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89 Cards in this Set
- Front
- Back
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How are motor circuits in the spinal cord regulated?
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By input from descending motor pathways.
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3 Cortical structures that regulate motor circuits in the spinal cord:
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-Primary motor cortex
-Prefrontal cortex -Somatosensory and parietal association cortex |
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3 Subcortical structures that regulate motor circuits in the spinal cord:
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-Basal ganglia
-Cerebellum -Thalamus |
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What else regulates motor circuits in the spinal cord?
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The Brainstem
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What did John Hughling's jackson observe about patient movement during a seizure?
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That it often progressed from more distal to more proximal structures.
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What did Fritsch and Hitzig observe when electrically stimulating a dog brain?
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That it resulted in contralateral limb movements.
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What required the least amount of stimulus to evoke a response by Fritsch and Hitzig?
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The primary motor cortex
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What does more intense stimulation of the premotor area do?
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Evokes complex movements involving multiple joints.
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What is the basis for Brodmann's subdivisions of the brain?
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Cytoarchitecture
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What is in Brodmann's area 4?
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Primary motor cortex M1
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What is in Brodmann's area 6?
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-Supplementary motor area
-Premotor area |
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What is in Brodmann's area 3, 2 and 1?
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Parietal lobe
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What gyri contain the Primary Motor Cortex?
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-Precentral gyrus
-Paracentral gyrus |
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Where do the neurons from the Primary Motor Cortex project?
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To Rexed Laminae layers 6-9
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What do Primary M1 neurons synapse on in laminae 6-9?
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Small groups of motor neurons in the brainstem and spinal cord.
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What will result from injury to M1?
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Contralateral paralysis - especially loss of fine motor skills
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What gyri contain the Premotor Area?
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-Anterior precentral gyrus
-Posterior parts of frontal gyri |
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What is the function of the Premotor area?
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To prepare the Primary motor cortex for an impending action.
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What happens when Premotor cortex is injured?
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Complex movements are slower than normal.
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Where is the Supplementary Motor Area located?
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On the medial surface of the cerebral hemisphere, anterior to the paracentral lobule.
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What is the SMA functional in?
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-Complex movements of many muscle groups, postural mvmts.
-Plans/integrates movements performed on both sides of the body simultaneously. |
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What is the result of a unilateral lesion of the SMA?
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The inability to perform complex bi-manual tasks.
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In what gyrus is Brodmann's area 3,2,1?
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Postcentral gyrus - the somatosensory cortex.
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Where do the neurons in the somatosensory cortex originate?
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-Rexed laminae 4 and 5
-Posterior column nuclei |
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How is the somatosensory cortex in the parietal lobe involved in motor control?
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It transmits sensory info
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How is the primary motor cortex organized?
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Somatotopically
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What areas are biggest in the primary motor cortex?
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Those areas that are used for tasks that require great precision.
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Where is tongue motor control on the primary motor cortex?
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Most lateral (near ear)
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What is above the tongue?
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The mouth, lips, face, and eye
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Where is the neck?
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Just above the eye
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What is above the neck?
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The thumb, then rest of the hand.
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What is most medial on the primary motor cortex, before dipping into the longitudinal fissure?
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The hip
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What motor control is in the longitudinal fissure area?
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Knee, ankle, and toes.
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What motor control would an infarct in the middle cerebral artery most disrupt?
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Movements of the face
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What motor control would an infarct in the ACA most affect?
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The knee, and lower limb.
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What artery supplies most of the supplementary motor area?
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ACA
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What artery supplies the trunk, hand and face area of M1 and PMA?
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MCA
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Can a patient recover from a stroke? How/why?
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Yes because of plasticity and the ability for some areas of the cortex to take over for others.
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What happens to the motor cortex if the left forearm is amputated?
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The area controlling the upper arm / biceps on the right brain will get larger.
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What does the firing rate of INDIVIDUAL neurons in M1 cortex encode?
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Force of contraction
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What do populations of M1 neurons encode?
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The DIRECTION of movement
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So what do M1 neurons encode?
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The VELOCITY with which a force is applied
-FORCE -DIRECTION |
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What is M1 connected to?
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Alpha lower motor neurons that innervate a particular skeletal muscle.
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How do the M1 neurons get to the lower motor neurons?
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Via the Corticospinal (pyramidal) tract
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What is the function of the Corticospinal tract?
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Voluntary skilled movement of distal muscles of the limbs
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Where do the axons of the corticospinal tract originate?
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-33% from M1
-33% from SMA & Prefrontal Cortex -33% from Parietal lobe |
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What do 3% of the 33% of neurons that arise in M1 arise from?
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Betz cells - the largest pyramidal cells in lamina V in the precentral gyrus.
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After originating in their various areas, where do the fibers of the corticospinal tract pass through?
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-Corona radiata
-Posterior limb of the internal capsule |
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How do the corticospinal tracts pass through the midbrain and brainstem?
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By passing through the:
-Middle of crus cerebri and cerebral peduncle -Medullary pyramids |
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What does the corticospinal tract split into? What percentage is each?
