cortical control of movement

Question 1

types of movement

Answer 1

Reflexes: stereotyped responses to stimuli

Automatic postureal adjustments

Voluntary: goal directed, internally generated, and improve with practice

Question 2

motor circuits in the spinal cord are regulated by input from the descending motor pathways

Answer 2

cortical structures: primary moter cortex, pre frontal cortex, somatosensory and parietal association cortex

Subcortical structures: basal ganglia, cerebellum thalamus

Brainstem

Question 3

motor pathways

Answer 3

2 main systems

Lateral: lateral corticospinal tract, and the rubrospinal tract

Medial: anterior corticospinal tract, lateral vestibulospinal tract, medial vestibulospinal tract, corticotectal/ tectospinal tract, and reticulospinal tract

Question 4

primary motor cortex

Answer 4

somatotopically organized, structures used for tasks that require great precision (hands and face) have large portion of homunculus

theres overlap of the overlap, theres plasticity

Question 5

corticospinal tract

Answer 5

one neuron- upper motor neuron

Projects to lower motor neuron (LMN) in ventral horn of ALL levels of spinal cord

Function: voluntary movements of distal extremities, skilled movements, excites flexors and inhibits extensors

(connects to alpha motor neuron that innervates a skeletal muscle)

Question 6

route of corticospinal tract

Answer 6

CST axons arise from:
1’ motor cortex (33%)
Betz cells (large pyramidal cells in lamina 5 of precentral gyrus)- 3%
Premotor cortex and supplementary motor cortex-33%
Parietal lobe - 33%

CST axons pass through:
Corona radiata
Posterior limb of internal capsule
the middle of cerebral peduncle (crus cerebri)
medullary pyramids

Question 7

lateral corticospinal tract

Answer 7

90% of fibers decussare in pyramidal decussation and descend in lateral funiculus to all sp cd levels

Question 8

Anterior/ventral corticospinal tract

Answer 8

10% of fibers do not decussate in pyramids but descend in the anterior funiculus and decussate in ventral white commisure to thoracic sp cd

Question 9

lesions above the pyramidal decussation result in…

lesions below the pyramidal decussation result in…

Answer 9

lesions ABOVE= contralateral weakness

Lesions below= ipsilateral weakness

Question 10

upper motor neuron lesion

Answer 10

paresis (weakness) or paralysis
Spasticity 
hyperreflexia
loss of abdominal reflexes
Babinski sign- stroking the plantar surface of the foot along the lateral border--> dorsiflexion of the great toe (normal= plantar flexion)

Question 11

lower motor neuron lesion

Answer 11

muscle atrophy, fasciculations, hypotonia, hyporeflexia

Question 12

Corticospinal tract lesions

Answer 12

lesion in the cortex: contralateral paresis of a particular body part corresponding to area of cortical damage

lesion in the posterior limb of internal capsule: contralateral hemplegia

lesion in the cerebral peduncle crus cerebri: weber syndrome (due to occlusion of PCA)

Question 13

cortico spinal tract lesion

Answer 13

contralateral paresis of lower face, tongue, arm and leg

Question 14

CN3 injury

Answer 14

ipsilateral oculomotor palsy

eye devates laterally, ptosis, pupil is dilated and fixed

Question 15

lesion in the medullary pyramid

Answer 15

medial medullary syndrome

could be due to occlusion of vertebral a or anterior spinal a.

Question 16

cn XII lesion

Answer 16

ipsilateral paralysis and atrophy of tongue