Motor Processing Pathways

Question 1

Motor System:

Answer 1

Controls all voluntary, involuntary, and reflexive movements
Often it is described as a hierarchical system
less sophisticated as it descends down

Motor system is not organized in the three neuron system of the sensory system (Upper Motor Neurons)

1. PreMotor Cortex highest level of the system
2. Basal Ganglia Next
3. Cerebellum (regulates balance/coordination
4. Spinal Cord (sends the impulses)

Question 2

Motor Speech Progammer

Answer 2

The subconscious planning and programming of speech movements involve both cognitive and linguistic goals which rely heavily on the prefontal area, premotor area, the Broca’s area and PMC.

Remember Broca’s area contributes to both simultaneous and sequential movements

Question 3

UMN vs LMN

Answer 3

Upper motor neuron = neurons that arise in the cortex and will descend to the brainstem (medulla) or on the spinal cord tract

Lower motor neuron = arise in the ventral horn of the spinal cord to send motor info to the peripheral nerves
LMN Lesion Characteristics:
flaccidity –

Motor units are LMN (all outside of the CNS):

1. single anterior/ventral horn or cranial nerve neuron
2. its peripheral axon and its branches
3. myoneural (neuromuscular) junction
4. muscle fibers

Once an impulse leaves the ventral (ant) horn of the spinal cord, it changes from UMN to LMN

Spastic or flaccid vocal folds, pharyngeal, tongue, muscles of swallowing/mastication

Babinski is indiciative of corticospinal issue – Babinski is an abnormal reflex (healthy response = no flexing of the big toe)

Question 4

Primary Motor Cortex

Answer 4

The PMC is on the post central gyrus (anterior to the central sulcus)

The PMC contains large Betz cells which are unique to this area & very important in voluntary motor movements

The face, speech muscles are represented in the lower 1/3 of the PMC near the lateral sulcus

There are descending motor tracts running from:
PMC, premotor area, and PSC
Top 2/3 of PMC = body mvmnts neck down; Lower 1/3 = face

Sensorymotor area = combo of premotor, PMC, PSC; contains Betz cells

Question 5

Pyramidal System:

Answer 5

• Lateral corticospinal tract
• Anterior corticospinal tract

-corticonuclear/corticobulbar (deals with cranial nerves)

Pyramidal delas with most motor mvments

Question 6

Extra-Pyramidal System:

Answer 6

• Tectospinal tract
• Rubrospinal tract
• Vestibulospinal tract
• Reticulospinal/Reticular Descending tract

Question 7

Pyramidal Tracts

Answer 7

Pyramidal tracts are sometimes called direct activation pathways; primary pathway for voluntary movement (PMC: specialized muscle area)

1. Corticospinal Pathways
   BODY movments
2. Corticonuclear Pathway (used to be called corticobulbar)
   Cranial nerves

Question 8

Corona Radiate:

Answer 8

• radiation of myelinated, projection fibers that carries information (sensory & motor) from the cerebral cortex to the brainstem
• white matter and subcortical tissue (projection fibers)

help connect info from body to brain/brain to body; does both M and S, but predominantly M; I from body to this area; fibers reach premotor, PMC, PSC

Question 9

Internal Capsule:

Answer 9

-bundle of myelinated, projection fibers travel past the basal ganglia for both sensory/motor tracts

-white matter and (deep) subcortical tissue
in the middle of the basal ganglia; where all the fibers start to bundle, collect; deep subcortical structure; M and S

Question 10

Corticonuclear tract (AKA Corticobulbar)

Answer 10

Similar to the fibers of the corticospinal tract in that it deals with fine motor movement.

However, they exclusively control movement for muscles of head, mouth and face via _____________.

These fibers arise from the lower 1/3 of PMC and travel through the internal capsule to the Pes pendunculi of midbrain and will eventually cross the midline somewhere in the brainstem.

Once it crosses over at brainstem, it will synapse with the appropriate cranial nerve for motor innervation.

Question 11

The extrapyramidal system

Answer 11

The extrapyramidal system has a important role for speech production/disorders and may be called the indirect activation pathway.

Function: primary function is to regulate reflexes and maintain posture and tone
(essentially, subconscious control of the integration of many muscles)

The major players of the extrapyramidal system: Basal ganglia and its parts

Question 12

Rubrospinal

Answer 12

-motor commands for muscle tone for limb extension and supporting body against gravity

Question 13

Upper Motor Neuron Syndrome:

Answer 13

lesions to the neurons in the motor cortex and descending axons (before the synapse with cranial nerves/spinal nerves)

UMN Lesion Characteristics:
spacistiy – contracted or excessively tensed muscles
Hyperactive reflexive responses

Question 14

Lower Motor Neuron Syndrome:

Answer 14

lesions to neurons in the spinal nerves (ventral horn) or cranial nerve tracts in the

Clinical characteristics: Paresis and paralysis of muscles; decreased muscle tone; atrophy; absent reflexes

May affect speech and swallowing muscles – impulse from brain cannot reach muscles; muscles atrophy
May also affect diaphragm, respiratory system = too loose, too weak to support speech

LMN may have worse prognosis; muscles continue to decline –don’t use it, lose it -; higher risk of aspiration, swallowing d/o

Question 15

Proprioception

Answer 15

the sense of body position

Question 16

Kinesthesia

Answer 16

the sense of body movement

Question 17

Betz cells

Answer 17

(also known as pyramidal cells of Betz) are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex.

Question 18

Motor planning

Answer 18

the ability to process information various sensory systems including tactile, visual, proprioceptive (body awareness), auditory and vestibular and use that information to plan and execute motor skills.

Question 19

Tectospinal tract

Answer 19

coordinates head and eye movements

Question 20

vestibulospinal

Answer 20

maintain equilibratory reflexes from the input of the vestibular apparatus. They will reach the axial muscles, i.e. intercostal and back muscles, as well as the extensors of the limbs.

Question 21

reticulospinal

Answer 21

motor neurons supplying the trunk and proximal limb muscles.