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Neuromotor Function 1 > Lecture 10 - Brainstem Descending Pathways > Flashcards

Lecture 10 - Brainstem Descending Pathways Flashcards

1
Q

What is the goal of parallel motor systems coordinating posture and movement?

A

To maintain CoG safely within the manageable distance of BoS

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2
Q

Postural control involves an _______ mechanism that predicts a disturbance in body stability with limb movement, and generates an appropriate stabilizing response.

A

Anticipatory (feedforward)

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3
Q

_____ mechanisms exist to control for unanticipated postural instability.

A

Feedback

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4
Q

______ are made in preparation for movement. Impaired coordination of this leads to _____.

A

1) Anticipatory postural adjustments (APAs)

2) Loss of balance

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5
Q

Describe what a typical anticipatory postural adjustment would be to lifting the arm in front of you.

A

Lifting the arm causes the CoM to shift forward as mass is added in the anterior direction. In anticipation of this, you move slightly posterior at the ankle joint to redistribute the weight. This allows the CoM to remain within the BoS.

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6
Q

The brainstem forms a narrow thru-way for all ____, _____, _____ and ______ pathways.

A

1) Sensory
2) Motor
3) Cerebellar
4) Cranial nerve

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7
Q

List the 5 maintenance functions of the brainstem.

A

1) level of consciousness
2) muscle tone
3) HR
4) BP
5) respiratory rate

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8
Q

T/F: The tectospinal tract is part of the lateral motor systems.

A

False.

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9
Q

List the 2 branches of the lateral motor systems.

A

1) Lateral corticospinal tract

2) Rubrospinal tract

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10
Q

List the 4 branches of the medial motor system.

A

1) Anterior corticospinal tract
2) Vestibulospinal tract
3) Tectospinal tract
4) Reticulospinal tract

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11
Q

Where the does the rubrospinal tract originate and terminate?

A

It originates in the red nucleus (caudal part) of the midbrain.

It terminates at the cervical level of the spinal cord.

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12
Q

Does the rubrospinal tract cross over? If so, where?

A

Yes, the rubrospinal tract crosses over immediately in midbrain, and travels contralaterally, controlling the opposite side.

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13
Q

What are the 2 divisions of the red nucleus?

A

1) Caudal portion - gives rise to the rubrospinal tract

2) Rostral portion - involved in cerebllar control of movement

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14
Q

T/F: The rubrospinal tract axons project only on to LMN for upper limb movements.

A

False. Axons synapse primarily on INTERNEURONS of the anterior horn cells in cervical spinal segments.

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15
Q

The rubrospinal tract influences large movements of the _____, facilitating _____ and inhibiting _____.

A

1) upper extremities
2) flexion
3) extension

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16
Q

The divisions of the medial motor system control the ______ and ________ for postural control, orienting movements of the head and neck, and _______________.

A

1) Proximal trunk
2) Girdle muscles
3) Automatic gait-related movements.

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17
Q

Why are unilateral lesions in the medial motor system not detrimental?

A

The divisions terminate on interneurons that project to both sides of the spinal cord.

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18
Q

Where does the tectospinal tract originate and terminate?

A

It originates from the superior colliculus (midbrain) and projects to medial cell groups in the anterior horn cell bilaterally in the cervical spinal cord.

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19
Q

Does the tectospinal tract travel contrallaterally or ipsilaterally?

A

Contralaterally (crosses over in the midbrain)

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20
Q

You are crossing the road and see a cyclist in your periphery. You quickly turn your head in response to this sudden visual stimulus. What motor system branch is coordinating these head and eye movements?

A

Tectospinal tract (medial motor system)

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21
Q

Where does the tectospinal tract terminate?

A

Cervical spinal cord

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22
Q

What is the reticular formation? What originates here and in what particular areas?

A

A central core of nuclei that runs through the entire length of the brainstem. The reticulospinal tract originates here (specifically the pons and medullary reticular formation).

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23
Q

What is the function of the rostral and caudal reticular formations?

A

A) Rostral reticular formation: (midbrain) maintains an alert, conscious state
B) Caudal reticular formation (pons and medulla) works together with cranial nerve nuclei and spinal cord to carry out motor, reflex and autonomic functions

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24
Q

T/F: The pontine reticulospinal tract facilitates extensors and inhibits flexors.

A

True.

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25
Q

T/F: The medullary reticulospinal tract travels contralaterally.

A

False.

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26
Q

T/F: The reticulospinal tracts are involved in automatic posture and gait related movements and influence muscle tone.

A

True.

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27
Q

How many vestibular nuclei are there in TOTAL?

