Neuro Lab 5 Quiz Full List of Terms

What are the three major spinal cord white matter regions?

Dorsal, lateral, and ventral funiculi; they contain ascending sensory and descending motor tracts.

What is the main role of the dorsal horn?

Receives and processes incoming sensory information.

What is located in the ventral horn?

Cell bodies of lower motor neurons that send motor output to skeletal muscles.

Where are the cell bodies of first-order sensory neurons for the body?

In the dorsal root ganglia (DRG).

What are the main parts of a first-order sensory neuron?

A peripheral process connected to a sensory receptor, a cell body in the DRG, and a central process entering the spinal cord.

Which dorsal root division carries large, heavily myelinated sensory fibers?

The medial division; it carries information such as joint position, vibration, and discriminative touch.

Which dorsal root division carries small sensory fibers for pain and temperature?

The lateral division; fibers enter through Lissauer’s tract before reaching the dorsal horn.

What is Lissauer’s tract?

A tract near the tip of the dorsal horn where incoming pain and temperature fibers can ascend or descend before synapsing.

What does a first-order spinothalamic neuron do before synapsing?

Enters Lissauer’s tract and travels approximately 1–2 spinal segments upward or downward before synapsing in the dorsal horn.

What does decussation mean?

Crossing from one side of the central nervous system to the other.

What is the typical three-neuron chain for conscious sensation from the body?

First-order neuron carries information into the CNS; second-order neuron projects to the thalamus; third-order neuron projects to the somatosensory cortex.

What information does the dorsal column–medial lemniscus (DC/ML) pathway carry?

Conscious joint position sense, vibration, and discriminative touch from the body.

Through which dorsal root division do DC/ML fibers enter?

The medial division.

Where does the first-order DC/ML neuron travel within the spinal cord?

It ascends ipsilaterally in the dorsal columns.

What are the two dorsal column fasciculi?

Fasciculus gracilis and fasciculus cuneatus.

What information travels in the fasciculus gracilis?

DC/ML information from the lower limb and lower trunk.

What information travels in the fasciculus cuneatus?

DC/ML information from the upper limb and upper trunk.

How are gracile and cuneate fibers positioned in the dorsal columns?

Gracile fibers are medial; cuneate fibers are lateral.

Where do first-order DC/ML neurons synapse?

In the gracile or cuneate nucleus of the medulla.

Where does the DC/ML pathway cross?

Second-order neurons cross in the medulla as internal arcuate fibers.

What is the medial lemniscus?

The ascending pathway formed by second-order DC/ML axons after they cross in the medulla.

Where do second-order DC/ML neurons synapse?

In the ventral posterolateral (VPL) nucleus of the thalamus.

Where do third-order DC/ML neurons terminate?

In the primary somatosensory cortex of the postcentral gyrus.

What deficit results from a right dorsal column lesion in the spinal cord?

Loss or reduction of right-sided vibration, discriminative touch, and joint position sense below the lesion.

What deficit results from a right medial lemniscus lesion in the pons?

Loss or reduction of left-sided vibration, discriminative touch, and joint position sense because the pathway has already crossed.

What information does the spinothalamic pathway carry?

Pain and temperature; the broader anterolateral system also carries crude touch.

Where does the first-order spinothalamic neuron synapse?

In the dorsal horn of the spinal cord.

Where does the spinothalamic pathway cross?

Second-order neurons cross in the spinal cord through the anterior white commissure.

On which side does the spinothalamic tract ascend after crossing?

Contralateral to the body region where the sensory information originated.

Where is the spinothalamic pathway located in the spinal cord?

In the anterolateral white matter.

Where do second-order spinothalamic neurons synapse?

In the VPL nucleus of the thalamus.

Where do third-order spinothalamic neurons terminate?

In the primary somatosensory cortex of the postcentral gyrus.

Which pathway is assessed with sharp/dull testing on the body?

The spinothalamic or anterolateral pathway.

Which pathway is assessed with joint position sense testing on the body?

The DC/ML pathway.

What deficit results from a right spinothalamic tract lesion in the spinal cord?

