Spinal Nerves
The 31 sets of spinal nerves:
Composition of Spinal Nerves
Spinal nerves are, as you can guess, nerves.
They meet the spinal cord as sensory information enters through the dorsal root and motor/autonomic information leaves through the ventral root.
Dorsal Root
- sensory, both from somatic and visceral
- axons from pseudounipolar neurons whose bodies are in the dorsal root ganglia
- visceral neurons extend through paravertebral ganglia and white ramus communicantes through
- medial bundle contains large, myelinated fibres
(Aα and Aβ)
- typically enter and ascend ipsilaterally through dorsal finiculus
- proprioreceptors and fine touch
- lateral bundle contains smaller Aδ and C fibres
- enter and synapse in dorsal horn substantia gelatinosa
- generally nociceptor and temperature
Ventral Root
The ventral root is the site of exit of from the spinal cord following synapse of upper motor neurons of the corticospinal tract
Lower alpha motor neuron axons are distributed peripherally to skeletal muscle.
Autonomic outflow, originating from the lateral horn, leaves the ventral root but leaves the spinal nerve through the white ramus communicantes and enters the paravertebral ganglia, where they can ascend or descend, or synpase
- can leave through the splanchnic nerves and join pre-vertebral ganglia
- can also leave the gray ramus communicantes to rejoin spinal nerves and innervate blood vessels, glands, hairs
Cervical Spinal Nerves
| motor | sensory | reflex | |
| C3 | |||
| C4 | |||
| C5 | |||
| C6 | |||
| C7 | |||
| T1 | |||
| T2 |
C3
C4
C5 - deltoids, rhomboids
C6 - wrist extension