of GIP receptor antagonists
reduce insulin release after a meal
45
why does food injected into the blood trigger less insulin than that ingested
incretin effect - GIP regulate the level of insulin in the GI tract
46
describe peptide YY
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

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