NIHD Week 4: Motor Systems & Movement Control: (Frank), Upper vs. Lower Motor Neurons; Localization of Weakness & Sensory Syndromes (First Aid 469, 470, 495)

____________ Peduncle (Brachium Pontis) - is an afferent pathway to the Cerebellum. Most of the cell bodies that give rise to the Middle Peduncle arise from the Pontine Nuclei at the base of the ***________________ Pons. Inferior Peduncle (Restiform Body) - is both and afferent AND efferent pathway to and from the ____________. It is the smallest, but most complex, of the cerebellar peduncles. Afferent pathways in the Inferior Peduncle include axons from the Vestibular Nuclei, Spinal Cord, and several regions of the Brainstem Tegmentum. Efferent pathways project from the Flocculo-nodular lobe to the Vestibular nuclei and Reticular Formation. Superior Peduncle (Brachium Conjunctivum) - is almost entirely an _____________ pathway from the Cerebellum. Efferents in the Superior Peduncle arise from the deep cerebellar nuclei (Fasitgial, Interposed, and Dentate) and project to the motor nuclei of the Thalamus (Ventral Lateral, Ventral Medial , and Ventral Intermedius nuclei) as well as to the Superior Colliculus.

*Middle* Peduncle (Brachium Pontis) - is an afferent pathway to the Cerebellum. Most of the cell bodies that give rise to the Middle Peduncle arise from the Pontine Nuclei at the base of the *CONTRALATERAL* Pons. Inferior Peduncle (Restiform Body) - is both and afferent AND efferent pathway to and from the *Cerebellum*. It is the smallest, but most complex, of the cerebellar peduncles. Afferent pathways in the Inferior Peduncle include axons from the Vestibular Nuclei, Spinal Cord, and several regions of the Brainstem Tegmentum. Efferent pathways project from the Flocculo-nodular lobe to the Vestibular nuclei and Reticular Formation. Superior Peduncle (Brachium Conjunctivum) - is almost entirely an *efferent* pathway from the Cerebellum. Efferents in the Superior Peduncle arise from the deep cerebellar nuclei (Fasitgial, Interposed, and Dentate) and project to the motor nuclei of the Thalamus (Ventral Lateral, Ventral Medial , and Ventral Intermedius nuclei) as well as to the Superior Colliculus.

Cerebellar Cortex - Hemispheres: 1. Cerebrocerebellum - occupies most of the __________ cerebellar hemispheres and receives input indirectly from many areas of the cerebral cortex. - motor __________ 2) Spinocerebellum - occupies the median and paramedian zones of the cerebellar hemispheres and is the ONLY part that receives input __________ from the spinal cord. - motor _____________ 3) Vestibulocerebellum (oldest part of the cerebellum) - comprises the caudal-inferior Flocculo-nodular lobes and receives input from the Vestibular nuclei in the brainstem - balance and _____ movement

1. Cerebrocerebellum - occupies most of the *lateral* cerebellar hemispheres and receives input indirectly from many areas of the cerebral cortex. - motor *planning* 2) Spinocerebellum - occupies the median and paramedian zones of the cerebellar hemispheres and is the ONLY part that receives input *DIRECTLY* from the spinal cord. - motor *execution* 3) Vestibulocerebellum (oldest part of the cerebellum) - comprises the caudal-inferior Flocculo-nodular lobes and receives input from the Vestibular nuclei in the brainstem - balance and *eye* movement

4 Neural Centers Responsible for Movement: 1. Local circuitry within the gray matter of spinal cord and tegmentum of ________ _______ The lower motor neurons convey commands of movement (whether reflexive or voluntary) through the lower motor neurons known as "the final common pathway". 2) _________ motor neurons from cortex and brainstem that synapse with local circuit neurons or lower motor neurons directly at the spinal cord level 3) The ____________ - synapsing on upper motor neurons as a servomechanism - detecting and attenuating the difference or "motor error" between intended movement and the movement actually performed 4) The ________ __________ that suppress unwanted movements and prepare upper motor neuron circuits for the initiation of movements

4 Neural Centers Responsible for Movement: 1. Local circuitry within the gray matter of spinal cord and tegmentum of *brain stem*. The lower motor neurons convey commands of movement (whether reflexive or voluntary) through the lower motor neurons known as "the final common pathway". 2) *Upper* motor neurons from cortex and brainstem that synapse with local circuit neurons or lower motor neurons directly at the spinal cord level 3) The *cerebellum* - synapsing on upper motor neurons as a servomechanism - detecting and attenuating the difference or "motor error" between intended movement and the movement actually performed 4) The *basal ganglia* that suppress unwanted movements and prepare upper motor neuron circuits for the initiation of movements

