Spinal Cord & Spinal Nerves – Review Flashcards

These flashcards cover anatomy, physiology, clinical procedures, plexuses, dermatomes, and common disorders related to the spinal cord and spinal nerves.

Where does the spinal cord begin and end within the vertebral column?

It begins at the foramen magnum and ends at the level of the L1 or L2 vertebra.

What are the two primary functions of the spinal cord?

1) Provides two-way communication between the brain and body. 2) Acts as a major reflex center where reflexes are initiated and completed.

Which type of tract carries sensory information toward the brain?

Ascending (sensory) tracts.

Which type of tract carries motor commands away from the brain?

Descending (motor) tracts.

Name the three protective structures surrounding the spinal cord.

Bone (vertebrae), meninges, and cerebrospinal fluid (CSF).

How is spinal dura mater different from cranial dura mater?

Spinal dura mater is a single layer and does not attach to surrounding bone.

Why is the extension of the dural and arachnoid membranes to the sacrum clinically important?

It creates a CSF-filled region used for lumbar puncture (spinal tap).

What is the cone-shaped terminal end of the spinal cord called?

The conus medullaris.

What fibrous structure anchors the spinal cord to the coccyx?

The filum terminale.

Define cauda equina.

A collection of nerve roots at the inferior end of the vertebral canal.

How many pairs of spinal nerves exist?

31 pairs.

Which regions of the spinal cord are enlarged and why?

Cervical and lumbar enlargements—these give rise to nerves serving the upper and lower limbs.

What two roots unite to form a spinal nerve?

The dorsal (sensory) root and the ventral (motor) root.

What type of fibers are contained in a ventral root?

Motor (efferent) fibers from ventral horn neurons.

What type of fibers are contained in a dorsal root?

Sensory (afferent) fibers whose cell bodies lie in the dorsal root ganglion.

Describe the arrangement of gray matter in a spinal-cord cross-section.

It is H- or butterfly-shaped with dorsal, ventral, and (in thoracic/upper lumbar levels) lateral horns joined by the gray commissure surrounding the central canal.

Which horns of gray matter contain somatic motor neurons?

The ventral (anterior) horns.

Which horns exist only in thoracic and superior lumbar segments and what neurons do they house?

The lateral horns; they contain sympathetic (visceral motor) neurons.

Name the four functional zones of spinal gray matter.

Somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM).

In which three directions do spinal white-matter fibers run?

Ascending, descending, and transverse.

List the three white columns (funiculi) of the spinal cord.

Dorsal (posterior), lateral, and ventral (anterior) columns.

How many cervical spinal-nerve pairs are there?

Eight pairs (C1–C8).

Give the number of spinal-nerve pairs for each region of the cord.

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal pair.

Define a nerve plexus.

An interlacing network of ventral rami of spinal nerves.

Which ventral rami do NOT form plexuses?

T2–T12, which become the intercostal nerves.

What major nerve of the cervical plexus is vital for breathing?

The phrenic nerve (C3–C5).

What happens if the spinal cord is damaged above the origin of the phrenic nerves?

Respiratory arrest occurs because the diaphragm no longer receives motor impulses.

Which spinal segments contribute to the brachial plexus?

Ventral rami of C5–T1.

Name the five principal nerves of the brachial plexus.

Axillary, musculocutaneous, median, ulnar, and radial nerves.

Which brachial-plexus nerve innervates most wrist and finger flexors plus thumb opposition muscles?

The median nerve.

Which nerve innervates virtually all extensor muscles of the upper limb?

The radial nerve.

The lumbar plexus is formed by which ventral rami?

L1–L4.

Which two major nerves arise from the lumbar plexus?

The femoral and obturator nerves.

The sacral plexus is composed of which ventral rami?

L4–S4.

What is the largest nerve in the body, and from which plexus does it arise?

The sciatic nerve; it emerges from the sacral plexus.

Define dermatome.

A skin region innervated by the cutaneous branches of a single spinal nerve.

Why does loss of one spinal nerve seldom cause complete numbness in its dermatome?

Most dermatomes overlap with adjacent ones.

What is a lumbar puncture (spinal tap)?

A procedure in which CSF is withdrawn from the subarachnoid space, usually between L3–L4 or L4–L5.

Describe the three-neuron chain in ascending (sensory) pathways.

First-order neuron: receptor to spinal cord/brainstem; second-order: to thalamus (decussates); third-order: thalamus to primary somatosensory cortex.

Define a reflex.

A rapid, automatic response to a stimulus mediated through the spinal cord (or brainstem).

List three spinal or peripheral-nerve disorders mentioned.

Neuritis, shingles, and poliomyelitis.

What virus causes shingles and what are typical symptoms?

Reactivation of the chicken pox (varicella-zoster) virus; produces pain, skin discoloration, and a line of blisters along the affected nerve.

Contrast the functions of spinal white matter and gray matter.

White matter conducts impulses to and from the brain, whereas gray matter integrates incoming and outgoing information.

What occupies the epidural space surrounding the spinal cord?

Fat and blood vessels.

What are rami communicantes?

Small branches that connect the ventral ramus to the sympathetic trunk ganglion.

Which meningeal layer adheres directly to the spinal cord surface?

The pia mater.

The spinal cord’s central canal is continuous superiorly with which brain cavity?

The fourth ventricle.

What is the role of transverse (commissural) fibers in the spinal cord?

They allow communication from one side of the cord to the other.

What is the function of denticulate ligaments?

Pia-mater extensions that laterally anchor the spinal cord to the dura mater.