39 Questions
What is a motor unit?
Alpha motor neurons and muscle fibers that activate it
Why is communication of sensory, motor & interneurons important?
To prevent injury and coordinate muscle action
What is the function of reciprocal inhibition?
To inhibit contraction of antagonist muscles
What is the role of myotome in the motor system?
Group of muscles innervated by a single spinal nerve
Which of the following is a characteristic of the clasp knife response?
Muscle being slowly stretched with initial resistance then quick give when resistance suddenly drops
What is myoplasticity?
Change in muscle due to altered neuromuscular activity or prolonged position
What can cause contracture leading to further weakness?
Changes in actin-myosin bonds
What does hypotonia refer to?
Decreased muscle tone
What is a characteristic of spinal shock?
Flaccidity
What is the result of complete motor neuron lesions?
Paralysis, hyporeflexia, and hypotonia
What is the presentation of upper motor neuron lesions?
Paresis, hyperreflexia, hypertonia
What is the result of a lower motor neuron lesion?
Lack of muscle activation, hypotonia, hyporeflexia or areflexia
What are the characteristics of deceberate posturing?
Complete disconnect between midbrain and pons, extension of arms, flexion of wrists
What is a characteristic of babinski sign in the context of motor neuron lesions?
Feet exhibiting abnormal response to stimulation
What is the impact of a lesion affecting motor tracts on muscle synergies?
Abnormal muscle synergies presented at rest, higher muscle tone in UE encouraging elbow flexion/forearm supination
What type of signaling from the periphery, interneurons, and motor neurons provides proprioception?
Type 2 afferent signaling
Which structure informs about tendon tension and lengthening, affecting muscle activation through spinal interneurons?
Golgi tendon organ
What coordinates a rudimentary stepping pattern by connecting sensory and motor signals at or near the spinal level?
Highway of interneurons
What type of stretch activates afferent nerves to the spinal cord, initiating a reflex?
Phasic stretch
Which reflex coordinates muscle activation in response to a noxious stimulus, occurring at multiple spinal levels without the need for cortical input?
Withdrawal/crossed extension reflex
What do motor nerve conduction velocity tests help identify?
Problems in motor nerves
What does electromyography measure in muscles?
Electric activity
What does heightened muscle activity with needle electromyography indicate?
Motor neuron lesions
What can be identified through electromyography and nerve conduction studies?
Myopathy
Which tracts within the spinal cord convey signals for movement and muscle activation to different parts of the body?
Vertical motor tracts
Which motor tracts are responsible for controlling posture and muscle innervation?
Medial motor tracts
Which tracts form the emotional motor system, impacting movement in response to emotions?
Nonspecific motor tracts
Which motor tract primarily innervates axial and girdle musculature, facilitating posture and core strength?
Medial corticospinal tract
Where are the cell bodies for the medial corticospinal tract located?
Medial anterior horn of the gray area of the spinal cord
Where does the reticulospinal tract begin?
Reticular formation of the brainstem
Which motor tract responds to signals coming from the inner ear, helping orient the body towards gravity?
Lateral Vestibulospinal Tract
Where do the medial motor tracts arise?
Primary motor cortex and supplementary motor area within the cortex
Which tracts in the spinal cord are responsible for distal limb movement and fractionation of movements?
Lateral Tracts
Where does the Lateral Corticospinal Tract start?
Premotor cortex
Which tract begins at the red nucleus in the midbrain and plays a smaller role than the lateral corticospinal tract?
Rubrospinal Tract
Which of the following is a motor system dysfunction characterized by repeated, involuntary, rhythmic contractions of a single muscle group?
Clonus
What is the term for the motor system dysfunction that includes abnormal reflexes like Babinski's sign?
Phasic stretch hyperreflexia
What is the term for the motor system dysfunction characterized by heightened muscle activity with needle electromyography?
Tonic stretch reflex
Which motor system dysfunction includes abnormal reflexes like Babinski's sign and tonic stretch reflex?
Phasic stretch hyperreflexia
Study Notes
Motor System: Spinal Cord and Nerve Assessment
- Type 2 afferent signaling from periphery, interneurons, and motor neurons provides proprioception, informing about the body's position in space and time.
- The Golgi tendon organ informs about tendon tension and lengthening, affecting muscle activation through spinal interneurons.
- A rudimentary stepping pattern is coordinated by a highway of interneurons connecting sensory and motor signals at or near the spinal level.
- Phasic stretch, such as the reflex hammer stretch to the patellar tendon, activates afferent nerves to the spinal cord, initiating a reflex.
- The withdrawal/crossed extension reflex coordinates muscle activation in response to a noxious stimulus, occurring at multiple spinal levels without the need for cortical input.
- Motor nerve conduction velocity tests locate areas of damage along muscle activation, helping to identify problems in motor nerves, neuromuscular junctions, or muscles.
- Electromyography measures electric activity in muscles, aiding in understanding the location of lesions in the motor nervous system.
- Motor neuron lesions result in heightened muscle activity with needle electromyography, while motor tract lesions may present with degeneration in specific tracts.
- Myopathy, damage to the muscle itself, can be identified through electromyography and nerve conduction studies.
- Vertical motor tracts within the spinal cord convey signals for movement and muscle activation to different parts of the body.
- Medial motor tracts, including the reticulospinal, medial vestibulospinal, and lateral vestibulospinal tracts, are responsible for controlling posture and muscle innervation.
- Nonspecific motor tracts, such as the ceruleospinal and raphespinal tracts, form the emotional motor system, impacting movement in response to emotions.
Motor Tracts and Dysfunctions in the Spinal Cord
- Medial corticospinal tract primarily innervates axial and girdle musculature, facilitating posture and core strength
- Cell bodies for these tracts are located in the medial anterior horn of the gray area of the spinal cord
- Automatic motor control primarily coordinated at the brainstem level, where these 3 tracts derive
- Reticulospinal Tract begins in the reticular formation of the brainstem, sending signals to both ipsilateral and contralateral motor neurons at the spinal level
- Lateral Vestibulospinal Tract responds to signals coming from the inner ear, helping orient the body towards gravity
- Medial Vestibulospinal Tract responds to signals regarding head movement and position, activating and coordinating muscle activity in the neck and upper back
- Medial Motor Tracts arise in the primary motor cortex and supplementary motor area within the cortex, providing signals for bilateral control of axial and upper girdle muscles
- Lateral Tracts in the spinal cord responsible for distal limb movement and fractionation of movements
- Lateral Corticospinal Tract starts at the premotor cortex, descending downwards through the spinal cord
- Rubrospinal Tract begins at the red nucleus in the midbrain and plays a smaller role than the lateral corticospinal tract
- Motor System Dysfunctions include paresis vs paralysis, abnormal reflexes like Babinski's sign, and phasic stretch hyperreflexia
- Motor System Dysfunctions also include tonic stretch reflex and clonus, which are repeated, involuntary, rhythmic contractions of a single muscle group
Test your knowledge of the motor system, spinal cord, and nerve assessment with this quiz. Explore topics such as afferent signaling, reflexes, nerve conduction studies, electromyography, motor tracts, and dysfunctions in the spinal cord. Perfect for students, medical professionals, and anyone interested in understanding the complexities of the motor nervous system.
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