regulation of the gut : Flashcards
what is the enteric system?
this is the control of the gut
how many neurones does the wall of the gut contain?
10 - 100 million
contains a rich plexus of ganglia interconnected by tracts of mine unmyelinated nerve fibres
what is the function of the enetric nervous system?
enteric system integrates the motor and secretory activities of the GI system.
is the enteric nervous system independent or dependent?
- can function independently
- if the sympathetic and parasympathetic nerves to the gut are cut then many motor and secretory activities carry on
what does the enteric nervous system regulate?
Motility Blood flow Water and electrolyte transport Secretion Absorption
what are the three types of neurones in the enteric system?
- 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
what is the myenteric plexus?
located between the circular and longitudinal smooth muscle layers
- controls the activity of the muscularis externa
function to control the gut motor function
what is the Submucosal plexus ?
- Sensing environment within lumen
function : - Blood flow, epithelial and endocrine cell function.
what are the minor plexuses?
including deep muscular plexus (inside circular muscle), and the ganglia supplying biliary system and pancreas
what sympathetic nerves carry innervation to the midgut?
- thoracic splanchnic nerves
what nerves carry sympathetic innervation to the remainder of the gut?
Lumbar splanchnic nerves
what is the main sympathetic neurotransmitter?
noradrenaline
what does the sympathetic nervous system do to the gut?
Activation of the sympathetic nerves usually inhibit the activities of the GI system.
what parasympathetic nerves innervate the GI tract?
vagus nerve
what parasympathetic nerves innervate the rest of the gut?
pelvic nerves
what is the main parasympathetic neurotransmitter?
acetyl choline
where do most sympathetic fibres innervate?
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
what is the interinsic and extrinsic innervation of the GI tract?
- Intrinsic innervation:
Neurons of the enteric nervous system - Extrinsic innervation:
Afferents (pain, nausea, fullness)
Efferents (coordination - sympathetic and parasympathetic nervous systems).
**how is the central nervous system involved?
what are the overall actions of the parasympathetic
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
what are the overall actions of the sympathetic
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
**what is the main gut hormones?
what cells in the gut sense nutrients?
- enteroendocrine
what is the function of the gastrointestinal endocrine system.
?
- 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
