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Questions and Answers
What are the two sets of upper motor neurons that control the local circuitry in the brainstem and spinal cord?
What are the two sets of upper motor neurons that control the local circuitry in the brainstem and spinal cord?
The reticular formation and the vestibular nuclei.
What type of control does the reticular formation play in posture?
What type of control does the reticular formation play in posture?
Feedforward control
What type of control does the vestibular nuclei play in posture?
What type of control does the vestibular nuclei play in posture?
Feedback control
What part of the brain is responsible for movement execution?
What part of the brain is responsible for movement execution?
What part of the brain is responsible for planning and selecting movements?
What part of the brain is responsible for planning and selecting movements?
What are the two ways that the motor cortex influences movements?
What are the two ways that the motor cortex influences movements?
What are the two types of tracts that make up the pyramidal tract?
What are the two types of tracts that make up the pyramidal tract?
What are the four types of tracts that make up the extrapyramidal tracts?
What are the four types of tracts that make up the extrapyramidal tracts?
The brainstem pathways can independently organize gross motor control.
The brainstem pathways can independently organize gross motor control.
What are the distal parts of the limbs that are crucial for everyday life?
What are the distal parts of the limbs that are crucial for everyday life?
What are the two groups of muscles that are affected by damage to the descending motor pathways?
What are the two groups of muscles that are affected by damage to the descending motor pathways?
Where do the projections from the vestibular nuclei that control axial muscles originate?
Where do the projections from the vestibular nuclei that control axial muscles originate?
Where do the projections from the vestibular nuclei that influence proximal limb muscles originate?
Where do the projections from the vestibular nuclei that influence proximal limb muscles originate?
What type of response do direct projections from the vestibular nuclei to the spinal cord ensure?
What type of response do direct projections from the vestibular nuclei to the spinal cord ensure?
What is the reticular formation similar in structure and function to?
What is the reticular formation similar in structure and function to?
What are some of the functions of neurons within the reticular formation?
What are some of the functions of neurons within the reticular formation?
What is the function of the skeletomotor control by the reticular formation?
What is the function of the skeletomotor control by the reticular formation?
The descending motor control pathways from the reticular formation to the spinal cord are similar to those of the vestibular nuclei.
The descending motor control pathways from the reticular formation to the spinal cord are similar to those of the vestibular nuclei.
What are the motor centers in the reticular formation largely controlled by?
What are the motor centers in the reticular formation largely controlled by?
What mechanism does the reticular formation use to stabilize posture during ongoing movements?
What mechanism does the reticular formation use to stabilize posture during ongoing movements?
Where do the upper motor neurons in the cerebral cortex reside?
Where do the upper motor neurons in the cerebral cortex reside?
What type of regulatory input do the cortical areas receive?
What type of regulatory input do the cortical areas receive?
Which cortical layer has the pyramidal cells of the primary motor cortex?
Which cortical layer has the pyramidal cells of the primary motor cortex?
What two tracts do the axons of the pyramidal cells descend in?
What two tracts do the axons of the pyramidal cells descend in?
What structure do the tracts pass through before entering the cerebral peduncle?
What structure do the tracts pass through before entering the cerebral peduncle?
Where are the axons located as they pass through the base of the pons?
Where are the axons located as they pass through the base of the pons?
Where do the axons coalesce again as they pass through the brainstem?
Where do the axons coalesce again as they pass through the brainstem?
What structure do the axons form on the ventral surface of the medulla?
What structure do the axons form on the ventral surface of the medulla?
Where do the components of the upper motor neuron pathway that innervate cranial nerve nuclei, the reticular formation, and the red nucleus leave the pathway?
Where do the components of the upper motor neuron pathway that innervate cranial nerve nuclei, the reticular formation, and the red nucleus leave the pathway?
What happens to most of the axons in the pyramidal tract at the caudal end of the medulla?
What happens to most of the axons in the pyramidal tract at the caudal end of the medulla?
