Module 10 Flashcards
Upper Motor Neurons & Descending Control Systems
Which descending tract modulates activity of the lower motor neurons in the brainstem and spinal cord respectively?
Corticospinal tract
Damage to which tract will result in weakness or paralysis of the lower muscles of facial expression and hemiparesis or hemiplagia of the body, respectively?
Corticonuclear Tract
Lower muscles are getting contralateral input from the corticonuclear tract= **weakness in lower muscles= injury to the corticonuclear system
What movement parameters are encoded by neurons in the primary motor cortex?
-The magnitude of force needed to produce the overall movement
-The direction of the movement
-The extent of the movement
-The speed of the movement
If your patient had a stroke involving middle cerebral artery would you expect to see greater weakness in the contralateral upper or lower limb?
Contralateral upper limb and face region
Which of the motor cortices play a role in motor planning?
Primary motor cortex
Which upper motor neuron systems are instrumental in producing skilled limb movements?
Lateral Corticospinal Tract
-rubrospinal tract
Which brainstem upper motor neuron systems are important for regulation of anticipatory postural control and gait?
Anterior Corticospinal tract (bilateral)
What clinical signs would you expect to see when working with someone with upper motor neuron dysfunction?
What tonal changes would you expect to see if your patient sustained an injury above the level of the red nucleus?
damage above the level of the midbrain disrupts the corticorubral and corticoreticular tracts resulting in decreased modulation of the rubrospinal and reticulospinal tracts (meaning they become hyperactive). This results in increased flexor tone in the UE and increased extensor tone in the lower extremities.
Clinical signs associated with upper motor neuron damage, and decorticate and decerebrate rigidity.
The classic upper motor neuron signs include: initially flaccidity followed by paresis or plegia, hypertonia (not indicated above) and hypereflexia. The paresis and plegia will impact multiple muscle groups because of the lack of UMN signals to LMN pools. Hypertonia and hyperrefleixa are the result of the decreased modulation of the spinal cord circuitry (increased firing rate of gama motor neurons and decreased modulation of the monosynaptic stretch reflex)
Location and function of upper motor neurons.
Which of the following tracts is considered the major descending control tract for the production of skilled limb movement and dexterity of the hand?
Anterior corticospinal tract
Lateral corticospinal tract
Rubrospinal tract
Lateral corticospinal tract
Explanation:
The cotricospinal tract gives rise to the lateral (crossed fibers) and anterior (uncrossed fibers) corticospinal tracts. The lateral CST will project ipsilaterally at all levels of the spinal cord to terminate on laterally located local circuit neurons and LMNs that control appendicular muscles for skilled limb movement and dexterity of the hand/foot. The anterior corticospinal tract will project bilaterally at all levels of the spinal cord to terminate on medially located local circuit neurons and LMNs that control axial and proximal limb musculature for postural control. The rubrospinal tract is a tract that originates in the brainstem and it will play a small role in complimenting the lateral corticospinal tract.
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
Vestibulospinal tract
Explanation:
The reticulospinal and vestibulospinal tracts are upper motor neuron tracts that originate in the brainstem and terminate on medially located local circuit neurons and LMN forming part of the ventromedial system mediating postural control. The anterior corticospinal tract is also part of the ventromedial system, but it originates in the cortex. The rubrospinal tract is an upper motor neuron tract that originates in the brainstem but it is NOT part of the ventromedial system. It plays a small role in the dorsolateral system that mediates skilled limb movements. The corticonuclear tract originates in the cortex and projects to LMN in the 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
Explanation:
This statement is true: damage to the corticospinal tract above the motor decussation will result in contralateral motor deficits (aka hemiparesis or plegia (depending on the extent of the damage).
True or False: A small vascular lesion impacting the lateral aspect of the medulla at the mid-level of the motor decussation can result in contralateral upper limb paresis/plegia and ipsilateral lower limb paresis/plegia.
False
Explanation:
This statement is false: damage at this level of the motor decussation would result in ipsilateral upper limb paresis/plegia (upper limb fibers of this tract have crossed rostral in the medulla - they are below the level of their decussation) and contralateral lower limb paresis/plegia (lower limb fibers of this tract have NOT yet crossed - they cross in the caudal medulla - they are above the level of their decussation).