Caudate Nucleus Putamen Globus Pallidus Internus Externus Subthalamic Nucleus Substantia Nigra Pars Compacta Pars Reticulata ___________ = Caudate Nucleus + Putamen Lentiform Nucleus = Putamen and Globus Pallidus

Caudate Nucleus Putamen Globus Pallidus Internus Externus Subthalamic Nucleus Substantia Nigra Pars Compacta Pars Reticulata *Striatum* = Caudate Nucleus + Putamen Lentiform Nucleus = Putamen and Globus Pallidus

Summary of _________________: - Receives input from cortex to plan and initiate movements - Receives input from sensory system to monitor the course of the movements - Projects to motor cortex via the Thalamus (VL) and many major brainstem nuclei and to the spinal cord - Allows a "real time" comparison of intended versus actual movements - Allows for storage of __________ movements known as "muscle memory" - Disorder of Cerebellum are ***********ipsilateral to the lesion and cause severe ataxia

Cerebellum - Receives input from cortex to plan and initiate movements - Receives input from sensory system to monitor the course of the movements - Projects to motor cortex via the Thalamus (VL) and many major brainstem nuclei and to the spinal cord - Allows a "real time" comparison of intended versus actual movements - Allows for storage of *learned* movements known as "muscle memory" - Disorder of Cerebellum are ipsilateral to the lesion and cause severe *ataxia*

Corticospinal Tract Origination: 55% - _________ ________ (Brodman's area ___) - Betz cells (layer V of Brodman's area 4): only about 5% - Brodman's area ___ (movement planning/initiation) 35% - Post central gyrus (Brodman's areas 3, 1, 2) 10% from other frontal and parietal areas

Corticospinal Tract Origination: 55% - *Precentral gyrus* (Brodman's area *4*) - Betz cells (layer V of Brodman's area 4): only about 5% - Brodman's area *6* (movement planning/initiation) 35% - Post central gyrus (Brodman's areas 3, 1, 2) 10% from other frontal and parietal areas

Corticospinal Tract Decussation: - Corticospinal fibers decussate in the lower ventral _________ (pyramidal decussation) - Most fibers continue in the cord as the _______ corticospinal tract - A small percentage descend as the anterior corticospinal tract

Corticospinal Tract Decussation: - Corticospinal fibers decussate in the lower ventral *medulla* - Most fibers continue in the cord as the *lateral* corticospinal tract - A small percentage descend as the anterior corticospinal tract

Corticospinal Tract Internal Capsule: Corticospinal tract travels through the anterior portion of the posterior limb of the internal capsule Corticobulbar (corticonuclear) tract travels through the ____ of the internal capsule

Corticospinal Tract Internal Capsule: Corticospinal tract travels through the anterior portion of the posterior limb of the internal capsule Corticobulbar (corticonuclear) tract travels through the *genu* of the internal capsule

Corticospinal Tract Midbrain: - Corticospinal tract travels in the crus (most ventral part of the midbrain) - CN _____ (oculomotor nerve) exits the midbrain in close proximity to the corticospinal fibers, explaining one of the vascular syndromes, Weber syndrome (stroke in this region causes ipsolateral third nerve palsy with contralateral hemiparesis)

Corticospinal Tract Midbrain: - Corticospinal tract travels in the crus (most ventral part of the midbrain) - CN *III* (oculomotor nerve) exits the midbrain in close proximity to the corticospinal fibers, explaining one of the vascular syndromes, Weber syndrome (stroke in this region causes ipsolateral third nerve palsy with contralateral hemiparesis)

Dopaminergic output from the Substantia Nigra Pars ______________ is EXCITATORY to the Direct Pathway and INHIBITORY to the Indirect Pathway to the Striatum (Putamen). It stimulates D1 receptors in the Putamen in the direct pathway and will excite and cause the output of the circuit will be excitatory and the Thalamus will excite the cortex to increase motor output! It also stimulates D2 receptors in the Putamen in the indirect pathway will be excited and the Thalamic output will be inhibited and, therefore, there will be less motor output stimulated. Acetylcholine is released by small inhibitory neurons in the Putamen that counteracts the effects of Dopamine by blocking the D1 and D2 receptors in Putamen. ________________ will inhibit the direct pathway and allow the indirect pathway to function and counteract the effects of Dopamine. Therefore, for Parkinson's Disease, you can treat with Dompamine or with Acetylcholine esterases (anti-cholinergics). Remember that output from the Cortex releases Glutamate and is always EXCITATORY. Also remember that the output from the Striatum (Caudate and Putamen) releases ________ and is always _______________

