Phys- Neural Factors Flashcards
The ____ is the innermost layer of smooth muscle cells.
muscularis mucosa
Contraction results in folding _____ of the entire mucosal layer, which _____ exposure of epithelial cells to luminal contents.
fluctuations
increases
Contraction of the muscle layers of the muscularis exerna are primarily responsible for the __ and ___ of luminal contents.
mixing
propulsion
The submucosal plexus (Meissner’s plexus) is best developed where?
small intestine
The myenteric plexus (Auerbach’s plexus) is located where and best developed where?
between the circular longitudinal smooth muscle layer of the muscularis externa
entire gut length
Interneurons within the plexuses connect ____ sensory fibers to ___ fibers innervation smooth muscle cells and secretory cells and create local reflex arcs within the GI tract.
afferent
efferent
The presence of extrinsic nerves from the autonomic nervous system is necessary for ____ of most GI functions.
coordination
Afferent fibers from ____ and ____ within the gut wall run to the CNS, which then influence central neural control of the GI tract as well as elicit _____ via the ENS.
chemoreceptors
mechanoreceptors
local reflexes
Parasympathetic innervation to the GI tract is nerve fibers from what nerves?
vagus and pelvic (sacral)
vagus above and including transverse colon, below transverse colon is pelvic
Preganglionic fibers terminate mostly on the ganglia of the intramural plexuses and share their postganglionic neurons with the ENS. They are mostly what?
cholinergic
Activation of parasympathetic nerves (vagus) is most often ____ and ____ either ___ or ____.
excitatory
increasing
motility
secretion
Release of VIP (and NO) ____ _____ of GI smooth muscle. ACh (and SubP) released from postganglionic neurons ____ ____.
inhibit contraction
excites contraction
Activation of sympathetic nerves usually results in ___ of motor and secretory activity.
inhibition
NE is released in the ____ plexus, ____ parasympathetic ___ release by activating alpha2 presynaptic receptors.
submucosal, inhibits, ACh
Pathways which influence the muscularis externa (_____) and muscularis mucosae (______) act though the intramural plexuses.
inhibitory
stimulating
Sympathetic fibers innervate blood vessels of the gut directly causing ____ and is ___ receptor mediated.
vasoconstriction
alpha 1
GI smooth muscle is therefore, an example of ____ smooth muscle. The ____ of the cells in adjacent muscle bundles is a major determinant of how far the electrical signal is transmitted down the GI tract.
single unit
excitability
The BER varies from ___/min in the stomach to __/min in the duodenum. The BER of each segment is set by a group of faster cells called what?
3
12
pacemakers
The ___ of the slow waves can be modulated by intrinsic and extrinsic neural input. Sympathetic ______, parasympathetic stimulation ______.
amplitude
decreases amplitude
increases amplitude
The initial rising phase of the action potential is due primarily to ___ entry into the cell through L-type ___ channels.
Ca^2+
Ca^2+
Extracellular calcium entering ___ smooth muscle cells during an action potential is a major source of calcium for ___.
visceral
contraction
Does the stomach need an action potential to contract? What about the intestine?
no
yes the intestine does
