8 - Brainstem Centers that Influence Motor Activity Flashcards Preview

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Flashcards in 8 - Brainstem Centers that Influence Motor Activity Deck (31)
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1
Q

What tract controls voluntary movement of muscles in head and neck?

A

Corticobulbar tract.

2
Q

What is the function of the rubrospinal tract in humans? Where does it terminate?

A

Provides feedback loop for cerebellum. Very small. Terminates in upper spinal cord.

3
Q

What are the components of the rubrospinal tract?

A

Cell bodies in the red nucleus, axons decussate in the anterior tegmentum and descend in the lateral funiculus to the cervical spinal cord.

4
Q

What is decorticate posturing/rigidity? What symptoms are seen? This is indicative of what type of injury?

A

Cortical input to the red nucleus is eliminated, but cerebellar input to red nucleus is intact. Rubrospinal tract is intact.

Pt exhibits upper limb flexed at the elbow and lower limbs extended.

Indicative of injury to the cerebral cortex, internal capsule, or supper midbrain.

5
Q

What is benedikt’s syndrome? What are the symptoms?

A

A unilateral lesion of the red nucleus.

Oculomotor palsy on IPSI side of lesion (can’t adduct the eye). Tremor on the CONTRA side.

Also effects the medial lemniscus so there may be loss of fine touch/proprioception from the contralateral side (b/c it has already decussated in the medulla).

6
Q

What are the four brainstem centers that influence motor activity?

A

Vestibulo-spinal tract

Reticulo-spinal tract

Rubro-spinal tract

Tecto-spinal tract

7
Q

What provides input to the tectospinal tract? What is the tectospinal tract?

A

Input from visual cortex goes to the superior colliculi.

The tectospinal tract is the motor pathway from the superior colliculi to the motor neurons on the contralateral side to control neck muscles.

8
Q

What is the function of the tectospinal tract?

A

Coordinate reflexive turning movements of head and eyes. Superior colliculus also facilitates upward gaze.

9
Q

What should you think of when you hear tectospinal tract?

A

LOOK SQUIRREL

Innervation of your SCM to turn your head to look at something.

10
Q

What provides input to the ateral vestibulospinal tract ? What is the function of the LVT?

A

The vestibular nuclei, which gets info from the vestibular nerve and the cerebellum.

Innervates extensor (antigravity) muscles, mainly in the trunk and lower limbs to maintain balance and posture.

11
Q

What is the path and location of the lateral vestibulospinal tract?

A

Cell bodies in the vestibular nuclei (located laterally) in the brainstem project ipsilaterally within the anterior funiculus (more medial) to ALL levels of the sp cd.

12
Q
A
13
Q

What does the medial vestibulospinal tract get info from? What is the MVST?

A

The vesitbular nerve and the cerebellum provide information to the vestibular nuclei.

The MVST has cell bodies in the vestibular nuclei within the brainstem and projects bilaterally within the anterior funiculus to the cervical spinal cord.

14
Q

What is the funciton of the MVST?

A

Adjusts head position in response to postural changse.

Coordinates eye movements with each other.

Vestibuloocular reflex: coordinates eye movements to compensate for head movements

15
Q

How does the MVST coordinate eye movements with each other?

A

The vestibular nuclei sends sensory input regarding head movement to the contralateral abducens nucleus.

Each abducents nucleus communicated via the medial longitudinal fasiculus with the contralateral oculomotor nucleus.

16
Q

How does the medial vestibulospinal tract (MVST) coordinate eye movements with each other?

A

The vestibular nuclei sense sensory input regarding head movement to the contralateral abducens. Each abducens nucl. is in communication via the MLF with the contra oculomotor nucl. The eyes are yoked together resulting in conjugate horizontal gaze.

17
Q

What happens when you have a peripheral nerve lesion of the abducens nerve? What about a peripheral nerve lesion of the oculomotor nerve?

A

Abducens nerve: can’t abduct the eye and it will deviate medially.

Oculomotor nerve: deviates laterally because the medial rectus can’t be innervated

18
Q

What happens if you have a lesion of the abducens nucleus?

A

Not only will you have CN 6 fibers not firing, you won’t have yolked eye movement.

The abducens nuclei that projects to the contralateral oculomotor nucleus won’t be firing so the oculomotor nerve and that nucleus doesn’t get a signal to contract the medial rectus (and won’t be able to look past the midline).

19
Q

What results from a lestion of the medial longitudinal fasciculus?

A

This is the communication between the abducens nucleus and the contralateral oculomotor nucleus.

You’re still able to use the lateral rectus, but when the abducens tries to communicate with the contralateral oculomotor nuelcus it can’t.

20
Q

What is internucleus ophthalmoplegia?

A

Lesion of the medial longitudinal fasciculus between nuclei of tCN VI and CN III.

Impaired adduction IPSI to the lesion (this is because the MFL decussates IMMEDIATELY so the lesion is IPSI to the oculomotor nucleus).

Horizontal nystagmus of the abducting eye contralateral to the lesion (like saying “come on, come on, let’s move to this side”)

21
Q

What are some causes of lateral medullary syndrome?

A

Vertebral a. or PICA occlusion.

22
Q

What are the symptoms of a lateral medullary syndrome that occur on the same side as the lesion?

A

Dysphagia, dysarthria (difficulty speaking), decreased gag reflex.

Loss of pain and temp from face.

Vertigo, nausea, comitting, nystagmus.

23
Q

What are the symptoms of a lateral medullary syndrome that occur on the opposite (contralateral) side to the lesion?

A

Loss of pain and temperature sensation from the body because the spinothalamic tract is affected.

24
Q

What are the classic symptoms of lateral medullary syndrome?

A

Checkerboard pattern for loss of pain and temperature.

Loss of pain and temperature on IPSI side of face and CONTRA side of body.

25
Q

What provides input to the reticulospinal tract? What are the two reticulospinal tracts?

A

The cortex provides input to the reticular nuclei.

One from medulla (lateral RST) and one from pontine (medial RST)

26
Q

Describe the function of the medullary (lateral) RST and the pontine (medial) RST?

A

Medullary: bilateral, inhibits LMNs to inhibit extensor muscle constraction (MEDULLARY MELLOW)

Pontine: Ipsilateral, excited LMNs to simualte extensor muscles (PONTINE PUMPED)

27
Q

What is decerebrate posturing/rigidity? When does it show up in humans?

A

Cutting of the brainstem between the superior and inferior colliculi - causes hyperactivity of the extensor muscles. Both lower and upper limbs extended.

Shows up in humans following trauma, vascular disease, or tumors in the lower midbrain.

28
Q

What tracts are and aren’t communicating with each other when a patient has decerebrate posturing/rigidity?

A

No cortical input to the medullary tract (can’t mellow out).

No cortical input to the pontine reticular formation means you can’t inhibit being pumped up.

Therefore removing cortical input results in everything being excited/extended because the reticulosponal tracts are acting independently of the cortex.

29
Q

What are the lateral motor pathways? What is their function? Where are these tracts located?

A

Lateral corticospinal tract and rubrospinal tract.

Goal-directed limb movements

Innervate lateral LMNs in the lateral part of the anterior horn.

30
Q

What are the medial motor pathways? What is their function? Where are these tracts located?

A

Anterior corticospinal tract

Vestibulospinal tract

Reticulospinal tract
Tectospinal tract

Poster, head and neck movements, eye movements.

Innervate medial LMNs in the medial part of the ventral horn.

31
Q
A