Dopaminergic output from the Substantia Nigra Pars *Compacta* is EXCITATORY to the Direct Pathway and INHIBITORY to the Indirect Pathway to the Striatum (Putamen). It stimulates D1 receptors in the Putamen in the direct pathway and will excite and cause the output of the circuit will be excitatory and the Thalamus will excite the cortex to increase motor output! It also stimulates D2 receptors in the Putamen in the indirect pathway will be excited and the Thalamic output will be inhibited and, therefore, there will be less motor output stimulated. Acetylcholine is released by small inhibitory neurons in the Putamen that counteracts the effects of Dopamine by blocking the D1 and D2 receptors in Putamen. *Acetylcholine* will inhibit the direct pathway and allow the indirect pathway to function and counteract the effects of Dopamine. Therefore, for Parkinson's Disease, you can treat with Dompamine or with Acetylcholine esterases (anti-cholinergics). Remember that output from the Cortex releases Glutamate and is always EXCITATORY. Also remember that the output from the Striatum (Caudate and Putamen) releases *GABA* and is always *INHIBITORY*.

First Aid pg. 469 . https://www.youtube.com/watch?v=ReV0mBblXTc . Cerebellum: Modulates (controls) ______________; aids in coordination and balance. - Input: Contralateral ________ via middle cerebellar peduncle. Ipsilateral proprioceptive information via inferior cerebellar peduncle from spinal cord. - Output: The only output of cerebellar cortex = Purk*in*je cells (always *in*hibitory) deep nuclei of cerebellum contralateral cortex via superior cerebellar peduncle. Deep nuclei (lateral to medial)—*D*entate, *E*mboliform, *G*lobose, *F*astigial ("*D*on't *E*at *G*reasy *F*oods"). - *L*ateral lesions—affect voluntary movement of extremities (*L*imbs); when injured, propensity to fall toward injured (ipsilateral) side. - *M*edial lesions—involvement of *M*idline structures (vermal cortex, fastigial nuclei) and/or occulonodular lobe truncal _________ (wide-based cerebellar gait), nystagmus, head tilting. Generally result in bilateral motor deficits affecting axial and proximal limb musculature.

First Aid pg. 469 . https://www.youtube.com/watch?v=ReV0mBblXTcCerebellum: Modulates (controls) *movement*; aids in coordination and balance. - Input: Contralateral *cortex* via middle cerebellar peduncle. Ipsilateral proprioceptive information via inferior cerebellar peduncle from spinal cord. - Output: The only output of cerebellar cortex = Purk*in*je cells (always *in*hibitory) deep nuclei of cerebellum contralateral cortex via superior cerebellar peduncle. Deep nuclei (lateral to medial)—*D*entate, *E*mboliform, *G*lobose, *F*astigial ("*D*on't *E*at *G*reasy *F*oods"). - *L*ateral lesions—affect voluntary movement of extremities (*L*imbs); when injured, propensity to fall toward injured (ipsilateral) side. - *M*edial lesions—involvement of *M*idline structures (vermal cortex, fastigial nuclei) and/or occulonodular lobe truncal *ataxia* (wide-based cerebellar gait), nystagmus, head tilting. Generally result in bilateral motor deficits affecting axial and proximal limb musculature.

Functional Organization of the Premotor Cortex: Involves Brodmann's areas 6, 8, 44/45 on the lateral surface and areas 23 and 24 on the medial surface Broca's area (Brodmann's area 44/45) is critical for the production of ____________. The medial region (Brodmann's areas 23 and 24) appears to be specialized for initiating movements specified by internal rather than external cues and lie in the cingulate gyrus (associated with the Limbic system).

Functional Organization of the Premotor Cortex: Involves Brodmann's areas 6, 8, 44/45 on the lateral surface and areas 23 and 24 on the medial surface Broca's area (Brodmann's area 44/45) is critical for the production of *speech*. The medial region (Brodmann's areas 23 and 24) appears to be specialized for initiating movements specified by internal rather than external cues and lie in the cingulate gyrus (associated with the Limbic system).

Basal Ganglia (First Aid pg. 470): https://www.youtube.com/watch?v=vyXz_IaUaOM Important in voluntary movements and making ____________ adjustments. Receives cortical input, provides negative feedback to cortex to modulate movement. Striatum = putamen (motor) + caudate (cognitive). Lentiform = putamen + globus pallidus. *D1-R*eceptor = *D1R*ect pathway. *In*direct = *In*hibitory. Excitatory pathway—cortical inputs stimulate the striatum, stimulating the release of GABA, which inhibits GABA release from the GPi, disinhibiting the thalamus via the GPi ( motion). Inhibitory pathway—cortical inputs stimulate the striatum, releasing GABA that disinhibits STN via GPe inhibition, and STN stimulates GPi to inhibit the thalamus ( motion). Dopamine binds to D1, stimulating the excitatory pathway, and to D2, inhibiting the inhibitory pathway motion. Substantia Nigra: Dopamine will stimulate the Excitatory/Direct pathway (D1), and inhibit the inhibitory/indirect pathway (D2)

