Trunk nerves (intercostal, sympathetic, vagus nerve)
Anterior horn of the spinal cord (Cornu anterius)
Cornu anterius medullae spinalis
- Origin
- Ventral extension of the grey matter along the whole length of the cord; it holds the motor anterior horn cells, the alpha and gamma motor neurons
- Insertion
- Their axons leave the cord as the anterior root (radix anterior) and reach striated muscle through the spinal nerve
- Function
- Final common pathway of movement: every voluntary movement and every reflex reaches the muscle through these cells
- Innervation
- Motor nuclei of the central nervous system; alpha motor neurons for the working fibres, gamma motor neurons for the muscle spindles
- Movement & chain
- Turns the motor command into muscle contraction
- Palpation
- Not palpable; assessed through muscle strength, tone, atrophy, fasciculations and the tendon reflexes
- Clinical
- Poliomyelitis and spinal muscular atrophy destroy the anterior horn cells selectively (flaccid paresis, areflexia, atrophy and fasciculations without sensory loss); amyotrophic lateral sclerosis (ALS) affects them together with the upper motor neuron. An anterior horn lesion always gives a peripheral, flaccid paresis, unlike the spastic paresis of a lesion higher up the pathway.
- Segmental innervation
- Along the whole length C1-Co1, widening in the cervical (C4-T1) and lumbosacral (L1-S3) enlargements that supply the limbs
- In clinical practice
- Grading muscle strength on the MRC scale, noticing atrophy and fasciculations, and in flaccid paresis preventing contractures and transferring safely
- Region in the model
- Trunk nerves (intercostal, sympathetic, vagus nerve)