Motor System II EXAM 2

medial and inferior vestibular nuclei

where does the medial VST originate

the medial VST

what part of the VST Originates in the medial and inferior vestibular nuclei

descends bilaterally

How does the medial VST descend?

the medial VST

which descending pathway of the vestibulospinal tract descends bilaterally

lateral vestibular nuclei

where does the lateral VST originate

descends ipsilaterally

how does the lateral VST descend

the lateral VST

which descending pathway of the vestibulospinal tract descends ipsilaterally

upper cord as part of medial longitudinal fasciculus (MLF)

where does the medial VST descend bilaterally to

medial laminae VII/VIII alpha motoneurons & interneurons

what is the target or termination site of the medial VST

the medial VST

what pathway of the VST descends bilaterally and terminates at the medial laminae VII/VIII alpha motoneurons & interneurons

- control of neck musculature

- head-on-trunk stabilization

what is the function of the medial VST

the medial VST

which pathway of the VST is responsible for the control of neck musculature and head-on-trunk stabilization

head-on-trunk stabilization reflex

what reflex is the medial VST responsible for

Descend ipsilateral to all cord in anterior funiculus

where does the lateral VST descend ipsilaterally to

medial laminae VII/VIII alpha neuron & interneurons

what is the target or termination site of the lateral VST

the lateral VST

what pathway of the VST descends ipsilaterally and terminates at the medial laminae VII/VIII alpha neuron & interneurons

paravertebral and proximal limb extensor

posture and balance

flexor

Lateral VST

• Mainly excites motoneurons to _____ and _____ muscles = antigravity mm = control of _____ and _____

• some inhibits _____ muscles

the lateral VST

what pathway of the VST is responsible for the excitation of paravertebral and proximal limb extensors for control of posture and balance

the lateral VST

which pathway of the VST can be found throughout the entire spinal cord

the medial VST

which pathway of the VST can be found throughout the upper spinal cord

1. Vestibular apparatus - excitatory

2. Fastigial nu - excitatory

3. Purkinje cells - inhibitory

what are the 3 inputs to the vestibulospinal tract (name if they’re excitatory or inhibitory)

the vestibular apparatus and fastigial nucleus

what inputs to the vestibulospinal tract are excitatory

Purkinje cells

what inputs to the vestibulospinal tract are inhibitory

the cortex

what part of the CNS has no direct input to the vestibular nucleus

any signal from the cortex has to pass through the thalamus first

why does the cortex have no direct input to the vestibular nucleus

- Coordination of head and body in space (vestibular input)

- Maintenance of body and limb posture (cerebellar/vestibular input)

what are the 2 main functions of the Vestibulospinal Tracts

pontine (oral and caudal) reticular nuclei

what is the origin of the medial reticulospinal tract

medial reticulospinal tract

what tract of the reticulospinal tract originates at the pontine (oral and caudal) reticular nuclei

ipsilateral

anterior funiculus

• (a few may cross)

The descending pathway of the medial reticulospinal tract tends to be ________ in the _______

medial reticulospinal tract

what descending reticular pathway originates at the pontine (oral and caudal) reticular nuclei and descends ipsilaterally in the anterior funiculus

medullary (gigantocellular) reticular nuclei

what is the origin of the lateral reticulospinal tract

lateral reticulospinal tract

what pathway of the reticulospinal tract originates at the medullary (gigantocellular) reticular nuclei

bilateral with ipsilateral predominance in anterior funiculus (but a few decussate)

what is the descending pathway of the lateral reticulospinal tract

lateral reticulospinal tract

what descending reticular pathway originates in the medullary (gigantocellular) reticular nuclei and descends bilateral with ipsilateral predominance in anterior funiculus (but a few decussate)

anteromedial laminae VII/VIII interneurons

what is the target site for the descending reticulospinal tract

to regulate motor activity by controlling posture, balance, and locomotion in both axial and appendicular skeletal muscle

what is the function of the descending reticulospinal tract that terminates at the anteromedial laminae VII/VIII interneurons

bilateral

somatosensory

reticulospinal tracts activated by ______ descending cortical projections (corticoreticular) and ascending ______ (spinoreticular/pain fibers of ALS)

alpha motoneurons

what is influenced heavily by the reticulospinal tract to maintain posture and modulate muscle tone