Important in voluntary movements and making *postural* adjustments. Receives cortical input, provides negative feedback to cortex to modulate movement. Striatum = putamen (motor) + caudate (cognitive). Lentiform = putamen + globus pallidus. *D1-R*eceptor = *D1R*ect pathway. *In*direct = *In*hibitory. Excitatory pathway—cortical inputs stimulate the striatum, stimulating the release of GABA, which inhibits GABA release from the GPi, disinhibiting the thalamus via the GPi ( motion). Inhibitory pathway—cortical inputs stimulate the striatum, releasing GABA that disinhibits STN via GPe inhibition, and STN stimulates GPi to inhibit the thalamus ( motion). Dopamine binds to D1, stimulating the excitatory pathway, and to D2, inhibiting the inhibitory pathway motion. Substantia Nigra: Dopamine will stimulate the Excitatory/Direct pathway (D1), and inhibit the inhibitory/indirect pathway (D2)

Negative signs of Upper Motor Neuron Injury: - Paralysis, or paresis (partial paralysis) or ________ (complete paralysis). - Loss of control is more pronounced for distal muscles --> lack of dexterity. - Loss of superficial abdominal and cremasteric reflexes.

Negative signs of Upper Motor Neuron Injury: - Paralysis, or paresis (partial paralysis) or *plegia* (complete paralysis). - Loss of control is more pronounced for distal muscles --> lack of dexterity. - Loss of superficial abdominal and cremasteric reflexes.

Positive signs (of UMN injury) develop over time due to increased abnormal motor function: - Spasticity: term describing the positive signs after UMN lesions. - Hypertonia (increased muscle tone, stiffness) - _______________ (exaggerated reflexes); Babinski sign + - Conus (an oscillatory movement due to exaggerated reflex): a muscle stretch elicits alternating contractions of agonist and antagonist muscle groups. Hypothesis: spasticity is due to a loss of inhibitory descending input that keeps the stretch reflex from being over-active.

Positive signs (of UMN injury) develop over time due to increased abnormal motor function: - Spasticity: term describing the positive signs after UMN lesions. - Hypertonia (increased muscle tone, stiffness) - *Hyperreflexia* (exaggerated reflexes); Babinski sign + - Conus (an oscillatory movement due to exaggerated reflex): a muscle stretch elicits alternating contractions of agonist and antagonist muscle groups. Hypothesis: spasticity is due to a loss of inhibitory descending input that keeps the stretch reflex from being over-active.

Posterior Columns Decussation: Decussation and synapses: Dorsal columns synapse in the nucleus gracilis and cuneatus then decussate in the lower __________ and synpase again in the VPL (thalamus) before projecting to the cortex

Posterior Columns Decussation: Decussation and synapses: Dorsal columns synapse in the nucleus gracilis and cuneatus then decussate in the lower *medulla* and synpase again in the VPL (thalamus) before projecting to the cortex

Posterior Columns/ Dorsal Column: - Conveys tactile discrimination, vibration, joint position sense - Peripheral receptors that convey the information: Position sense: muscle spindles, Golgi tendon organs; Vibration: Pacinian corpuscles; Superficial touch: Meissner corpuscles; - Nerve fibers involved: Large, myelinated, fast-conducting nerve fibers

Posterior Columns/ Dorsal Column: - Conveys tactile discrimination, vibration, joint position sense - Peripheral receptors that convey the information: Position sense: muscle spindles, Golgi tendon organs; Vibration: Pacinian corpuscles; Superficial touch: Meissner corpuscles; - Nerve fibers involved: Large, myelinated, fast-conducting nerve fibers

Posterior Columns/ Dorsal Column: - Pathway: Skin sensation -> afferent sensory nerve -> ipsilateral dorsal column -> lower _________ -> synapse in nucleus gracilis and cuneatus -> arcuate fibers - cross to contralateral side into medial __________ -> ascend to VPL (thalamus) -> synapse -> project through posterior limb of internal capsule -> postcentral gyrus of cortex

Posterior Columns/ Dorsal Column: - Pathway: Skin sensation -> afferent sensory nerve -> ipsilateral dorsal column -> lower *medulla* -> synapse in nucleus gracilis and cuneatus -> arcuate fibers -cross to contralateral side into medial *lemniscus* -> ascend to VPL (thalamus) -> synapse -> project through posterior limb of internal capsule -> postcentral gyrus of cortex

