Chapter 9

Front 1

foramen magnum

Back 1

Large opening at the base of the occipital bone through which the medulla is continuous with the spinal cord.

Front 2

conus medullaris

Back 2

The conical-shaped caudal end of the spinal cord; located at the caudal edge of vertebra at L1 or rostral edge of L2.

Front 3

filum terminale externum

Back 3

Caudal thin extension of the spinal dura that surrounds the filum terminale internum; also known as the coccygeal ligament.

Front 4

cauda equina

Back 4

Consists of a bundle of nerve roots of all the spinal nerves caudal to the second lumbar vertebra.

Front 5

cervical enlargement

Back 5

Includes four lower cervical segments and the first thoracic segment. The nerves emerging from this enlargement for the brachial plexus.

Front 6

lumbar plexus

Back 6

nerve roots from L1- L4. Innervate the lower extremities

Front 7

sacral plexus

Back 7

nerve roots from L4- S2. Contain parasympathic fibers and motor fibers innervating the bladder and its sphincters respectively

Front 8

funiculus

Back 8

A bundle containing one or more tracts or fasciculi in the spinal cord.

Front 9

lateral funiculus

Back 9

White matter of the lateral aspect of spinal cord; contains both ascending (spinothalamic, spinocerebellar) and descending (corticospinal, rubrospinal) fibers.

Front 10

dorsal (posterior) funiculus

Back 10

Is located between the dorsal horn and a midline structure called the dorsal (posterior) median septum. Consists of the fascuculi gracilis and cuneatous.

Front 11

anterior (ventral) funiculus

Back 11

Located between the anterior (ventral) median fissure and the site where the ventral root exits.

Front 12

gray commissure

Back 12

A band of gray matter extending onto both sides of the spinal cord.

Front 13

anterior (ventral) white commissure

Back 13

Located ventral to the gray commissure; consists of decussating axons.

Front 14

central canal

Back 14

Extends throughout the spinal cord; in the adult, it is patent only in the upper cervical segments. Located in the gray commisure.

Front 15

zone of Lissauer (Lissauer's tract)

Back 15

(dorsolateral tract or fasciculus) Refers to the tract formed by central axons of sensory neurons mediating pain that branch into ascending and descending collaterals.

Front 16

substantia gelatinosa

Back 16

Region of gray matter of the dorsal horn of spinal cord that receives mainly pain and temperature inputs from the periphery.

Front 17

dorsal nucleus of Clarke (Nucleus Dorsalis of Clarke)

Back 17

Group of large neurons located at the base of the dorsal horn in all thoracic spinal segments C8–L3; receives muscle spindle and tendon afferents predominantly from the caudal aspect of the body and lower limbs; gives rise to dorsal spinocerebellar tract, which terminates in ipsilateral cerebellum.

Front 18

intermediolateral cell column (IML)

Back 18

Lateral extension of spinal gray matter (lateral horn); present in thoracic (T1–L2) and sacral (S2–S4) cord; thoracic IML contains preganglionic sympathetic neurons; sacral IML contains parasympathetic preganglionic neurons.

Front 19

fasciculus cuneatus

Back 19

First-order sensory neurons contained in the dorsal funiculus that project to the nucleus cuneatus and that convey the modalities of conscious proprioception and tactile sensation from the ipsilateral side of the upper limb. T6 and above

Front 20

fasciculus gracilis

Back 20

First-order sensory neurons contained in the dorsal funiculus that project to the nucleus gracilis and that convey the modalities of conscious proprioception and tactile sensation from the ipsilateral side of the lower limb. T-7 and below

Front 21

nucleus gracilis

Back 21

Second-order neurons located in the lower medulla that receive conscious proprioceptive and tactile inputs from the fasciculus gracilis; projects through the medial lemniscus to the ventral posterolateral nucleus of thalamus, conveying information from the lower limb.

Front 22

internal arcuate fibers

Back 22

Fibers arising from dorsal column nuclei that pass ventrally for a short distance in an arc-like trajectory before crossing over to the contralateral side as the medial lemniscus.

