Nueromotor pathways of speech

What are UMNs?

-descending motor fibers coursing through the CNS -that eventually make a synaptic connection to the motor neurons in the PNS (LMN)

Where do the UMNs originate?

cerebral hemisphere (gray matter of motor cortex)

Where do most of the UMNs decussate?

level of medulla

Why does the cerebral cortex largely control the opposite side of the body?

because they decussate to the other side

What functions within the UMN?

direct and indirect activation pathways

Broadly, where is the UMN?

CNS

Broadly, where is the LMN?

PNS

What does the UMN cell body descend in the form of?

axon

Do more UMN fibers follow a contralateral path or a ipsilateral path?

contralateral

Within the UMN what are the two pathways that cooperate with one another for motor control?

-Direct Activation Pathway -indirect Activation Pathway

What does the direct activation pathway transmit?

impulses of voluntary fine motor movements

What is the direct activation pathway also known as?

-direct motor pathway -pyramidal system

What does the indirect activation pathway provide?

automatic postural support needed by those fine movements

What does the indirect activation pathway transmit?

impulses that regulate reflexes and muscle tone

What is an example of an involuntary action that the indirect activation pathway would control?

balance

What does the direct activation pathway involve?

lateral motor systems

What are the lateral motor systems?

-lateral corticobulbar tract -corticospinal tract

What is the function of the direct activation pathway?

voluntary motor movement of contralateral limbs/speech muscles

Where does the corticobulbar tract originate from?

facial region of the motor homunculus within the primary motor cortex

With the corticobulbar tract axons extend to?

the brainstem

The corticobulbar tract can decussate at any structure depending on what?

the nerve it is going to

What do the corticobulbar tract axons do once they extend to the brainstem?

synapse with lower motor neuron cell bodies

Where are the LMN cell bodies housed?

within brainstem cranial nerve nuclei

What do the axons of the LMN help form?

cranial nerves

The corticobulbar tract transmits motor information to control what cranial nerves?

CN III - CNXII

The corticobulbar tract transmits motor information to control cranial nerves 3 - 12. Which cranial nerves control eye movement?

CN III -oculomotor CN IV -trochlear CN VI -abducens

The corticobulbar tract transmits motor information to control cranial nerves 3 - 12. Which cranial nerves control the cranial, facial, pharyngeal, and laryngeal muscles?

CN V -trigeminal CN VII -facial CN IX -glossopharyngeal CN X -vagus

The corticobulbar tract transmits motor information to control cranial nerves 3 - 12. Which cranial nerve control some superficial muscles of the back and neck?

CN XI -accessory

The corticobulbar tract transmits motor information to control cranial nerves 3 - 12. Which cranial nerve control intrinsic and extrinsic tongue muscles?

CN XII -hypoglossal

What can damage to the direction motor pathway lead to?

-spastic dysarthria -Unilateral UMN dysarthria

If there is damage to the corticobulbar tract or the corticospinal tract you will see __________

spasticity

CN VII (Facial) has ___________ innervation

bilateral

CN VII (facial) has bilateral innervation. What does that mean?

each side of CN VII gets motor information from both hemispheres

What does CN VII (Facial) provide bilateral innervation to?

upper half of the face (above eyebrows)

What does CVII (facial) provide unilateral innervation to?

lower half of the face (below eyebrows)

UMN lesion to CN VII (Facial), Where will you see the damage in the face?

-due to bilateral innervation of upper face, it retains some function -while lower face that receives unilateral innervation becomes nonfunctional

CN VII -Facial If there is a lesion to the LMN, Where will you see the damage in the face?

The whole ipsilateral side of the face (top and bottom)

For CN VII (facial), at what point is considered the transition from UMN to LMN?

CN VII nucleus

What course does the cortico-spinal tract take?

-Starts at the motor cortex -crosses over at the pyramids within the medulla -meets cell body of the LMN

The cortico-spinal tract starts at the motor cortex then crosses over at the pyramids within the medulla then meets the cell body of the LMN. What function does it then do?

Innervates all the body muscles

What is the indirect activation pathway also known as?

-indirect motor pathway -extrapyramidal pathway

What does the indirect motor system include?

•Rubrospinal •Vestibulospinal •Reticulospinal •Tectospinal •Basal ganglia •cerebellar circuits

What are the medial motor systems?

•Rubrospinal •Vestibulospinal •Reticulospinal •Tectospinal

What is the indirect activation pathway?

Structures involved in motor functions that lie outside the pyramidal system and are beyond voluntary control of movements.

What does the extrapyramidal system control?

-automatic, repetitive, emotional movements -posture and tone.

What is responsible for maintaining involuntary movements?

indirect activation pathway

In the indirect motor pathway, which medial motor systems are contralateral tracts?

-Rubrospinal -Tectospinal

What is the origin of the rubrospinal tract?

Red nucleus (in the midbrain)

What is the rubrospinal tract responsible for?

fine motor movements

What is the origin of the tectospinal tract?