Reticulospinal Tract and Tectospinal Tract: The ____________ ___________ is a complicated network of circuits in the core of the brainstem that extends from the rostral midbrain to the caudal medulla. It is similar in structure and function of the intermediate gray matter of the spinal cord! The reticulospinal tract has two divisions - Medial or pontine (MRST) and Lateral or medullary (LRST) The fibers of the MRST arise from the caudal pontine reticular nucleus and the oral pontine reticular nucleus , descend in the anterior funciculus and project to the lamina VII and VIII (intermediate zone) of the spinal cord. The function of this system is to fascilitate muscle of the trunk and proximal limb for postural adjustment of the head, trunk, and limbs. The fibers of the LRST arise from the medullary reticular formation (mostly from the gigantocellular nucleus) and descend the length of the spinal cord in the anterior part of the lateral column. The tract terminated in Lamina VII (intermediate zone) and IX (ventral horn) of the spinal cord. Its function is to have an inhibitory influence on extensors of the trunk and proximal limb and fascilitate the extensors of the trunk and proximal limb. The tectospinal tract begin as nerve cell bodies in the ___________ _________ of the midbrain. The nerve fibers cross the midline in the midbrain and descend close to the medial longitudinal fasciculus (anteriorly and medially in the spinal cord and terminate in the anterior gray column of the upper cervical segments of the spinal cord. The function of this tract is to coordinate __________ movement of the head and neck in response to *visual* stimuli.

Reticulospinal Tract and Tectospinal Tract: The *Reticular Formation* is a complicated network of circuits in the core of the brainstem that extends from the rostral midbrain to the caudal medulla. It is similar in structure and function of the intermediate gray matter of the spinal cord! The reticulospinal tract has two divisions - Medial or pontine (MRST) and Lateral or medullary (LRST) The fibers of the MRST arise from the caudal pontine reticular nucleus and the oral pontine reticular nucleus , descend in the anterior funciculus and project to the lamina VII and VIII (intermediate zone) of the spinal cord. The function of this system is to fascilitate muscle of the trunk and proximal limb for postural adjustment of the head, trunk, and limbs. The fibers of the LRST arise from the medullary reticular formation (mostly from the gigantocellular nucleus) and descend the length of the spinal cord in the anterior part of the lateral column. The tract terminated in Lamina VII (intermediate zone) and IX (ventral horn) of the spinal cord. Its function is to have an inhibitory influence on extensors of the trunk and proximal limb and fascilitate the extensors of the trunk and proximal limb. The tectospinal tract begin as nerve cell bodies in the *superior colliculus* of the midbrain. The nerve fibers cross the midline in the midbrain and descend close to the medial longitudinal fasciculus (anteriorly and medially in the spinal cord and terminate in the anterior gray column of the upper cervical segments of the spinal cord. The function of this tract is to coordinate *reflex* movement of the head and neck in response to visual stimuli.

Rubrospinal Tract: The _______ __________ is located in the tegmentum of the midbrain (at the level of the superior colliculus) in a region between the medial lemniscus (remember DC-ML tract?) and reticular formation and the Substantia Nigra and Crus cerebri (remember Corticospinal tact?). The red nucleus does have a reddish color in fresh specimens (and plastinates), and perhaps we will be able to see this in the Experiential Leaning session on "Brain Cutting". The Rubrospinal tract begins at the level of the Red Nucleus as cell bodies with their axons descending in the Lateral White Regions of the spinal cord (ventral to the Lateral Corticospinal Tracts). The axons immediately cross the midline in the ventral tegmental decussation and descend alongside the cerebral peduncles into the Pons and medulla and lateral spinal cord before terminating in the lateral regions of the of the ventral horn and intermediate zones. The synapse on interneurons or lower motor neurons that govern the distal musculature of the upper extremities to fascilitate the activity of flexor muscles. Although there is much scientific debate about the presence of the Rubrospinal tract in human, it is known that much of the Red Nucleus outflow is to the Inferior Olive and this information is an important source of learning signals for the cerebellum.

Rubrospinal Tract: The *Red nucleus* is located in the tegmentum of the midbrain (at the level of the superior colliculus) in a region between the medial lemniscus (remember DC-ML tract?) and reticular formation and the Substantia Nigra and Crus cerebri (remember Corticospinal tact?). The red nucleus does have a reddish color in fresh specimens (and plastinates), and perhaps we will be able to see this in the Experiential Leaning session on "Brain Cutting". The Rubrospinal tract begins at the level of the Red Nucleus as cell bodies with their axons descending in the Lateral White Regions of the spinal cord (ventral to the Lateral Corticospinal Tracts). The axons immediately cross the midline in the ventral tegmental decussation and descend alongside the cerebral peduncles into the Pons and medulla and lateral spinal cord before terminating in the lateral regions of the of the ventral horn and intermediate zones. The synapse on interneurons or lower motor neurons that govern the distal musculature of the upper extremities to fascilitate the activity of flexor muscles. Although there is much scientific debate about the presence of the Rubrospinal tract in human, it is known that much of the Red Nucleus outflow is to the Inferior Olive and this information is an important source of learning signals for the cerebellum.

