Exam 3-

Motor hierarchy consists of the

Direct (pyramidal) pathway and Indirect (extrapyramidal) pathway

Direct (pyramidal) pathway consists of the ?

Brainstem and Spinal cord

Indirect (extrapyramidal) pathway consists of?

Basal ganglia, thalamus, cerebellum, pons

What is the Direct (pyramidal) pathway and its functions?

It is a pathway that originates at the motor cortex which then sends signals to the brainstem and spinal cord through UMN and LMN to innervate skeletal muscles to create an initiated voluntary movement and fine motor movements.

What is the Indirect (Extrapyramidal) pathway and its functions? If damaged what does it cause?

The indirect pyramidal pathway originates in the brainstem/spinal cord providing connections between various structures within/between the motor system and brainstem nuclei to refine and modulate movements initiated by the direct motor system

Its function is to modulate involuntary movements, muscle tone, balance, and posture, acting like a clutch for fluid movement

What are the motor pathways in the spinal cord?

• Lateral Corticospinal tract

• Anterior corticospinal tract

• Rubrospinal

• Tectospinal

• Vestibulospinal

What are the tracts included in the pyramidal system

1. Corticospinal tract: Orignates in the primary motor cortex with axons extending down to the spinal cord

2. Corticobulbar tract: UMNs originate in the face/head area of the motor cortex and travel to the brainstem synapsing into the motor cranial nerve nuclei

Where does the Corticospinal tract originate? What is its innervation pattern?

Originates in the primary motor cortex with its upper motor neurons extending down to synapse to the cell bodies of LMNs in spinal cord and its innervation pattern is primarily contralateral

What is the origination of the corticobulbar tract? What is its innervation pattern?

Upper motor neurons that originate in the face/head area of the motor cortex travel down to the brainstem where they synapse into the motor cranial nerve nuclei making its innervation pattern mostly bilateral.

What occurs at the level of the medulla in the corticospinal tract after axons extends from the motor cortex and bundles to form internal capsules

Lateral and anterior corticospinal tracts separate

What is the function, decussation, origination and termination of the lateral corticospinal tract?

voluntary motor control, specifically governing fine, dexterous movements of the distal limbs, such as finger and hand manipulation

1. After axons decussate at the level of the medulla

2. It then innervates the limbs and has the motor control of the arms/ legs, hands/feet

3. Axons extending from the left motor cortex would cross over to the right in the medulla

4. It will continue descending down the lateral portion of the spinal cord

5.  Then UMNs terminate and synapse onto the cell bodies of the LMNs in the ventral horn of the spinal cord

6. The axons of the LMNs then exit the spinal cord and make up the motor component of the spinal nerve

7. LMNs then end at the neuromuscular junction and synapse with muscles

What is the function, decussation, origination and termination of the anterior corticospinal tract?

Controlling voluntary movement of proximal muscles, particularly in the trunk and axial skeleton

1. Separates from lateral corticospinal tract in the caudal medulla

2. Then innervates the trunk for motor control of the trunk, axial/girdle muscles

3. It remains ipsilateral before synapsing on LMNs and provide bilateral innervation (fibers crossing over at each lvl synapsing on a LMN)

4. UMNs synapse on LMNs in the anterior and ventral spinal cord

5. Maps of somatotopy of the trunk portion in the motor strip homunculus to the body

What is the function, decussation, origination and output/input of the Rubrospinal tract?

It provides a fraction of controlled fine motor movements in the fingers and hands

1. Inputs come from the frontal cortex

2. Outputs to the LMNs to arms and legs

What is the function, decussation, origination and output/input of the Tectospinal tract?

The head turner track! It influences voluntary motor movement of the neck, trunk, and shoulders while also orienting eye and head to any external stimuli

1. Receives information from visual and auditory-vestibular systems (super/inferior colliculi)

2. Outputs to trunk

What is the function, decussation, origination and inputs of the Vestibulospinal tract balance?

It is voluntary control by balancing the head and help support an upright, and balanced posture

1. Lateral vestibulospinal provides inputs to extensor muscles in legs

2. Medial vestibulospinal provides inputs to neck and upper back

What is the function, decussation, origination and where it arises and output of the Reticulospinal tract?

Assists with upright posture and influences respiration, heart rate and blood circulation

1. Arises from the reticular formation

2. Outputs to extensor leg muscles and spinal reflexive circuits

3. Connections with autonomic nervous system to influence respiration, heart rate and blood circulation

What happens at the neuromuscular junction?

When a muscle contracts a synapse with the LMN and muscle fibers happens creating an electrical current that moves down to the lower motor neuron triggering a release of acetylcholine

Explain the reflex arc

An outside stimuli is detected (pain, heat) this stimuli transmits as an impulse to the spinal cord through a sensory nerve, which then connects with a motor neuron transmitting impulse to muscles or gland in response to the outside stimuli

UMN damage causes?

1. Weakness

2. Hyperactive reflexes

3. Increased tone

4. No atrophy

5. No fasciculations

6. Spasticity present= Meaning that their is increased tone and hyperactive reflexes making it to tight to respond

Speech impairments= Spastic dysarthria

LMN damage causes?