True or False: The trigeminal motor nucleus will receive descending control signals from both the right and left corticonuclear tracts?
True
Explanation:
This statement is true: as a general rule the cranial nerve somatic motor nuclei will receive input from both corticonuclear tracts. This creates redundancy in the system. There are however some notable exceptions to this rule. It is these exceptions that are most clinically relevant.
Which of the following lower motor neurons will receive predominantly contralateral input from the corticonuclear tract? Select all that apply.
Lower motor neurons innervation the upper muscles of facial expression
Lower motor neurons innervation the lower muscles of facial expression
Lower motor neurons innervating the trapezius
Lower motor neurons innervating the genioglossus
Lower motor neurons innervating the muscles of the soft palate
Lower motor neurons innervation the lower muscles of facial expression
Lower motor neurons innervating the genioglossus
Lower motor neurons innervating the muscles of the soft palate
Explanation:
Lower motor neurons innervating the lower muscles of facial expression, muscles of the soft palate, and the genioglossus will all receive predominantly contralateral input from the cotriconuclear tract. The trapezius and the SCM receive predominantly ipsilateral input, and the upper muscles of facial expression receive bilateral input.
Which area of the motor cortices is primarily involved with generating execution commands that encode the direction, extent, speed, and force needed to produce a voluntary movement?
Supplementary motor areas
Premotor cortex
Primary motor cortex
Primary motor cortex
Explanation:
The primary motor cortex is thought to play a major role in generating commands that will lead to appropriate motor execution, encoding the direction, extent, speed and force needed to produce voluntary movements.
Which areas of the brain are thought to be involved with the sensorimotor transformations that are needed to convert and intention into an action? Select all that apply.
Primary motor cortex
Premotor cortex
Posterior parietal cortex
Brainstem
Supplementary motor areas
Premotor cortex
Posterior parietal cortex
Supplementary motor areas
Explanation:
The premotor cortex, SMA, and the posterior parietal cortices are all thought to play a role in the sensorimotor transformations that are needed to convert and intention into an appropriate action.
Which of the following clinical deficits is considered an upper motor neuron sign? Select all that apply.
Fasciculations
Paresis or plegia
Hypotonia
Hyperreflexia
Atrophy
Paresis or plegia
Hyperreflexia
Explanation:
The classic upper motor neuron signs include: initially flaccidity followed by paresis or plegia, hypertonia (not indicated above) and hypereflexia. The paresis and plegia will impact multiple muscle groups because of the lack of UMN signals to LMN pools. Hypertonia and hyperrefleixa are the result of the decreased modulation of the spinal cord circuitry (increased firing rate of gama motor neurons and decreased modulation of the monosynaptic stretch reflex). Atrophy, fasciculations, and hypotonia are classic lower motor neuron signs.
True or False: Damage above the level of the red nucleus results in decreased cortical modulation of the rubrospinal and reticulospinal tracts resulting in an increase in upper extremity flexor tone and lower extremity extensor
True
Explanation:
This statemtent is true: damage above the level of the midbrain disrupts the corticorubral and corticoreticular tracts resulting in decreased modulation of the rubrospinal and reticulospinal tracts (meaning they become hyperactive). This results in increased flexor tone in the UE and increased extensor tone in the lower extremities.
What is the primary function of basal nuclei?
“Gate Keeper”
motor control
Which nuclei are considered the input and output zones of the basal nuclei, respectively?
Striatum: Input Zone of Basal Nuclei
Pallidum: Output Zone
What structures from the limb and trunk motor loop?
What structures form the eye motor loop?
Does activation of the direct pathway of the basal nuclei result in excitation or inhibition of motor neurons in the cortex?
Excitation
Activation of which pathway is thought to suppress unwanted motor plans?
Indirect pathway
What is the function of the D1 dopaminergic pathway?
The dopaminergic pathway of the basal nuclei is thought to be instrumental in helping us learn motor habits.
What clinical signs would you expect to see if your patient had a hyperkinetic movement disorder?
excessive involuntary movements (increased motor activity)
What is the difference between dyskinesia and akinesia?
Dyskinesia= abnormal uncontrolled involuntary movements
Akinesia= “without movement” - an absence or loss of power of voluntary movements
What clinical signs would you expect to see when working with someone with Parkinson’s disease?
Which of the following structures are considered part of the input zone of the basal nuclei? Select all that apply.
