Term
Where are the cell bodies of the corticospinal tract located? |
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Definition
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Term
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Definition
part of the medulla which is formed by the fibers of the corticospinal tract; gives the name to the pyramidal tract |
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Term
5 places where the cell bodies of the pyramidal tract are located |
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Definition
1. precentral gyrus (Brodmann's area 4) 2. area 6 3. SI 4. SII 5. posterior parietal cortex |
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Term
What are elicited by the primary motor area (precentral gyrus/Brodmann's area 4)? |
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Definition
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Term
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Definition
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Term
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Definition
the cells with the largest cell bodies of the pyramidal tract |
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Term
Where do the fibers of the SI that go into the pyramidal tract come from within the SI? |
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Definition
area 3a (the part of the SI adjacent to area 4 & receives input from muscle spindles) |
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Term
Where to the pyramidal cells (cells of the pyramidal tract) lie? |
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Definition
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Term
Where does the pyramidal tract pass downward? |
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Definition
through the internal capsule |
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Term
What is the difference in location of the pallidothalamic fibers of the internal capsule & the optic radiation of the internal capsule? |
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Definition
pallidothalamic fibers: lie anteriorly optic radiation: pass through posteriorly on its way to the occipital lobe |
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Term
Can damage to the internal capsule produce sensory & other deficits in addition to pareses of the muscles of the opposite body half? |
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Definition
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Term
What happens to the pyramidal tract fibers in the mesencephalon? |
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Definition
they distribute over the middle 2/3 of the crus & mix with other descending fibers |
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Term
What type of fibers are collected in the medullary pyramid? |
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Definition
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Term
What happens to the corticospinal fibers after they cross the midline at the caudalmost level of the medulla? |
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Definition
they continue in the lateral funicle of the cord as the lateral corticospinal tract |
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Term
What mediates pyramidal-tract actions on the muscles of the distal extremities? |
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Definition
fibers that cross in the lower medulla |
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Term
What mostly influences axial muscles (muscles of the back, thorax, & abdomen)? |
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Definition
the small contingent of uncrosses fibers |
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Term
What is the path of the pyramidal tract fibers that control the muscles of the head? |
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Definition
they leave the corticospinal fibers in the brain stem to end in or close to the motor & sensory cranial nerve nuclei |
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Term
Are glutamatergic corticospinal neurons excitatory or inhibitory? |
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Definition
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Term
Do some of the pyramidal tract fibers coming from MI end monosynaptically on the motoneurons? |
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Definition
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Term
Muscles from what part of the body generally have monosynaptic connections from the MI to the motoneurons? |
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Definition
motoneuron groups that control the distal muscles of the extremities (in particular, the intrinsic muscles of the hand) |
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Term
Are monosynaptic connections of particular importance for the movements that require the highest or lowest degree of voluntary control (least or most autonomic)? |
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Definition
highest degree of voluntary control (least autonomic) (ex. independent or fractioned finger movements) |
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Term
Does a single pyramidal tract axon have narrow or widespread ramifications? |
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Definition
widespread; it is enables to contact numerous motoneurons in different segments of the cord that supply several muscles |
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Term
Does contact with inhibitory interneurons increase or decrease the specificity of actions? |
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Definition
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Term
Do commands from the motor cortex elicit reciprocal inhibition in the cord? |
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Definition
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Term
Do flexors of the thumb have a higher or lower threshold for activation than the extensors? |
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Definition
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Term
Can the pyramidal tract control the sensitivity of the muscle spindle? |
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Definition
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Term
Can the strength of the long-latency strength reflex be increased or decreased? |
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Definition
yes! depending on what is appropriate during motor learning |
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Term
Why is it significant that the Renshaw cells are subject to supraspinal control? |
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Definition
the strength of the recurrent inhibition can be increased or decreased selectively in various motoneuronal groups |
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Term
Can the autogenic inhibition elicited by stimulation of tendon organs be reversed to excitation during voluntary contraction of the muscle? |
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Definition
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Term
After a unilateral transection of the pyramid, can you move around apparently normally? |
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Definition
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Term
After a unilateral transection of the pyramid, can you move your fingers independently of each other (fractioned movements)? |
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Definition