Left-sided pain and temperature loss below the lesion, typically beginning about 1–2 segments below it.

Why can spinothalamic sensory loss begin below the actual lesion level?

First-order fibers may travel 1–2 segments in Lissauer’s tract before synapsing and crossing.

What is the major crossing difference between DC/ML and spinothalamic pathways?

DC/ML crosses in the medulla; spinothalamic crosses in the spinal cord.

Where do spinocerebellar pathways terminate?

In the cerebellum.

Why is spinocerebellar information non-conscious?

It reaches the cerebellum rather than the somatosensory cortex for conscious perception.

What information do spinocerebellar pathways provide?

Non-conscious proprioceptive feedback and information about ongoing spinal motor activity used to coordinate movement.

Which receptors provide proprioceptive input to spinocerebellar pathways?

Muscle spindles and Golgi tendon organs.

Which body regions does the dorsal spinocerebellar tract (DSCT) serve in these slides?

The lower trunk and lower extremities, described as below C8.

Where does the first-order dorsal spinocerebellar neuron synapse?

In Clarke’s nucleus in the intermediate gray matter of the spinal cord.

Does the dorsal spinocerebellar tract cross?

No; it ascends ipsilaterally to the cerebellum.

Where is the dorsal spinocerebellar tract located?

At the dorsolateral outer border of the spinal cord, near the dorsal horn.

Through which peduncle does the dorsal spinocerebellar tract enter the cerebellum?

The inferior cerebellar peduncle (ICP).

Which body regions does the cuneocerebellar tract serve in these slides?

The upper trunk and upper extremities, described as above C8.

Where does the first-order cuneocerebellar neuron synapse?

In the accessory cuneate nucleus of the medulla.

Where do incoming cuneocerebellar fibers ascend in the spinal cord, according to the slides?

In dorsal white matter lateral to the cuneate fasciculus.

Through which peduncle does the cuneocerebellar tract enter the cerebellum?

The inferior cerebellar peduncle.

What information would a cuneocerebellar lesion disrupt?

Non-conscious proprioceptive feedback from the ipsilateral upper limb and upper trunk.

How do dorsal spinocerebellar and cuneocerebellar pathways differ?

DSCT serves lower body regions and relays through Clarke’s nucleus; cuneocerebellar serves upper body regions and relays through the accessory cuneate nucleus.

What is the main function of the ventral spinocerebellar tract (VSCT)?

Reports ongoing spinal motor circuit activity so the cerebellum can compare actual motor output with the intended movement.

Which neurons relay information into the ventral spinocerebellar pathway?

Spinal border neurons.

Where is the ventral spinocerebellar tract relative to the dorsal spinocerebellar tract?

Ventral to the DSCT along the lateral region of the spinal cord.

Which cranial nerve carries the facial sensory information emphasized in these slides?

The trigeminal nerve, CN V.

Which nucleus receives first-order pain and temperature information from the face?

The spinal trigeminal nucleus.

What is the spinal trigeminal tract?

The ipsilateral pathway carrying incoming facial pain and temperature fibers toward the spinal trigeminal nucleus.

Which nucleus receives facial discriminative touch and vibration information?

The chief sensory nucleus of the trigeminal nerve in the pons.

Which neurons form the ascending trigeminothalamic tract?

Second-order neurons from trigeminal sensory nuclei that cross and ascend toward the thalamus.

Which thalamic nucleus receives trigeminothalamic information?

The ventral posteromedial (VPM) nucleus.

What is the key distinction between VPL and VPM?

VPL receives somatosensory information from the body; VPM receives somatosensory information from the face.

Where does the third-order trigeminal sensory neuron project?

To the face region of the primary somatosensory cortex.

How do the upper and lower portions of the trigeminothalamic tract differ in these slides?

The lower portion mainly carries pain and temperature; the upper portion contains both pain/temperature and discriminative sensory information.

What determines whether a descending pathway is dorsolateral or ventromedial?

Its location within spinal cord white matter.

Where do dorsolateral descending pathways terminate?

On lateral motor neurons and interneurons.

