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118 Cards in this Set
- Front
- Back
What two principal sources in the brain do alpha motorneurons receive input from? |
1. Cerebral Cortex (direct)
2. brainstem pathways (indirect) |
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the cerebellar control circuit influences movements of ______________ muscles through its connections to the _____________ and ____________.
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the cerebellar control circuit influences movements of IPSILATERAL muscles through its connections to the CEREBRAL CORTEX and BRAINSTEM
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The basal ganglia control circuit influences movements of _________ muscles through connections with the ____________
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The basal ganglia control circuit influences movements of CONTRALATERAL muscles through connections with the CEREBRAL CORTEX
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Medial Systems mainly provide control of what?
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posture and balance, including orienting movements
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With one exception, medial system pathways course in what part of the spinal cord?
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ventromedial
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What tract excites alpha & gamma motorneurons to extensor muscles in the proximal limbs and axial muscles and inhibits alpha/gamma motorneurons to flexor muscles?
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lateral vestibulospinal tract
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The lateral vestibulospinal tract excites what muscles & inhibits what muscles?
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excites extensor muscles in proximal limbs and axial muscles
inhibits flexor muscles |
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True or False:
The vestibulospinal tract courses through the length of the spinal cord |
True
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The medial vestibulospinal tract mainly excites alpha/gamma motoneurons that innervate what muscles?
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neck muscles
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True or False:
the medial vestibulospinal tract courses throughout the length of the spinal tract? |
False
The medial vestibulospinal tract (MVS) does not descend paths the portion of the spinal cord containing neurons that innervate neck muscles |
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What tract coordinates head movements in response to stimulation of the semicircular canals?
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The medial Vestibulospinal tract (MVS)
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The Medial (Pontine) Reticulospinal tract originates where?
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pontine reticular formation
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What muscles does the Medial Reticulospinal tract excite and inhibit?
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excites extensor muscles in proximal limbs and axial muscles
inhibits flexor muscles (much like the lateral vestibulospinal tract) |
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True or False
the Medial (pontine) Reticulospinal Tract courses throughout the length of the spinal cord? |
True
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Which tract provides a counterbalance to the lateral vestibulospinal and medial reticulospinal tracts because it mainly excites alpha/gamma motoneurons to flexor muscles in proximal limbs and axial muscles and inhbits extensor muscles?
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the Lateral (Medullary) Reticulospinal Tract
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Where does the Lateral Reticulospinal tract originate?
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medullary reticular formation
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Which tract is the only medial system that courses in the ventrolateral portion of the spinal tract, overlapping with the spinothalamic tract?
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the Lateral (medullary) reticulospinal tract
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What does the tectospinal tract do?
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it excites alpha/gamma motoneurons in the cervical cord that innervate muscles that move the head.
It's primary function is to coordinate head and eye movements |
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The lateral systems provide what?
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control of fractionated, skilled, dextrous movements
They mainly excite flexors and inhibit extensors of upper limb, but excite both flexors and extensors of the distal muscles |
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Where does the corticospinal tract originate?
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cerebral cortex
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What does the corticospinal tract do?
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excites alpha/gamma motoneurons in flexors and inhibits extensors of proximal limbs but excites both in distal limbs and digits
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What is unique and important about the Corticospinal tract?
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it's the only tract that coordinates movement of the fingers
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Where does the rubrospinal tract originate?
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red nucleus of the midbrain
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What does the Rubrospinal tract do?
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excites alpha/gamma motoneurons of the flexor muscles in upper arms down to the wrists
and inhibits extensors |
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True or False
The Rubrospinal tract courses throughout the length of the spinal cord? |
False
The Rubrospinal tract does not project below the level of the cord that innervates the arms |
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Why is the corticospinal tract terms the direct activation pathway?
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because it is the most direct (one synapse) pathway from cortex to alpha motor neuron
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What part of the cord do the lateral systems pathways course?
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posterior (dorsal) half of cord
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Both reticulospinal tracts receive input from what higher level?
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cerebral cortex
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What mechanism ensures postural muscles will be affected before the muscles that are needed to make skilled voluntary movements?
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The cerebral cortex activates the Reticulospinal tracts slightly before the Corticospinal tracts
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What pathways are primarily involved with feedfoward adjustments of posture in the anticipation of movements, so that the movement does not destabilize you?
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the Reticulospinal pathways
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Where does the major input to the vestibular nuclei originate from?
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the vestibular apparatus of the inner ear
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Which tracts adjust posture following an alteration of postural stability that is detected by the vestibular apparatus?
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vestibulospinal tracts
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Which pathways are primarily involved with feedback adjustments to posture?
