Basic Neuroscience · Neuroanatomy
Spinal Cord Nuclei & Tracts
The spinal cord nuclei and the ascending (sensory) and descending (motor) tracts, with their functions and lesion effects.
Spinal cord nuclei
| Nucleus | Function | Clinical |
|---|---|---|
| Renshaw cells | Inhibit alpha motor neurons via negative feedback (alpha → ↑Renshaw → ↓alpha) | Target for tetanus toxin → prevents glycine release from Renshaw cells → tetanic contraction |
| Substantia gelatinosa of Rolando (SGR) | Second-order neuron for STT; projects to thalamic VPM nucleus | Pain can be modulated here via opioid receptors |
| Marginal nucleus | Receives input from Lissauer's tract; relays pain and temperature | Pain cannot be modulated at this level |
| Nucleus proprius | Second-order neuron for STT; projects to spinal and supraspinal relay centers | — |
| Intermediolateral nucleus | Extends T1–L2; gives presynaptic sympathetic fibers | — |
| Clarke's nucleus | Extends T1–L4; relays proprioception from muscle spindles to cerebellar cortex via the dorsal spinocerebellar tract | — |
| Onuf's nucleus | Anterior horn of the sacral region; innervates the voluntary external urethral sphincter | Preserved in MND; affected in Shy-Drager disease |
Spinal cord tracts
| Tract | Function | Notes |
|---|---|---|
| Sensory (ascending) | ||
| Posterior column | Proprioception (position), pressure, vibration and fine touch | — |
| Lateral spinothalamic | Pain and temperature | — |
| Anterior spinothalamic | Crude touch | — |
| Dorsal & ventral spinocerebellar | Proprioception from ipsilateral caudal body and leg | — |
| Cuneocerebellar | Proprioception from ipsilateral arm | — |
| Spinoreticular | Arousal and alertness response to pain | — |
| Spino-olivary | Conveys proprioception to the olivary nucleus, then to the cerebellum | — |
| Motor (descending) | ||
| Anterior corticospinal | Controls movements of axial muscles | — |
| Lateral corticospinal | Controls fine movements of the limbs | — |
| Rubrospinal | Controls large-muscle and fine movements of the upper limb | Facilitates flexor tone; can enlarge and assume corticospinal functions after a pyramidal lesion |
| Vestibulospinal | Maintains head and eye coordination, upright posture and balance | Facilitates extensor tone; keeps upright position |
| Tectospinal | Mediates reflex postural movements of the head to visual and auditory stimuli | — |
| Reticulospinal | Coordinates automatic movements of locomotion and posture; mediates withdrawal to painful stimuli | Inhibited by the corticospinal tract; causes decerebrate rigidity in lesions below the red nucleus |
LIGHTS on RITE by Ahmed Koriesh