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523 - Neuroscience - Exam 3 > 03_Descending Motor Pathways of the Spinal Cord > Flashcards

03_Descending Motor Pathways of the Spinal Cord Flashcards

1
Q

What are the tracts associated with lateral motor systems?

A

Lateral corticospinal tract and Rubrospinal tract

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1
Q

The biceps are innervated by which spinal cord levels?

A

C5-C6

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2
Q

What are the tracts associated with medial motor systems?

A

Anterior corticospinal, Vestibulospinal, Reticulospinal and Tectospinal tracts

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2
Q

The triceps are innervated by which spinal cord levels?

A

C6, C7 and C8

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3
Q

What is the function of the Lateral corticospinal tract (one of the lateral motor systems)?

A

Movement of contralateral limbs

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3
Q

The diaphragm is innervated by which spinal cord levels?

A

C3, C4 and C5

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4
Q

What is the function of the Rubrospinal tract (one of the lateral motor systems)?

A

Movement of contralateral limbs (function is uncertain in humans)

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4
Q

If only one or two ventral roots are damaged, partial paralysis or weakness occurs. What is the term for this condition?

A

Paresis

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5
Q

What is the function of the Anterior corticospinal tract (one of the medial motor systems)?

A

Control of bilateral axial and girdle muscles

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5
Q

What events may result in paralysis?

A

Paralysis results if all roots innervating a particular muscle are destroyed. [Paralysis can also occur when upper motor neurons (e.g., corticospinal tract neurons) are damaged as in stroke].

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6
Q

What is the function of the Vestibulospinal tract (one of the medial motor systems)?

A

Medial VST: positioning of head and neck Lateral VST: balance

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6
Q

The bladder and bowels are innervated by which spinal cord levels?

A

S2, S3 and S4

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7
Q

What is the function of the Reticulospinal tract (one of the medial motor systems)?

A

Automatic posture and gait-related movements

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7
Q

Motor neuron and axon classification: Alpha MN (Diameter, Conduction Velocity, Function)

A

Fiber diameter (microns): 12-20 Conduction velocity (m/sec): 15-120 Function: Innervates extrafusal skeletal muscle fibers (i.e., the motor unit); heavily myelinated

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8
Q

What is the function of the Tectospinal tract (one of the medial motor systems)?

A

Coordination of head and eye movement (uncertain in humans)

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8
Q

Motor neuron and axon classification: Gamma MN (Diameter, Conduction Velocity, Function)

A

Fiber diameter (microns): 2-10 Conduction velocity (m/sec): 10-45 Function: Innervates intrafusal muscle fibers of muscle spindle; myelinated

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9
Q

Lateral corticospinal tract (one of the lateral motor systems)-Site of origin

A

Primary motor cortex, and other frontal and parietal areas

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9
Q

Motor neuron and axon classification: Autonomic pre-ganglionic (B motor) (Diameter, Conduction Velocity, Function)

A

Fiber diameter (microns): about 3 Conduction velocity (m/sec): 3-15 Function: pre-ganglionic autonomic fibers; lightly myelinated

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10
Q

Rubrospinal tract (one of the lateral motor systems)-Site of origin

A

Red nucleus, magnocellular division

10
Q

Motor neuron and axon classification: Autonomic post-ganglionic (C motor) (Diameter, Conduction Velocity, Function)

A

Fiber diameter (microns): about 1 Conduction velocity (m/sec): 2 Function: post-ganglionic autonomic fibers; unmyelinated

11
Q

Anterior corticospinal tract (one of the medial motor systems)-Site of origin

A

Primary motor cortex and supplementary motor area

12
Q

Vestibulospinal tract (one of the medial motor systems)-Site of origin

A

Medial VST: medial and inferior vestibular nuclei Lateral VST: lateral vestibular nucleus

13
Q

Reticulospinal tract (one of the medial motor systems)-Site of origin

A

Pontine and medullary reticular formation

14
Q

Tectospinal tract (one of the medial motor systems)-Site of origin

A

Superior colliculus

15
Q

Lateral corticospinal tract-Site of Decussation

A

Pyramidal decussation, at the cervicomedullary junction

16
Q

Rubrospinal tract-Site of Decussation

A

Ventral tegmental decussation, in the midbrain

17
Q

Anterior corticospinal tract-Site of Decussation

A

Not relevant

18
Q

Vestibulospinal tract-Site of Decussation

A

Not relevant

19
Q

Reticulospinal tract-Site of Decussation

A

Not relevant

20
Q

Tectospinal tract-Site of Decussation

A

Dorsal tegmental decussation, in the midbrain

21
Q

Lateral corticospinal tract-Levels of Termination

A

Entire cord (predominantly at cervical and lumbosacral enlargements)

22
Q

Rubrospinal tract-Levels of Termination

A

Cervical cord

23
Q

Anterior corticospinal tract-Levels of Termination

A

Cervical and upper thoracic cord

24
Q

Vestibulospinal tract-Levels of Termination

A

Medial VST: Cervical and upper thoracic cord Lateral VST: entire cord

25
Q

Reticulospinal tract-Levels of Termination

A

Entire cord

26
Q

Tectospinal tract-Levels of Termination

A

Cervical cord

27
Q

The descending motor pathways work directly (monosynaptically, the minority) and indirectly (through interneurons, the majority) on what types of neurons?

A

alpha and gamma motor neurons of the ventral horn of the spinal cord and cranial nerve motor nuclei

28
Q

What are upper motor neurons?

A

The descending pathways and the somas they arise from are considered upper motor neurons.

29
Q

What are lower motor neurons?

A

The alpha and gamma motor neurons (whose axons innervate muscle) are considered lower motor neurons.

30
Q

From where do axons of the corticobulbar tract arise and to where do they descend?

A

Axons arise from somas in the face region of motor cortex; descend through corona radiata, internal capsule, and cerebral peduncles.

31
Q

Most of the corticobulbar tract projections are crossed. Which projectections are bilateral?

A

projections to the facial nucleus are bilateral

32
Q

Axons of the corticobulbar tracts project to and synapse with motor nuclei of which cranial nerves in the brainstem?

A

CN III, IV, V, VI, VII, IX, X, XI and XII

33
Q

What are the two main tracts that make up the reticulospinal tract?

A

Medullary (lateral) and Pontine (medial) reticulospinal tracts

34
Q

In general, the lateral reticulospinal tract is thought to inhibit which groups of muscles?

A

lower extremity extensors and facilitate flexors, reducing muscle tone in the lower extremities

35
Q

How does the pontine (medial) reticulospinal tract affect the lower extremities?

A

This pathway facilitates lower extremity extensor (alpha and gamma) motor neurons, increasing muscle tone, especially to musculature of the lower extremity.

523 - Neuroscience - Exam 3 (5 decks)

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