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Vestibulospinal tracts
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Input to the lateral vestibulospinal tracts originates from the vestibular apparatus and the _______________
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cerebellum
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Where does the medial pontine reticulospinal tract receive input from? (3)
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1. cerebellum
2. Cerebral cortex (corticoreticular tract) 3. Somatosensory (nociceptive) input via the anterolateral system; the sources of this input are the spinoreticular tracts and axon collaterals of the spinothalamic tracts |
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What is the primary input to the lateral reticulospinal tract?
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the corticoreticular tract
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The Rubrospinal tract receives primary input from where? and also from where?
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primary - cerebellum
also from the cerebral cortex (corticorubral system) |
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Which tracts of the medial/lateral systems are not important to proximal muscle coordination?
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corticospinal tract (not as important as the others)
Medial vestibulospinal tract and tectospinal tracts do not descend to the level of the cord that innervates the muscles |
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Decerebrate rigidity is caused by a lesion from where?
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between the superior and inferior colliculi in the midbrain
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What pathways are cut in decerebrate rigidity?
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Corticoreticular tract (thereby removing the excitatory cortical influence on the medullary reticulospinal tract)
rubrospinal tract Cortical influence to the pontine reticulospinal tract (but is still activated by cerebellar input and somatosensory sources) |
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What is the net result in decerebrate rigidity?
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rigidity in arm extensor muscles
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What is the affect of a more rostral lesion in decorticate rigidity?
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The red nucleus is undamaged (rubrospinal tract) thereby leaving the excitatory influence of flexors and inhibitory influence of extensors leading to flexion of the arms
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Which is more overpowering when both have excitatory input? Flexion or extenstion?
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flexion
the reason for this is unknown |
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Why are the legs still extended in decorticate rigidity?
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The legs do not receive input from the red nucleus; therefore they remain extended
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What is an antigravity muscle?
Leg ___ Foot ___ Toe ___ Arms: ____ Wrist and finger ____ Neck ____ |
any muscle that resists gravity during the routine activities of the species- i.e. when standing
Leg extensors Foot extensors Toe Flexors Biceps Wrists and finger flexors Neck Extensors |
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What muscles become rigid in decorticate posture?
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antigravity muscles
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The brainstem motor mechanisms mainly regulate when?
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involuntary responses (most notably postural)
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Loss of the corticospinal tracts prevents what, while the preservation of indirect activation pathways permits a person to still do what?
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Loss of the corticospinal tracts prevents a person to make SKILLED, FRACTIONATED MOVEMENTS OF THE EXTREMITIES, white the preservation of indirect activation pathways permits a person to still make CRUDE MOVEMENTS OF THE DISTAL LIMBS
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The cerebral cortical motor regions control what?
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voluntary movements
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What requires low intensity electrical stimulation in order to produce focal movements?
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Primary motor cortex
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What constitutes the premotor cortex?
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lateral premotor cortex
supplementary and cingulate motor cortices on medial portion of brain |
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How can the premotor cortex evoke movement?
& which muscle group is generall excited? |
by electrical stimulation w/ intensity that is greater than the primary motor cortex
larger muscle groups |
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What, although considered to be motor cortex, does not connect w/ the primary motor cortex?
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the frontal eye fields
instead they project to the regions controlling the saccadic eye movements |
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What cortical regions can influence movements through synaptic connects w/ the motor area?
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Somatosensory and parietal regions
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The primary motor cortex is what broadmann's area #?
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4
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Where is the primary motor cortex located?
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Anterior to the central sulcus
in the precentral gyrus On the medial surface, the primary motor cortex is located on the anterior portion of the paracentral lobule |
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from medial to lateral, list the parts of the body innervated by the primary motor cortex
Which body parts have larger representation? |
foot, leg, trunk, arm, hand, face
Larger representation: fingers and thumb, and muscles used in speech |
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What describes the primary motor cortex in regards to the body:
ipsilateral or contralateral? |
Contralateral; it's also unilateral
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Major thalamic input to the primary motor cortex comes from where?
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posterior portion of the ventral lateral nucleus (which relays information from the cerebellum)
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Where do the major cortical input to the primary motor cortex come from?
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the premotor cortex: supplementary motor cortex, lateral premotor cortex, and the somatosensory cortex
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Output from the primary motor cortex goes where? (3)
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1. striatum
2. brainstem 3. spinal cord |
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What permits the primary cortex to rapidly respond to sensory stimuli?
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input to the primary motor cortex from the complementary region of the somatosensory cortex
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What Brodmann's number is the supplementary motor cortex?
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6
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Where is the supplementary motor cortex located?
