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15 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Rubrospinal Tract:
• Start - also where the starting point receives input (2) • End - what kind of connections are formed? What neurons are involved? What level of the spinal cord? Sidedness? • Route - where the tract decussates - where the tract descends • Function |
Rubrospinal Tract:
• Start - at the red nucleus which receives excitatory input from > the ipsilateral motor nucleus (corticorubrotract) > contralateral cerebellar nuclei • End - on excitatory α- and γ- LMNs in the anterior/ventral horn of the cervical spinal cord • Route - The tract decussates in the ventral midbrain - and descends through the lateral brain stem and spinal cord • Facilitate voluntary flexion of the contralateral upper limb |
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Lateral/Medullary Reticulospinal Tract
• Start - where the starting point receives input (2) • End - What kind of connections are formed? What neurons are involved? Sidedness? • Route • Function |
Lateral/Medullary Reticulospinal Tract
• Start - at the Reticular nuclei in the medulla - It receives excitatory input > bilaterally from the corticoreticular fibers > contralaterally through the spinothalamic tract, from the trunk and limbs • End - will form excitatory connections bilaterally in the spinal cord with interneurons. These interneurons will in turn excite α- and γ- LMNs on the anterior horn of the spinal cord • Route - The tract has fibers that stay ipsilaterally through the medulla and spinal cord as well as fibers that decusate at the medulla and descend contralaterally in the spinal cord. Both routes eventually synapse on interneurons • Facilitate voluntary contraction of the flexor muscles of the limbs |
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Medial/Pontine Reticulospinal Tract:
• Start - also where the starting point receives input (2) • End - what kind of connections are formed? What neurons are involved? What level of the spinal cord? Sidedness? • Route - where the tract descends • Function |
Medial/Pontine Reticulospinal Tract:
• Start - Reticular nuclei in the pons which receive excitatory input bilaterally from the corticoreticular fibers and contralaterally through the spinothalamic tract, from the runk and limbs • End - It synapses on interneurons in the ipsilateral anterior horn of the spinal cord. - The interneurons excite mainly γ-motor neurons • Route - the tract descends ipsilaterally through the medulla and spinal cord • Excite axial muscles and facilitate extension of limb muscles |
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Spinoreticular Tract:
• Type of pathway • Start • End • Route - where the tract arises from • Function and reason behind the function |
Spinoreticular Tract:
• Sensory pathway • Start - Pain and temperature receptors • End - Reticular nuclei in the pons and medulla • Route - arises from collateral branches of the Anterolateral system • To relay info about pain and temperature from one side of the body to the contralateral pontine reticular nuclei. It helps facilitate contraction of the extensor muscles of the limb & trunk and helps make postural adjustments to minimize injury associated with the painful stimuli that activated the pathway. |
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Lateral Vestibulospinal Tract:
• Start - also where the starting point receives input (2) and the kinds of input it receives (2) • End - what kind of connections are formed? What neurons are involved? What level of the spinal cord? Sidedness? • Route - where the tract decussates - where the tract descends • Function (2) |
Lateral Vestibulospinal Tract:
• Start - Lateral Vestibular Nucleus which receive > excitatory input from the organs of the inner ear and cerebellum > inhibitory input from Purkinje cells of the cerebellum • End - It synapses in the ipsilateral anterior horn of the spinal cord on excitatory interneurons. - The interneurons excite α-motor neurons • Route - the tract descends ipsilaterally through the medulla and spinal cord • Facilitate contraction of the extensor muscles of the limb. Coordinate the position of the head and body in space to maintain balance |
Lateral Vestibulospinal Tract:
• Start - Lateral Vestibular Nucleus which receive > excitatory input from the organs of the inner ear and cerebellum > inhibitory input from Purkinje cells of the cerebellum • End - It synapses in the ipsilateral anterior horn of the spinal cord on excitatory interneurons. - The interneurons excite α-motor neurons • Route - the tract descends ipsilaterally through the medulla and spinal cord • Facilitate contraction of the extensor muscles of the of limb. Coordinate the position of the head and body in space to maintain balance |
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Medial Vestibulospinal Tract:
• Start - also where the starting point receives input (2) and the kinds of input it receives (2) • End - what kind of connections are formed? What neurons are involved? What level of the spinal cord? Sidedness? • Route - where the tract descends and serves as an extension to this structure • Function (2) |
Medial Vestibulospinal Tract:
• Start - Medial Vestibular Nucleus which receives excitatory input from the organs of the inner ear and cerebellum > inhibitory input from Purkinje cells of the cerebellum • End - It forms inhibitory synapses (glycine as the NT) on α-motor neurons in the ipsilateral anterior horn of the cervical and upper thoracic levels of the spinal cord • Route - the tract descends ipsilaterally through the medulla and spinal cord, running as a caudal extension of the MLF • Fxns to stabilize head position and assist w/ head & neck movements in relation to gaze |
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Which of the following tracts excite both α- and γ- LMNs:
• Rubrospinal Tract • Lateral/Medullary Reticulospinal Tract • Medial/Pontine Reticulospinal Tract • Spinoreticular Pathway • Lateral Vestibulospinal Tract • Medial Vestibulospinal Tract |
Rubrospinal and Lateral/Medullary Reticulospinal Tracts
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Which of the following tracts excite only α- LMNs:
