Motor Control Flashcards
What is the purpose of the spinal cord in motor programs?
Executive control over motor neurons
What and where are motor neurons, what do they do?
Alpha motor neurons, in the spinal stem, ventral horn of the spinal cord. They are the final pathway for all motor commands
What higher order structures of the brain generate motor programs?
Association cortex, basal ganglia, cerebellum
In what three areas would one find upper motor neurons? What do they project to?
Cerebral cortex, reticular formation, vestibular nuclei. They project to cranial nerve nuclei and lower motor neurons in the spinal cord
What are the two types of lower motor neurons?
Alpha and delta
How are alpha motor neurons arranged?
Arranged somatotopically in the ventral horn
What is the basic reflex arc?
Sensory neuron –> (dorsal horn) inter neuron–> motor neuron
Are interneurons stimulators or inhibitory?
Inhibitory (renshaw 1a inhibitory interneurons)
What two reflexes are tested clinically?
Superficial reflexes (flexor withdrawal, pain response. Tests brain stem, transcortical and propriospinal pathways) Deep tendon reflexes (stretch and tension reflex using 1a, II, Ib afferent pathways to elicit or inhibit muscle contraction)
What are muscle spindles and what do they detect?
Intrafusal fibers, parallel to extramural fibers and surrounded in CT. They respond to changes in muscle length and velocity by stimulating primary (Ia) and secondary (II) afferent neurons
How do spindle neurons work?
Na/Ca physically gated channels connected to each other by spectrin open when the muscle is stretched, allowing influx of ions and AP to travel through the axon
The patellar tap tests the integrity of what reflex?
The myotactic stretch reflex
What is the jendrassik maneuver?
Holding hands against each other to distract the patient during testing of the myotactic reflex
What is reciprocal innervation?
Relaxation if antagonist muscles during agonist muscle contraction
What is the function of gamma motor neurons? How do they work?
Regular muscle spindle sensitivity by contracting around the muscle ends of the spindles. This tonically (not passively stretches the spindle, making Ia fibers more sensitive)
How are game motor neurons controlled?
Brain and brain stem (as speed and difficulty of the movement increase, spindle sensitivity is increased)
Golgi tendon organs regulate:
Muscle tension
What is the inverse myotactic reflex? How does it work?
IIb fibers in the GTOs stimulate excitatory interneurons to antagonist muscles and inhibitory interneurons to agonist fibers
The flexor withdrawal (crossed extensor) reflex involves what neurons?
Propriospinal, interneurons and a motor neurons
What are two purposes of the propriospinal system?
Integrating intersegmental motor responses (eg walking)
Mediates regulatory impact of upper limb cutaneous stimulation on lower limb motor reflexes
Where are propriospinal neurons located?
Medial and lateral ventral horn
What are medial propriospinal neurons, what do they do?
Long propriospinal axons that span the whole spinal cord. Regulate proximal, axial muscles and posture
What are lateral propriospinal neurons, what do they do?
Short propriospinal neurons that regulate distal muscles for independent control of fine movements
What are some function of upper motor neurons?
Fine motor control, posture balance
The motor cortex forms three tracts. What are they and where do they go?
Corticospinal to the ventral horn of the spinal cord
Corticonuclear to cranial nerve nuclei
Corticoreticular tract to the pontine and medullary reticular formation
What are the four descending motor pathways?
Lateral corticospinal tract
Anterior corticospinal tract
Vestibulospinal tract
Reticulospinal tracts
What is the corticonuclear tract, what does it control?
Motor Neurons that join with the cranial nerve nuclei, control muscles of the face, head and neck
What two tracts does the corticospinal tract turn into? Where does this happen and what kinds of motor neurons are involved?
The lateral and ventral (anterior) spinal tract. This occurs at the pyramids (and decussation of the pyramids) in the medulla. Alpha and gamma motor neurons are involved
Which corticospinal tract contains the 10% of uncrossed neurons and controls posture of the neck and trunk?
Ventral (anterior) corticospinal tract
Which corticospinal tract contains 90% crossed neurons and controls fine movement?
Lateral corticospinal tracts
What are the three extrapyramidal pathways?
Corticoreticular, vestibulospinal, reticulospinal
What is the purpose of the vestibulospinal tract? How does it work?
To maintain posture and balance. Information from semicircular canals, saccule, utricle go to the medulla go to the spinal cord to activate extensors of the lower limb and Flexors of the upper limb
Of the lateral and medial vestibular nuclei pathways, which is purely ipsilateral, courses to the lower limbs and is mainly in the ventral part of the spinal cord?
The lateral vestibular nucleus
Of the lateral and medial vestibular nuclei, which contains pathways both ipsilateral and controlateral and controls mainly thoracic, axial and neck muscles?
The medial vestibular nucleus
What does the reticulospinal tract do?
Complex posture, muscle tone, orienting, stretching
Which reticulospinal tract comes from the pons, facilitates voluntary movements, increases muscle tone and “anti-gravity” posture?
Medial (anterior) reticulospinal tract
Which reticulospinal tract comes from the medulla inhibits voluntary action and reduces muscle tone?
Lateral reticulospinal tract
What is the purpose and pathway of the corti reticular pathway?
Smoothes out movements. Neurons from the primary motor and ore motor cortices project to medullary and pontine reticular formations, reticulospinal tracts.
Lesions of alpha motor neurons cause what kind of paralysis?
Flaccid paralysis
What are the two kinds of paralysis?
Spastic and flaccid paralysis
What causes a decrease in fine motor control after a stroke to the motor cortex?
