Motor Systems

Question 1

When we speak of an upper motor neuron legion, we usually mean a problem with which tract?

Answer 1

Lateral CST

Question 2

Lower motor neurons

Answer 2

Neurons in spinal cord/ brainstem which innervate skeletal muscle

Located in the ventral/anterior horns of the gray mater

Question 3

Organization of lower motor neurons based on innervation

Answer 3

Medial- innervate axial muscles

Lateral- distal muscles

Neurons for extensors are located ventrally

Flexors are located dorsally

Question 4

Motor Units associated with LMN’s

Answer 4

S-Units: Slow, for things you do all day long (Red muscle fibers)

FF-units- Fast and fatigable (White muscle fibers)

FR-units- Fast and Resistant to fatigue (White muscle fibers)

Question 5

The ventral horn gets ______ as they’re more muscles to innervate

Answer 5

Fatter

Question 6

As you go from S to FF, the anterior horn cell becomes…

Answer 6

Bigger and the amount of force which can be generated becomes larger.

Question 7

Main descending pathway of interest for motor activity

Answer 7

Corticospinal tract (lateral)- all excitatory

Question 8

Basic characteristics of the CST

Answer 8

CORTICALSPINAL TRACT

• There are many non-motor fibers which run through this tract– sensorimotor integration
• As a result, it has multiple origins
• Only 50% of their fibers come from motor cortex

Question 9

Betz cells

Answer 9

Concentrated in CST and have some control of hand and leg movement– likely have a large role in walking.

Question 10

Most of the anterior spinal tract descends in the…

Answer 10

Posterior limb of the internal capsule

Question 11

Corticobulbar tract fibers are located where?

Answer 11

Genu of internal capsule

Question 12

Legion in the posterior limb if internal capsule mostly affect what?

Answer 12

Those fibers going to body or limbs on OPPOSITE side of the body.

Question 13

Corticalspinal tract from the pyramids become…

Answer 13

Lateral corticospinal tract

Question 14

Corticospinal tract is generally responsible for…

Answer 14

Fine motor movements of our hand

Question 15

The layers which control motor function ultimately…

Answer 15

Drive lower motor neurons

Question 16

Primary motor cortex

Answer 16

Location where the motor fibers are concentrated– NOT where learning occurs.

Question 17

Lesion of anterior horn cell will give…

Answer 17

Lower motor neuron syndrome.

Weakness, twitches, atrophy of muscles

Question 18

Legion of upper motor neurons wills give

Answer 18

Upper motor neural syndrome

Often affiliated with a stroke
Causes spasticity and some atrophy (but no twitches and minimal weakness)

Question 19

Issue in cerebellum, association cortex or basal ganglia would cause…

Answer 19

Motor problem but no weakness

Question 20

Oculomotor, trochlear and abducens nuclei receive what type of innervation from corticobulbar neurons?

Answer 20

NO DIRECT INNERVATION

They’re controlled by other collections of neurons in the brainstem

Question 21

Cranial nerve nuclei associated with upper motor neurons

Answer 21

XII, V (mostly to opposite side)

VII (some bilateral, some opposite)

IX, X (bilateral)

Question 22

Cranial nerve VII and its crossing over pattern

Answer 22

Cut of VII will cause facial paralysis on one side– Bell’s palsy

Stroke in cerebrum— Upper face would be spared on both sides. Opposite lower face would be paralyzed.