Motor Systems

Question 1

Location of neurons involved in corticospinal motor system

Answer 1

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)

Question 2

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

Answer 2

Pyramidal; contralateral; ipsilateral

Question 3

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?

Answer 3

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

Question 4

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?

Answer 4

Receives input from parietal lobe

Function: organizing or planning sequence of muscle activation required to make a movement (then M1 stimulates the actual movement)

Question 5

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

Answer 5

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

Question 6

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

Answer 6

Internal capsule

Upper; lower

Question 7

Cell groups embedded in cerebral hemispheres including subthalamic, substantia nigra, and pedunculopontine tegmental; function in sets of parallel circuits

Answer 7

Basal nuclei

Question 8

Parallel circuit involving basal nuclei

Answer 8

Corticostriated fibers from cerebral cortex —> basal nuclei —> thalamus —> cerebral cortex

Question 9

Components of neostriatum

Answer 9

Caudate nucleus

Putamen

Question 10

Components of ventral striatum

Answer 10

Nucleus accumbens

Olfactory tubercle

Question 11

Components of striatum

Answer 11

Neostriatum
Ventrostriatum

[so in total = caudate + putamen + nucleus accumbens + olfactory tubercle]

Question 12

Components of dorsal striatum

Answer 12

Caudate
Putamen

[same as neostriatum]

Question 13

Components of paleostriatum

Answer 13

Globus pallidus

Question 14

Components of corpus striatum

Answer 14

Globus pallidus
Caudate nucleus
Putamen

Question 15

Components of lenticular nucleus

Answer 15

Globus pallidus

Putamen

Question 16

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?

Answer 16

Caudate nucleus

Question 17

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?

Answer 17

Putamen

Question 18

Gray matter sandwiched by white matter just lateral to putamen

Answer 18

Claustrum

Question 19

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?

Answer 19

Globus pallidus

Question 20

Which basal nucleus is in the most ventral part of the midbrain, consisting of the pars compacta and pars reticulate?

Answer 20

Substantia nigra

Question 21

What is the difference between the pars compacta and pars reticulte that make up the substantia nigra?

Answer 21

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

Question 22

2 types of pathways of basal nuclear activity

Answer 22

Direct = facilitates flow of info through thalamus

Indirect = inhibits flow of info through thalamus

Question 23

5 primary basal nuclei tracts

Answer 23

Pallidal fibers
Subthalamic fasciculus
Nigro-thalamic fibers
Nigro-striatal fibers
Striatonigral fibers

Question 24

Pallidal fibers make up the basal nuclei tract that is typically ______ergic with high rates of spontaneous activity, thus typically _____their targets

Answer 24

GABA; inhibiting

Question 25

Pallidothalamic fibers target _____ ____ and _____ ____ thalamic nuclei

Answer 25

Ventral anterior

Ventral lateral

Question 26

Subthalamic fasciculus makes up reciprocal fiber tracts between the _____ and ________

They are _______ fibers (excitatory or inhibitory?)

Answer 26

Globus pallidus; subthalamus

Excitatory

Question 27

Nigrothalamic fibers are non-dopaminergic fibers originating in the __________ of the substantia nigra. They terminate in the _____ ____ and ____ ____ thalamic nuclei

Answer 27

Pars reticularis; ventral anterior; ventral lateral

Question 28

Nigro-striatal fibers are dopaminergic fibers that originate in the _______ of the substantia nigra, terminating in the ____ and ______

Answer 28

Pars compacta; caudate nucleus; putamen

Question 29

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

Answer 29

GABA; putamen

Pars compacta

Huntington

Question 30

Second most common neurodegenerative disease caused by loss of neurons in substantia nigra (or excitotoxicity, oxidative stress, mitochondrial malfunction, or toxin exposure)

Answer 30

Parkinson’s disease

Question 31

Symptoms of parkinsons

Answer 31

Resting tremor
Cogwheel rigidity
Akinesia
Bradykinesia
Eye movement disturbance
Loss of postural reflexes

Question 32

Neurodegenerative disease characterized by absentmindedness, irritability, depression, clumsiness, and/or sudden falls, prior to choreiform movements which increase until pt is bedridden

Answer 32

Huntington disease

Question 33

Childhood autoimmune disease that is a major manifestation of Rheumatic fever

Answer 33

Syndenham’s chorea

Question 34

Symptoms of syndenham’s chorea

Answer 34

Rapid, irregular, aimless movements of limbs, face, and trunk

Some muscle weakness, hypotonia, irritability, OCD behavior, and anxiety

Question 35

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

Answer 35

Ballismus

Question 36

Rapid, irregular, involuntary dance-like movements that flow randomly from one body region to another, characteristic of huntington disease and tardive dyskinesia

Answer 36

Chorea

Question 37

Chorea results from loss of neurons in which type of basal nuclei pathway?

Answer 37

Indirect

[lose inhibition of flow of info through thalamus]

Question 38

Continuous writhing of distal portions of 1+ extremities

Answer 38

Athetosis

Question 39

______ = athetosis that is more brisk, resembling chorea

Answer 39

Choreoathetosis

Question 40

_____ = athetosis that is more intense, sustained, and resembles dystonia

Answer 40

Athetotic dystonia