Spinal Cord Anatomy

The anterior median fissure continues from the anterior aspect of the medulla to the end of the SC

A dermatome is a skin segment that receives its innervation from one specific spinal nerve

Occurs when a specific body region shares its spinal nerve innervation with a separate dermatomal skin segment

The pain experienced by the body part is misinterpreted by the cortex as pain coming from a separate dermatomal skin segment level

This cortical misinterpretation occurs because the cortex does not have prior experience interpreting pain from the heart. The cortex relies on past experience when interpreting pain from a visceral source. Because it is uncommon for pain sensations to originate in the viscera, the cortex initially interprets the pain as coming from the left arm (dermatome T1)

As the pain increases, the cortex is able to correctly identify the source of the pain as the heart.

For example, if a patient cannot perceive sensation on the dorsal forearm, the therapist is able to determine that there is some impairment at C6 level

The use of transcutaneous electrical nerve stimulation (TENS) is based on the dermatomal distribution

The therapist places the TENS unit on the identified dermatome region to stimulate nerve regeneration or to reduce pain in a peripheral nerve injury

Consist of ascending sensory pathways and descending motor pathways

Ascending sensory spinal nerves extend from a sensory receptor to the dorsal rootlets.

Descending motor spinal nerves extend from the ventral horn of the SC to skeletal muscles

8 cervical

12 Thoracic

5 lumbar

5 sacral

1 coccygeal

the dorsal root ganglion contains the cell bodies of sensory nerves that are part of the Somatic PNS

Each sensory never has its own dorsal root ganglion

The dorsal root emerges from the dorsal ganglia

The dorsal roots are ascending spinal nerves that carry sensory data from the sensory receptors in the PNS to the dorsal horn of the SC

Dorsal roots are axon bundles that emerge from a spinal nerve

The dorsal root leads into the dorsal rootlets, which are thin string-like axons that emerge from the dorsal root and synapse in the dorsal horn of the SC

Contains cell bodies of many sensory SC tracts

When the spinal nerves have synapsed with an SC tract, the SC tract ascends through the SC and brainstem and travels to the cortex

Descending motor SC tracts travel from the Cerebrum down through the brainstem and SC

Motor SC tracts synapse with interneurons in the ventral horn

The ventral rootlets merge into the ventral roots and extend to skeletal muscles

From C1 to C7, the spinal nerves exit above their corresponding vertebrae

There is a pair of C8 spinal nerves but no C8 vertebra

This means that the C8 spinal nerve must exit below C7 vertebra and above T1 vertabra

Comes from the Vertebral Arteries

The vertebral arteries are 2 branches that give rise to 1 anterior and 2 posterior spinal arteries

A reflex that is mediated solely at the SC level; no cortical involvement, no conscious decision making

Spinal reflexes allow sensory information to be processed and acted upon quickly, without cortical processing

carries motor messages from the primary motor cortex

to the cranial nerve nuclei in the brainstem

to the Interneurons in the ventral horn.

UNMs are considered to be part of the CNS

In an UNM lesion, spasticity occurs below the lesion level

Extend from the foramen Magnum to the Conus Medularis

The Cauda Equina are spinal nerves that have not yet exited the vertebral column

The dorsal intermediate sulcus continues from the posterior aspect of the medula and extends only throughout the thoracic levels of the SC

This sulcus separates 2 ascending sensory pathways; the fasciculus gracilis and cuneatus of the dorsal columns

The SC has an hourglass shape. Enlargements occur in the cervical and lumbar sections.

The cervical enlargement is due to the brachial plexus, a network of spinal nerves from C5 to T1 that extend from the Cervical vertebrae to the upper extremities

When the spinal nerves of the bracihal plexus enter the SC, they account for the large area of white matter in the cervical SC

The lumbar enlargement is due to the lumbar plexus, a network of spinal nerves from L1 to S3 that extend from the lumbar vertebrae to the lower extremities

When the spinal nerves of the lumbar plexus enter the SC, they account for the large area of white matter in the lumbar SC

The dorsal median sulcus continues from the posterior aspect of the medulla to the end of the SC

The central canal contains cerebrospinal fluid

The white matter is divided into 3 pairs of funiculi

Gray matter contains the cell bodies of the sensory SC tracts (in the dorsal horn) and the cell bodies of the motor spinal nerves ( in the ventral horn)

The cell bodies for the motor spinal nerves that innervate the proximal muscle groups are located in the medial ventral horn

The cell bodies for the motor spinal nerves that innervate the distal muscle groups are located in the lateral ventral horn

The meninges of the SC are the same as those of the brain

a reflex arc in which a muscle contracts when its tendon is prcussed

In a Lower Motor Neuron (LMN) injury, deep tendon reflexes become hyporeflexive

Arnold Chiari Malformation