1. The sympathetic Chain 2. Prevertebral ganglia -celiac -superior mesenteric -inferior mesenteric

Lecture 6: Autonomic Nervous System Flashcards by Elle Chapman

Autonomic NS

involuntary motor (efferent) branch of the NS that innervates smooth & cardiac muscle, viscera and glands. Regulates unconscious processes to maintain homeostasis

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another name for the ANS

visceral motor system

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when is the SNS most active

during exertion, stress, emergency

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when is the PNS most active

under resting conditions

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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

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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

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what is myelin sheath

lipid-rich sheath that surrounds some nerve cell axons

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how many neurons are used on a somatic system

one neuron between CNS and target (skeletal muscle)

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how many neurons used in an autonomic system

two neurons between CNS and target. preganglionic and postganglionic

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preganglionic location of neuronal cell bodies

brainstem or spinal cord

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is preganglionic or postganglionic myelinated

preganglionic

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postganglionic location of neuronal cell bodies

autonomic ganglion

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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

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Parasympathetic cranial nerves

III, VII, IX, X

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Sympathetic ganglia

The sympathetic Chain
Prevertebral ganglia
-celiac
-superior mesenteric
-inferior mesenteric

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preganglionic sympathetic neurons are limited to

T1-L2

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paired sympathetic ganglia linked together to form

a chain along the length of the vertebral column: C1-S2

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purpose of the sympathetic chain

this coordinates and spreads sympathetic responses to many target tissues simultaneously

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prevertebral ganglia

-situated anterior to the vertebral column, along the aorta
-celiac ganglion
-superior mesenteric ganglion
-Inferior mesenteric ganglion

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how are prevertebral ganglia named

relative to blood vessels branching from the abdominal aorta

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Length of preganglionic neuron vs postganglionic neurons in sympathetic NS

pre - short (b/c gnaglia are located close to vertebral column)

post - long

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Rami communications

connection between the spinal nerve and the sympathetic trunk (on and off ramps)

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white rami are only from

T1-L2

*grey rami are at all levels

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sympathetic outflow origination

lateral horn of the spinal cord, from segments T1-L2

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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

1. Synapse within the chain at the same level 2. Change level within the chain and then synapse 3. 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