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anterior to the primary motor cortex on the medial surface of the brain
it is located in parts of the paracentral gyrus and superior frontal gyrus |
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Is the supplementary motor cortex somatotopically organized like the primary motor cortex?
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yes, but less so
the leg region is more posterior and the head region is more anterior |
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Which describes the supplementary motor cortex?
unilateral or bilateral |
bilateral
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What is the thalamic input of the supplementary motor cortex?
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the anterior portion of the ventral lateral nucleus (VLa) and the ventral anterior nucleus (VA)
both of these nuclei relay information from the basal ganglia |
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Where does the supplementary cortex receive major cortical input from? (4)
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1. lateral premotor cortex
2. somatosensory cortex 3. prefrontal cortex 4. posterior parietal cortex |
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The supplementary motor cortex projects to what? (4)
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1. primary motor cortex
2. lateral premotor cortex 3. spinal cord 4. motor regions of the brainstem |
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What are the 4 functions of the supplementary motor cortex?
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1. coordinates movements on both sides of the body (esp. bimanual)
2. learns new movement sequences and mentally rehearses sequences 3. adjusts posture for movement (provides input to the reticulospinal pathways for feedfoward regulation of posture) 4. controls the selection of movements generated from memory (tying shoes) |
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What is an apraxia and how is it diagnosed?
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An apraxia is the inability to perform learned skilled movements
to diagnose, the physician must determine that the patient has no sensory deprivation, no spasticicty, paralysis or altered tone & demonstration that the pt. can understand the command |
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What Brodmann's number is the lateral premotor cortex?
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6 (along w/ the supplemental motor cortex)
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Where is the Lateral Premotor Cortex located?
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anterior to the primary motor cortex on the lateral convexity
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Is the Lateral Premotor Cortex somatotopically organized?
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yes, but not as much as the primary motor cortex
Superior - leg Inferior - head |
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Which of the following describes the premotor cortex?
unilateral or bilateral single muscle or multiple muscles |
unilateral
multiple muscles |
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What is the major thalamic input to the Lateral premotor cortex?
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Anterior portion of the ventral lateral nucleus (VLa)
Ventral anterior nucleus (same as supplemental cortex) |
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Where does the Lateral Premotor Cortex receive input primarily from? (4)
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1. Somatosensory Cortex
2. Supplementary Cortex 3. Posterior Parietal cortex 4. Prefrontal cortex |
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Where does the Lateral premotor cortex primarily project to?
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1. Primary Motor Cortex
2. Spinal Cord 3. Motor regions of the brainstem |
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What are the functions of the Lateral Premotor Cortex? (3)
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1. Movements reacting to environment
2. adjusts posture for a movement (via the reticulospinal feedfoward) 3. Mirroring |
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What Brodmann's number is the cingulate motor cortex?
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24
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What Brodmann's number is the Frontal Eye Field?
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ventral portion of 8
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Where is the cingulate motor cortex located?
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in the cingulate sulcus inferior to the supplementary cortex
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What does the cingulate motor cortex do?
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involved in controlling the involuntary movements associated w/ emotional responses (laughing at a joke or motor control of crying)
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What does the Frontal eye Field do?
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controls voluntary saccadic eye movements (the fast eye movements)
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Does stimulation of the frontal eye field causes saccadic eye movements on the same side or toward the opposite side
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toward the opposite side
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A lesion produced in the Frontal Eye Fields causes the eyes to deviate.....
toward side of lesion or away from side of lesion |
toward side of lesion
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What percentage of Corticospinal fibers orginate in the primary motor cortex?
in the premotor areas? in the postcentral gyrus? |
primary - 30%
premotor - 30% postgentral - 40% |
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What are the largest neurons conducting at 70 m/s only found in the primary motor cortex that were orginally thought to make up the entire corticospinal system but acutally make up 3%?
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Betz cells
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Where do the premotor corticospinal tracts project to?
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mainly the spinal areas controlling postural movement
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Where do the postcentral corticospinal fibers terminate & what do movemetns do they modulate?
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terminates in the dorsal horn (not alpha motor neuron)
modulates propioceptive and somatosensory transmission |
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Describe the pathway of the corticalspinal tract from the cortex to spinal cord including location in the midbrain, pons, medulla, and Spinal cord
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cortex through corona radiata to posterior limb of internal capsule
midbrain: central region of crus cerebri pons: ventromedial regions pons: medulla 90% dessucates in pyramids then travels in the dorsolateral portion of SC 10% doesn't cross over until it reaches its destination in the spinal cord (fibers destined to influence medial system pathways) |
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What is the blood supply to the corticospinal tract lower extremity area on the MEDIAL SURFACE OF PRECENTRAL GYRUS?