A

8 (4 on each side: superior, inferior, medial, lateral)

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28
Q

What are the branches of the vestibulospinal tract?

A

Medial and lateral vestibulospinal tracts

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29
Q

From which vestibular nuclei does each branch of the vestibulospinal tract originate?

A

Lateral: lateral vestibular nucleus

Medial: medial and inferior vestibular nuclei

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30
Q

The medial vestibulospinal tract functions to control head and neck position. For this reason, it facilitates ______ and inhibits _______.

A

1) Facilitates extensors

2) Inhibits flexors

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31
Q

What is different between the lateral and medial vestibulospinal tracts descent towards the spinal cord?

A

The medial branch descends bilaterally (has two components that travel to the spinal cord).

32
Q

List 3 functions of the lateral vestibulospinal tract.

A

1) Facilitate extensors
2) Inhibit flexors
3) Maintain balance

33
Q

List 3 similarities between the medial and lateral vestibulospinal tracts.

A

1) Both tracts travel ipsilaterally to the spinal cord
2) Both are involved in the control of posture relative to the vestibular system information
3) Both facilitate extensor muscle activity for maintenance of balance

34
Q

T/F: Corticobulbar tracts conveying motor signals from the cerebral cortex to motor neurons in the cranial nerve nuclei in the brainstem project bilaterally, except to CN VII nucleus and CN IX.

A

False:

Exceptions are CN VII (facial) and CN XII (hypoglossal)

35
Q

T/F: Unilateral lesions in the corticobulbar tracts to motor nuclei typically cause no UMN deficits, with a few exceptions.

A

True.

36
Q

Corticobulbar tract fibers cross and synpase in the facial nucleus at the ____ on the _______.

A

1) pons

2) opposite side

37
Q

A stroke patient undergoes facial muscle testing. They are able to lift their eyebrows, but cannot pucker their lips. on the left side. Explain.

A

For the superior part of the face, projections descend from the contralateral and ipsilateral motor cortex.

A unilateral UMN lesion spares the forehead but causes weakness of the inferior part of the contralateral face.

Therefore, this patient has experienced a unilateral UMN on the right side of the corticobulbar tract.

38
Q

T/F: A LMN lesion affects mainly the lower part of the opposite side of the face.

A

False.

39
Q

A LMN lesion would affect what parts of the face?

A

Upper and lower parts of the same side of the face would be affected

40
Q

What are 2 differences between corticobulbar and peripheral nerve lesions related to the face?

A

1) Corticobulbar (UMN) vs. facial nerve (LMN)
2) Unilateral lesion of the corticobulbar tract would affect opposite side of the face (lower portion), while unilateral lesion of facial nerve would affect the same side of the face (upper and lower).

41
Q

UMN for tongue movement arise from the _______ area of the _______, travel in the corticobulbar pathway, and _______ over before reaching the _________.

A

1) tongue
2) primary motor cortex
3) cross
4) hypoglossal nucleus

42
Q

A patient has a left UMN lesion of the corticobulbar tract to the hypoglossal nucleus. In which direction will the tongue deviate towards?

A

The tongue will deviate to the right (side opposite to the lesion).

43
Q

There is a lesion of the right hypoglossal nerve. In which direction will the tongue protrude?

A

Right

44
Q

What are the two type of LMNs that carry motor signals to the periphery?

A

Alpha and gamma motor neurons.

45
Q

T/F: Alpha motor neurons innervate intrafusal muscle fibers within a muscle spindle.

A

False. A gamma motor neuron is described.

46
Q

As motor axon reaches the muscle it innervates, it loses _______, and synapses on the muscle. This is referred to as the _________.

A

1) myelin sheath

2) neuromuscular junction

47
Q

The _________ is the part of the muscle that contains receptors and receives neurotransmitter.

A

Motor end plate

48
Q

A _____ synapse between ______ axons and _______ occurs at the NMJ.

A

1) chemical
2) LMN
2) skeletal muscle

49
Q

T/F: An AP in the motor axon always causes an AP in the muscle cell it innervates.

A

True

50
Q

What neurotransmitter is released at the neuromuscular junction?

A

Acetylcholine

51
Q

T/F: The action of acetylcholine is mostly excitatory, but sometimes it can be inhibitory at the NMJ.

A

False. Acetylcholine is always excitatory.

52
Q

Explain what happens when a AP arrives as the pre-synaptic axon terminal within the NMJ.

A

Voltage gated Ca2+ channels at presynaptic cleft open –> Ca2+ enters the presynaptic terminal –> the influx of calcium causes synaptic vesicles containing Ach to fuse with the presynaptic membrane and release Ach into the synaptic cleft –> Ach binds to receptors on the post-synaptic muscle fiber membrane –> causes an increase in permeability of Na+ channels –> increased sodium permeability results in depolarization of post-synpatic membrane

53
Q

Depolarizing potential on the postynaptic membrane that spreads out over the surface of the muscle fiber is known as the ___ ___ ___.

