Lecture 9- Motor Systems, Cortical Pathways

Question 1

What are the 4 functions of the motor system

Answer 1

1. goal of movement and movement planning that best achieves the goal
2. squencing of muscle contraction to smoothly and accurately achieve goal
3. execution of goal-directed movement
4. mechanics of the whole body and adjusts postural responses in adaptive ways for movement

Question 2

the motor system is _____ motor control from the cortex and is the control of discrete ______ _____

Answer 2

• decending

- voluntary movements

Question 3

what is motor homunclus?

Answer 3

disproportionate representation of hands, face and mouth in primary motor cortex

Question 4

upper motor neuron (UMN) is the ___ order neuron

Answer 4

1st

Question 5

UMN carries information from ____ to ____ and ____ ___

Answer 5

• cortex
• brainstem (corticobulbar tract)
• spinal cord (corticospinal tract)

Question 6

lower motor neuron (LMN) is the _____ order neuron

Answer 6

2nd

Question 7

LMN carries information in the ____ and ___ ___ that directly projects to the ____ in the periphery

Answer 7

• brainstem
• spinal cord
• muscles

Question 8

T/F: lateral motor system controls movements of the limbs

Answer 8

True

Question 9

Medial motor system controls what?

Answer 9

• posture
• balance
• axial control

Question 10

what are the 2 corticospinal tracts?

Answer 10

• lateral corticospinal tract

- anterior corticospinal tract

Question 11

corticobulbar are fibers projecting from ____ to nuclei in _____

Answer 11

• cortex

- brainstem

Question 12

corticobulbar tract travels with the _____ tract in the cerebral ____ in the midbrain

Answer 12

• corticospinal

- peduncles

Question 13

corticobulbar tract projects to motor nuceli of what cranial nerves?

Answer 13

• CN 5, 7, 9, 10, 11, 12

Question 14

corticobuulbar tract controls LMN innverating muscles of the ___, ____, ____ and ____

Answer 14

• face
• tongue
• pharynx
• larynx

Question 15

T/F: over 50% of cotricospinal tract fibers originate in the primary sensory cortex

Answer 15

False: over 50% of cotricospinal tract fibers originate in the primary MOTOR cortex

Question 16

other tract fibers of the corticospinal tract originate from what 3 areas other then the primary motor cortex

Answer 16

• motor association cortex (premotor and supplmentary motor cortex),
• somatosensory cortex
• related association areas

Question 17

describe corona radiata

Answer 17

• initial path of the corticospinal and cortocobulbar tracts

- travel from the cortical regions, axon fibers enter upper portion of cerebral white matter called corona radiata

Question 18

describe internal capsule

Answer 18

• large fiber bundle carrying most of the axons running to and from the cerebral hemispheres
• corticospinal and corticobulbar tract pathway is from the corona radiata to the internal capsule

Question 19

what are the 3 parts of the internal capsule

Answer 19

• anterior limb
• genu
• posterior limb

Question 20

describe the pathway in which the corticobulbar tracts take from cortex to brainstem

Answer 20

cortical regions –> corona radiata –> internal capsule –> basis ppedunculi (in midbrain)–> brain stem cranial nerves (project onto associated CN)

Question 21

the corticospinal and corticobulbar tracts enter the midbrain at the ___ portion of cerebral peduncles called the ____ ____

Answer 21

• ventral

- bassis peduculi

Question 22

corticobulbar tract terminates on motor nuclei for CN on _____ side to control LMN

Answer 22

• opposite

Question 23

describe the pathway in which the corticospinal tracts take from cortex to brainstem

Answer 23

cortical regions –> corona radiata –> internal capsule –> basis pedunculi (in midbrain)–> ventral pons–> medulla (which becomes the spinal cord)

Question 24

T/F: the corticospinal trac form the pyramids at ventral medulla

Answer 24

true

Question 25

the corticospinal tract axons cross to the opposite side at the ____-____ junction also called the ____ ____

Answer 25

- cervical-medullary junction | - pyramid decussation (great motor cross over)

Question 26

corticospinal tract= ____ % cross over while ____% remain on ipsilateral course

Answer 26

- 85% | - 15%

Question 27

corticospinal tract fibers that have crossed to controlateral side enter ____ colummns of spinal cord and form the ____ _____ tract

Answer 27

- lateral columns | - lateral cotricospinal tract

Question 28

corticospinal fibbers that did not cross over course down the spinal cord on the ____ columns forming the _____ ______ tract

Answer 28

- anterior columns | - anterior corticospinal tract

Question 29

functions of the lateral corticospinal tract (lateral motor system)

Answer 29

- controls movement of the extremities

Question 30

functions of the anterior corticospinal tract (medial motor system)

Answer 30

- controls proximal axial and girdle muscles

Question 31

for the lateral motor system: the pyramidal decussation allows clinicians a clue about location of lesion on corticospinal tract.... the right motor cortex directly commands movement on what side?

Answer 31

- left

Question 32

for the lateral motor system: the pyramidal decussation allows clinicians a clue about location of lesion on corticospinal tract.... right side of body movements get controls by what side of the motor cortex?

Answer 32

- left

Question 33

T/F: lesions above pyramidal decussion produce ipsilateral deficits in both upper and lower extremities

Answer 33

false: contralateral deficits

Question 34

lateral corticospinal tract fibers controlling upper extremity are ___ to those controlling lower extermity

Answer 34

- medial

Question 35

T/F: lesions below medulla produce ipsilateral deficits below level of lesion

Answer 35

true

Question 36

LMB terminate at motor end plates of skeletal muscles of limb... known as _____ _____

Answer 36

- neuromuscular junction

Question 37

lateral corticospinal tract enter spinal cord and terminate on what 2 areas?

Answer 37

- interneurons (modulatory function) | - ventral horn cells of the lower motor neurons (anterior horn cells)

Question 38

what are the functions of the lateral corticospinal tract?

Answer 38

- strongly influences muscles of the extremities; Especially distal muscles important for execution of fine, skilled movements - tends to have a facilitative action upon anterior horn cells with motor neurons to flexor muscles inhibitory influence on anterior horn cells of motor neurons to extensor muscles - tends to have a facilitative action upon gamma motor neurons - Also projects on sensory neurons in the dorsal horn and control the amount of information to be sent to the CNS

Question 39

what is the most common lession for corticospinal tract and examples. what are the other causes?

Answer 39

- vascular - typically middle cerebral artery or vertebrobasilar artery - other causes: tumor, trauma, demylinating diseases

Question 40

what do we typicall find when lesions of the lateral corticospinal tract occur

Answer 40

- hypertonia (increased muscle tone): increased resistance to passive stretch - increased velocity-dependent muscle response (spasticity) - increased deep tendon reflexes (hyperreflexia) - Babinski’s sign- positive - Clonus- positive - muscle weakness

Question 41

what is the function of the anterior corticospinal tract

Answer 41

- Critical to control of bilateral axial muscles and muscles of shoulder and pelvic girdles

Question 42

T/F: the anterior corticospinal tract first project on the interneurons which in turn project on anterior horn cells

Answer 42

true

Question 43

upper motor neurons contributing to lateral corticospinal tract originate predominantly in _____ _____ cortex

Answer 43

- primary motor cortex

Question 44

upper motor neurons contributing to anterior corticospinal tract originate mainly in _____ _____ cortex

Answer 44

- motor association cortex

Question 45

T/F: unilateral lesions of the medial motor system cause deficits on ipsilateral side

Answer 45

False: Since medial motor systems terminate on interneurons that project to both sides of spinal cord unilateral lesions of medial motor systems do not produce obvious deficits