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Anterior cerebral artery (A2 segment)
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What is the blood supply that provides blood to the trunk, upper extremity, and head portion of the corticospinal tract mostly on the LATERAL SURFACE OF PRECENTRAL GYRUS
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Middle Cerebral Artery (M2)
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What is the blood supply of the internal capsule?
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Lenticulostriate branches of the M1
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What is the blood supply of the midbrain portion of the corticospinal tract?
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Paramedian branches of the Posterior Cerebral Artery (P1)
& brahnces of Posterior communicating artery (most lateral parts-leg and trunk) |
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What is the blood supply to the corticospinal tract of the pons?
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paramedian branches of the basilar artery
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What is the blood supply to the medulla oblongata portion of the corticospinal tract?
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branches of the anterior spinal artery
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What is the blood supply to the spinal cord's portion of the corticospinal tract?
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branches of the arterial vasocorona and sulcal branches of anterior spinal artery
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Input to trigeminal (V) and facial (VII) nuclei is....
unilateral or bilateral |
bilateral
except muscles on the lower half of the face which are innervated mainly CONTRALATERALLY |
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Cortical input to the upper half of the face originates from where?
Cortical input to the lower half of the face originates where? |
upper half - anterior cingulate gyrus
lower half- motor homunculus |
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Lesions to the corticobulbar pathway above the level of the facial nucleus produces what?
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Contralateral drooping of the corner of the mouth and lower face (central seven)
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Lesion of the facial nerve produces what?
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ipsilateral drooping of the whole side of the face (Bell's palsy)
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Is input to the nucleus ambiguus in the medulla unilateral or bilateral?
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bilateral except for motor neurons innervating the soft palate and uvula (contralateral)
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Lesions of the corticobulbar pathway above the level of the nucleus ambiuguus causes what to happen to the uvula?
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to deviate toward the side of the lesion (due to unopposed contraction of ipsilateral muscles)
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Input to the hypoglassal nuclues (XII) is ipsilateral or contralateral?
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contralateral
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What happens to the tongue in a lesion in the corticobulbar pathway above the level of the hypoglossal nucleus?
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the tongue deviates away from the leasion due to unopposed action of the ipsilateral genioglossus muscle)
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Is input to the accessory muscle (XI) ipsilateral or contralateral?
What do you see in lesions of this pathway? |
contralateral
difficulty shrugging shoulders or turning head toward the side of the lesion |
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Where does the corticorubral system originate?
Where does it project? |
primary motor cortex, supplementary motor cortex, lateral premotor cortex, some posterior parietal cortex
projects to the ipsilateral red nuclues |
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The corticorubral system coordinates which two functions/pathways?
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the corticospinal and rubrospinal fxns
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Where does the Corticoreticular system originate?
Where does it project |
lateral premotor cortex and supplemental motor cortex
pontine (medial) and medullary (lateral) reticulospinal tracts |
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What does the corticopontine system consist of?
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pathways from nearly all regions of the cortex that project to ipsilateral pontine nuclei which then project to the cerebellum
this system communicates cortical info to cerebellum |
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What is a lower motor neuron?
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spinal motoneurons or nerves, or cranial nerve motor neurons
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What does damage to the lower motor neurons cause? (5)
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1. decreased muscle tone
2. Neurogenic muscular atrophy (not as strong as muscle size) 3. Muscle fasciculations or fibrillations of single fibers 4. Reduction of tendon reflexes (hyporeflexia) 5. No babinski sign |
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What is an upper motor neuron?
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corticospinal neurons and other descending neurons
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What does damage to the upper motor neurons cause? (5)
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1. decreased muscle tone initially, becoming increased muscle tone w/ time
2. Rarely have muscle atrophy 3. Affects groups of muscles (instead of single muscle) 4. Enhanced stretch reflexes (hyperreflexia - indirect pathway) 5. Babinski sign |
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What is spasticity?
What are the characteristics? |
condition of hypertonic and hyperreflexive muscles in which there is enhanced resistance to passive movements
1. Unidirectional - resistance is greater in antigravity muscles 2. Velocity dependent - resistance to movement depends on speed 3. Hyperreflexive tendon jerk |
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What probably causes spasticity?
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changes in functional synaptic connections related to stretch reflex
There is reduction in inhibitory influences on motor pathways due to abnormal fxn of the INDIRECT activation pathways, not the direct activation pathway |
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What is clinical rigidity and what is it associated with?
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Assoc. w/ Parkinsonism
It's 1. Bidirectional: resistance to movement in any direction 2. Less velocity dependent 3. No hyperactive tendon jerk |