Nervous System: Spinal Cord and Spinal Nerves

Comprehensive practice flashcards covering the anatomy and physiology of the spinal cord, spinal nerves, and nervous system pathways.

What are the dimensions and the general shape of a typical adult spinal cord?

It is roughly cylindrical, having a diameter of approximately $\frac{3}{4}$ inch and a length between $16-18$ inches.

What is the name of the tapering inferior end of the spinal cord?

Conus medullaris

What are the two longitudinal grooves that extend along the outer surface of the spinal cord?

The posterior median sulcus and the anterior median fissure

Into which five parts is the spinal cord partitioned?

Cervical, thoracic, lumbar, sacral, and coccygeal

What is the function of the cervical and lumbar enlargements?

The cervical enlargement contains neurons innervating the upper limbs, while the lumbar enlargement contains neurons innervating the lower limbs.

How many pairs of spinal nerves are there in total, and how are they specifically distributed by region?

There are $31$ pairs total: $8$ cervical, $12$ thoracic, $5$ lumbar, $5$ sacral, and $1$ coccygeal.

Identify the three connective tissue wrappings of a nerve from outermost to innermost.

Epineurium (around the nerve), perineurium (around the fascicle), and endoneurium (around the axon)

What is the structural difference between the posterior root and the anterior root of a spinal nerve?

The posterior root contains sensory neurons and a posterior root ganglion, while the anterior root contains motor neurons.

Why are spinal nerves classified as mixed nerves?

Because each spinal nerve is formed by the union of sensory and motor neurons from the posterior and anterior roots.

What is the cauda equina?

A structure formed by the roots of lumbar, sacral, and coccygeal spinal nerves that extend inferiorly from the conus medullaris.

List the structures and spaces surrounding the spinal cord from outermost to innermost.

Vertebra, epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, and pia mater

What defines the subarachnoid space, and what does it contain?

It is the space between the arachnoid mater and the pia mater, and it contains cerebrospinal fluid (CSF).

What are denticulate ligaments?

Extensions of the pia mater that suspend and anchor the spinal cord laterally to the dura mater.

During a lumbar puncture, where is the needle typically inserted and why?

It is inserted into the subarachnoid space below $L1$ (usually above or below $L4$) to avoid damaging the spinal cord, which ends at the $L1$ vertebra.

What types of neurons are housed in the anterior, lateral, and posterior horns of the spinal cord gray matter?

The anterior horns house somatic motor neurons, lateral horns house autonomic motor neurons, and posterior horns house axons of sensory neurons and cell bodies of interneurons.

In which regions of the spinal cord are the lateral horns present?

Segments $T1-L2$

What are the three main regions of white matter in the spinal cord?

The posterior funiculus, lateral funiculus, and anterior funiculus

What is the difference between an ipsilateral and a contralateral pathway?

An ipsilateral pathway stays on the same side of the body, while a contralateral pathway decussates (crosses the midline) to the opposite side.

In a somatosensory pathway, what are the roles of the primary, secondary, and tertiary neurons?

The primary neuron relays signals from the receptor to the CNS; the secondary neuron is an interneuron that extends to the tertiary neuron or cerebellum; and the tertiary neuron relays the signal to the somatosensory cortex.

Which sensory pathway transmits signals for discriminative touch and conscious proprioception?

The posterior funiculus-medial lemniscal pathway

What types of sensory information are carried by the anterolateral pathway?

Crude touch, pressure, pain, and temperature

What is the primary function of the spinocerebellar pathway?

It transmits signals about subconscious proprioception to the cerebellum using a two-neuron chain.

Distinguish between upper and lower motor neurons in motor pathways.

Upper motor neurons originate in the cerebral cortex or brainstem and contact lower motor neurons, which are located in the cranial nerve nuclei or spinal cord anterior horn and excite muscles.

What is a dermatome?

A specific segment of skin supplied by a single spinal nerve.

What causes shingles (Herpes Zoster) and where does the virus remain latent?

It is caused by the reactivation of the varicella-zoster virus, which remains latent in the posterior root ganglia.