Lecture 6: Autonomic Nervous System Flashcards
Autonomic NS
involuntary motor (efferent) branch of the NS that innervates smooth & cardiac muscle, viscera and glands. Regulates unconscious processes to maintain homeostasis
another name for the ANS
visceral motor system
when is the SNS most active
during exertion, stress, emergency
when is the PNS most active
under resting conditions
examples of functions of the SNS
-stimulates metabolism by releasing glucose stores
-increase HR, BP and force of contraction
-downregulates digestive activity
-dilates blood vessels in skeletal muscle
examples of functions of the PNS
-promotes relaxation, nutrient uptake and energy storage
-decreases HR, BP, and force of contraction
-stimulates digestive secretions and increases gut motility
-dilates blood vessels in GI tract
what is myelin sheath
lipid-rich sheath that surrounds some nerve cell axons
how many neurons are used on a somatic system
one neuron between CNS and target (skeletal muscle)
how many neurons used in an autonomic system
two neurons between CNS and target. preganglionic and postganglionic
preganglionic location of neuronal cell bodies
brainstem or spinal cord
is preganglionic or postganglionic myelinated
preganglionic
postganglionic location of neuronal cell bodies
autonomic ganglion
what is a ganglion
collection of neuronal cell bodies found in the PNS
-function as relay stations between preganglionic and postganglionic neurons of the ANS
Parasympathetic cranial nerves
III, VII, IX, X
Sympathetic ganglia
- The sympathetic Chain
- Prevertebral ganglia
-celiac
-superior mesenteric
-inferior mesenteric
preganglionic sympathetic neurons are limited to
T1-L2
paired sympathetic ganglia linked together to form
a chain along the length of the vertebral column: C1-S2
purpose of the sympathetic chain
this coordinates and spreads sympathetic responses to many target tissues simultaneously
prevertebral ganglia
-situated anterior to the vertebral column, along the aorta
-celiac ganglion
-superior mesenteric ganglion
-Inferior mesenteric ganglion
how are prevertebral ganglia named
relative to blood vessels branching from the abdominal aorta
Length of preganglionic neuron vs postganglionic neurons in sympathetic NS
pre - short (b/c gnaglia are located close to vertebral column)
post - long
Rami communications
connection between the spinal nerve and the sympathetic trunk (on and off ramps)
white rami are only from
T1-L2
*grey rami are at all levels
sympathetic outflow origination
lateral horn of the spinal cord, from segments T1-L2
preganglionic neuron exits the spinal cord via the
ventral horn & root to enter the spinal nerve
preganglionic neuron enters te sympathetic chain via the
white ramus communicans
3 main routes upon entering the sympathetic chain
- Synapse within the chain at the same level
- Change level within the chain and then synapse
- Formation of sphlanic nerve
route for preganglionic neuron at same level
preganglionic neuron synapses with postganglionic neuron at the same level & exits via the grey ramus, travelling with spinal nerve to target
is white or grey ramus communicans myelinated
white
example of when preganglionic neuron would synapse at same level
innervation of blood vessels and sweat glands
preganglionic neurons located between T1-L2 target
-body wall
-abdominal and thoracic viscera
-limbs
route for preganglionic neurons that change level
they can ascend or descend within the symp chain then synapse, entering via white ramus and exiting via grey ramus
Ascending nerves target
-head/neck viscera
-thoracic viscera
-upper limbs
Descending nerves target
-abdominopelvic viscera
-lower limbs
postganglionic axons contribute to autonomic plexuses including:
-cardiac plexus
-pilmonary plexus
route of formation of splanchnic nerves
form when autonomic fibres do not rejoin from the spinal nerve. Preganglionic fibres bypass the sympathetic chain and synapse in peripheral (prevertebral) ganglion near the target organ
does the formation of a sphlancnic nerve still use the white and grey ramus communicans
NO only uses white
What do splanchnic nerves target
absominopelvic viscera
sympathetic splanchnic nerves synapse in
prevertebral ganglia
Thoracic and lumbar splanchnic nerves
-Greater (T5-9)
-Lesser (T10-11)
-Least/Lumbar (T12-L2)
Greater splanchnic –>
celiac ganglion
Lesser splanchnic –>
superior mesenteric ganglion
Least/Lumbar
inferior mesenteric ganglion
what only recieves sympathetic nerve activity
sweat glands and limb vasculature
what does the PNS target
-viscera of head and neck
-abdominal and thoracic viscera
-pelvic viscera
Length of preganglionic neuron vs postganglionic neurons in parasymp NS
pre = long
post = short
where are parasympathetic ganglia located
near or within the target organ
where are sympathetic ganglia located
close to vertebral column
PNS, cranial outflow
preganglionic cell bodies within brainstem cranial nuclei; axons travel via CN: III, VII, IX, X
Cranial outflow had and neck
-preganglionic neurons leave brainstem from parasympathetic nuclei
-synapse on post-ganglionic neuron within parasympathetic ganaglia
what happens when the sublingual/submandibular glands are stimulated
increase secretion of saliva
what happens when the lacrimal gland is stimulated
increased tear production
what ganglion must be reached for the lacrimal gland to be stimulated
pterygopalatine ganglion
facial nerve: what ganglion must be reached for the submandibular and sublinguinal glads to be stimulated
submandibular ganglion
parasympathetic innervation of the eye
Brainstem -> CN III -> Ciliary ganglion -> Ciliary muscles & sphincter pupilae of eye (opens pupil)
cranial outflow: thoracic and abdominal viscera
-preganglionic neurons leave the brainstem via CN X
-supplies parasympathetics to pharaynx, larynx, and midgut structures
-preganglionic neurons synapse on ganglia within or close to target organ
Sacral Outflow: distal GI tract and pelvic viscera
-preganglionic neuronal cell bodies loacted in spinal segments S2-S4
-axons travel via pelvic splanchnic nerves
-preganglionic fibers synapse within ganglia in or near effector organ to supply targets
which nerve supplies parasymp innervation to lungs
CN X
Visceral afferent fibers conduct:
sensory information from autonomic targets to the CNS
Are visceral affterent fibres parasymp or symp?
neither; they are distinct from the ANS and are not considered either
visceral reflexes
simplest functional units in the autonomic NS
visceral reflex arcs
consist of a sensory nerve and visceral motor neurons
Enteric NS
-network of neurons located in the walls of the digestive tract
-recieves regulatory signals via sympathetic and parasympathetic divisions
*can operate independant ly of the other two via self-regulation