1. Weakness

2. Hypoactive reflexes= Barely almost No reflexes

3. Decreased tone= Example used in class is baby’s loose flabby skin

4. Atrophy present= wasting, shrinkage, loss of muscle tissue

5. Fasciculations present= Flickering like involuntary twitches of muscles

6. Flaccidity present= hypoactive and decreased tone

Speech impairments= Tongue atrophy and fasciculations

What happens at the neuromuscular junction?

A synapse between the LMN and muscle fibers where the release of acetylcholine happens creating a bind of muscle fibers and muscles itself to form a contraction

What is the function, decussation, origination and termination of the Corticobulbar tract?

Innervates CN nuclei- motor function ONLY

1. Cell bodies start at the UMN and are in the motor cortex

2. Those UMN move down in the brainstem synapse with cranial nerve nuclei

3. Most cranial nerve motor nuclei get bilateral innervation but may be asymmetrical

What is the difference in UMN and LMN lesions in the facial muscles?

UMN= Bilateral innervation of the upper face and Contralateral innervation of the lower face

LMN= remains ipsilateral

What does cerebral palsy impact? What damage is most common?

Can impact the pyramidal, extrapyramidal or both systems and damage most common is Spastic (most common), dyskinetic, ataxic and mixed

What does Amyotrophic Lateral Sclerosis (ALS) impact and how does it commence? What do SLPs do to treat?

ALS impacts UMN and LMN and can commence in the muscles of the limbs or the muscles of speech and swallowing. SLPs work to support speech that include augmented communication, and swallowing

What does Primary lateral sclerosis impact and cause?

Impacts UMN and it is a progressive neurogenerative diesease that causes muscle stiffness, weakness, and balance issues

What is Corticobasal degeneration? What is the cause and when is it present ?

It is a progressive neurodegenerative disease that causes atrophy of the cerebral cortex and basal ganglia causing severe motor, cognitive and speech/language dysfunction. Usually present between ages 50-70 first signs being clumsy limbs

The basal ganglia is part of what system?

The extrapyramidal system that focuses on refining and modulating volitional movement while also controlling involuntary movements

What is the basal ganglia’s function?

Its function is to refine voluntary movements while suppressing unwanted or competed. It is also involved in cognition and language processing

List the symptoms of basal ganglia damage and provide descriptions of each.

1. Involuntary movement

2. Slowness of movement

3. Difficulty initiating movement

4. Too little or much movement

5. Stiffness in muscles

6. Involuntary muscle contractions

What is the function of the Striatum (caudate + putamen)

It receives input from the brainstem, thalamus, and the cortex

What is the function of the globus pallidus internal and the substantia nigra pars reticulata?

They are major outputs from the basal ganglia by sending signals to the thalamus, brainstem, frontal lobes, and cerebellum.

What are the structures of the basal ganglia?

Straitum= caudate nucleus, putamen

Globus Pallidus= Internal and external

Subthalamic nucleus

Substantia nigra= consists of the pars compacta (dopamine) and Pars reticulata (GABA)

Thalamus

Substantia nigra pars reticulata

What is the difference between direct and indirect circuits?

The direct circuit facilitates signals and movement via the primary motor cortex while the indirect circuit inhibits or dampens signals which results in inhibition of movement to suppress unwanted movements

Describe the process direct circuits go through to facilitate or enhance motor signals

1. First the motor cortex sends excitatory signals to the striatum excite it

2. Then the excited striatum inhibits via GABA the globus pallidus internal and substantia nigra

3. Since globus pallidus internal and substantia nigra are inhibited now they cant inhibit the thalamus, to allow movement facilitation rather then inhibiting it

4. The thalamus sends excitatory signals to the motor cortex for movement facilitation.

What is the function of the indirect circuit?

1. Motor cortex sends excitatory signals to the striatum to excite it

2. The excited striatum then fires actions potentials that causes the release of an inhibitory neurotransmitter causing an inhibition of the globus pallidus external

3. The inhibited globus pallidues external can not inhibit the subthalamic nucleus

4. The subthalamic nucleus then excites the globus pallidus internal and the substantia nigra

5. Both the globus pallidus internal and the substantia nigra then inhibit the thalamus

6. Since thalamus is already inhibited it cannot send signals that excite the motor cortex for movement facilitation or enhancement of movement

7. Therefore the thalamus sends sends to the motor cortex that is dampened movement or inhibited

What are the types of involuntary movement or changes in movements caused by damage to the basal ganglia

1. Dyskinesia (includes sub categories: Chorea, athetosis, ballism, tremor)

2. Bradykinesia

3. Akinesia

4. Rigidity

5. Hypokinesia

6. Hyperkinesia

7. Dystonia

What is Dyskinesia and what are its subcategories?

Dyskinesia is an involuntary movement disorder and its subcategories are…

1. Chorea

2. Athetosis

3. Ballism

4. Tremor

What is chorea?

An involuntary rhythmic and quick movement disorder of the muscles and proximal extremities

What is Athetosis?

A slow twisting movement disorder of the upper extremities

What is Ballism?

