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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