Superior colliculus (in the midbrain)

What is the tectospinal tract responsible for?

coordination of head and eyes

In the indirect motor pathway, which medial motor systems are unilateral tracts?

-Vestibulospinal -Reticulospinal

What is the origin of the vestibulospinal tract?

vestibular nucleus (in the pons)

What is the vestibulospinal tract responsible for?

responsible for balance

What is the origin of the reticulospinal tract?

reticular formation (in the medulla)

What is the reticulospinal tract responsible for?

responsible for tone of the body

What are the motor control circuits?

-basal ganglia -cerebellum

What does the basal ganglia do? especially what?

-Regulates motor function -especially tone and posture

Why is tone and posture important?

so we have smooth, precise motor movements

If there is damage to the basal ganglia what will that result in?

dyskinesia

What are dyskinesias?

movement disorders

What does the cerebellum do?

Coordinates muscle movements so that they are skilled and sequential ex. riding a bite

What does damage to the extrapyramidal system lead to?

-hyperkinetic dysarthria or -hypokinetic dysarthria

What is hyperkinetic dysarthria commonly seen in?

Huntington's disease

What is hypokinetic dysarthria commonly seen in?

Parkinson's disease

What is the final common pathway (FCP)?

last leg of a motor signal's journey

What is the final common pathway apart of?

Part of the LMN

What does the final common pathway involve?

•Cranial nerves in the case of speech •Spinal Nerves in case of movements

If there is damage to the final common pathway, what will that lead to?

flaccid dysarthria

What cranial nerves can be affected when there is LMN damage?

•CN V trigeminal nerve •CN VII facial nerve •CN IX glossopharyngeal nerve •CN X vagus nerve •CN XI accessory nerve •CN XII hypoglossal nerve

What does damage to multiple motor pathways lead to?

Mixed dysarthria

What is mixed dysarthria common in?

ALS

If there is damage to the basal ganglia, what type dysarthria will occur?

hypokinetic dysarthria

How does the stretch reflex work?

1. a body part moves passively

2. sensory receptors in your muscle tell you spinal cord and brainstem it's moving

3. The spinal cord pulls the extremity back to stop the movement since the muscles wasn't told to move

What kind of reflex is the stretch reflex?

a spinal cord reflex

What does it mean when you say a body part moved passively?

your brain didn't send out a message to make it move

When does the Indirect activation pathway suppress the stretch reflex?

-volitionally movement -at rest

What happens to the stretch reflex if the UMN is damaged?

-indirect activation pathway no longer suppresses the stretch reflex during volitional movement or rest -spinal cord constantly sends message pulling on your muscles -causes spasticity

Where do reflexes originate?

below the level of awareness

What does the brainstem monitor?

efferent motor plans as they pass through UMNs and LMNs

What should the afferent nerve fibers from muscles confirm?

efferent motor plans are being executed properly

What happens if the sensory information doesn't match motor plans?

-the spinal cord takes action without waiting for input from cortex -Spinal cord sends signal to oppose passive, non-volitional movement

What kind of state does the stretch reflex exist in?

subdued/inhibited state where the cortex is keeping the spinal cord from over applying it

Muscle tone regulatory signals and stretch reflex inhibition signals from extrapyramidal system coming from where?

cortex along the indirect activation pathway

Muscle tone regulatory signals and stretch reflex inhibition signals from extrapyramidal system coming from cortex along the indirect activation pathway. Why does this happen?

keep your muscles appropriately toned and keeps the stretch reflex from being overactive

Pathological Stretch Reflex If there is an UMN and the direct activation pathway is compromised, what will we see?

weakness of volitional movement

If the direct activation pathway or the indirect activation pathway is damaged, then signs won't reach the _____ ______

spinal cord

Pathological Stretch Reflex If there is an UMN and the indirect activation pathway is compromised, what will we see?

no signals to maintain appropriate: -muscle tone -reflex regulation -posture (hypertonia)

Pathological Stretch Reflex If there is damage to the UMN and there is a hyperactive stretch reflex, what will we see?

opposition to all muscle movement (resistance to movement)

If there is a pathological stretch reflex and lesion to the UMN, over all what are we going to see?

spasticity (hypertonia + resistance to movement + weakness)

Pathological Stretch Reflex If there is a LMN lesion and there is no direct activation pathway signal, What will we see?

weakness

Pathological Stretch Reflex If there is a LMN lesion and there is no indirect activation pathway signal, What will we see?

hypotonia

Pathological Stretch Reflex If there is damage to the LMN and there is a compromised reflex arc, what will you see?

hyporeflexia

If there is a Pathological Stretch Reflex and a LMN lesion, What will we see over all?

Result: flaccidity (weakness + hypotonia + hyporeflexia)

Both the UMN and the LMN have _______ ________

growth factors

What are growth factors?

gives the muscles mass and power

Does the UMN or LMN have more growth factors?

LMN

What does an UMN lesion result in?

•Increased muscle tone (hypertonia) •Hyperreflexia •Spastic paralysis

What is the UMN responsible for?

initiation/inhibition

If there is an UMN damage / is affected

initiation/inhibition