Wild swinging movement disorder

What is a tremor?

Rhythmic small movement disorder

Define Bradykinesia

Slowness of movement

Define Akinesia

Difficulty initiating movement

Define Rigidity

Stiffnes in the muscles

Define Hypokinesia

Too little movement, usually small amplitude movements that happen quickly

Define hyperkinesia

Too much movement

Define Dystonia

Involuntary muscle contractions that cause repetitive, twisting, or abnormal postures

What is Parkinson’s disease?

A disease that results from degeneration of the substantia nigrea that reduces dopamine causing too much and not enough movement usually diagnosed by age 50 and up with a long life expectancy of 10-20 or more years.

What is Parkinson’s disease characterized by?

akinesia, bradykinesia, hypokinesia and “pill-rolling” tremor, masked face, reduced involuntary movements

What is huntington’s disease?

A rare genetic neurodegenerative disease characterized by involuntary “chorea” type movements, trouble with thinking, and planning, and mental health symptoms with a typical onset of 30-40 years and a life expectancy of 15-20 years after diagnosis.

What is the function of the cerebellum?

Targeting, smooth tracking and coordination; is applied to movements of the eyes, trunk, limbs, speech, swallowing

What are the parts of the cerebellum?

1. Vestibulocerebellum

2. Spinocerebellum

3. Cerebrocerebellum

4. Cerebellar Peduncles

What is the function of the Vestibulocerebellum and what does it contain?

It is connected to the vestibular and visual nuclei in the brainstem to control balance, head coordination, vestibular reflexes, and eye movements that contribute to initiation, planning, and timing of movements.

What does the Spinocerebellum consist of? what is its function?

The spinocerebellum consist of the vermis and intermediate regions. Its function is to receive somatosensory and propropceptive info from the spinal cord.

Function of the vermis?

Visual, auditory, vestibular, and somatosensory inputs to control posture, locomotion, and eye movements

Function of the intermediate regions?

Receive signals from distal limbs and digits. primarily concerned with the control of distal muscles—those responsible for precise movements of the hands and feet.

What does the cerebrocerebellum include? What is its function?

Includes lateral portions of the cerebellar hemispheres

1. Its function it to receive input from the cerebral cortex

2. Then sends output to the cerebral hemispheres (premotor, motor, and prefrontal areas.

3. These signals then influence movement planning, programming, timing, and execution.

This region also has control over the influences of cognitive processing of time (judging time) and influences working memory, social cognition, and language

The cerebellar peduncles contain 3 pairs of what? What is its function?

The cerebellar peduncles contain 3 pairs listed and called as follows;

1. Inferior peduncle

2. Middle peduncle

3. Superior cerebellar

It has both afferent and efferent fibers traveling to and from the cerebellum pass through one of the cerebellar peduncles.

Afferent= inferior and middle peduncles

Efferent= superior peduncle

Explain the circuits of the cerebellum

Circuits influence the sequence and timing of muscle coordination while also contributing to motor learning. The connections between the circuits provide comparisons about intended movements and actual movements.

Explain motor learning of the cerebellum

The cerebellum is active in motor learning and it begins with conscious control of skilled movement. After repeating the same skilled movement sensorimotor adjustment occurs requiring less conscious regulation.

Example: Your UNCG login, what happens after changing?

What happens to a patient who losses the ability to motor learn?

Patients with cerebellar pathologies often lose movement automaticity and require more conscious control of movement

What fibers does the cerebellum consist of?

1. Parallel fibers

2. Mossy fibers

3. Climbing Fibers

Function of the parallel fibers

They are granule cells in the most superficial layer

Function of the mossy fibers

Carryout learned movements (e.g., riding a bike, playing a piano)

Function of the climbing fibers

Provides inputs to Purkinje cells, either sensory from the body or from motor cortex and are important for motor learning

What cells does the cerebellum consist of?

1. Granule cells

2. Purkinje cells

What is Purkinje cells?

A broad but flat shape that is stacked like dominos and connected by parallel fibers. They also control cerebellar outputs and movement refinement.

What is granule cells?

receive inputs to the cerebellum

What are the types of cerebellum damage

1. Hypotonia

2. atasia

3. abasia

4. ataxia

5. action or intention tremor

6. nystagmus

What is hypotonia?

Reduced muscle tone

What is atasia?

Lack of coordination of limb and body postures across joints (difficulty walking)

What is abasia?

Inability to maintain upright body posture agaisnt force of gravity (difficulty standing)

What is ataxia?

Uncoordinated movements with Dysmetria (impaired targetting of movements) and dysdiadochokinesis (impaired alternating of movements)

What is action or intention tremor?

Tremor at the end of movements; corresponds with impaired smooth tracking of movements

What is nystagmus?

Irregular, beat like movement of the eyes (can be lateral or vertical)

The corticobulbar tract primarily innervates motor nuclei of cranial nerves such as ?

V (#5 Trigeminal), VII (#7 Facial), IX (#9 Glossopharyngeal), X (#10 Vagus), XI (#11 Accessory), and XII (#12 Hypoglossal)