Brainstem Motor Pathways - Foundations of Medicine flashcards

50 flashcards covering brainstem motor pathways, tracts, posturing signs, and key clinical correlations.

Rubrospinal Tract: what is its main proposed function in humans?

Helps put the upper limb into a functional position.

Rubrospinal Tract: where are its cell bodies located?

The red nucleus in the midbrain.

Rubrospinal Tract: where do its axons descend to?

Cervical spinal cord.

Decorticate Posturing: how are the upper and lower limbs positioned?

Upper limbs flexed; lower limbs extended.

Decorticate Posturing: what level of brain injury does it indicate?

Injury to the midbrain or above.

Tectospinal Tract: what is its main function?

Coordinate reflexive turning movements of the head and eyes in response to visual stimuli.

Tectospinal Tract: what midbrain structures are the origin?

Superior colliculus (midbrain tectum).

What memory cue is associated with the Tectospinal Tract in this lecture?

“Squirrel!” (reflex head turning to a visual stimulus).

Lateral Vestibulospinal Tract: what is its primary function?

Excites anti-gravity/extensor muscles in trunk and lower limbs to maintain posture.

Lateral Vestibulospinal Tract: what happens when this tract is damaged?

Falling toward the side of the lesion.

Medial Vestibulospinal Tract: primary function?

Adjusts head position in response to postural changes; helps coordinate eye movements.

Medial Vestibulospinal Tract: how do signals reach CN nuclei?

Via the medial longitudinal fasciculus (MLF) to cervical CN nuclei.

Reticulospinal Tract: general role?

Maintains upright posture via brainstem reticular formation.

Pontine vs Medullary Reticulospinal Tracts: effect on extensor muscles?

Pontine excites extensor muscles; medullary inhibits extensor muscles (pumps you up vs mellow).

Decerebrate Posturing: describe the limb posture.

Back arched; both upper and lower limbs extended.

Decerebrate Posturing: what does it imply about rubrospinal tract function?

Rubrospinal tract is not functional.

Corticospinal Tract: origin (O) and termination (T)?

O: Cerebral cortex (UMNs); T: LMNs in contralateral spinal cord.

Corticospinal Tract: where does it decussate?

In the medulla (pyramidal decussation).

Corticospinal Tract: typical signs of injury?

Hyperreflexia, Babinski sign, contralateral paralysis, spasticity.

What is the Final Common Pathway (FCP) in motor control?

Lower motor neurons (LMNs) in the ventral horn.

Which neurons innervate distal limb muscles?

Lateral LMNs.

Which neurons innervate axial and proximal muscles?

Medial LMNs.

Stretch reflex: afferents involved?

Ia afferents from muscle spindles and Golgi tendon organs.

Stretch reflex: monosynaptic component involves which neurons?

α-LMNs (alpha motor neurons) to stimulate contraction of homonymous muscles.

Stretch reflex: how are antagonists inhibited?

Interneurons inhibit antagonists via disynaptic pathways.

Corticonuclear Tract: what does it connect?

Cerebral cortex (UMNs) to CN nuclei (LMNs) of motor cranial nerves.

Corticonuclear Tract: pattern of input to most CN nuclei?

Bilateral input to most nuclei.

Corticonuclear Tract: which CN nuclei receive contralateral input?

Facial nucleus and hypoglossal nucleus.

Cortico-Ponto-Cerebellar Tract: what is its role?

Transmits information about intended movement from cortex to the lateral cerebellar hemispheres.

Spinocerebellar Tracts: general function?

Provide sensory feedback re: position and movement to the cerebellum.

Posterior Spinocerebellar Tract: input origin?

Body and lower limbs to ipsilateral cerebellum.

Posterior Spinocerebellar Tract: destination?

Ipsilateral cerebellum.

Anterior Spinocerebellar Tract: decussation pattern?

Decussates twice before reaching the cerebellum.

Cuneocerebellar Tract: input origin?

Upper limbs to ipsilateral cerebellum.

Basal Nuclei Motor Loop: role?

Motor loop with cerebral cortex to modulate movement and posture.

What are LMN signs of injury?

Hyporeflexia, muscle atrophy, fasciculations.

Which tract carries information about intended movement to the cerebellum?

Cortico-ponto-cerebellar tract.

Where are red nucleus cells located?

Midbrain (in the tegmentum).

Spinocerebellar Tracts: which tract carries input from moving limbs that decussates twice?

Anterior Spinocerebellar Tract.

Which tract is involved in reflexive head turning in response to a visual cue?

Tectospinal Tract.

Which tract is primarily involved in head position adjustment and VOR via MLF?

Medial Vestibulospinal Tract.

Which tract maintains upright posture via vestibular nuclei projecting to LMNs across levels?

Lateral Vestibulospinal Tract.

Which tract originates from the superior colliculus and projects to CN XI nucleus for neck control?

Tectospinal Tract.

Which tract is affected in decerebrate posture but not in decorticate posture?

Rubrospinal Tract (often not functional in decerebrate posture).

What is the typical prognosis warning sign associated with decerebrate posturing?

Agnal sign with very poor prognosis and potential tonsillar herniation.

Where are the vestibular nuclei located that give rise to LVST and MVST?

In the brainstem (vestibular nuclei).

Which tract directly influences eye movements via CN nuclei for VOR?

Medial Vestibulospinal Tract.

Which tract is a reflex pathway that helps maintain posture with vestibular input?

Lateral Vestibulospinal Tract.

What is the origin of the Corticonuclear (corticobulbar) tract?

Cerebral cortex (UMNs) to brainstem CN nuclei.

Which brain region is the red nucleus a part of?

Midbrain (tegmentum).

Which tract is described as having a role in 'flexion of the upper limbs' in decorticate posture?

Rubrospinal Tract.

What is the termination point of the Rubrospinal Tract?

Cervical spinal cord.

Which tract has a strong connection to the cerebellum for movement planning?

Cortico-ponto-cerebellar Tract.

What is the role of the Spinocerebellar Posterior tract in terms of spinal segments?

Carries proprioceptive information from the body and lower limbs to the ipsilateral cerebellum.

What is unique about the anterior spinocerebellar tract's path to the cerebellum?

Decussates twice en route to the cerebellum.

Where do LMNs reside in the spinal cord?

Ventral horn.

What is the clinical sign Babinski indicative of?

Upper motor neuron lesion (corticospinal tract injury).

Which tract's destruction produces limb extension and arching in posturing?

Reticulospinal tract (decerebrate posture involves extension from brainstem).