Structural and Functional Organization of the Spinal Cord

Detailed practice flashcards covering the anatomy, functions, meninges, nerve plexuses, and pathways of the human spinal cord based on lecture notes.

The central nervous system (CNS) is composed of two primary structural components: the __________ and the spinal cord.

brain

The spinal cord is housed within a protective bony structure known as the __________ or the spine.

spinal vertebrae

The three connective tissue layers that protect the spinal cord are collectively called the __________.

spinal meninges

The outermost, thick, and inelastic layer of the meninges is the __________.

dura mater

The __________ is the middle layer of the meninges, featuring delicate trabeculae that form a meshwork for cerebrospinal fluid recirculation.

arachnoid mater

The innermost layer of the meninges, which is directly adherent to the surface of the spinal cord, is the __________.

pia mater

At the level of the first and second lumbar vertebrae, the spinal pia gathers into a thin structure called the __________ that anchors the cord to the coccygeal vertebra.

filum terminale

In adults, the spinal cord measures approximately __________ for women and about __________ for men.

$16.5\,\text{inches}$; $18\,\text{inches}$

There are a total of __________ pairs of spinal nerves projecting from the spinal cord.

$$31$$

The spinal cord has two bulges known as the __________ and the __________ which serve the nerves of the upper and lower extremities respectively.

cervical enlargement; lumbar enlargement

The spinal cord itself terminates at the level of the __________ vertebrae.

$$L1/L2$$

The tapered, cone-like tip at the end of the spinal cord is called the __________.

conus medullaris

The bundle of spinal nerve roots that extends inferiorly from the conus medullaris and resembles a horse's tail is called the __________.

cauda equina

In the spinal cord, __________ matter is peripheral while __________ matter is internal.

white; gray

Gray matter is organized into three distinct regions: the anterior horn, the posterior horn, and the __________ horn.

lateral

The __________ horn contains cell bodies of neurons involved in processing both somatic and visceral incoming sensory stimuli.

posterior (dorsal)

Each general region of spinal white matter is called a __________, with three located on each side of the cord.

funiculus

The term __________ refers to neural pathways crossing from one side of the brain or spinal cord to the other.

decussate

The __________ motor neuron originates in the cerebral cortex or brainstem and terminates on a lower motor neuron.

upper (UMN)

The __________ is the connective tissue layer that covers individual fascicles inside a nerve.

perineurium

The __________ ramus of a spinal nerve serves the anterior portion of the trunk and the upper and lower limbs.

ventral

A __________ is a network of nerves formed by the joining of axons from the ventral rami of adjacent spinal nerves.

plexus

The __________ nerve, originating from $C3$, $C4$, and $C5$, is essential for diaphragmatic breathing.

phrenic

A __________ is an area of skin that provides sensory input to the CNS via the posterior root of a single pair of spinal nerves.

dermatome

A __________ is a rapid, automatic, involuntary reaction of muscles or glands in response to a stimulus.

reflex

In a __________ reflex, the sensory neuron synapses directly with the motor neuron without an interneuron.

monosynaptic

The __________ system is responsible for conscious or voluntary movements of skeletal muscles and includes the corticospinal and corticobulbar tracts.

pyramidal

Sensory pathways typically involve three neurons: the primary (first-order), the secondary (second-order), and the __________ (third-order) neuron.

tertiary

The __________ tract is an ascending pathway primarily responsible for transmitting pain and temperature sensations.

spinothalamic

Damage to the lower motor neurons (LMN) results in __________ paralysis, characterized by a loss of muscle tone.

flaccid

The __________ system includes tracts like the tectospinal and vestibulospinal that regulate involuntary movements, balance, and posture.

extrapyramidal