Intermediolateral cell column T1–L2 via white rami communicantes
Preganglionic · T1–L2 White rami T1–L2 only ACh
Myelinated preganglionic axons leave in the ventral roots of T1–L2 only, enter the spinal nerve, then pass through the white ramus communicans into the sympathetic trunk. Each fibre then synapses at its own level, ascends or descends the chain to synapse elsewhere, or passes straight through as a splanchnic nerve.
Traced from the start
- Sympathetic (thoracolumbar) outflow
- Intermediolateral cell column T1–L2 via white rami communicantes
Detail
- Three fates in the trunk
- Synapse at same level; ascend or descend to synapse at another level (cervical and sacral ganglia have no white rami of their own); pass through unsynapsed as thoracic or lumbar splanchnic nerves
- Oculosympathetic origin
- Ciliospinal centre of Budge, C8–T2 (mainly T1) — fibres ascend the cervical trunk to the superior cervical ganglion
- Splanchnic levels
- Greater T5–T9, lesser T10–T11, least T12, lumbar L1–L2 — carry preganglionic fibres to prevertebral ganglia and adrenal medulla
When it goes wrong
Apical lung (Pancoast) tumour, cervical rib, neck or brachial plexus trauma, thyroid or carotid surgery invading the T1 root or cervical chain
Preganglionic (second-order) Horner syndrome: ptosis and miosis with anhidrosis of the whole ipsilateral face and neck, often with T1 hand wasting; hydroxyamphetamine still dilates the pupil
Complete cervical or upper thoracic cord transection interrupts all descending sympathetic drive
Neurogenic shock: hypotension with warm dry peripheries and bradycardia (cardiac accelerators T1–T4 cut, vagus intact) — distinguishes it from haemorrhagic shock
Practise this structure
1 question in the bank tagged Autonomic.