Spinal cord and spinal nerves

What is the spinal cord apart of?

Central nervous system

What is the spinal cord?

The major communication link between the brain and the PNS

What is the spinal cord involved with?

The reflex mechanisms and the integration of incoming information

Where does the spinal cord extend from?

It extends from the medulla oblongata to L1 and L2

Where is the spinal cord located?

within the vertebral canal

What forms the vertebral canal?

formed by the vertebral foramen of the vertebrae

What surrounds the spinal cord?

by connective tissue membranes called meninges

What are meninges continuous with?

Continuous with the meninges of the brain

What are the three meninges of the spinal cord?

• Dura mater

• arachnoid mater

• pia mater

What is the lumbar puncture?

A procedure in which the CSF is drawn from the subarachnoid space

Where is lumbar puncture done at?

Done at L3-L4 or L4-L5

What are the major structures of the spinal cord?

• Cervical enlargement

• Lumbar enlargement

• Conus medullaris

What is the cervical enlargement?

A region where axons supplying the upper extremities enter or leave the spinal cord

What is the lumbar enlargement?

A region where axons supplying the lower extremities enter or leave the spinal cord

What is the cauda equina?

A collection of nerve roots that extend from the lumbar enlargement

What is the conus medullaris?

The cone shaped end of the spinal cord

Where is the conus medullaris anchored?

To the coccyx by the film terminale (which is a continuation of the Pia mater)

What is the spinal cord composed of?

Of gray matter (cell bodies) and white matter (myelinated axons)

What are the major structures of gray matter?

• The anterior horns

• lateral horns

• posterior horns

• central canal

What are the anterior (ventral) horns?

Structures that contain cell bodies of motor neurons supplying skeletal muscle

What are the lateral horns?

Structures that contain cells bodies of motor neurons supplying smooth or cardia muscle

Where are lateral horns located?

Only located at the T1-L2 vertebral levels

What are the posterior (dorsal) horns?

Structures that contain axons of sensory neurons

What is the central canal?

A canal located in the center of the gray matter (which is continuous with the fourth ventricle of the brain)

What is the central canal filled with?

CSF

What are the major structures of white matter?

• Ventral columns

• Dorsal columns

• lateral columns

What is each column in white matter divided into?

Into tracts also called pathways

What is each tract in white matter composed of?

a group of axons that carry a specific type of sensory of motor information

What carries sensory information in white matter?

Carried by ascending tracts

What carries motor information in white matter?

Carried by descending tracts

How many pairs of spinal nerves are associated with the spinal cord?

31 pairs

What does each spinal nerve contain?

Contains thousands of axons (both motor and sensory)

What do spinal nerves give rise to?

To peripheral nerves that supply all parts of the body (except the head and some parts of the neck)

What are spinal nerves attached to?

To the spinal cord by way of dorsal roots and ventral roots

What are dorsal roots?

Roots that that contain axons of unipolar sensory neurons

Where are the cell bodies of the unipolar sensory neurons in dorsal roots located?

In the dorsal root ganglia

What are ventral roots?

Roots that contain axons of motor neurons

What does each spinal nerve split into?

A dorsal ramus and a ventral ramus

What is the dorsal rami?

A branch of the spinal nerve that contain axons that supply the skin near the midline of the back and deep muscles responsible for movement of the vertebral column

What is the ventral rami?

A branch of the spinal nerve that, in the thoracic region, form intercostal nerves?

What are intercostal nerves?

Nerves that contain axons that supply the intercostal muscles and skin of the thorax

What does the ventral rami of the remaining spinal nerves form?

Five major plexuses