The Motor System Flashcards
- Upper Motor Neurons (UMNs) are located in = ?
- Lower Motor Neurons (LMNs) are located in = ?
Motor System
- Upper Motor Neurons (UMN’s):
- Neurons located in the brain that convey signals to lower motor neurons in the spinal cord or brainstem.
- Lower Motor Neurons (LMN’s):
- Neurons located in the spinal cord or brainstem that directly innervate skeletal muscles.
Clinical Signs and Symptoms
- UMN Lesions = ?
- LMN Lesions = ?
Motor System
Clinical Signs and Symptoms:
- UMN Lesions :
- Hyperreflexia
- Spasticity
- Muscle weakness
- ↑ muscle tone
- LMN Lesions :
- Hyporeflexia
- Muscle atrophy
- Fasciculations
- Flaccidity
- ↓ muscle tone
Factors Accounting for Spasticity
Spasticity is primarily due to = ?
Motor System
- Spasticity is primarily due to ↑ excitability of the stretch reflex caused by loss of inhibition from descending pathways.
- Other contributing factors include
- ↑ reflex sensitivity,
- Altered muscle properties,
- Changes in spinal cord circuitry.
Stroke, Traumatic Brain Injury, Spinal Cord Injury, Multiple Sclerosis, and Cerebral Palsy are examples of UMN or LMN conditions ?
Motor System
UMN Conditions:
- Stroke
- Traumatic Brain Injury
- Spinal Cord Injury
- Multiple Sclerosis
- Cerebral Palsy
Polio, Guillain-Barré syndrome, spinal muscular atrophy, peripheral nerve injuries, and progressive muscular atrophy are examples of UMN or LMN conditions ?
Motor System
LMN Conditions:
- Polio
- Guillain-Barré Syndrome
- Spinal Muscular Atrophy
- Peripheral Nerve Injuries
- Progressive Muscular Atrophy
A progressive neurodegenerative disease affecting both UMN and LMNs = ?
Motor System
Amyotrophic Lateral Sclerosis (ALS):
- ALS is a progressive neurodegenerative disease affecting both UMN and LMNs.
- Symptoms include muscle weakness, muscle atrophy, difficulty speaking and swallowing, and eventual respiratory failure.
ALS: Pathophysiology
Characterized by = ?
Motor System
ALS - Pathophysiology:
- Characterized by degeneration of motor neurons in the brain and spinal cord.
- Exact cause unknown, but genetic and environmental factors implicated.
ALS Diagnosis
Based on = ?
Motor System
ALS - Diagnosis:
- Based on clinical presentation, electromyography (EMG), nerve conduction studies, and exclusion of other conditions.
- No specific diagnostic test; diagnosis often clinical.
- 20% more common men > women
- 90% of cases occur without family history (sporadic); other 10% - Familial
ALS Treatment
True or False:
- There is a cure for ALS.
Motor System
ALS Treatment:
- NO cure for ALS; treatment aims to manage symptoms and improve quality of life.
- Medications (e.g., riluzole, edaravone), physical therapy, occupational therapy, speech therapy, and respiratory support may be utilized.
ALS Prognosis = ?
Motor System
Prognosis & Complications:
- ALS is typically fatal , with median survival of 2-5 years from onset of symptoms.
- Complications include respiratory failure, pneumonia, and nutritional deficiencies due to difficulty swallowing.
UMN Neural Control of Movement
The motor cortex, brainstem centers, and cerebellum work together to _ ? _ voluntary movements
Motor System
UMN - Neural Control of Movement:
- Involves a hierarchical organization of neural structures, including the motor cortex, brainstem centers, and cerebellum.
- These structures work together to plan, initiate, and execute voluntary movements.
Functions of UMN
- UMNs in the motor cortex are involved in = ?
- UMNs in brainstem centers modulate = ?
- UMNs in the cerebellum play a role in = ?
Motor System
Functions - Upper Motor Neurons (UMNs):
- UMNs in the motor cortex are involved in the planning and initiation of voluntary movements.
- UMNs in brainstem centers modulate reflexes and coordinate movements.
- UMNs in the cerebellum play a role in fine-tuning motor output and maintaining balance.
What Pathway = ?
Are neural tracts that carry signals from higher brain centers to lower motor neurons in the spinal cord or brainstem.
Motor System
Descending Control Pathways:
- Descending pathways are neural tracts that carry signals from higher brain centers to lower motor neurons in the spinal cord or brainstem.
- These pathways regulate muscle tone, reflexes, and voluntary movements.
Descending pathways
Are neural tracts that carry signals from higher brain centers to lower motor neurons in the spinal cord or brainstem.
- These pathways regulate = ?
Motor System
Descending Control Pathways:
- Descending pathways are neural tracts that carry signals from higher brain centers to lower motor neurons in the spinal cord or brainstem.
