Spinal Cord

Question 1

Which of the following describes an essential function of the spinal cord? Select all that apply.

recevies and integrates sensory information

sends motor commands to target tissue

process visual information

carries tracts that convey information to and from the brain

mediates spinal level reflexes

process auditory information

Answer 1

recevies and integrates sensory information

sends motor commands to target tissue

process visual information

carries tracts that convey information to and from the brain

mediates spinal level reflexes

Explanation

The four essential functions of the spinal cord include: receiving and beginning integration of sensory information; sending motor commands to target tissue; carrying tracts that convey information to/from the brain and mediating spinal level reflexes. The visual and auditory systems are special sensory systems that don’t directly involve the spinal cord.

Question 2

The spinal cord extends to the level of the S5 vertebra.

True or False

Answer 2

False

Explanation

The spinal cord extends from the foramen magnum to the level of the L1-L2 vertebrae ending at what is called the conus medullaris.

Question 3

The spinal cord is segmentally organized giving rise to 31 pairs of spinal nerves and each nerve will form ipsilateral dermatomes and myotomes.

True

False

Answer 3

True

Explanation

The spinal cord is segmentally organized with each segment giving rise to a pair of spinal nerves. There are 31 pairs of spinal nerves & each of these spinal nerves will innervate select areas of the skin and select muscles ipsilaterally creating dermatomes and myotomes.

Question 4

The dural sac surrounds the spinal cord and is attached to the vertebral column via which of the following structures?

Filum terminale externum

Filum terminale internum

Denticulate ligaments

Answer 4

Filum terminale externum

Explanation

The filum terminale externum is an extension of the dura mater that anchors the dural sac to the vertebral column. Denticularte ligaments and the filum terminale internum are extensions of the pia mater that anchor the spinal cord inside the dural sac laterally and caudally, respectively.

Question 5

The gray matter of the spinal cord consists of the cell bodies of neurons and is arranged in three columns that include the dorsal, lateral and ventral horns.

True

False

Answer 5

True

Explanation

This statement is true: the gray matter mainly contains the cell bodies of neurons and is divided into three main columns of cells: dorsal horn, lateral horn (intermediate area) and ventral horn.

Question 6

Which laminae make up the ventral horn?

Laminae I - VI

Laminae VII - VIII

Laminae VIII - IX

Answer 6

Laminae VIII - IX

Explanation

Laminae VIII - IX make up the ventral horn containing somatic motor neurons; laminae I - VI make up the dorsal horn and contain sensory neurons, and Laminae VII makes up the lateral horn/intermediate area and contains visceromotor neurons and at C8-L3 contains the dorsal nucleus of Clarke.

Question 7

The internal structure of each spinal cord segment looks the same with respect to the ratio of gray and white matter.

True

False

Answer 7

False

Explanation

This statement is false: The shape and size of the gray matter varies according to spinal cord level. At the lower levels, the ratio between gray and white matter is greater than in higher levels, mainly because lower levels contain less ascending and descending nerve fibers.

Question 8

The ventral horn of the spinal cord is somatotopically organized. Which of the following statements best reflects this organization?

Motor neurons that innervate axial muscles are located laterally and those that innervate appendicular muscles are located medially.

Motor neurons that innervate axial muscles are located medially and those that innervate appendicular muscles are located laterally.

Motor neurons that innervate axial and appendicular muscles are equally distributed between the medial and lateral aspects of the ventral horn.

Answer 8

Motor neurons that innervate axial muscles are located medially and those that innervate appendicular muscles are located laterally.

Explanation

The ventral horn is somatotopically organized: motor neurons that innervate axial muscles are located medially and those that innervate appendicular muscles are located laterally. There is also an orderly progression such that motor neurons that innervate proximal muscles are located more medially as compared to those that innervate distal muscles.

Question 9

The left anterolateral system will carry pain and temperature sensations from the left side of the body.

True

False

Answer 9

True

Explanation

This statement is true: touch, pressure, vibratory, and proprioceptive information from the left side of the body will remain uncrossed in the spinal cord. We will see that this information will eventually cross in the brainstem.

Question 10

The left posterior columns will carry touch and proprioceptive information from the left side of the body.

True

False

Answer 10

False

Explanation

This statement is false:the anterolateral system will carry pain and temperature information from the right side of the body.

Question 11

Which of the following funiculi is located between the dorsal and ventral roots of each spinal cord segment?

Posterior

Anterior

Lateral

Answer 11

Lateral

Explanation

The lateral funiculus (largest of the funiculi) is located between the posterolateral sulcus (dorsal entry zone) and the anterolateral sulcus (ventral root exit zone). The posterior funiculus is located between the posterior median sulcus and the posterolateral sulcus, and the anterior funiculus is located between the anterior median fissure and the anterolateral sulcus.

Question 12

Which funiculus contains only ascending (sensory) tracts?

Posterior

Anterior

Lateral

Answer 12

Posterior

Explanation

The posterior funiculus contains only ascending tracts; the anterior funiculus contains only descending tracts (modify neurons in the spinal cord), and the lateral funiculs contains both ascending and descending tracts.

Question 13

Which funiculus contains the lateral corticospinal tract?

Anterior

Posterior

Lateral

Answer 13

Lateral

Explanation

The lateral corticospinal tract is contained in the lateral funiculus; the anterior corticospinal tract will be contained in the anterior funiculus. The posterior funiculus will not contain descending tracts (recall a tract is descending if its name begins with a rostral brain structure (cortex) and ends with a caudal structure (spinal cord).

Question 14

Medially located fibers of the corticospinal tract will influence the activity of motor neurons that innervate the muscles of the upper limb.

True

False

Answer 14

True

Explanation

This statement is true: the lateral corticospinal tract is somatotopically organized such that medially located fibers will modulate the activity of motor neurons that innervate muscles of the upper limb and laterally located fibers will modulate the activity of motor neurons that innervate the lower limb.

Question 15

A complete spinal cord injury at the level of C5 will result in tetraplegia.

True

False

Answer 15

True

Explanation

This statement is true: a compete spinal cord injury results in motor and sensory loss below the level of the lesion - lose of function below the level of C5 would involve all four extremities as well as the trunk.

Question 16

Which of the following spinal cord injuries would result in ipsilateral hemiplegia, contralateral loss of pain and temperature sensations,and ipsilateral loss of touch, pressure, vibration and proprioception sensations below the level of the injury?

Anterior cord syndrome

Posterior cord syndrome

Brown Sequard syndrome

Answer 16

Brown Sequard syndrome

Explanation

Brown-Séquard Syndrome: hemi-section of the SC will produce the following deficits below the level of the lesion: hemiparesis or hemiplegia ipsilaterally; loss of pain/temp/crude touch sensation contralaterally; and a loss of proprioception, vibratory sense and discriminative touch ipsilaterally. Anterior Cord Syndrome: caused by leads to variable paralysis below the lesion level with loss of pain and temperature perception; touch, proprioception, & vibration sense are mainly preserved; Posterior cord syndrome: loss of proprioception, vibration and discriminative touch sensations; motor function and pain/temperature sensation preserved.