Sensory Exam: Posterior/Dorsal Column: Joint position sense (JPS): With patient's eyes closed, grasp the sides of the thumb or great toe and flex or extend and ask the patient which direction the digit is pointing. ______________ sense (pallesthesia) is testing using a tuning fork (128 Hz or 256 Hz): place vibrating tuning fork over bony prominence (e.g., medial malleolus, thumb). Most people should be able to perceive vibration for at least 10 seconds.

Sensory Exam: Posterior/Dorsal Column: Joint position sense (JPS): With patient's eyes closed, grasp the sides of the thumb or great toe and flex or extend and ask the patient which direction the digit is pointing. *Vibratory* sense (pallesthesia) is testing using a tuning fork (128 Hz or 256 Hz): place vibrating tuning fork over bony prominence (e.g., medial malleolus, thumb). Most people should be able to perceive vibration for at least 10 seconds.

Sensory Exam: Spinothalamic Tract: Testing spinothalamic tracts: - Pain: Use ______ object (broken wooden Q-tip stick or pin) to test sensation. If necessary, test in dermatomes or cutaneous nerve distributions to determine presence or extent of a lesion. - Temperature: Need to use an object (test tube with either cold or warm water; cold tuning fork tines are examples) to determine presence or extent of a lesion.

Sensory Exam: Spinothalamic Tract: - Testing spinothalamic tracts: - Pain: Use *sharp* object (broken wooden Q-tip stick or pin) to test sensation. If necessary, test in dermatomes or cutaneous nerve distributions to determine presence or extent of a lesion. - Temperature: Need to use an object (test tube with either cold or warm water; cold tuning fork tines are examples) to determine presence or extent of a lesion.

Spinal reflexes are regulation by 1) Muscle Spindles - regulates muscle __________ - alpha motor neurons - extrafusal fibers - gamma motor neurons - intrafusal fibers - sensory neurons - Ia & II 2) Golgi Tendon Organs - regulates muscle _________ - alpha motor neurons - to antagonist muscles - sensory (afferent) neurons - ___ They both contribute to the reflex pathways 1) Stretch Reflex 2) Lengthening Reflex 3) Flexion Reflex

Spinal reflexes are regulation by 1) Muscle Spindles - regulates muscle *length* - alpha motor neurons - extrafusal fibers - gamma motor neurons - intrafusal fibers - sensory neurons - Ia & II 2) Golgi Tendon Organs - regulates muscle *force* - alpha motor neurons - to antagonist muscles - sensory (afferent) neurons - *Ib* They both contribute to the reflex pathways 1) Stretch Reflex 2) Lengthening Reflex 3) Flexion Reflex

Spinothalamic Tracts: - Convey: pain, temperature, crude touch - In the periphery, small myelinated and unmyelinated nerve fibers carry the information - Three synapses: skin sensation -> afferent sensory nerve -> substantia ____________ of ipsilateral (BEFORE CROSS OVER) dorsal horn -> synapse -> cross via anterior white commisure -> contralateral spinothalamic tract -> ascent to VPL nucleus (thalamus) -> synapse -> through posterior limb of internal capsule -> postcentral gyrus of cortex

Spinothalamic Tracts: - Convey: pain, temperature, crude touch - In the periphery, small myelinated and unmyelinated nerve fibers carry the information - Three synapses: skin sensation -> afferent sensory nerve -> substantia *gelatinosa* of ipsilateral (BEFORE CROSS OVER) dorsal horn -> synapse -> cross via anterior white commisure -> contralateral spinothalamic tract -> ascent to VPL nucleus (thalamus) -> synapse -> through posterior limb of internal capsule -> postcentral gyrus of cortex

Spinothalamic Tracts: Level of decussation and synapses: - Decussate at the level they enter the cord, _______ synapsing at Rexed's lamina II (substantia gelatinosa) - Also synapse in VPL of thalamus In the internal capsule, spinothalamic afferent fibers travel through the posterior aspect of the posterior limb of the internal capsule

Spinothalamic Tracts: Level of decussation and synapses: - Decussate at the level they enter the cord, *AFTER* synapsing at Rexed's lamina II (substantia gelatinosa) - Also synapse in VPL of thalamus In the internal capsule, spinothalamic afferent fibers travel through the posterior aspect of the posterior limb of the internal capsule

Sturge-Weber syndrome (encephalotrigeminal angiomatosis): First Aid 495 Congenital, noninherited (sporadic), developmental anomaly of neural crest derivatives due to somatic mosaicism for an activating mutation in one copy of the GNAQ gene. Affects small (capillary-sized) blood vessels port-wine stain of the face A (nevus ammeus, a non-neoplastic "birthmark" in CN V1/V2 distribution); ipsilateral leptomeningeal angioma B seizures/ epilepsy; intellectual disability; and episcleral hemangioma IOP early-onset glaucoma. *STURGE*-Weber: *S*poradic, port-wine Stain; *T*ram track calci cations (opposing gyri); *U*nilateral; *R*etardation (intellectual disability); *G*laucoma, *G*NAQ gene; *E*pilepsy. --- Ipsilateral third nerve palsy _________________ hemiparesis

