Spino-thalamic pathway

Spino-thalamic pathway > projected onto sagittally sectioned brain

KEY CONCEPTS

The course of the spino-thalamic pathway from sensory ending to somatosensory cortex is illustrated here, emphasising the sequence of three sets of neurons (three synapses) between the periphery and the cortex. (Advanced explanation: see 'Further information' tab above)

First synapse in spinal cord.
Second synapse is in the thalamus (lateral ventro-posterior nucleus, VPL).
Third synapse is in the somato-sensory cortex.
Pathway decussates (crosses sides) in the spinal cord ventrally
Carries:

• Pain
• Temperature
• Crude (light) touch

Is a slow conduction route

Spino-thalamic pathway > projected onto sagittally sectioned brain

The three neuron pathway from spinal cord to cortex consists of:

A first order sensory neuron with peripheral sensory endings in skin, connective tissue, muscles etc. and cell body in a dorsal root ganglion. Axon enters the spinal cord through the dorsal root.

Then it synapses with a second order sensory neuron located in dorsal horn of the spinal cord (grey matter); the axon of this neuron passes across the midline ventrally to enter the spino-thalamic tract (in the lateral and ventral white columns of the cord) on the opposite side. This tract passes to the thalamus in the diencephalon of the brain.

Here each axon synapses with a third-order sensory neuron located in the thalamus whose axon passes through the thalamo-cortical tract (somatosensory radiation) to the somatosensory cortex located in the post-central gyrus of the cerebral hemisphere's parietal lobe where lt synapses with one or more cortical neurons.

Spino-thalamic pathway > projected onto sagittally sectioned brain

Click/tap on the image 6 times to advance the animation. Wait for each action potential to reach its destination at the end of the neuron before clicking/tapping again. Click/tap again to re-start the animation.