block I: GI autonomics Flashcards
mention the sympathetic and parasympathetics
sympathetic: T1-L2,L3
Parasympathetic: cranial nuclei & S2-S4
explain the disynaptic pathways
Autonomic nervous system:
1. sympathetic:
-soma in CNS
-Preganglionic fibers that release ACh
-autonomivm sympathetic ganglion synapses and has nicotinic receptors
-postganglionic fibers with NE trasnmitters synapse in smooth muscle, cardiac muscle and gland cells with adrenergic receptros. (except for sweat glands that trasnmitter is ACh thoguth muscarinic receptors)
- parasympathetic:
-soma in CNS
-preganglionic fibers
-autonomic parasympathetic ganglion with ACh trasnmitter, fiber makes synapse here in nicotinic receptors
-postganglionic fibers with ACh transmitter make synapse in smooth muscle, cardiac uscle and gland cells with muscarinic receptors.
Somatic motir system:
-soma in SNS
monosynaptic pathway somatic motor fiber synpses durectly in skeletal muscle with nicotinic receptors and ACh transmitter
identify
1st thoracic segment (sympathetic division) [T1-L2,L3]
identify
lumbar segment (sympathetic division) [T1-L2,L3]
identify
2nd sacral segment (parasympathetic division [Brainstem & S2-S4]
Mention the functions of the sympathetic division in the abdomen:
(adrenergic receptors)
*Vasoconstriction
*Inhibition of GI peristalsis
*Decrease in secretory activity of GIglands
*Contraction of GI sphinchters
*In the liver, promotes breakdownof glycogen to glucose and itsrelease into the blood
*Relaxation of the gallbladder
*Release into the bloodstream of
epinephrine / norepinephrine from
the medulla of the adrenal glands
(nicotinic ACh receptors)
Mention the functions of the parasympathetic division in the abdomen
(muscarinic ACh receptors
-Vasodilation
Stimulation of GI peristalsis
-Increase in secretory activity of GI glands
-Relaxation of GI sphinchters
Contraction of gallbladder
*Although this is primarily induced by cholecystokinin released from mucosal endocrine cells
mention the ganglia sympathetic
- paravertebral
- celiac
- superior mesenteric
- renal/aorticorenal
- inferior mesenteric
mention the plexuses (mixed)
- celiac
- superior mesenteric
- renal/aorticorenal
- intermesenteric
- inferior mesenteric
- superior hypogastric
- inferior hypogastrics
- periarterial
Note: There are scattered postsynaptic autonomic
neurons (both sympathetic & parasympathetic)
throughout the plexuses that do not group to form
ganglia
What are the abdominopelvic splachnic nerves?
Formed by presynaptic fibers
Sympathetic:
-(Lower) Thoracic splanchnic nerves
*Greater (T5-T9) celiac g.
*Lesser (T10- T11) superior mesenteric g.
*Least (T12) renal/ aorticorenal g.
-Lumbar splanchnic nerves
inferior mesenteric g. and p. &
superior hypogastric p.
-Sacral splanchnic nerves
inferior hypogastric p.
Parasympathetic:
-Pelvic splanchnic nerves (S2 S4)
inferior hypogastric & enteric p.
and walls of viscera
Whcih are the vagus nerves?
anterio vagal trunk and posterior vagal trunk
What is the enteric nervous system?
Semiindependent network within walls
of the gut, often considered as the 3 rd
division of the autonomic nervous
system, that functions to control:
*Gut motility
*Ion transport, associated with
secretion and absorption
*Gastrointestinal blood flow
What is the enteric nervous system composed of?
It is composed of two anatomically
distinct, but interconnected networks of
neurons embedded in the wall of the
digestive tract:
Myenteric Plexus (of Auerbach)
between inner circular and outer
longitudinal smooth muscle layers,
coordinates peristalsis along the gut
Submucosal Plexus (of Meissner)
in submucosal layer of gut, regulates
ion and water transport and blood flow
across the gut, and senses the
environment within the gut’s lumen.
describe the enteric nervous system
- Complex network with as many neurons
as those found in the spinal cord, often
referred to as the body ´ s second brain - Structures in common with those of CNS:
* Sensory neurons
* Motor neurons
* Interneurons
* Glia
3.Large array of neurotransmitters
4. Capacity for independent functioning
5. Communication links with CNS, through
parasympathetic and sympathetic
components of the ANS
where does the enteric nervous system come from?
Neural crest cells form
all of the ganglia for the ANS, including the enteric
ganglia, which serve as the parasympathetic ganglia for the GI tract.
What is congenital aganglionic megacolon (Hirscprungs disease)
Rare congenital abnormality (~1 in 5000), more common in males, in which section
of colon lacks enteric neurons (aganglionic),
due to failure of proper migration of neural crest
cells
Nerve cells stop growing at the end of the large intestine, just before the rectum and anus
In some children, the cells are missing at other places in the digestive system as
well
the body can’t sense when waste material reaches a certain point, so the waste
material gets stuck and forms a block in the system
symptoms and complications of hirschsprungs disease
No peristalsis through denervated
segment
Fecal matter accumulates proximal to
denervated area, resulting in a dilated
section of colon (megacolon)
When pressure in dilated section is
sufficiently high, feces are forced
through the rectum, resulting in
overflow diarrhea
Nutritional status of affected children
is negatively affected
Treatment is removal of aganglionic
portion of colon and reconnection of
working parts
identify
Sharply localized somatic
identify
poorly localized visceral