Substantia nigra pars compacta
Substania nigra pars reticulata
Caudate
Putamen
Globus pallidus
Caudate
Putamen
Explanation:
The caudate and the putamen are considered the input zone of the basal nuclei (BN). The globus pallidus (internal segment) and the substantia nigra pars reticulata are the output zone of the BN. The substantia nigra pars compacta is the source of dopaminergic projections to the input zone of the BN.
True or False: The neurons of the striatum (input zone of the BN) and the pallidum (output zone of the BN) secrete the neurotransmitter glutamate.
False
Explanation:
This statement is false: the neurons of the striatum and pallidum secrete the neurotransmitter GABA - thus, they inhibit the neurons they synapse with.
Which of the following neurons form the only purely excitatory intrinsic connections of the basal nuclei circuitry?
Striatopallidial (neurons that project from the striatum (input zone) to the pallidum (output zone) neurons
Pallidothalamic (neurons that project from the pallidum (output zone) to the thalamus neurons
Subthalamopallidal (neurons that project from the subthalamic nucleus to the pallidum (output zone) neurons
Pallidosubthalamic (neurons that project from the external segment of the pallidum to the subthalamic nucleus) neurons
Subthalamopallidal (neurons that project from the subthalamic nucleus to the pallidum (output zone) neurons
Explanation:
Projections from the subthalamic nucleus to the output zone of the BN (subthalamopallidal neurons) are the only purely exicatory connections of the BN circuitry. These neurons secrete the neurotransmitter glutamate. All of the other neurons mentioned will secrete GABA, thus they have inhibitory influences.
True or False:
Dopaminergic input to the striatum (input zone of the BN) will result in the excitation of some medium spiny neurons and the inhibition of other medium spiny neurons.
True
Explanation:
This statement is true: dopaminergic input from the substantia nigra pars compacta will cause excitation of some medium spiny neurons (those of the direct pathway) and the inhibition of others (those of the indirect pathway).
Which of the following statements best reflects the structure and function of the direct pathway of the basal nuclei?
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 upper motor neurons in the cortex.
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 upper motor neurons in the cortex.
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 upper motor neurons in the cortex.
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 upper motor neurons in the cortex.
Explanation:
The end result of excitation of the medium spiny neurons of the striatum that output to the direct pathway is excitation of upper motor neurons in the cortex: excitatory input from the cortex will excite medium spiny neurons that secrete the neurotransmitter GABA. Secretion of GABA into the internal segment of the globus pallidus results in inhibition of pallidal neurons that were previous tonically active. This results in releasing the thalamus from its tonic inhibition (disinhibition of the thalamus). Thalamocortical neurons become active exciting upper motor neurons in the cortex.
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
Explanation:
This statement is true: the subthalamic nucleus in inhibited by the external segment of the globus pallidus. When this inhibition is decreased, coupled with excitation provided by the cortex, the subthalamic nucleus is released from inhibition. The subthalamopallidal neurons will secrete the neurotransmitter glutamate which results in excitation of the pallidal neurons. The pallidal neurons will increase their tonic activity providing enhanced inhibition of the thalamus.
Which of the following statements best reflects the roles of the direct and indirect pathways in the production of purposeful goal-directed movements?
The direct pathway selects out the appropriate functional movement primitives in the appropriate temporal sequence, while the indirect pathway suppresses competing primitives.
The indirect pathway selects out the appropriate functional movement primitives in the appropriate temporal sequence, while the direct pathway suppresses competing primitives.
The direct pathway selects out the appropriate functional movement primitives in the appropriate temporal sequence, while the indirect pathway suppresses competing primitives.
True or False: The dopaminergic pathway of the basal nuclei is thought to be instrumental in helping us learn motor habits.
True
True or False: Dysfunction of the basal nuclei can result in hyperkinetic or hypokinetic movement disorders.
True
Which of the following is considered a clinical deficit associated with hyperkinesia? Select all that apply.
Akinesia
Bradykinesia
Chorea
Motor tics
Athetosis
Chorea
Motor tics
Athetosis
Explanation:
Hyperkinesia is excessive involuntary movements and includes chorea, motor tics, and athetosis (among others). Akinesia (absence of voluntary movement) and bradykinesia (slowness/poverty of movement) are examples of hyopkinesia.