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-Lateral corticospinal tract 90%
-Antero/ventral corticospinal tract 10% |
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What happens to the lateral corticospinal tract?
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Its 90% fibers decussate in the pyramidal decussation and descend in the lateral funiculus to all spinal cord levels.
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What happens to the anteroventral corticospinal tract?
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Its 10% fibers DO NOT decussate; they descend in the anterior funiculus and decussate in ventral white commissure
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How low do the anterior/ventral corticospinal tracts descend?
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To thoracic spinal cord levels.
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What is the goal function of the corticospinal tract?
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-Excites flexor muscles
-Inhibits extensor muscles |
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What are the pyramids?
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2 elongated swellings on the ventral aspect of the medulla.
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What does each pyramid contain?
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A million CORTICOSPINAL AXONS
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What are the corticospinal tract fibers?
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Upper motor neurons
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What are the skeletal muscle nerve fibers upon which the corticospinal tract fibers synapse?
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Lower motor neurons
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Where does the lateral corticospinal tract begin?
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At the pyramidal decussation
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What will a lesion of the Internal Capsule result in?
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Contralateral hemiparesis
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What is hemiparesis?
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Weakness
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So a lesion to the left internal capsule will cause:
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Right hemiparesis
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What will a lesion to the left brainstem above the pyramidal decussation at the level of the midbrain result in?
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-Right hemiplegia of all extremities
-Left paralysis of most eye movements |
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What will a lesion to the left brainstem above the pyramidal decussation at the level of the pons result in?
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-Right hemiplegia of all extremities
-Left paralysis of most eye movements AND facial or lateral rectus muscles |
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What will a lesion to the left brainstem above the pyramidal decussation at the level of the medulla result in?
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-Right hemiplegia of all extremities
-Left paralysis of most eye movements AND facial or lateral rectus muscles AND tongue mvmt |
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What will happen if there is a rostral lesion the brainstem AT the level of the pyramidal decussation?
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Bilateral paresis of the upper extremities
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What will happen if there is a caudal lesion the brainstem AT the level of the pyramidal decussation?
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Bilateral paresis of the lower extremities
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What will result from a unilateral cervical spinal cord lesion?
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Ipsilateral weakness or paralysis of both the upper and lower limbs.
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What will result from a bilateral cervical spinal cord lesion?
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Bilateral weakness/paralysis of both upper and lower limbs.
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What is bilateral weakness/paralysis of both the upper and lower limbs called?
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Quadriplegia
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When patients have hemiplegia or hemiparesis due to a unilateral lesion of the cervical spinal cord, what develops later?
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Signs of UMN lesions - spacticity
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What will result from a unilateral lesion of the thoracic spinal cord?
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Paralysis of the lower limb on one side
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What will result from a bilateral lesion of the thoracic spinal cord?
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Paraplegia - loss of both lower limbs.
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Lesions above the pyramidal decussation result in:
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Contralateral weakness
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Lesions below the pyramidal decussation result in:
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Ipsilateral weakness
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5 cardinal signs of an UMN lesion:
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-Paresis or paralysis
-Spasticity -Hyperreflexia -Loss of abdominal reflexes -Babinski sign |
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What is the babinski sign?
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Stroking of the plantar foot results in big toe dorsiflexion instead of plantarflexion
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4 cardinal signs of a LMN lesion:
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-Muscle atrophy
-Fasciculations -Hypotonia -Hyporeflexia |
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3 examples of Corticospinal tract lesions:
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1. Weber syndrome
2. Medial Medullary Syndrome 3. Brown-Sequard syndrome |
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What causes Weber syndrome?
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Posterior cerebral artery occlusion - loss of blood supply to the midbrain.
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What major nerve tracts are injured in Weber syndrome?
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-CN III
-corticospinal tract |
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What deficits result in Weber Syndrome?
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-Ipsilateral oculomotor palsy
-Contralateral paralysis of the lower face, tongue, arm, and leg |
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What will ipsilateral oculomotor palsy consist of?
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-Lateral deviation of the eye
-Ptosis -Pupil fixed and dilated |
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What major nerve tracts are injured in Medial Medullary syndrome?
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-Cn XII
-Corticospinal tract -Medial Lemniscus |
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What deficits result in Medial Medullary Syndrome?
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-Ipsilateral paralysis and atrophy of the tongue
-Contralateral hemiparesis of the arm and leg, but the face is spared -Contralateral loss of touch, vibration and proprioception from half the body |
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What is Brown Sequard syndrome?
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A lesion of the spinal cord
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So where will deficits be seen in Brown Sequard syndrome?
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On the ipsilateral side of the body b/c you're below the pyramidal decussation.
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What will be seen in a lower motor neuron lesion?
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MUSCLE ATROPHY
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What will be seen in a Corticospinal tract lesion at the level of the spinal cord?
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-Ipsilateral spastic paralysis
-Ipsilateral babinski sign -Ipsilateral loss of abdominal and cremasteric reflexes |
