Motor Systems Flashcards
Location of neurons involved in corticospinal motor system
Primary motor cortex (M1, area 4)
Premotor cortex (area 6, just rostral to anterolateral part of M1)
Supplementary motor cortex (medial portion of area 6, rostral to M1 near curve of hemisphere extending medially to paracentral gyri)
CST fibers in motor cortex cross midline in the ________ decussation, so lesions rostral to this decussation cause ______ motor deficits while lesions caudal to the decussation (within SC) cause ____ motor deficits
Pyramidal; contralateral; ipsilateral
Premotor cortex has less precise organization than the primary cortex, and receives input from sensory areas of parietal cortex. Where does it project to and what are its functions?
Projects to M1, SC, and RAS (forms reticulospinal fibers which influence spinal motor neurons)
Function: preparation to move — organizes postural adjustments required to produce movement
The supplementary motor area is also less precisely organized than M1, and receives info from parietal lobe. Where does it project to and what are its functions?
Receives input from parietal lobe
Function: organizing or planning sequence of muscle activation required to make a movement (then M1 stimulates the actual movement)
Differentiate brain areas activated for random finger movement of 1 finger vs. random finger movement of multiple fingers vs. mentally rehearsing specific sequence of movement without actually moving fingersq
Random finger movement of one finger = neural activity ONLY in hand region of M1
Random finger movements of multiple fingers = neural activity in M1 and supplementary cortex
Mentally rehearsing specific sequence WITHOUT finger movement =supplementary cortex ONLY
Fibers of the CST motor system descend through the ______ _____, passing through the corona radiata and converging on that structure
Fibers maintain their somatotopic arrangement with rostral axxons terminating in _______ SC and caudal axons terminating in progressively ______ SC
Internal capsule
Upper; lower
Cell groups embedded in cerebral hemispheres including subthalamic, substantia nigra, and pedunculopontine tegmental; function in sets of parallel circuits
Basal nuclei
Parallel circuit involving basal nuclei
Corticostriated fibers from cerebral cortex —> basal nuclei —> thalamus —> cerebral cortex
Components of neostriatum
Caudate nucleus
Putamen
Components of ventral striatum
Nucleus accumbens
Olfactory tubercle
Components of striatum
Neostriatum
Ventrostriatum
[so in total = caudate + putamen + nucleus accumbens + olfactory tubercle]
Components of dorsal striatum
Caudate
Putamen
[same as neostriatum]
Components of paleostriatum
Globus pallidus
Components of corpus striatum
Globus pallidus
Caudate nucleus
Putamen
Components of lenticular nucleus
Globus pallidus
Putamen
Which basal nucleus forms a bulge in lateral ventricle and contains nucleus accumbens at its most anterior level, making connections with the temporal lobe via inferior horn?
Caudate nucleus
Which basal nucleus is lateral to the internal capsule and globus pallidus, separated from the globus pallidus by the lateral medullary lamina, and separates white matter into external and internal capsules?
Putamen
Gray matter sandwiched by white matter just lateral to putamen
Claustrum
What basal nucleus is medial to the putamen (separated from it be lateral medullary lamina) and consists of lateral and medial segments - separated by the medial medullary lamina?
Globus pallidus
Which basal nucleus is in the most ventral part of the midbrain, consisting of the pars compacta and pars reticulate?
Substantia nigra
What is the difference between the pars compacta and pars reticulte that make up the substantia nigra?
Pars compacta = pigmented, melanin containing, dopamine-producing neurons that project to the caudate nucleus and putamen via nigrostriatal path
Pars reticulate = functional homologue of medial segment of globus pallidus
2 types of pathways of basal nuclear activity
Direct = facilitates flow of info through thalamus
Indirect = inhibits flow of info through thalamus
5 primary basal nuclei tracts
Pallidal fibers Subthalamic fasciculus Nigro-thalamic fibers Nigro-striatal fibers Striatonigral fibers
Pallidal fibers make up the basal nuclei tract that is typically ______ergic with high rates of spontaneous activity, thus typically _____their targets
GABA; inhibiting
Pallidothalamic fibers target _____ ____ and _____ ____ thalamic nuclei
Ventral anterior
Ventral lateral
Subthalamic fasciculus makes up reciprocal fiber tracts between the _____ and ________
They are _______ fibers (excitatory or inhibitory?)
Globus pallidus; subthalamus
Excitatory
Nigrothalamic fibers are non-dopaminergic fibers originating in the __________ of the substantia nigra. They terminate in the _____ ____ and ____ ____ thalamic nuclei
Pars reticularis; ventral anterior; ventral lateral
Nigro-striatal fibers are dopaminergic fibers that originate in the _______ of the substantia nigra, terminating in the ____ and ______
Pars compacta; caudate nucleus; putamen
Striatonigral fibers are ______ergic fibers (inhibitory) that originate in the ________
They terminate in the _________ of the substantia nigra as well as the globus pallidus
These fibers may contribute to _____ disease
GABA; putamen
Pars compacta
Huntington
Second most common neurodegenerative disease caused by loss of neurons in substantia nigra (or excitotoxicity, oxidative stress, mitochondrial malfunction, or toxin exposure)
Parkinson’s disease
Symptoms of parkinsons
Resting tremor Cogwheel rigidity Akinesia Bradykinesia Eye movement disturbance Loss of postural reflexes
Neurodegenerative disease characterized by absentmindedness, irritability, depression, clumsiness, and/or sudden falls, prior to choreiform movements which increase until pt is bedridden
Huntington disease
Childhood autoimmune disease that is a major manifestation of Rheumatic fever
Syndenham’s chorea
Symptoms of syndenham’s chorea
Rapid, irregular, aimless movements of limbs, face, and trunk
Some muscle weakness, hypotonia, irritability, OCD behavior, and anxiety
Uncontrolled flinging movements of a limb, usually only affecting one side of the body. Common with vascular lesions localized to contralateral subthalamic nucleus or subthalamic fasciculus
Ballismus
Rapid, irregular, involuntary dance-like movements that flow randomly from one body region to another, characteristic of huntington disease and tardive dyskinesia
Chorea
Chorea results from loss of neurons in which type of basal nuclei pathway?
Indirect
[lose inhibition of flow of info through thalamus]
Continuous writhing of distal portions of 1+ extremities
Athetosis
______ = athetosis that is more brisk, resembling chorea
Choreoathetosis
_____ = athetosis that is more intense, sustained, and resembles dystonia
Athetotic dystonia