- These pathways regulate muscle tone , reflexes , and voluntary movements .
What Tract ?
The primary pathway for voluntary motor control, particularly of the distal extremities.
Motor System
Corticospinal Tract:
- The corticospinal tract originates from the motor cortex and descends through the brainstem to the spinal cord.
- It is the primary pathway for voluntary motor control, particularly of the distal extremities.
The corticobulbar tract originates from the motor cortex and projects to = ?
Motor System
Corticobulbar Tract:
- The corticobulbar tract originates from the motor cortex and projects to cranial nerve nuclei in the brainstem.
- It controls voluntary movements of the head and neck via cranial nerves, such as chewing, facial expressions, and swallowing.
What Tract ?
EDIT THIS ONE
Controls voluntary movements of the head and neck via cranial nerves, such as chewing, facial expressions, and swallowing.
Motor System
Corticobulbar Tract:
- The corticobulbar tract originates from the motor cortex and projects to cranial nerve nuclei in the brainstem.
- It controls voluntary movements of the head and neck via cranial nerves, such as chewing, facial expressions, and swallowing.
What cortex ?
Is located in the frontal lobe, is responsible for planning, initiating, and executing voluntary movements = ?
Motor System
Role of Motor Cortex:
- The motor cortex, located in the frontal lobe, is responsible for planning, initiating, and executing voluntary movements.
- It contains the primary motor cortex (M1) and supplementary motor area (SMA), which coordinate complex movements.
Integrates sensory information and coordinate movements, particularly in response to environmental cues = ?
Motor System
Role of Brainstem Centers:
- Brainstem centers, including the reticular formation and vestibular nuclei, modulate muscle tone, balance, and posture.
- They integrate sensory information and coordinate movements, particularly in response to environmental cues.
The cerebellum plays a critical role in = ?
Motor System
Role of Cerebellum:
- The cerebellum plays a critical role in motor coordination , precision , and timing of movements .
- It receives input from the motor cortex and sensory systems to adjust motor output and maintain smooth, coordinated movements.
Function of muscle spindles
- Muscle spindles detect changes in = ?
Motor System
Function of muscle spindles:
- Muscle spindles detect changes in muscle length and contribute to proprioception.
- Muscle spindles provide feedback to the central nervous system about muscle stretch, helping to regulate muscle tone and coordinate movement.
- Extrafusal fibers are innervated by = ?
- Intrafusal fibers are innervated by = ?
Motor System
Description of Muscle Fibers:
- Extrafusal fibers :
- These are the ordinary muscle fibers responsible for generating force and movement by contracting.
- They are innervated by alpha motor neurons.
- Intrafusal fibers :
- These are specialized muscle fibers found within muscle spindles.
- They are innervated by gamma motor neurons and play a crucial role in detecting changes in muscle length.
Explain how muscle spindles maintain tone and regulate reflexes = ?
Motor System
- Muscle spindles are essential for maintaining muscle tone by providing constant feedback to the CNS about muscle length and stretch.
- They play a critical role in regulating muscle reflexes, such as the stretch reflex, by modulating the sensitivity of alpha motor neurons based on muscle length changes.
Signs of Motor Neuron Lesions = ?
Motor System
Signs of Motor Neuron Lesions:
- Paresis and paralysis
- Involuntary muscle contractions
- Muscle atrophy
- Abnormal muscle tone
- Abnormal reflexes
- Disturbances of movement efficiency and speed
- Impaired postural control
Paresis vs. Paralysis
- What’s the difference = ?
- UMN or LMN = ?
Motor System
Motor Neuron Lesions - Paresis & Paralysis:
- Paresis : Partial loss of voluntary contraction.
- Paralysis : Complete loss of voluntary contraction, such as complete spinal cord injury (SCI).
- Both UMN and LMN lesions can cause paresis and paralysis.
Disuse atrophy vs. Denervation atrophy
- What’s the difference = ?
- Associated with UMN or LMN = ?
Motor System
Motor Neuron Lesions - Atrophy:
- Due to lack of muscle use (UMN).
- Severe atrophy due to loss of neural stimulation (LMN).
Spasticity is also called = ?
Motor System
Spasticity - Velocity-Dependent Hypertonia :
- Characterized by a velocity-dependent increase in tonic stretch reflexes.
- UMN syndrome
- Limits joint ROM and interferes with function.
Example: Significant bilateral plantarflexor hypertonia leading to toe-walking.
- “How stiff or tight your muscles are depends on how fast you move them. So, if you move your muscles slowly, they might not feel as stiff, but if you move them quickly, they might feel much stiffer or tighter.”
Reflexes
- UMN lesions often cause ↑ or ↓ reflexes ?
- LMN lesions often cause ↑ or ↓ reflexes ?
Motor System
- UMN lesions often cause ↑ reflexes (hyperreflexia).