Where does the lateral corticospinal tract form the direct pathway to the spinal cord?
Where does the lateral corticospinal tract form the direct pathway to the spinal cord?
Where does the lateral corticospinal tract terminate primarily?
Where does the lateral corticospinal tract terminate primarily?
What are the axons that enter the spinal cord without crossing called?
What are the axons that enter the spinal cord without crossing called?
Where do the axons of the ventral corticospinal tract terminate?
Where do the axons of the ventral corticospinal tract terminate?
What are the two sources of upper motor neurons in the brainstem that the indirect pathway to lower motor neurons in the spinal cord runs to?
What are the two sources of upper motor neurons in the brainstem that the indirect pathway to lower motor neurons in the spinal cord runs to?
Where do the axons to the red nucleus originate?
Where do the axons to the red nucleus originate?
Where do the axons to the reticular formation originate?
Where do the axons to the reticular formation originate?
The premotor cortex is rostral to the primary motor cortex.
The premotor cortex is rostral to the primary motor cortex.
What are the two components of the premotor region?
What are the two components of the premotor region?
What function does the lateral premotor cortex seem to be involved in?
What function does the lateral premotor cortex seem to be involved in?
What do patients with frontal lobe damage have difficulty learning to do?
What do patients with frontal lobe damage have difficulty learning to do?
What function does the medial premotor cortex mediate?
What function does the medial premotor cortex mediate?
What type of cues does the medial premotor cortex appear to be specialized for initiating movements in response to?
What type of cues does the medial premotor cortex appear to be specialized for initiating movements in response to?
What is the effect of injury to the medial premotor area on the number of self-initiated or spontaneous movements?
What is the effect of injury to the medial premotor area on the number of self-initiated or spontaneous movements?
What ability remains largely intact after injury to the medial premotor area?
What ability remains largely intact after injury to the medial premotor area?
What is the main symptom that occurs when upper motor neurons in the motor cortex or descending motor axons in the internal capsule are damaged?
What is the main symptom that occurs when upper motor neurons in the motor cortex or descending motor axons in the internal capsule are damaged?
What term is used to describe the immediate flaccidity that occurs after upper motor neuron injury?
What term is used to describe the immediate flaccidity that occurs after upper motor neuron injury?
What is spinal shock a reflection of?
What is spinal shock a reflection of?
Where are the acute manifestations of upper motor neuron injury most severe?
Where are the acute manifestations of upper motor neuron injury most severe?
What is the typical condition of trunk muscles after upper motor neuron injury?
What is the typical condition of trunk muscles after upper motor neuron injury?
What is the normal response in an adult when the sole of the foot is stroked?
What is the normal response in an adult when the sole of the foot is stroked?
What is the abnormal plantar reflex seen after damage to descending upper motor neuron pathways called?
What is the abnormal plantar reflex seen after damage to descending upper motor neuron pathways called?
What is the primary symptom of spasticity?
What is the primary symptom of spasticity?
Spasticity is probably caused by the removal of inhibitory influences exerted by the cortex on the postural centers of the vestibular nuclei and reticular formation.
Spasticity is probably caused by the removal of inhibitory influences exerted by the cortex on the postural centers of the vestibular nuclei and reticular formation.
Spasticity can be eliminated by sectioning the dorsal roots.
Spasticity can be eliminated by sectioning the dorsal roots.
What is another symptom that may occur with spasticity?
What is another symptom that may occur with spasticity?
What happens to the ability to perform fine movements when the lesion involves the descending pathways that control the lower motor neurons to the upper limbs?
What happens to the ability to perform fine movements when the lesion involves the descending pathways that control the lower motor neurons to the upper limbs?
What is the effect of damage to the facial motor nucleus or its nerve on the muscles of facial expression?
What is the effect of damage to the facial motor nucleus or its nerve on the muscles of facial expression?