• Rubrospinal Tract • Lateral/Medullary Reticulospinal Tract • Medial/Pontine Reticulospinal Tract • Spinoreticular Pathway • Lateral Vestibulospinal Pathway • Medial Vestibulospinal Pathway |
Lateral Vestibulospinal Tract
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Which of the following tracts excite only γ- LMNs:
• Rubrospinal Tract • Lateral/Medullary Reticulospinal Tract • Medial/Pontine Reticulospinal Tract • Spinoreticular Pathway • Lateral Vestibulospinal Tract • Medial Vestibulospinal Tract |
Medial/Pontine Reticulospinal Tract
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Which of the following tracts participate in inhibitory synapses:
• Rubrospinal Tract • Lateral/Medullary Reticulospinal Tract • Medial/Pontine Reticulospinal Tract • Spinoreticular Pathway • Lateral Vestibulospinal Tract • Medial Vestibulospinal Tract |
Medial Vestibulospinal Tract
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Explain the Gamma Loop using the terms
• α- LMNs and extrafusal fibers • γ- LMNs and intrafusal fibers • "stretch," "slack" and "tuning" • muscle spindle |
Muscle spindles are sensory receptors in the belly of the muscle that detect positive changes (stretch) in muscle length. Groups of intrafusal fibers form muscle spindles and these fobers are iNN by γ-LMNs
Extrafusal fibers are units of skeletal that fxn to contract. They are iNN by α- LMNs When α- LMNs excite the extrafusal fibers, they skeletal muscle contracts and the muscle spindle with its intrafusal fibers lose their tension and become slack at their ends. The γ- LMNs will help the intrafusal fibers adapt to this new change in muscle length, causing them to contract. This "tuning" helps ensure the muscle spindle can still measure muscular stretch. |
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Stimulation of these neurons causes indirect stimulation of muscle spindles
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γ-LMNs; Stimulating these neurons will cause muscular contraction through excitation of α-LMNs via Ia fibers of the reflex arc
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Myotactic reflex
• the fiber involved, its role and the muscle it excites |
Myotactic Reflex
• Ia muscle fiber excites α-motor neurons serving the homonymous muscle |
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Decorticate Posturing:
• Location of the lesion • The Presentation of the patient • Of the following tracts, discuss which are affected, which are intact and how the patient’s presentation coincides with the location of the lesion - Corticospinal Tract - Corticobulbar Tract - Rubrospinal Tract - Lateral/Medullary Reticulospinal Tract - Medial/Pontine Reticulospinal Tract - Lateral Vestibulospinal Tract - Medial Vestibulospinal Tract |
Decorticate Posturing:
• Rostral to the Red Nucleus of the midbrain • The upper limb (fingers, wrists and elbows) are flexed while the lower limb is extended with feet turned inward • Discussion of the affected/unaffected tracts - Corticospinal Tract: Affected; It's fxn is to voluntarily contract the distal flexor muscles - Corticobulbar Tract: Affected; It's fxn is to iNN the motor nuclei of cranial nerves to control muscles of the eye, head and neck - Rubrospinal Tract: Unaffected; It's fxn is to flex the muscles of the upper limb - Lateral/Medullary Reticulospinal Tract: Unaffected; It's fxn is to flex muscles of the extremities - Medial/Pontine Reticulospinal Tract; Unaffected; It's fxn is to extend the extremities - Lateral Vestibulospinal Tract: Unaffected; It's fxn is to extend the extremities - Medial Vestibulospinal Tract: Unaffected; It's fxn is to extend the extremities Because the lesion is above the red nucleus, tracts beginning at the cortex will be interrupted, while those beginning at the level of and below the red nucleus will be in tact. The Rubrospinal and Medial/Pontine Reticulospinal Tracts supplies flexor muscles of the upper extremities and their function will override the extensor innervation of the other tracts. Because the Lateral Corticospinal tract has been damaged, the Medial/ Pontine and Vestbulospinal tracts will be unopposed, facilitating the extension of the legs and inward rotation/pronation of the feet. |
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Decerebrate Posturing:
• Location of the lesion • The Presentation of the patient • Of the following tracts, discuss which are affected, which are intact and how the patient’s presentation coincides with the location of the lesion - Corticospinal Tract - Corticobulbar Tract - Rubrospinal Tract - Lateral/Medullary Reticulospinal Tract - Medial/Pontine Reticulospinal Tract - Lateral Vestibulospinal Tract - Medial Vestibulospinal Tract |
Decerebrate Posturing:
• Caudal to the Red Nucleus of the midbrain • The upper limb (fingers, wrists and elbows) and lower limbs are extended while the lower with feet turned inward • Discussion of the affected/unaffected tracts - Corticospinal Tract: Affected; It's fxn is to voluntarily contract the distal flexor muscles - Corticobulbar Tract: Affected; It's fxn is to iNN the motor nuclei of cranial nerves to control muscles of the eye, head and neck - Rubrospinal Tract: Affected; It's fxn is to flex the muscles of the upper limb - Lateral/Medullary Reticulospinal Tract: Unaffected; It's fxn is to flex muscles of the extremities - Medial/Pontine Reticulospinal Tract; Unaffected; It's fxn is to extend the extremities - Lateral Vestibulospinal Tract: Unaffected; It's fxn is to extend the extremities - Medial Vestibulospinal Tract: Unaffected; It's fxn is to extend the extremities Because the lesion is below the red nucleus, tracts beginning at the cortex and red nucleus will be interrupted, while those beginning below the red nucleus will be in tact. The Medial/Pontine Reticulospinal and Vestibulospinal Tracts are the pathways that are preserved. Though the Medial/Pontine Reticulospinal Tract supply the flexor muscles of the upper extremities, they are overridden by the Extensor innervations of the Lateral and Medial Vestibulospinal Tracts leading to the extension of all extremities and inward rotation/pronation of the feet. No flexion is seen since the Lateral Corticospinal and Rubrospinal Tracts are damaged |
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