Regulation of gastrointestinal function Flashcards
Name the 2 plexuses involved in intrinsic (enteric) nervous and endocrine control.
Myenteric (auerbach’s) plexus
Submucosal (Meissner’s) plexus
Stimulation of the myenteric plexus causes?
Peristalsis, contractions along the whole GIT
Stimulation of the Meissner’s plexus causes?
Secretions
Name the 3 components of the intrinsic enteric nervous system
Meissner’s (submucosal) plexus
Myenteric (auerbach’s) plexus
Enteroendocrine cells in mucosa/ pancreas
Name and describe the 2 types of sensory (afferent) neurons.
Mechanoreceptors: within smooth muscle layers, measures gut distension
Chemoreceptors: within mucosa, measure chemical conditions in the lumen of the gut (e.g. peptides, pH)
Describe interneurons
Travel long distances within the MYENTERIC PLEXUS (AUERBACH’S PLEXUS) and connect the myenteric and submucosal (meissners) plexus
List the excitatory neurocrine neurotransmitters
Cholinergic (secrete Ach)
peptide substances
List the inhibitory neurocrine transmitters
Peptides - somatostatin
Nitric oxide, ATP
Name a dual purpose peptide and its actions
Vasoactive intestinal peptide (VIP) which inhibits smooth muscle, and stimulates
List the 2 true endocrine hormones., why are these considered true hormones
Somatostatin and gastrin, true hormones as they have to travel via blood
What do enterochromaffin cells secrete
Secretin
Explain the process of paracrine secretion.
Cell targeting a nearby cell (no blood required)
Explain the process of endocrine secretion.
Cell targeting a distant cell via a bloodstream
Explain the process of holocrine secretion.
Cell breaking apart to release its contents
What hormone acts as a paracrine molecule?
Somatostatin
What nerve is the main supply for the GIT, and what is the common term for it?
CNX, vagus nerve
What additional nerve supplies some of the caudal GIT?
Pelvic nerve
Name the 3 sympathetic innervation (ganglia) to the GIT
coeliac, cranial mesenteric ganglion, caudal mesenteric ganglion
What are 2 locations postganglionic fibres will synapse with in the sympathetic nervous system?
The ENS or to the smooth muscle/ glands directly
Is the sympathetic innervation usually inhibitory/ excitatory? why?
Inhibitory, as its related to the stress response fight/ flight
What are the effects on the gut from sympathetic nerve stimulation? what benefit does this serve?
Decreased motility, decreased blood flow to the area, decreased secretion. Allows the animal to direct more energy to the fight/ flight stimuli
Describe the trophic effect.
An increase in food intake results in an increase of regulatory protein released (e.g. gastrin -> increases HCl secretion). This increases the amount of food that can be digested/ absorbed