What is the effect of unilateral injury to the motor areas in the lateral frontal lobe on facial expression?
What is the effect of unilateral injury to the motor areas in the lateral frontal lobe on facial expression?
What is the recent interpretation of the reason why strokes involving the middle cerebral artery spare the superior aspect of the face?
What is the recent interpretation of the reason why strokes involving the middle cerebral artery spare the superior aspect of the face?
Superior facial sparing in strokes involving the middle cerebral artery may arise because the cingulate motor area sends descending projections through the corticobulbar pathway that bifurcate and innervate dorsal facial motor cell columns on both sides of the brainstem.
Superior facial sparing in strokes involving the middle cerebral artery may arise because the cingulate motor area sends descending projections through the corticobulbar pathway that bifurcate and innervate dorsal facial motor cell columns on both sides of the brainstem.
What type of paralysis is often associated with an upper motor neuron lesion?
What type of paralysis is often associated with an upper motor neuron lesion?
Superficial reflexes are often lost in both upper and lower motor neuron lesions.
Superficial reflexes are often lost in both upper and lower motor neuron lesions.
The plantar reflex is present in upper motor neuron lesions.
The plantar reflex is present in upper motor neuron lesions.
Deep reflexes are often exaggerated in upper motor neuron lesions.
Deep reflexes are often exaggerated in upper motor neuron lesions.
Clonus is often present in upper motor neuron lesions.
Clonus is often present in upper motor neuron lesions.
Electrical activity is often normal in upper motor neuron lesions.
Electrical activity is often normal in upper motor neuron lesions.
Groups of muscles are often affected in upper motor neuron lesions.
Groups of muscles are often affected in upper motor neuron lesions.
Individual muscles are often affected in lower motor neuron lesions.
Individual muscles are often affected in lower motor neuron lesions.
Fascicular twitch is present in upper motor neuron lesions.
Fascicular twitch is present in upper motor neuron lesions.
Flashcards
Vestibulospinal Tracts
Vestibulospinal Tracts
Upper motor neurons in the brainstem that control axial muscles and proximal limb muscles.
Vestibulo-ocular Pathway
Vestibulo-ocular Pathway
The pathway that controls eye movements to maintain fixation while the head moves.
Reticular Formation
Reticular Formation
A network of circuits in the brainstem extending from the midbrain to the medulla, responsible for coordinating movements and controlling various bodily functions.
Skeletomotor Control
Skeletomotor Control
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Feedforward Mechanism
Feedforward Mechanism
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Betz Cells
Betz Cells
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Pyramidal Tract
Pyramidal Tract
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Corticobulbar Tract
Corticobulbar Tract
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Lateral Corticospinal Tract
Lateral Corticospinal Tract
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Ventral Corticospinal Tract
Ventral Corticospinal Tract
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Indirect Pathway
Indirect Pathway
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Premotor Cortex
Premotor Cortex
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Lateral Premotor Cortex
Lateral Premotor Cortex
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Medial Premotor Cortex
Medial Premotor Cortex
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Upper Motor Neuron Syndrome
Upper Motor Neuron Syndrome
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Spinal Shock
Spinal Shock
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Babinski Sign
Babinski Sign
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Spasticity
Spasticity
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Clonus
Clonus
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Decerebrate Rigidity
Decerebrate Rigidity
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Loss of Fine Motor Control
Loss of Fine Motor Control
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Lower Motor Neuron Facial Weakness
Lower Motor Neuron Facial Weakness
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Upper Motor Neuron Facial Weakness
Upper Motor Neuron Facial Weakness
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Superior Facial Sparing
Superior Facial Sparing
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Corticobulbar Pathway
Corticobulbar Pathway
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Cingulate Motor Area
Cingulate Motor Area
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Feedback Postural Mechanisms
Feedback Postural Mechanisms
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Reticular Formation (Postural Control)
Reticular Formation (Postural Control)
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Vestibular Nuclei (Postural Control)
Vestibular Nuclei (Postural Control)
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Study Notes
Upper Motor Neurons Maintaining Balance and Posture
- Vestibular nuclei are upper motor neurons in the brainstem
- Projections from vestibular nuclei control axial and proximal limb muscles, using medial and lateral vestibulospinal tracts
- Other vestibular nuclei project to cranial nerves (3, 4, and 6) for eye movements during head movement
- Direct projections from vestibular nuclei to spinal cord allow rapid compensatory responses to postural instability sensed by inner ear.