Front 23

medial lemniscus

Back 23

Major ascending sensory pathway arising from the nucleus gracilis and nucleus cuneatus, mediating conscious proprioception and tactile sensations from the limbs to the contralateral ventral posterolateral thalamic nucleus

Front 24

ventral posterolateral nucleus

Back 24

Nucleus situated in the ventrolateral aspect of the posterior thalamus; receives inputs from the medial lemniscus and spinothalamic tract and projects to the postcentral gyrus.

Front 25

nucleus cuneatus

Back 25

Second-order neurons located in the lower medulla that receive conscious proprioceptive and tactile inputs from the fasciculus cuneatus; projects through the medial lemniscus to the ventral posterolateral nucleus of thalamus, conveying information from the upper limb.

Front 26

Fasciculus Gracilis and Cuneatous (Dorsal Column)

Back 26

Crosses at decussation medial lemniscus; terminates in sensorimotor cortex; symptoms appear ipsilateral; include loss of tactile sense (vibration, deep touch, and two point discrimination) and kinesthetic touch (position and movement)

Front 27

Dorsal (Posterior) Spinocerebellar Tract (DCST)

Back 27

The central processes project to the nucleus dorsalis of Clarke the extends from C8 to L2 (ascend ipsilaterally), reach the inferior cerebellar peduncle in the medulla, and terminate ipsilaterally in the cerebellar vermis; transmits information about muscle spindle and tendon afferents from caudal aspect of the body and legs; coordinates and integrates nerural signals of individual lower limb muscles.

Front 28

Ventral (Anterior) Spinocerebellar Tract

Back 28

Crosses first in the spinal cord and crosses again in superior cerebellar peduncle and terminates in vermal region of the anterior lobe of the cerebellum; involved in attempted movement

Front 29

Cuneocerebellar Tract

Back 29

Only in C1- C7; Ascends ipsilaterally in the fasiculus cuneatus; and project to neurons located in the accessory cuneate nucleus; goes through cerebellar peduncle and terminates in cerebellar cortex; convery unconscious proprioception

Front 30

Lateral spinothalmic tract (ALS)

Back 30

Arises form nucleus proprius; cross via the ventral (anterior) white commissure where the ascend in the lateral funiculus; axons synapes in the ventral posterolateral nucleus of the thalmus and project into the primary sensory cortex; mediates pain, temperature and simple tactile sensations

Front 31

nucleus proprius

Back 31

Located in the dorsal horn; neurons of this nucleus give rise to the spinothalamic tract.

Front 32

cortiocspinal tract

Back 32

Arises from the motor cortex (homunculus), passes through the pyramaids and crosses at the decussation of the pyramaids (the majority do) to form lateral spinal tract

Front 33

Brown-Sequard Syndrome

Back 33

Loss of conscious proprioception and two-point discrimination occurs below the level of the lesion on the ipsilateral side, and loss of pain and temperature sensation occurs one or two segments below the level of the lesion on the contralateral side as well as bilaterally. There is also an upper motor neuron paralysis below the level of the lesion on the ipsilateral side and a lower motor neuron paralysis at the level of the lesion on the ipsilateral side. This kind of incomplete transection may occur by fracture dislocation of vertebrae, tumor, or missile wounds.

Front 34

Myotatic Reflex (Stretch, Deep Tendon, or Two Neuron Reflex)

Back 34

pg 157

Front 35

Flexion (Withdrawal) Reflex

Back 35

When a noxious stimulus is applied to the skin or deeper structures, free nerve endings are stimulated, and the resulting impulses are conducted through myelinated afferent fibers of small diameter (group III fibers) and unmyelinated afferent fibers. These fibers synapse with a number of alpha motor neurons located in the spinal cord. These connections are polysynaptic, and at least three to four interneurons are involved. Activation of these polysynaptic pathways in the spinal cord results in contraction of ipsilateral flexor muscles, producing flexion and relaxation of ipsilateral antagonist extensor muscles.

Front 36

Crossed Extension Reflex

Back 36

This neuronal circuitry of the flexion and crossed extension reflexes permits extension of the limb contralateral to the site of noxious stimulation and withdrawal (flexion) of the limb ipsilateral to it. Crosses anterior commissure.