What muscles do lateral motor neuron pools primarily control?

Limb muscles involved in individual limb movements.

Where do ventromedial descending pathways terminate?

On medial motor neurons and interneurons.

What muscles do medial motor neuron pools primarily control?

Axial muscles and proximal limb girdle muscles.

Why can ventromedial pathways coordinate both sides of the body?

Medial spinal circuits share information across the cord through interneurons and overlapping dendritic trees.

What is the major function of the lateral corticospinal tract?

Voluntary limb movement, especially precise, fractionated movements such as independent finger movements.

Where does the corticospinal pathway originate in the lab’s simplified model?

The primary motor cortex of the precentral gyrus.

What is the corticospinal pathway through the brain?

Precentral gyrus → corona radiata → posterior limb of internal capsule → cerebral peduncle → pons → medullary pyramids.

Where does the lateral corticospinal pathway cross?

At the pyramidal decussation in the lower medulla.

Where is the lateral corticospinal tract located in the spinal cord?

In the dorsal portion of the lateral white matter.

Where do lateral corticospinal fibers terminate in the spinal cord?

On lateral motor neurons and interneurons in the ventral horn.

Which side is weak after a right corticospinal lesion above the pyramidal decussation?

The left side of the body.

Which side is weak after a right lateral corticospinal lesion in the spinal cord?

The right side below the lesion.

What are characteristic upper motor neuron signs listed in the slides?

Increased muscle tone, increased deep tendon reflexes, and an abnormal Babinski response.

Where do lower motor neurons supplying the body originate?

In the ventral horn of the spinal cord.

How does the ventral corticospinal tract differ from the lateral corticospinal tract?

It remains uncrossed at the pyramidal decussation and descends in ventromedial spinal white matter to influence axial and proximal muscles through medial circuits.

How does ventral corticospinal output influence both sides?

Through bilateral connections involving medial motor neurons and interneurons.

Where does the rubrospinal tract originate?

In the red nucleus of the midbrain.

What is the rubrospinal tract’s function emphasized in the slides?

Supports upper extremity movement.

What deficit is associated with damage to the red nucleus or rubrospinal fibers before their crossing?

Reduced motor influence on the contralateral upper extremity.

Where do vestibulospinal pathways originate?

In vestibular nuclei of the brainstem.

Where does the medial vestibulospinal tract originate?

In the medial vestibular nucleus.

What is the main function of the medial vestibulospinal tract?

Stabilizes head position relative to the body using vestibular input.

At which spinal levels does the medial vestibulospinal tract primarily terminate?

Cervical levels, on medial motor neurons and interneurons.

Where does the lateral vestibulospinal tract originate?

In the lateral vestibular nucleus.

What is the main function of the lateral vestibulospinal tract?

Maintains upright posture and balance by facilitating antigravity extensor muscles of the trunk and limbs.

At which spinal levels does the lateral vestibulospinal tract terminate?

All spinal levels, on medial motor neurons and interneurons.

Where are vestibulospinal pathways located in the spinal cord?

In ventromedial white matter.

What is the main function of the reticulospinal pathways?

Anticipatory postural control, including core stabilization before movement, locomotor initiation, and the postural background for voluntary action.

What inputs influence reticulospinal pathways?

Cortical, cerebellar, and multimodal sensory inputs.

How do reticulospinal and lateral vestibulospinal functions differ?

Reticulospinal control emphasizes anticipatory, preprogrammed postural adjustments; lateral vestibulospinal control emphasizes reactive responses to vestibular input and gravity.

How do medial and lateral reticulospinal functions differ in the slides?

Medial reticulospinal facilitates extensor and axial antigravity tone; lateral reticulospinal inhibits those same muscles.

Where are reticulospinal pathways located in the lab’s classification?

In ventromedial spinal white matter.

What is the corticobulbar pathway?

Descending cortical motor commands to cranial nerve motor nuclei, which then send output through cranial nerves.

Which components of the corticobulbar system are UMNs and LMNs?

Corticobulbar fibers are UMNs; motor neurons in cranial nerve nuclei and their outgoing axons are LMNs.