Sturge-Weber syndrome (encephalotrigeminal angiomatosis): First Aid 495 Congenital, noninherited (sporadic), developmental anomaly of neural crest derivatives due to somatic mosaicism for an activating mutation in one copy of the GNAQ gene. Affects small (capillary-sized) blood vessels port-wine stain of the face A (nevus ammeus, a non-neoplastic "birthmark" in CN V1/V2 distribution); ipsilateral leptomeningeal angioma B seizures/ epilepsy; intellectual disability; and episcleral hemangioma IOP early-onset glaucoma. *STURGE*-Weber: *S*poradic, port-wine Stain; *T*ram track calci cations (opposing gyri); *U*nilateral; *R*etardation (intellectual disability); *G*laucoma, *G*NAQ gene; *E*pilepsy. --- Ipsilateral third nerve palsy *Contralateral* hemiparesis

Syndrome of combined lesions in anterior horns and lateral _______________ tracts Amyotrophic Lateral Sclerosis (ALS)

Syndrome of combined lesions in anterior horns and lateral *corticospinal* tracts Amyotrophic Lateral Sclerosis (ALS)

The Corticobulbar Tract: The corticobulbar tract passes through the genu and accompanies the corticospinal tract into the brainstem where it ends on the motor nuclei of ___________ _________ III, IV, V, VI, VII, IX, X, XI, and XII. These nuclei largely receive BILATERAL input from the corticobulbar tract. Example, each left and right nucleus is innervated by both the left and right corticobulbar tracts - see Facial Nerve palsy (LMN lesion) vs. Stroke (UMN lesion). The corticobulbar tract innervates cranial motor nuclei bilaterally with the exception of the lower ________ nuclei which are innervated only unilaterally (below the eyes) and cranial nerve XII which is innervated unilaterally as well. Both the lower part of cranial nerve VII and XII are innervated by the contralateral cortex. Among those nuclei that are bilaterally innervated a slightly stronger connection contralaterally than ipsilaterally is observed. The corticobulbar tract directly innervates the nuclei for cranial nerves V, VII, XI, and XII. The corticobulbar tract also contributes to the motor regions of X in the nucleus ambiguus.

The Corticobulbar Tract: The corticobulbar tract passes through the genu and accompanies the corticospinal tract into the brainstem where it ends on the motor nuclei of *Cranial Nerves* III, IV, V, VI, VII, IX, X, XI, and XII. These nuclei largely receive BILATERAL input from the corticobulbar tract. Example, each left and right nucleus is innervated by both the left and right corticobulbar tracts - see Facial Nerve palsy (LMN lesion) vs. Stroke (UMN lesion). The corticobulbar tract innervates cranial motor nuclei bilaterally with the exception of the lower *facial* nuclei which are innervated only unilaterally (below the eyes) and cranial nerve XII which is innervated unilaterally as well. Both the lower part of cranial nerve VII and XII are innervated by the contralateral cortex. Among those nuclei that are bilaterally innervated a slightly stronger connection contralaterally than ipsilaterally is observed. The corticobulbar tract directly innervates the nuclei for cranial nerves V, VII, XI, and XII. The corticobulbar tract also contributes to the motor regions of X in the nucleus ambiguus.

The Olivospinal Tract is also referred to as the Tract of Helweg. It arises from the __________ __________ Nucleus of the medulla. Its neurons descend in the anterior part of the lateral cell column of the spinal cord and terminate in the anterior horn of the CERVICAL CORD ONLY. Its function is to fascilitate reflex movements arising from proprioceptors and muscle tone. As with the Rubrospinal Tract, the importance of this system in humans is questionable. - crosses over at ____________ _________

The Olivospinal Tract is also referred to as the Tract of Helweg. It arises from the *Inferior Olivary* Nucleus of the medulla. Its neurons descend in the anterior part of the lateral cell column of the spinal cord and terminate in the anterior horn of the CERVICAL CORD ONLY. Its function is to fascilitate reflex movements arising from proprioceptors and muscle tone. As with the Rubrospinal Tract, the importance of this system in humans is questionable. - crosses over at *brain stem*

The corticospinal tract is one of the pyramidal tracts, the other being the corticobulbar tract. The corticospinal tract originates in several parts of the brain, including not just the motor areas, but also the primary somatosensory cortex and premotor areas. Most of the neurons originate in the _________ _________ cortex (precentral gyrus, Brodmann area 4) or the premotor frontal areas. The lateral corticospinal tract neurons cross the midline in the spinal cord, and controls the limbs and digits. cross over in the _____________. The anterior corticospinal tract neurons, the remaining 10%, stay on the same side of the body, and control the trunk muscles.

