Spinal Cord

Spinal cord (ending)

Elongated part of the CNS extending from the foramen magnum to approximately the L2 vertebral level in adults

Spinal cord segments

31 total segments giving rise to paired spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

Conus medullaris

Tapered caudal end of the spinal cord

Filum terminale

Thin extension of pia mater anchoring the conus medullaris to the coccyx

Cervical enlargement

Region of the spinal cord (C5–T1) that supplies the upper extremities via the brachial plexus

Lumbosacral enlargement

Region of the spinal cord (L1–S3) that supplies the lower extremities

Spinal meninges

Three protective coverings of the spinal cord: dura mater, arachnoid mater and pia mater

Dorsal rootlets

Posterior rootlets that carry sensory (afferent) information into the spinal cord

Ventral rootlets

Anterior rootlets that carry motor (efferent) information out of the spinal cord

Dorsal root ganglion

Collection of sensory neuron cell bodies located on the dorsal root

Spinal nerve

Formed by the union of dorsal and ventral roots and contains mixed sensory and motor fibers

Rami

Branches of a spinal nerve that remain mixed and go on to form named peripheral nerves

Dermatome

Area of skin supplied by a single spinal nerve

Myotome

Group of muscles supplied by a single spinal nerve

Gray matter (spinal cord)

H- or butterfly-shaped central region of the spinal cord containing neuron cell bodies

White matter

Outer region of the spinal cord composed of ascending and descending axon tracts

Dorsal horn

Region of gray matter that receives sensory input

Ventral horn

Region of gray matter containing motor neurons that innervate skeletal muscle

Lateral horn

Gray matter region present from T1–L2 containing sympathetic preganglionic neuron cell bodies

Central canal

CSF-filled channel at the center of the spinal cord

Anterior median fissure

Deep ventral groove separating the anterior white matter

Posterior median sulcus

Shallow dorsal groove separating the posterior white matter

Alar plate

Embryologic dorsal neural tube region that develops into sensory structures

Basal plate

Embryologic ventral neural tube region that develops into motor structures

Ventricular zone derivative

Region that gives rise to spinal gray matter during development

Funiculi

Three major white matter regions of the spinal cord: dorsal, lateral and anterior

Dorsal columns

Ascending tracts that convey fine touch, proprioception, and vibration from the ipsilateral side of the body to the somatosensory cortex

Fasciculus gracilis

Dorsal column tract carrying sensory information from the legs (YELLOW) ipsilaterally to the primary somatosensory area

Fasciculus cuneatus

Dorsal column tract carrying sensory information from the arms (GREEN) ipsilaterally to the primary somatosensory area

Spinothalamic tract

Ascending tract conveying pain, temp, crude touch, contralateral to the primary somatosensory area (TEAL)

Lissauer’s tract

Region where pain and temperature fibers ascend or descend one to two levels before crossing

Spinocerebellar tracts

Ascending tracts conveying unconscious proprioceptive information ipsilaterally to the cerebellum (DARK BLUE/GREY)

Corticospinal tract

Descending motor pathway controlling voluntary movement (ORANGE)

Lateral corticospinal tract

Major corticospinal pathway (80-90%) that decussates in the caudal medulla and controls limb movement

Ventral corticospinal tract

Minor corticospinal pathway (10-20%) that decussates in the spinal cord and controls trunk muscles

Upper motor neuron

Neuron originating in the cortex that influences lower motor neurons

Lower motor neuron

Neuron in the ventral horn whose axon innervates skeletal muscle

Anterior spinal artery

Single artery from the vertebral artery supplying the anterior two-thirds of the spinal cord including motor tracts (symptoms of problem- lose muscle)

Posterior spinal arteries

Paired arteries from the vertebral arteries/PICAs supplying the dorsal columns of the spinal cord (symptoms of problem- lose sensation)

Artery of Adamkiewicz

Major radicular artery supplying the lumbosacral enlargement

Anterior spinal artery syndrome

Ischemic injury causing bilateral motor paralysis and loss of pain and temperature with preserved dorsal column function

Brown-Sequard syndrome

Hemicord lesion causing ipsilateral motor weakness and loss of proprioception with contralateral loss of pain and temperature

Spinal reflex

Involuntary stereotyped response mediated by a spinal circuit

Reflex arc

Pathway consisting of receptor, sensory neuron, integration, motor neuron, and effector

Monosynaptic reflex

Reflex involving a single synapse such as the patellar reflex

Polysynaptic reflex

Reflex involving multiple synapses such as the withdrawal reflex