- LMN lesions typically result in ↓ or absent reflexes (hyporeflexia).
Involuntary Movements
- UMN lesions may cause = ?
- LMN lesions lead to = ?
Motor System
- UMN lesions may cause
- Muscle spasms (flexor or extensor).
- LMN lesions lead to
- Fasciculations (muscle twitching), due to denervation
Medial Longitudinal Fasciculus (MLF)
- Origin = Pontine and medullary reticular formation.
- Crosses / Decussates = ?
- Effect = ?
Motor System
Medial Longitudinal Fasciculus (MLF):
- Function = Coordination of eye movements.
- Origin = Pontine and medullary reticular formation.
- Path = Ascends and descends through brainstem.
- Crosses / Decussates = Mostly ipsilateral?
- Effect:
- Ipsilateral control of eye movements.
Involved in = Coordination of gaze, especially during horizontal eye movements.
Lateral Corticospinal Tract
- Origin = Primary motor cortex.
- Crosses / Decussates = ?
- Effect = ?
Motor System
Lateral Corticospinal Tract:
- Origin = Primary motor cortex.
- Path = Descends through internal capsule, brainstem, spinal cord (cervical & lumbar).
- Crosses / Decussates = Decussates at cervical spinal cord level.
- Effect =
- Contralateral control of proximal limb (hand/wrist) muscles, and distal limb (foot) muscles.
- Ipsalateral control of proximal limb (hand/wrist) muscle
Involved in = Fine motor control, voluntary movement of hands and fingers.
Medial Corticospinal Tract
- Origin = Primary motor cortex.
- Crosses / Decussates = ?
- Effect = ?
Motor System
Medial Corticospinal Tract:
- Origin = Primary motor cortex.
- Path = Descends through internal capsule, brainstem, cervical spinal cord.
- Crosses / Decussates =
- Effect =
- Ipsilateral control of neck, shoulder, and trunk muscles (posterior ?)
- Stays ipsilateral
Rubrospinal Tract
- Origin = Red nucleus in midbrain.
- Crosses / Decussates = ?
- Effects = ?
Motor System
- Origin = Red nucleus in midbrain.
- Path = Descends through brainstem, spinal cord.
- Crosses / Decussates = Brainstem (midbrain).
- Effect =
- Contralateral control of proximal limb extensors.
- Motor coordination, especially extension of wrist and fingers / upper limb flexion.
Vestibulospinal Tracts (medial & lateral)
- Origin = Vestibular nuclei in brainstem.
- Crosses / Decussates = ?
- Effect = ?
Motor System
Vestibulospinal Tracts:
- Origin = Vestibular nuclei in upper medulla (brainstem).
- Path = Descends through brainstem, spinal cord.
- Medial stops/ends at cervical cord
- Crosses / Decussates = Medial VT at upper medulla
- Effect:
- Medial tract, ipsilateral and contralateral control of neck muscles.
- Lateral tract, ipsilateral control of postural muscles.
Involved in = Balance, regulation of posture, coordination of head and eye movements.
Reticulospinal Tracts
- Origin = Reticular formation in brainstem.
- Path = Descends through brainstem, spinal cord.
- Crosses / Decussates = ?
- Effect = ?
Motor System
Reticulospinal Tracts:
- Origin: Reticular formation in brainstem.
- Path: Descends through brainstem, spinal cord.
Crosses / Decussates: Mostly ipsilateral.
- Effect:
- Ipsilateral modulation of muscle tone and reflexes.
- Involved in : Modulation of autonomic functions, regulation of muscle tone, coordination of posture and locomotion.
What types of conditions or disorders can result in upper motor neuron (UMN) lesions within regions such as the internal capsule, brainstem, and spinal cord?
Motor System
What types of conditions or disorders can result in upper motor neuron (UMN) lesions within regions such as the internal capsule, brainstem, and spinal cord =
- Stroke, tumors, trauma, inflammation, Multiple Sclerosis (autoimmune), ALS
What types of conditions or disorders can result in upper motor neuron (UMN) lesions only within specific regions of the CNS?
4
Motor System
What types of conditions or disorders can result in upper motor neuron (UMN) lesions only within specific regions of the CNS =
- Cerebral white matter UMN lesions = Spastic cerebral palsy
- Basal Ganglia = Dystonic cerebral palsy
- Brain Stem = Chiari malformation
- Spinal cord = Spina bifida
What types of conditions or disorders can result in lower motor neuron (LMN) lesions in the cranial, spinal, and peripheral nerves?
Motor System
What types of conditions or disorders can result in lower motor neuron (LMN) lesions in the cranial, spinal, and peripheral nerves =
- Cranial & Spinal nerves = Polio or ALS
- Spinal nerves = Bulbar palsies
- Peripheral nerves = Guillain-Barree