Medial (pontine) RST

which reticulospinal pathway has excitatory effects to extensor and axial muscles

excitatory effects to extensors and axial muscles

what function is the Medial (pontine) RST responsible for

Lateral (medullary) RST

which reticulospinal pathway has inhibitory effects to extensor muscles of the neck and back

inhibitory effects to extensors, neck and back mm

what is the function of the Lateral (medullary) RST

when you want more posture and tone, cortex fires on reticular nuclei

when might the reticulospinal tract activate

diffuse activation of multiple inhibitory and excitatory neurons to muscles

What does a single pulse of stimulation to the reticulospinal tract result in and how does muscle respond

Motor evoked potential for normal motor cortex stimulation of the corticospinal

what is the outcome of a single pulse of stimulation to the corticospinal tract

Corticospinal stimulation

what type of stimulation

Reticulospinal stimulation

what type of stimulation

NE and serotonin

what 2 chemical messengers/neurotransmitters can increase the sensitivity of the reticulospinal tract

NE and serotonin increase the sensitivity of motor neurons in the reticulospinal tract

NE and serotonin have what type of effect on the reticulospinal tract

Activated by ipsilateral cortex (corticorubral) and contralateral cerebellum (cerebellorubral)

what activates the rubrospinal tract

the rubrospinal tract

what descending motor pathway is activated by ipsilateral cortex (corticorubral) and contralateral cerebellum (cerebellorubral)

Flexor motoneurons; supplement to corticospinal system

what are the cortical inputs to the rubrospinal tract

rubrospinal tract

what descending motor pathway has inputs from cortical influence of flexor motoneurons, and has supplemental input to corticospinal system

red nucleus

_________ receives many inputs from cerebellum, a circuitry for modifying motor performance or acquiring a new movement pattern

rubrospinal tract

what descending motor pathways receives inputs from the red nucleus and has a circuitry for modifying motor performance or acquiring new movement patterns stemming from the cerebellum

Excitation of UE flexors

what muscle action might the excitation of the rubrospinal tract result in

they’re "released" from their descending cortical control

what happens to spinal motor neurons during Decerebrate and Decorticate Lesions

RST and VST activity contribute to the spasticity or tonic extension of arms and legs seen in patients with damage to corticospinal tracts (CST) and RuST

If spinal motor neurons are "released" from their descending cortical control from Decerebrate and Decorticate Lesions, how does the reticulospinal and vestibulospinal tracts contribute to UMN signs

decerebrate rigidity

a severe neurological posture caused by damage to the brain stem (usually the midbrain) resulting in no input from the CST and RuST thus presenting with tonic extension of arms and legs

descending influences on cord motoneurons (CST,RuST) removed

what descending motor influences are lost during a decerebrate lesion

reticulospinal and vestibulospinal tracts

what 2 descending motor tracts are still intact with a decerebrate lesion

without cortical modulation from the CST and RuST, the reticulospinal and vestibulospinal tracts are constantly active having excitatory effects on extensor muscles for posture and balance

why do patients with a decerebrate lesion present with tonic extension of arms and legs

decorticate rigidity

an involuntary, abnormal reflex pose indicating severe damage to the brain's cerebral hemispheres, inner capsule, or thalamus. It is characterized by rigid, bent arms drawn toward the chest ("core"), clenched fists, and straight, internally rotated

removed cortical input to the Red nucleus (transaction of rostral to superior colliculus, brain injury or tumor)

decorticate rigidity results in:

the corticospinal tract

what descending motor pathway is cut off due to decorticate rigidity

- rubrospinal tract

- vestibulospinal tract

- reticulospinal tract

what 3 descending motor pathways are still intact with decorticate rigidity

red nucleus

what major brainstem structure of the rubrospinal tract is responsible for excitation of proximal UE flexors and is overactive in a decorticate lesion

increased flexor tone due to intact rubrospinal system that still activates proximal flexors of UE.

what happens to motor outputs as a result of loss of the upper corticospinal tract due to decorticate rigidity