Disruption if the lateral corticospinal tracts
What causes spasticity after a stroke to the motor cortex?
Disruption of cortical projections to the reticular formation that would normally smooth actions. Leads to hypertonicity, hyperreflexia. Also. Loss of cortical control over vestibulospinal and reticulospinal tracts –> antigravity posture
What is babinskis sign?
after stroke or in newborns, stroking the sole of the foot elicits fanning of the toes
What four aspects of muscle movement does the primary motor cortex do?
force, direction, extent and speed of movemets
Which motor area is somtotopically designed (homunculus)?
the primary motor cortex
What is the purpose of motor association areas like the supplemental and premotor cortices?
develop strategies/intent for motor programs, send intent to the primary motor cortex for implementation
What part of the cortex is involved in generating sequences of motions, transforming kinematic into dynamic information?
the supplementary cortex- transforms kinematic information (distance, angles) into dynamic info (force, tension necessary) for the primary motor cortex
What part of the cortex encodes intention for movement and is sensitive to behavioral context?
the premotor cortex
Where is Broca’s area? what is Broca’s area?
premotor cortex, encodes motor preparation for speech
What is the “efference copy”?
the motor cortex not only receives information but send info back to the visual, auditory and SS (posterior parietal) cortices to integrate sensory information with the expected sensation that will occur with movement
What does self-recognition depend on?
the forward model: combination of efference copy, actual sensory feedback and the internal model of body dynamics to estimate the state of the body
What is self-agency and what generates it?
the sense that you are causing the action- generated by matching of the efference copy and the subject intentions
What is self-ownership and what causes it?
the sense that you are the one undergoing an experience- generate by correspondence of sensory feedback with these intentions
What is mirroring?
capturing and understanding the actions of self and others at an involuntary level. mirror neurons unify action perception and execution, respond to both observed and executed actions
What are the two heirarchically organized systems in the motor cortex that manage self-other distinctions?
- preparation and execution of motor actions that are self realized an voluntary
- mirroring
Where is the “core mirror area”?
inferior premotor cortex and inferior parietal cortex
When does activity in the mirror area increase?
when the context of an observed action reveals context
Where is the area of the brain that responds solely to intention- not just action or context?
in the dorsal sector of the inferior prefrontal cortex (pars opercularis) where mirror activity is often seen
What separates the two cerebellar hemispheres?
the central vermis
What connects the cerebellum to the pons?
cerebellar peduncles
What are the three major lobes of the cerebellum?
anterior, posterior and the flocculonodular lobe
What is a general pathway of information in the cerebellum?
afferent neurons (spinocerebellar and inferior olive) –> granule cells –> interneurons –> purkinje cells –> deep nuclei in the cerebllar white matter (fastigial, interposed -globose and eboliform- and dentate)–>thalamus/cortex
What neurons in the cerebellum generate programs to transform sensory informaiton into motor coordinate systems?
interneurons such as basket and golgi cells
Where do purkinje cells receive sensory input from?
inferior olive and spinocerebellar tracts
What are three cerebellar functions?
motor, executive-cognitive, somato-visceral
What are the three longitudinal zones of the cerebellum?
vestivulocerebellar, spinocerebellar, cerebrocerebellar
Where does the vestibulocerebellum receive informaiton from? Where does it project to?
from the vestibular system, projects to vestibular nuclei in the medulla
What is the purpose of the vestibulocerebellum?
coordinate eye movements, posture, balance and enhances vestibulo-ocular reflex
Where does the spincerebellum recieve input from? Where does it project to?
from the spinal cord (spinocerebellar tracts) and cerebral cortex via the pons. to the thalamus/cortex, fastigial and interposed nuclei
What does the spinocerebellum do?
feedback control for ongoing movements, compares input to find discrepancies in internal/external representations of the world (compares efference copy to sensory input)
What does the cerebrocerebellum communicate with?
the cerebral cortex (and vice versa) via the dentate nucleus
What is the purpose of the cerebrocerebellum?
initiate and anticipate voluntary movements- plan, learn and precise skilled movements.
What is dysmetria?
inability to control range of movement
what is decomposition of movement?
inability to correclty sequence fine coordinated acts
what is ataxia?
lack of smoothly coordinated movements, combination of dysmetria and decomposition of movement
what is dysarthria?
inability to articulate words correctly, with slurring, inappropriate phasing
what is dysdiadochokinesia?
inability to perform rapid alterating movements
what is hypotonia?
decreased muscle tone
what is nystagmus?
involuntary rapid movement of the eyeball in all directions
what is scanning speech?
slow enunciation with a tendency to hesitate at the beginning of words. an ataxia of speech. prominent rhythm changes
what is tremor?
rhythmic, oscillatory movement of a limb as it approaches a target or of proximal structures during weight bearing or fixed posture
What parts of the brain does alcohol affect (long and short term?)
prefrontal cortex (impulsivity, behavior), limbic system (memory) and cerebellum (motor syndrome)
What does the DUI test for?
dysmetria and ataxia
autism is associated with low development of:
the vermis
dyslexia is associated with what abnormailites?
high/low volume of the vermis, caudate and putamen
What are 4 ore features of cerebellar cognitive affective syndrome?
- executive (planning, reasoning, strategy formation)
- spatial (visual-spatial organization and memory)
- affective (personality change, inappropriate laughter, pathological laughing/crying)
- linguistic difficulties
what are some somatovisceral effects of vermis dysfunction?
bradycardia, respiratory alkalosis, hyperventilation with gait ataxia