The corticospinal tract is one of the pyramidal tracts, the other being the corticobulbar tract. The corticospinal tract originates in several parts of the brain, including not just the motor areas, but also the primary somatosensory cortex and premotor areas. Most of the neurons originate in the *primary motor* cortex (precentral gyrus, Brodmann area 4) or the premotor frontal areas. The lateral corticospinal tract neurons cross the midline in the spinal cord, and controls the limbs and digits. cross over in the *medulla*. The anterior corticospinal tract neurons, the remaining 10%, stay on the same side of the body, and control the trunk muscles.

The primary function of the cerebellum is to detect the difference, or "motor ________" between the intended movement and the actual movement. When this feedback loop is damages, the afflicted will make persistent errors when executing movements - the specific pattern of incoordination depends on the location of the lesion.

The primary function of the cerebellum is to detect the difference, or "motor *error*" between the intended movement and the actual movement. When this feedback loop is damages, the afflicted will make persistent errors when executing movements - the specific pattern of incoordination depends on the location of the lesion.

The topographic map of movement in the primary motor cortex (Brodman's area 4) is located in the ____________ gyrus. Taking a section along the pre-central gyrus, we can see the distribution of the body representation in regards to the ________________ (Lower extremity, trunk, and upper extremity) and the Corticobulbar (Face) tracts. The primary motor cortex is responsible for eliciting movements. It receives regulatory input from the basal ganglia and cerebellum via relays from the ventrolateral thalamus (VPL and VPM) as well as inputs from sensory regions of the parietal lobe (via association fibers).

The topographic map of movement in the primary motor cortex (Brodman's area 4) is located in the *precentral* gyrus. Taking a section along the pre-central gyrus, we can see the distribution of the body representation in regards to the *Corticalspinal* (Lower extremity, trunk, and upper extremity) and the Corticobulbar (Face) tracts. The primary motor cortex is responsible for eliciting movements. It receives regulatory input from the basal ganglia and cerebellum via relays from the ventrolateral thalamus (VPL and VPM) as well as inputs from sensory regions of the parietal lobe (via association fibers).

Vestibulspinal Tract: The vestibular nuclei receives afferent information from the cerebellum and the inner ear (vestibular portion). The vesitbulospinal tracts are divided into the lateral and medial tracts. They originate from either the lateral or medial ___________ ___________- located in the pons and rostral medulla for the lateral nucleus and the rostral medulla for the medial nucleus. Also, other neurons from the vestibular nuclei project to local circuit neurons and lower motor neurons in the cranial nerve nuclei that control _____ movement (CN III, IV, & VI). This pathway produces the eye movements that maintain fixation while the head is moving. Unlike the Tectospinal and Reticulospinal tracts, the Lateral Vestibulospinal tract ************DOES NOT cross************* the midline and remains ____________ until it reaches the termination level of the spinal cord. It then crosses in the anterior white commissure of the cord to the corresponding ventral horn. The Medial Vestibulspinal tract descends bilaterally in the Medial Vestibulospinal tracts after diverging in the rostral spinal cord and terminating bilaterally in the medial ventral horn of the cervical spinal cord. The functions to regulate head position by reflex activation of neck muscles (_____________) in response to stimulation of the semicircular canals resulting from rotational accelerations of the head. By doing so, it helps with balance.

Vestibulspinal Tract: The vestibular nuclei receives afferent information from the cerebellum and the inner ear (vestibular portion). The vesitbulospinal tracts are divided into the lateral and medial tracts. They originate from either the lateral or medial *vestibular nuclei* - located in the pons and rostral medulla for the lateral nucleus and the rostral medulla for the medial nucleus. Also, other neurons from the vestibular nuclei project to local circuit neurons and lower motor neurons in the cranial nerve nuclei that control *eye* movement (CN III, IV, & VI). This pathway produces the eye movements that maintain fixation while the head is moving. Unlike the Tectospinal and Reticulospinal tracts, the Lateral Vestibulospinal tract ***********DOES NOT cross********* the midline and remains *ipsilateral* until it reaches the termination level of the spinal cord. It then crosses in the anterior white commissure of the cord to the corresponding ventral horn. The Medial Vestibulspinal tract descends bilaterally in the Medial Vestibulospinal tracts after diverging in the rostral spinal cord and terminating bilaterally in the medial ventral horn of the cervical spinal cord. The functions to regulate head position by reflex activation of neck muscles (*extensors*) in response to stimulation of the semicircular canals resulting from rotational accelerations of the head. By doing so, it helps with balance.