Transtentorial herniation

what can cause decorticate posturing to progress to decerebrate posturing

Decerebrate posturing

what is this called?

decorticate posturing

what is this called?

layer V of cerebral cortex subserving motor function (topographically organized with large pyramidal neurons)

what is the origins of the corticospinal system

corona radiata and internal capsule down through the brainstem

through what pathways does cortical communication occur between cortical areas for motor activity

- 80-90% decussate in caudal medulla; descend in lateral funiculus

- 10-20% uncrossed, ipsilateral descent in anterior funiculus

once the descending motor cortical pathways of the corticospinal tract pass through the corona radiata and internal capsule down through the brainstem… what happens to the descending motor pathways

descend in lateral funiculus

through which funiculus do the corticospinal fibers that decussate in the caudal medulla descend

ipsilateral descent in anterior funiculus

through which funiculus do the corticospinal fibers that do not decussate descend

- interneurons in laminae IV-VII

- alpha motoneuron in lamina IX to distal flexor muscles

what are the 2 termination sites for the corticospinal tract

the cervical enlargement

in what part of the cervical spine does the corticospinal tract terminate

the lumbar enlargement

in what part of the lumbosacral spine does the corticospinal tract terminate

feet → legs → trunk → arms → hands → face

(medial to lateral) what is the topographical organization of the primary motor cortex (M1)

true

true or false: Deficits post-stroke match arterial & topographical arrangements

base of brainstem in medulla

where does decussation of the upper corticospinal tract occur

1. Anterior - anterior funiculus - ipsilateral descent

2. Lateral - lateral funiculus - contralateral descent

what are the 2 parts of the corticospinal tract on the spinal cord

anterior funiculus

within what funiculus does the anterior corticospinal tract descend

lateral funiculus

within what funiculus does the lateral corticospinal tract descend

ipsilateral

is the anterior corticospinal tract an ipsilateral or contralateral pathway

contralateral

is the lateral corticospinal tract an ipsilateral or contralateral pathway

anterior corticospinal tract

which pathway of the corticospinal tract is an ipsilateral pathway

lateral corticospinal tract

which pathway of the corticospinal tract is a contralateral pathway

Corticonuclear (corticobulbar) system

a two-neuron white matter pathway that carries motor signals from the cerebral cortex to cranial nerve nuclei in the brainstem.

voluntary control of muscles of the face, head, and neck, including chewing, facial expression, swallowing, and speech.

what is the function of the Corticonuclear (corticobulbar) system

layer V of cerebral cortex subserving motor function for the face (face motor cortex)

what is the origin of the Corticonuclear (corticobulbar) system

Corticonuclear (corticobulbar) system

what corticospinal pathway originates in layer V of cerebral cortex subserving motor function for the face (face motor cortex)

The genu of internal capsule and descend into the pons and medulla (located medial to the corticospinal tract)

what pathway does the Corticonuclear (corticobulbar) system take from layer V of cerebral cortex subserving motor function for the face to the motor nuclei or through nearby reticular formation interneurons to nuclei of  V, VII, IX and X (both via nu ambiguus), XI and XII (i.e. motor nuclei)

Corticonuclear (corticobulbar) system

what corticospinal pathway passes Through the genu of internal capsule and descend into the pons and medulla (located medial to the corticospinal tract) to the motor nuclei responsible for facial movement

motor nuclei responsible for facial movement

what is the target for the Corticonuclear (corticobulbar) system

nuclei of V, VII, IX and X (both via nu ambiguus), XI and XII (i.e. motor nuclei)

what motor nuclei are responsible for facial and head movements and are the target nuclei of the Corticonuclear (corticobulbar) system

reticular formation interneurons

if the Corticonuclear (corticobulbar) system takes the indirect rout through the genu of internal capsule and descend into the pons and medulla (located medial to the corticospinal tract)…..what structure does it pass through before reaching the nuclei of  V, VII, IX and X (both via nu ambiguus), XI and XII (i.e. motor nuclei)

- trigeminal nucleus

- facial nucleus

- nucleus ambiguous

- hypoglossal nucleus

- spinal accessory nucleus

what motor nuclei are part of the corticobulbar tract