6 Descending Motor Systems

Question 1

Innervates striated muscle, directly signals muscle to contract, only way to initiate movement.

Answer 1

Lower Motor Neuron

Question 2

Lower Motor Neuron Types:

Answer 2

Alpha Motor Neuron- Extrafusal muscle fibers (actually contract)

Gamma Motor Neuron- intrafusal muscle fibers (regulate contraction)

Question 3

Loss of muscle tone (lower motor neuron lesion)

Answer 3

Atonia

Question 4

Loss of myotatic (knee jerk) reflex (lower motor neuron lesion)

Answer 4

Areflexia

Question 5

Spontaneous muscle contractions (lower motor neuron lesion)

Answer 5

Fasciculations

Question 6

Loss of muscle tissue (lower motor neuron lesion)

Answer 6

Atrophy

Question 7

Upper motor neuron lesions cause _____ paralysis including:

Answer 7

Spastic

1. Hypertonia (increased resting tension)
2. Hyperreflexia
3. Pathological reflexes (Babinski sign)
4. Big toe dorsoflexion

Question 8

In the ventral horn: Neurons controlling axial muscles are ____ to those controlling distal muscles. Neurons controlling flexors are located _____ to the extensor group.

Answer 8

Medial

Posterior

Question 9

1 motor neuron plus all myofibers it innervates.

Answer 9

Motor Unit

Question 10

______, ______, and association cortex are vital in design, choice, and monitoring of movement, but have no direct effect on the lower motor neuron. Damage to these areas may cause involuntary movements, incoordination, and difficulty initiating movement.

Answer 10

Basal ganglia

Cerebellum

Question 11

The _____ has hierarchical motor control (by controlling motor cortex which controls the LMN) and parallel motor control (by directly controlling LMN)

Answer 11

Premotor cortex

Question 12

Corticospinal tract origins:

Answer 12

1. Primary Motor Area
2. Somatosensory area
3. Premotor Area
4. Supplementary motor area
5. Superior parietal lobule

Question 13

Area of brain that controls execution of contralateral voluntary movements and fine digital movements.

Answer 13

Primary Motor Area

Question 14

Area of brain that plans movements in response to external cues, controls proximal and axial musculature, may assemble empathetic facial movements.

Answer 14

Premotor Area

Question 15

Area of brain that plans movements while thinking (assembles/learns new sequence [music], imagines movements).

Answer 15

Supplementary Motor Area

Question 16

Areas of brain that direct motor patterns in response to sensory input and modulate sensory signals.

Answer 16

Somatic Sensory Area

Superior Parietal Lobule

Question 17

The corticospinal tract originates in the _____ and _____ areas. It descends thru ______, ______, ______, and decussates at ________.

Answer 17

Cerebral Cortex
Precentral Gyrus

Cerebral Peduncle
Basis Points
Medullary Pyramid

Spinomedullary Junction

Question 18

Desc pathway. Controls shoulder and proximal arm musculature

Answer 18

Rubrospinal Tract

Question 19

Desc pathway. Controls axial musculature (walking)

Answer 19

Reticulospinal tract

Question 20

Desc pathway. Controls axial musculature (balance)

Answer 20

Vestibulospinal tract

Question 21

Desc pathway. Believed to be important in head turning reflexes in response to visual stimuli, unclear human function.

Answer 21

Tectospinal tract

Question 22

The _____ is the exception to the typical Corticobulbar Pathway pattern because the lower face is contralaterally innervated while the upper face is bilaterally innervated.

Answer 22

Facial Motor Nucleus

Question 23

The corticobulbar pathway originates in the face/mouth portion of the motor cortex area and descends with CST to level of target nucleus, but splits off and does not _____. It gives bilateral input to V, VII, XII, nucleus ambiguus, and XI.

Answer 23

Decussate