Reticular Formation as Upper Motor Neurons
- Reticular formation is a complex network in the brainstem
- Similar in structure and function to spinal cord's intermediate gray matter
- Involved in numerous functions (cardiovascular, respiratory, sensory-motor reflexes, eye movements, sleep-wake cycles)
- Reticular formation coordinates movements temporally and spatially.
- Descending motor control pathways from reticular formation target gray matter, impacting axial and proximal limb muscles
- Reticular formation is controlled by other motor areas (cortex/brainstem) to make adjustments for maintaining posture during movement
Origin of Pyramidal Tract
- Upper motor neurons in cerebral cortex initiate complex movements
- These cortical areas receive input from basal ganglia, cerebellum, and the parietal lobe's somatic sensory regions
- Primary motor cortex (Brodmann's area 4) is in precentral gyrus and has pyramidal cells (Betz cells) as upper motor neurons
- Axons descend to brainstem (corticobulbar tract), then spinal cord (corticospinal tract) through internal capsule and cerebral peduncle
- Axons run through pons, then form medullary pyramids
- Corticobulbar tract innervates cranial nerves, reticular formation, and red nucleus; leaving before reaching the spinal cord
Course of Pyramidal Tract
- Most pyramidal tract axons cross (decussate) into lateral corticospinal tract in the caudal medulla then spinal cord
- Smaller number of axons enter spinal cord uncrossed, forming ventral corticospinal tract, which targets axial and proximal muscles
- Axons project to red nucleus and reticular formation via an indirect pathway
The Premotor Cortex
- Lies rostral to primary motor cortex; interconnected frontal lobe areas
- Influences motor behaviour through connections with primary motor cortex and directly through corticobulbar/corticospinal pathways
- Lateral premotor cortex: involved in selecting movements based on external cues (e.g., visual, auditory)
- Medial premotor cortex: involved in selecting movements based on internal cues (self-initiated), reducing spontaneous movement in response to external stimuli
Summary
- Two sets of upper motor neurons contribute to brainstem and spinal cord control
- One set (reticular formation/vestibular nuclei) controls posture (feedforward/feedback)
- Other set (primary motor cortex/premotor areas) controls movement execution/planning
- Motor cortex influences movement by direct (corticospinal/corticobulbar) and indirect pathways (via brainstem centers) to lower motor neurons
Damage to Upper Motor Neuron Pathways
- Upper motor neuron damage causes symptoms like hypotonia, hyporeflexia and later, signs/symptoms like spasticity, abnormal reflexes (babinski)
- Gradual recovery of function generally occurs, but fine motor skills and some reflexes may not return
Patterns of Facial Weakness
- Lower motor neuron facial weakness affects all facial muscles on the affected side
- Upper motor neuron facial weakness affects contralateral facial muscles below the eyebrows/eyes/forehead, but superior muscles are unaffected
Upper vs Lower Motor Neuron Lesions
- Symptoms differ: Upper motor neuron lesions lead to hypertonia/spasticity, whereas lower neuron lesions result in hypotonia/flaccidity
- Reflexes (superficial and deep) differ/ abnormalities
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Description
This quiz explores the role of upper motor neurons in maintaining balance and posture, focusing on vestibular nuclei and the reticular formation. Learn how these areas of the brainstem control muscle movements and respond to postural challenges for efficient body positioning and coordination.
