10d: Cortex IV (Motor Neurons) Flashcards
Brainstem control of motor systems is mediated by (X) tracts. List them.
X = subcorticospinal
- Rubrospinal
- Tectospinal
- Reticulospinal
- Vestibulospinal
Cortical control of subcorticospinal tracts is mediated by (X) pathways. And cortical control of spinal cord is mediated by (Y) pathways.
X = corticobulbar Y = corticospinal
T/F: Subcorticospinal tracts, like corticospinal tract, travel through pyramids.
False - “extra-pyramidal”
(Lateral/medial) subcorticospinal pathways descend (ipsilaterally/contralaterally/bilaterally), but always terminate bilaterally on the interneurons. List these pathways.
Medial;
Either ipsilaterally or bilaterally;
- Tectospinal
- Medial vestibulospinal
- Medial reticulospinal
The tectospinal tract arises from (X), crosses at (Y), and descends to which SC segments? What’s its function?
X = deep layers of Superior Colliculus Y = dorsal midbrain (tegmentum)
Coordinate head/neck and eye movements
Reticulospinal pathways arise from (X) and descend to which SC segments? They have (excitatory/inhibitory) effect.
X = pontine and medullary reticular formation
Entire length of SC;
Excitatory (pontine) and inhibitory (medullary)
Premotor cortex, Brodmann’s area (X), is located immediately rostral to (Y), Brodmann’s area (Z).
X = 6; Y = primary motor cortex (pre-central gyrus) Z = 4
Movements involving discrete muscle groups, instead of entire limbs, occurs when evoking (primary/pre-) motor cortex.
Primary
Where is the supplementary motor cortex?
Subdivision of premotor cortex (medial/dorsal subdivision)
Mirror neurons are unique in that (X) causes them to fire. Where are these neurons found?
X = observing an action in others
Lateral premotor cortex
Frontal Eye Fields, Brodmann’s area (X), is located immediately rostral to (Y). Stimulation to this area evokes:
X = 8 Y = premotor cortex (BA 6)
Movement of eyes to contralateral side
Damage to Frontal Eye Fields area impairs:
Attention to contralateral visual field
Corticobulbar projections from Frontal Eye Fields area connect to (X). Lesions at (X) impair:
X = pontine gaze center (area of reticular formation)
Lateral eye movement to opposite visual field (but no effect on attention)
List the sources of cortical afferents to the primary motor cortex.
- Premotor cortex
- Somatosensory cortex
- Contralateral motor cortices
List the sources of subcortical afferents to the primary motor cortex.
VA/VL thalamus
Corticobulbar projections to CN (X) nuclei are bilateral.
X = 5, 10, 12
Corticobulbar projections to CN (X) nuclei are, in part, unilateral, specifically (ipsi/contra)-lateral.
X = 7
Contralateral
You notice your patient has slight drooping of R lower lip. When asking him to smile, he’s unable to produce smile on that side. Where’s the damage?
L primary motor cortex (BA 4) in lateral region (area of face)
You notice your patient has slight drooping of R lower lip. You discover damage to Area 4. Would he likely smile at a humorous joke you tell him?
Yes
The facial nucleus receives (unilateral/bilateral) corticobulbar innervation from which cortices?
- Unilateral from primary motor cortex
2. Bilateral from cingulate cortex
Tectobulbar connections refer to fibers projecting to (X) from (Y).
X = horizontal and vertical gaze centers (in midbrain reticular formation) Y = deep tectal nuclei (SC/IC)
T/F: In humans, unlike other mammals, the lateral vestibulospinal tract is largely restricted to control of lower limb extensors.
True
T/F: After bilateral corticospinal tract interruption, wide range of normal motor activity is largely lost in animal studies.
False - subcorticospinal pathways sufficient to guide wide range of these activities
The Pyramidal Syndrome is a result of damage to (X). This impairs (upper/lower) motor neurons. What are the signs of this syndrome?
X = either motor cortices or fibers in internal capsule
UPM
- Paralysis/paresis
- Hyper-reflexia
- Spasticity
- Babinski’s sign
Babinski’s sign is:
Dorsiflexion/extension of great toe when stroking lateral border of foot
Lesion that produces pyramidal tract signs may initially present with (spastic/flaccid) paralysis, which then gradually evolves into (spastic/flaccid) paralysis.
Flaccid; spastic
Lesions restricted to motor cortex produce paralysis mainly of (X) musculature. Which symptoms may be missing from this lesion, compared to pyramidal tract syndrome?
X = distal;
Babinski sign, spasticity, and/or hyper-reflexia
List the only signs that can be strictly called pyramidal/corticospinal.
- Sign of Babinski
2. Impairment of movement to most distal extremities
Target-related AP: neurons that fire maximally in response to specific direction of movement are found in which motor cortex?
Primary motor cortex
Neurons in (X) cortex fire AP in response to cue that indicates an action will be undertaken (ex: monkey sees red light and knows blue light to press button is coming).
X = ventral premotor (BA 6)
You’re about to do a bicep curl. Feedforward via (X) tract(s) regulate postural instability by (activating/inhibiting) gastrocnemius.
X = corticospinal and corticobulbar;
Activating
You’re about to do a bicep curl, but you begin to tilt back due to unanticipated postural instability. You don’t fall due to feedback from (X) tracts/structures for postural adjustment.
X = vestibulospinal, reticulospinal, and cerebellar
You’re about to do a bicep curl, so your gastrocnemius is involved to maintain posture. Will the biceps or the gastrocnemius EMG spike first?
Gastrocnemius EMG
