10: Descending Motor Control Systems; Basal Nucei Flashcards
Which of the following tracts is considered the major descending tract for the production of skilled limb movement and dexterity of the hand?
A. Anterior corticospinal tract
B. Lateral corticospinal tract
C. Rubrospinal tract
B
Which of the following tracts originate from the brainstem and form part of the Ventromedial System mediating postural control? Select all that apply.
- Rubrospinal tract
- Reticulospinal tract
- Vestibulospinal tract
- Anterior corticospinal tract
- Corticonuclear tract
Reticulospinal tract and Vestibulospinal tract: Both of these are UMN tracts originating in the brainstem and terminating on medially located LMNs forming the ventromedial system.
- Anterior corticospinal: part of VM system, but originates in the cortex.
- Rubrospinal: not part of VM system (DL system > skilled limb movement).
- Corticonuclear: originates in the cortex and projects to LMN in cranial nerve somatic motor nuclei.
True or false: An injury to the corticospinal tract above the level of the motor decussation results in contralateral motor deficits impacting the body.
True
True or false: A small vascular lesion impacting the lateral corticospinal tract of the medulla at the mid-level of the motor decussation can result in a contralateral upper limb paresis and ipsilateral lower limb paresis.
False
Damage at this level would result in ipsilateral UE (UE fibers crossed in rostral medulla, thus injury is below their decussation) and contralateral LE paresis (LE fibers cross in caudal medulla, thus injury is above their decussation).
True or false: The trigeminal motor nucleus will receive descending control signals from both the right and left corticonuclear tracts.
True
Which of the following lower motor neurons will receive predominately contralateral inputs from the corticonuclear tract? Select all that apply.
- LMNs innervating upper muscles of facial expression
- LMNs innervating lower muscles of facial expression
- LMNs innervating trapezius
- LMNs innervating genioglossus
- LMNs innervating the muscles of the soft palate
Contralateral = lower muscles of facial expression, genioglossus, muscles of the soft palate
- The trapezius and sternocleidomastoid receive predominately ipsilateral input.
- The upper muscles of facial expression receive bilateral input.
Which of the motor cortices is primarily involved with generating commands that encode the direction, extent, speed, and force needed to produce a voluntary movement?
A. Supplementary motor area
B. Premotor cortex
C. Primary motor cortex
C
Which areas of the brain are thought to be involved with the sensorimotor transformations that are needed to convert an intention into action? Select all that apply.
- Primary motor cortex
- Premotor cortex
- Posterior parietal cortex
- Brainstem
- Supplemental motor area
- Premotor cortex
- Posterior parietal cortex
- Supplemental motor area
Which of the following structures are considered part of the input zone of the basal nuclei? Select all that apply.
- Substantia nigra pars compacta
- substantia nigra pars reticulata
- Caudate
- Putamen
- Globus pallidus
Caudate and Putamen
True or false: The neurons of the striatum (input zone of the basal nuclei) and the pallidum (output zone of the basal nuclei) secrete the neurotransmitter glutamate.
False
They secrete GABA, inhibiting neurons they synapse with.
Which of the following neurons form the only excitatory intrinsic connections of the basal nuclei circuitry?
A. Stratopallidal
B. Pallidothalamic
C. Subthalamopallidal
D. Pallidosubthalamic
C
True or false: Dopaminergic input to the striatum will result in the excitation of some medium spiny neurons and the inhibition of other medium spiny neurons.
True
Which of the following statements best reflects the structure and function of the direct pathway of the basal nuclei?
A. Excitation of the striatum results in excitation of the internal segment of the globus pallidus, thereby reducing the tonic inhibition of the thalamus, resulting in excitation of the upper motor neurons of the cortex.
B. Excitation of the striatum results in inhibition of the internal segment of the globus pallidus, thereby reducing the tonic inhibition of the thalamus, resulting in excitation of the upper motor neurons of the cortex.
C. Excitation of the striatum results in inhibition of the internal segment of the globus pallidus, thereby increasing the tonic inhibition of the thalamus, resulting in excitation of the upper motor neurons of the cortex.
B
True or false: The indirect pathway of the basal nuclei produces increased inhibition of the thalamus secondary to the subthalamic nucleus being released from tonic inhibition.
True
Which of the following statements best reflect as the roles of the direct and indirect pathways in the production of purposeful goal-directed movements?
A. The direct pathway selects out the appropriate functional movement primitives in the appropriate temporal sequence, while the indirect pathway suppresses competing primitives.
B. The indirect pathway selects out the appropriate functional movement primitives in the appropriate temporal sequence, while the direct pathway suppresses competing primitives.
A
