8 - Brainstem Centers that Influence Motor Activity Flashcards
What tract controls voluntary movement of muscles in head and neck?
Corticobulbar tract.
What is the function of the rubrospinal tract in humans? Where does it terminate?
Provides feedback loop for cerebellum. Very small. Terminates in upper spinal cord.
What are the components of the rubrospinal tract?
Cell bodies in the red nucleus, axons decussate in the anterior tegmentum and descend in the lateral funiculus to the cervical spinal cord.
What is decorticate posturing/rigidity? What symptoms are seen? This is indicative of what type of injury?
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.
What is benedikt’s syndrome? What are the symptoms?
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).
What are the four brainstem centers that influence motor activity?
Vestibulo-spinal tract
Reticulo-spinal tract
Rubro-spinal tract
Tecto-spinal tract
What provides input to the tectospinal tract? What is the tectospinal tract?
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.
What is the function of the tectospinal tract?
Coordinate reflexive turning movements of head and eyes. Superior colliculus also facilitates upward gaze.
What should you think of when you hear tectospinal tract?
LOOK SQUIRREL
Innervation of your SCM to turn your head to look at something.
What provides input to the ateral vestibulospinal tract ? What is the function of the LVT?
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.
What is the path and location of the lateral vestibulospinal tract?
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.
What does the medial vestibulospinal tract get info from? What is the MVST?
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.
What is the funciton of the MVST?
Adjusts head position in response to postural changse.
Coordinates eye movements with each other.
Vestibuloocular reflex: coordinates eye movements to compensate for head movements
How does the MVST coordinate eye movements with each other?
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.
What happens when you have a peripheral nerve lesion of the abducens nerve? What about a peripheral nerve lesion of the oculomotor nerve?
Abducens nerve: can’t abduct the eye and it will deviate medially.
Oculomotor nerve: deviates laterally because the medial rectus can’t be innervated
What happens if you have a lesion of the abducens nucleus?
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).
What is internucleus ophthalmoplegia?
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”)
What are some causes of lateral medullary syndrome?
Vertebral a. or PICA occlusion.
What are the symptoms of a lateral medullary syndrome that occur on the same side as the lesion?
Dysphagia, dysarthria (difficulty speaking), decreased gag reflex.
Loss of pain and temp from face.
Vertigo, nausea, comitting, nystagmus.
What are the symptoms of a lateral medullary syndrome that occur on the opposite (contralateral) side to the lesion?
Loss of pain and temperature sensation from the body because the spinothalamic tract is affected.
Describe the function of the medullary (lateral) RST and the pontine (medial) RST?
Medullary: bilateral, inhibits LMNs to inhibit extensor muscle constraction (MEDULLARY MELLOW)
Pontine: Ipsilateral, excited LMNs to simualte extensor muscles (PONTINE PUMPED)
What is decerebrate posturing/rigidity? When does it show up in humans?
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.
What are the lateral motor pathways? What is their function? Where are these tracts located?
Lateral corticospinal tract and rubrospinal tract.
Goal-directed limb movements
Innervate lateral LMNs in the lateral part of the anterior horn.
What are the medial motor pathways? What is their function? Where are these tracts located?
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.
