Spinal cord

Spinal cord meninges

The spinal cord ends at around L1 and tapers into a cone, getting smaller and smaller towards the end, called the conus medullaris

The pia mater of the spinal cord

Adheres to the surface of the spinal cord the entire way down, eventually dangling as a string called the filum terminale

Cauda equina

“Horses tail”

Sciatic nerves

Large nerves that leave at the end of the cauda equina, attached to the greater sciatic notch

Posterior horn

This horn all has axon ends of sensory neuron axons.

Lateral horn

Anterior horn

Mostly cell bodies of motor neurons, forming neuromuscular junctions.

Connected to the anterior root.

Grey matter

Gathered in the center, shaped like a butterfly, filled with cell bodies

White matter

Surrounds the grey matter and is superficial to it

Posterior root ganglion

This is where cell bodies of sensory neurons are located. Senses come in through here, enters the posterior horn of the spinal cord, forming a synapse, and carrying the information up to the thalamus

Contains satellite cells,

Spinal nerve

The nerve that extends laterally on each vertebrae, in charge of transporting incoming and outgoing senses.

Posterior ramus

Anterior ramus

Spinal nerve plexus

The anterior rami of spinal nerves weave together to form this. The nerves that emerge all have unique names and have a combination of axons from multiple spinal nerves.

4 Types: Cervical, brachial, lumbar sacral.

First order neuron

Cell body in the posterior root, travels through to the axon terminal in the spinal cord and form a synapse with an interneuron

Second order neuron

Starts at posterior horn, runs up through white matter columns in the spinal cord. Axon terminal is in the thalamus. Can make third order neuron more or less sensitive

Third order neuron

Runs from cell body in the thalamus to the axon terminal in the somatosensory cortex

Decussation

The chain of axons in the brainstem or thalamus crosses over