A

End plate potential

54
Q

What are 2 differences between an action potential between 2 nerves and between a nerve and a muscle?

A

1) Action potential is not produced at the skeletal muscle level, but rather an end plate potential is produced.
2) Nerve carrying AP is unidirectional, while end plate potential is bi-directional.

55
Q

What is a motor unit?

A

A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron’s axon terminals.

56
Q

What is the innervation ratio?

A

The number of muscle fibers one motor unit contains

57
Q

A low innervation ratio is for _____ muscle force gradient control and _____ movement.

A

1) Fine

2) Precision

58
Q

A ________ is for greater muscle force and larger scale movements.

A

High innervation ratio

59
Q

What is amyotrophic lateral sclerosis?

A

A progressive degenerative disorder affecting motor nerve cells originating from cerebral cortex (upper) and brainstem and spinal cord (lower).

60
Q

In ALS, there is massive loss of _________ of the spinal cord and ______ of brainstem.

A

1) Anterior horn cells

2 motor cranial nerve nuclei

61
Q

A patient presents with painful muscle cramping, muscle atrophy, and respiratory compromise. What might be your diagnosis?

A

Amyotrophic Lateral Sclerosis

62
Q

The muscle atrophy and muscle weakness in ALS is attributed to loss of ____, while spasticity is the result of loss of ______.

A

1) LMN

2) UMN

63
Q

T/F: Peripheral neuropathies only affect small diameter fibers.

A

False. May affect large, small diameter fibers or both.

64
Q

Where is the site of pathology in peripheral neuropathies?

A

Axons, myelin or both

65
Q

What type of fiber does a peripheral neuropathy affect?

A

Typically affect both sensory and motor fibers in the nerve (but may be only sensory or motor)

66
Q

What are the 4 patterns of peripheral neuropathies?

A

1) Focal: mononeuropathy
2) Multifocal: multiple neuropathy
3) Generalized: polyneuropathy
4) Affecting the spinal nerve roots: radiculopathy

67
Q

List 4 causes of peripheral neuropathies.

A

1) Diabetes (compromised microvascular blood supply of peripheral nerves
2) Mechanical (ie. compression, traction, laceration, entrapment)
3) Immune disorders (ie. Guillan-Barre)
4) Other (HIV, toxins, malnutrition)

68
Q

What is the most common pattern of peripheral neuropathy stemming from diabetes?

A

Distal symmetrical polyneuropathy (glove and stocking pattern of sensory loss)

69
Q

______ are spontaneous twitches characteristic of single denervated muscle fibers, while ________ are spontaneous twitches from denervated motor units.

A

1) Fibrillations

2) Fasciculations

70
Q

What is Guillain-Barre Syndrome?

A

Acute inflammatory demyelinating polyradiculopathy (affecting many spinal nerves) triggered by an immune response (preceding infection). Patchy areas of demyelination along peripheral nerves and nerve roots results in slowed conduction velocity.

71
Q

Muscle weakness, hyoreflexia, hypotonia, muscle atrophy, fibrillations and fasciculations are signs of a ________.

A

LMN lesion

72
Q

A patient presents with progressive motor weakness in the limbs (distal to proximal), as well as tachycardia and mild sensory symptoms. What condition does this person have?

A

Guillain Barre Syndrome

73
Q

When will a patient with Guillain Barre Syndrome recover?

A

begins 2-4 weeks after plateau of the disease process

74
Q

Drooping of the eyelids, especially in the evening, is characteristic of what condition?

A

Myasthenia Gravis

75
Q

What is Myasthenia Gravis?

A

Immune mediated disorder in which circulating antibodies block acetylcholine receptors at the post-synaptic NMJ. (Unable to generate end plate potential, resulting in a muscle cell failing to contract)

76
Q

List 3 clinical features of myasthenia gravis.

A

1) generalized symmetrical muscle weakness, especially in proximal limb muscles, neck and diaphragm.
2) If facial muscles involved: may have facial weakness, nasal sounding voice and dysphagia
3) weakness becomes more pronounced over the day and with repeated muscle use.

77
Q

List the condition associated with each:

1) Loss of motor nerve cell bodies
2) Loss of function at NMJ
3) Loss of peripheral nerve conduction

A

1) Amytrophic Lateral Sclerosis
2) Myasthenia Gravis
3) Guillain-Barre Syndrome

Neuromotor Function 1 (21 decks)

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