Sympathetic Anatomy (Thoracolumbar Division)

Preganglionic neurons are in what spinal cord segment of the sympathetic division

thoracolumbar (T1-L2)

What are preganglionic sympathetic neuron cell bodies in, and where do sympathetic neurons come from

lateral horns of the spinal cord

The three gray matter of the spinal cord and what neurons

dorsal horn → afferent sensory

ventral horn → efferent motor

lateral → autonomic sympathetic

Pathway of preganglionic fiber

spinal cord → ventral root → spinal nerve → white ramus communicans → sympathetic trunk ganglion

Sympathetic trunk (paravertebral ganglia)

runs along the vertebral column allowing signals to move up and down and synapse at same level (spread)

After preganglionic fibers synapse in the ganglion →

turns into postganglionic fibers and leave through gray ramus communicans

white ramus communicans → enter

gray ramus communcans → exit

Fiber length of sympathetic neurons

Short preganglionic

Long postganglionic

because the ganglia is near the spinal cord

How many paravertebral ganglia are there in the sympathetic trunk

23

What are the three options of a preganglionic fiber after entering the sympathetic trunk

1. synapse with postganglionic neruon at the same ganglion

2. ascend or descend the sympathetic trunk to synpase in another trunk ganglion

3. pass through trunk ganglion and emerge without synapsing → splanchnic nerves

Adrenal medulla

Preganglionic sympathetic fibers go directly to adrenal medulla.

No postganglionic neuron

adrenal medulla acts as modified sympathetic ganglion → releasese epineprhine and norepineprhine into the blood

Where are the 5 sympathetic pathways sympathetic fibers can go to after entering the sympathetic trunk

head(ascend), thorax (same level), collateral ganglia (splanchnic nerves) (pass through), abdomen (descend), pelvic (Descend)

Where are ANS cell bodies in the CNS and outside the CNS

preganglionic cell bodies (in the CNS) → in lateral horn of spinal cord gray matter

post ganglionic cell bodies (outside the CNS) → Sympathetic chain ganglion (paravertebral ganglion)

Why sympathetic responses are widespread

the paravertebral trunk/ chain allows moving up and down

many postganglionic branches

adrenal medulla releases hormones into the blood

Visceral reflex arc

Same as somatic reflexes except its automatic and in visceral organs

except there is two neurons in the motor pathway

• sensory receptor → sensory neuron → integration center → efferent motor pathway (2 neurons - preganglionic and ganglionic neuron) → effector

Referred pain

Pain felt somewhere else than actual source because visceral pain afferents (sensory) travel along the same pathway as somatic pain fibers → pain in arm during heart attack