1 Intro To GI Phys Flashcards
Functions of the GI tract
Digestion, absorption of nutrients, motility, secretions
GI sphincters name (7) and function
UES, LES, pyloric, sphincter of Oddi, Ileocecal valve, internal and external anal sphincter
Fx: restrict passage of intestinal content and optimizes digestion and absorption
Functional layers of the GI tract
Mucosal, submucosa, muscle (circular and longitudinal), Serosa
What part of the Enteric Nervous System is in the layers of the GI tract?
What layers?
Innervated by what?
Does it need the CNS?
Submucosal plexus: submucosa
Myenteric plexus: muscle
Extrinsic autonomic nervous system
NO
Where does the ENS receive its information?
Parasympathetic and sympathetic NS and CNS
Sensory info from mechanoreceptors and chemoreceptors in the mucosa
Function of the ENS
Controls contraction, secretion, and endocrine function of the GI tract
CNS role in the regulation of the GI tract (3)
Vago-vagal reflex
Modulate ENS response
Centers that control food intake in brain
Sensory ganglion of the Vagal N
Nodose ganglion
Example of a vago-vagal reflex
Gastric receptive relaxation reflex
NTS
Nucleus of the tractus solitarius
Nerves of the parasympathetic innervation
Vagus and pelvic nerves
Location of the parasympathetic preganglionic nerve cell bodies
Brainstem or sacral spinal cord
Location of the parasympathetic postganglionic neurons
Wall of the organ (enteric neuron in the gut wall)
What type of synapse is between the parasympathetic pre and post ganglionic cells?
Nicotinic (nAChRs)
Where do the sympathetic preganglionic efferent fibers begin and end?
Begin in spinal cord (thoracic and lumbar)
End in prevertebral ganglia
Sympathetic postganglionic fibers from the prevertebral ganglia innervate _________
Myenteric and submucosal plexuses
Sympathetic preganglionic efferent fibers release______.
Sympathetic postganglionic efferent nerves release ______.
Ach
NE
Long preganglioic fibers, short postganglionic fibers
Parasympathetic NS
Short preganglionic fibers, long postganglionic fibers
Sympathetic NS
How do paracrine signals reach their target cells?
Where do they act?
Diffusion over short distances
Locally
Function of paracrine regulation
Action of peptides or other messenger molecules
Examples of paracrine signals
Somatostatin and histamine
Secreted by D cells in the GI mucosa
Somatostatin
Inhibits secretion of gastric H+ and other GI hormones
Somatostatin
Somatostatin is secreted by_______.
D cells of the GI mucosa
Hypothalamus
Delta cells of the exocrine pancreas
Stimulated by a decrease a in luminal pH
Why?
Somatostatin
Low pH signals somatostatin to inhibits gastric H+ secretion
Stored and secreted by enterochromaffin-like (ECL) cells
Histamine
Histamine is secreted in the _____.
Gastric glands of the stomach