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Term
What is the most enduring symptom of damage of the motor cortex or the pyramidal tract? |
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Definition
difficulty with tasks that require precise, fractioned finger movements (writing, tying shoelaces, buttoning a shirt, & picking up small objects) |
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Term
Are there indirect pathways (synaptically interrupted in the brain stem) that transmit signals from the cortex to the motoneurons? |
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Definition
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Term
Where do reticulospinal fibers come from? |
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Definition
the reticular formation of the pons & the medulla |
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Term
3 things reticulospinal tracts are important for |
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Definition
1. maintaining the upright position 2. orienting movements of the body toward external events 3. fairly crude, stereotyped voluntary movements of the extremities |
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Term
Where do fibers from the tectospinal tract come from? |
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Definition
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Term
Where do most descending fibers of the tectospinal tract that cross the midline shortly below the superior colliculus terminate? |
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Definition
cervical levels of the cord |
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Term
3 places that the superior colliculus gets signals from that are important for control of conjugate eye movements |
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Definition
1. retina 2. visual cortex 3. frontal eye field |
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Term
What does electrical stimulation of the superior colliculus cause? |
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Definition
coordinated movements of the eyes & the head |
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Term
What reflex is influenced by the tectospinal tract? |
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Definition
optic reflexes (moving the head & eyes toward something in the visual field) |
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Term
Where do primary sensory fibers from the vestibular apparatus terminate? |
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Definition
in the vestibular nuclei (in the pons & medulla) |
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Term
Where does the lateral vestibulospinal tract come from? Where does it reach? |
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Definition
comes from: lateral vestibular nucleus reaches: all levels of the spinal cord |
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Term
What funicle does the vestibulospinal tract lie in? |
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Definition
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Term
What is the medial vestibulospinal tract important for? |
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Definition
mediation of reflex head movements in response to vestibular stimuli |
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Term
What does the medial vestibulospinal tract use as a neurotransmitter? |
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Definition
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Term
What neurotransmitter is used in raphespinal fibers? What about in coeruleospinal fibers? |
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Definition
raphespinal: serotonin coeruleospinal: norepinephrine |
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Term
When do descending monoaminergic neurons show their lowest activity? |
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Definition
in deep sleep when all movements are suppressed |
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Term
How do monoaminergic pathways contribute to the effects of motivation on the performance of voluntary movements? |
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Definition
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Term
What does the "plateau potential" of monoamines do? |
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Definition
alters the excitability of the motoneurons |
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Term
Why are constant corrections necessary for maintaining an upright position? |
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Definition
it is liable (a small supporting area & a high center of gravity) |
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Term
4 types of receptors that provide information used for postural control |
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Definition
1. proprioceptors in the legs, the spine, & the neck 2. cutaneous receptors on the sole of the foot 3. vestibular receptors in the inner ear 4. photoreceptors in the retina |
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Term
Does the final motor command depend only on sensory signals? |
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Definition
no! also on the context in which they arise |
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Term
On what type of basis do postural reflexes operate? |
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Definition
feedback (they are responses to movements that have already started) |
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Term
Are commands about postural adjustments issued in advance in conjunction with voluntary movements? |
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Definition
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Term
What do rhythm generators do for the legs? |
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Definition
they produce rhythmic, alternating leg movements in the absence of any command signals from higher levels |
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Term
What make up rhythm generators? |
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Definition
fairly complicated spinal networks of interneurons with excitatory & inhibitory interconnections which eventually control the activity of motoneurons |
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Term
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Definition
neurons that fire brief trains of action potentials with silent periods between, without receiving a rhythmically alternating input |
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Term
Where is the mesencephalic locomotor region located? |
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Definition
just ventral to the inferior colliculus on the pontomesencephalic junction |
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Term
What causes the gait disturbance in Parkinson's disease? |
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Definition
dysfunction of connections between the basal ganglia & the PPN |
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Term
How long before a movement does the readiness potential start? |
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Definition
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Term
4 places of increased neuronal activity before a voluntary movement |
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Definition
1. cerebellum 2. basal ganglia 3. thalamus 4. limbic structures |
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