GI Flashcards
Neurocrine that mediates vagally-stimulated gastrin release
Bombesin
GRP
Neurocrine that relaxes smooth muscle and increases secretions whole inhibiting gastrin stimulated gastric acid
Vasoactive intestinal peptide (VIP)
Neurocrine that increases saliva, contracts sphincters and relaxes smooth muscles in wall
Norepinephrine (NE)
Neurocrine that increase GI secretions, relaxes features and contracts smooth muscle
Acetylcholine
Enkephalins (opiates)
Contraction of smooth muscle
Decrease of intestinal secretions
Neuropeptide Y
Relax smooth muscle
Decrease secretions
Substance P
Contract smooth muscle
Increase salivary secretions
Secreted by postganglionic parasympathetic peptide thick neurons of mucosa and smooth muscle
VIP
Bombesin
Secreted from neurons of mucosa and smooth muscle
Enkephalins
Neuropeptide Y
Secreted from adrenergic neurons
Norepinephrine
Substance P
Paracrines
Somatostatin
Histamine
GI Hormones
Gastrin Cholecystokinin Secretin Gastric inhibitory peptide Motilin
6 functions of GI system
Ingestion Mechanical digestion Propulsion Chemical digestion Absorption Defecation
Major smooth muscle coat if GI tract
Muscularis externa
Connective tissue layer that contains glands and blood vessels
Submucosa
Innermost layer of wall of GI tract
Mucosa
Smooth muscle that contracts and changes the shape and surface area of epithelial layer
Muscularis mucosae
-part if mucosa (innermost layer of wall)
2 tasks accomplished by portal vein
1- supplies liver with metabolic substrates
2- ensures that substances ingested are first processed by the liver
Advantages of parallel/series organization
Parallel: allows for regulation of flow to individual organs
Series: liver is exposed to all absorbed substances
Afferents to myenteric and sub mucosal plexuses come from
Chemo- and mechanoreceptors
The plexuses send afferents to CNS via
ANS
*ENS does not require ANS input to carry out most functions (self contained)
Located in muscularis externa between outer longitudinal and inner circular smooth muscle layers
Myenteric (Auerbach’s) plexus
- innervates the longitudinal and circular smooth muscle layers
Plexus primarily concerned with gut motility
Myenteric (Auerbach’s) plexus
Located in submucosa
Innervates glandular epithelium, intestinal cells, sub mucosal blood vessels
Submucosal (Meissner’s) plexus