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Histological Organization of the Spinal Cord

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zutonepu's version from 2016-09-24 10:34

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A bundle of nerve fibers (axons) that connects two CNS regionstract
In CNS, another name for a tractfasciculus
projects axons from spinal cord to brainascending tract
projects axons from brain to spinal corddescending tract
an area containing multiple different tracts/fasciculifuniculus
located between the two dorsolateral sulci, contains large diameter sensory axons from the DRG axonsdorsal (posterior) funiculus
The dorsal (posterior) funiculus is also referred to asdorsal columns
The dorsal funiculus contains large diameter sensory axons from the dorsal root ganglia axons
The dorsolateral fasciculus is also called Tract of Lissauer
Located just below dorsolateral sulcus, contains small diameter sensory axons from DRGDorsolateral fasciculus (Tract of Lissauer)
The dorsolateral fasciculous contains small diameter sensory axons from DRG
Located between ventrolateral sulcus and ventromedian (anterior) fissure; contains mostly motor tracts descending from the brainventral funiculus
Ventral funiculus contains mostlymotor tracts descending from the brain
Where is the dorsal funiculus located?between the two dorsolateral sulci
Where is the dorsolateral fasciculus located?just below the dorsolateral sulcus
Where is the lateral funiculus located?between the dorsolateral sulcus and ventrolateral sulcus
The lateral funiculus contains motor and sensory tracts
Located between dorsolateral sulcus and ventrolateral sulcus; contains motor and sensory tractsLateral funiculus
Where is the ventral funiculus located?between ventrolateral sulcus and ventromedian (anterior) fissure
Located dorsal to the ventromedian fissure; contains axons crossing from one side of the spinal cord to the otheranterior white commissure
The anterior white commissure containsaxons crossing from one side of the spinal cord to the other
Where is the anterior white commissure located?dorsal to the ventromedian fissure
How do motor neuron axons exit spinal cords?through ventral roots
Small, innervate proximal musculature, important from trunk/posture control, present throughout cordmedial motor neurons
large, innervate distal musculature, important for limb control, present only in enlargementslateral motor neurons
which type of motor neurons - lateral or medial - are important for limb controllateral
which type of motor neurons - lateral or medial - are important for trunk/posture controlmedial
Which type of motor neuron is present only in enlargementslateral - important for limb control
Connect neurons locally, within a segment of spinal cordinterneurons
connect neurons at different levels of the spinal cordpropriospinal neurons
connect the two sides of the spinal cordcommissural neurons
project to the brainstem and forebrain as ascending tracts tract neurons
preganglionic parasympathetic and sympathetic neurons - control smooth muscle, cardiac muscle, glandsautonomic neurons
Three subdivisions of spinal cord gray matterdorsal horn, intermediate gray, ventral horn
Contains neurons that process sensory information; located throughout spinal cord; neurons project axons to other spinal cord levels and to braindorsal (posterior) horn
Two important subdivisions of dorsal hornsubstantia gelatinosa and dorsal funicular gray (Nucleus proprius)
Where is the substantia gelatinosa located?at all spinal cord levels, at the top of the dorsal horn
What is the function of substantia gelatinosa?part of dorsal horn - receives and processes sensory information - primarily pain
Where do substantia gelatinosa axons project?locally to the spinal cord and distally to the brain
Where is the dorsal funicular gray (nucleus proprius) located?at all spinal levels in the dorsal horn, anterior to substantia gelatinosa
What is the function of dorsal funicular gray (nucleus proprius)?processes sensory information
Where do the axons of dorsal funicular gray (nucleus proprius) neurons project?locally to other spinal cord segments via propriospinal axons, and distally to brainstem and forebrain
Contains interneurons, autonomic preganglionic neurons, and neurons that transmit information to the cerebellumIntermediate gray
Important components of intermediate gray (3)Intermediolateral cell column, Clarke's nucleus, sacral parasympathetic nucleus
Located from T1-L2 in the lateral-most part of the intermediate gray; contains sympathetic pre-ganglionic neurons (autonomic innervation)intermediolateral cell column (lateral horn)
Where is the intermediolateral cell column (lateral horn) locatedfrom T1-L2 in the lateral-most part of the intermediate gray
What does the intermediolateral cell column (lateral horn) contain?sympathetic pre-ganglionic neurons
Component of intermediate gray, prominent nucleus located in T1-L2 only; processes and sends sensory (mostly proprioceptive) info to the cerebellum via the ipsilateral spinocerebellar tract Clarke's nucleus
Where is Clarke's nucleus located?only in T1-L2 (in intermediate gray)
What is the function of Clarke's nuclues?processes and sends sensory (mostly proprioceptive) info to the cerebellum via the ipsilateral spinocerebellar tract
Component of intermediate gray, located in S2-S4, contains parasympathetic preganglionic neurons, that project to bladder, bowels, and genitals Sacral parasympathetic nucleus
Where is the sacral parasympathetic nuclus located?In S2-S4 (intermediate gray)
What is the function of the sacral parasympathetic nucleus?Contains parasympathetic preganglionic neurons that project to bladder, bowels, and genitals
Contains alpha motor neurons, which project to muscles of trunk and limbs, as well as interneurons and gamma motor neuronsVentral (anterior) horn
Lower motor neurons located in ventral horn, project to muscles of trunk and limbsalpha motor neurons
Loss of alpha motor neurons from ventral horn causes what type of paralysisflaccid
Components of ventral hornalpha motor neurons, interneurons, gamma motor neurons
Innervate intrafusal fibers of muscle spindles, located in ventral horngamma motor neurons
Located throughout spinal cord, innervate proximal axial/trunk musculaturemedial motor nuclei
Located in cervical and lumbosacral enlargements only, innervate limb musculaturelateral motor nuclei
Located from C3-C7 (mostly C3-C5) - in ventral horn, neurons innervate diaphragm and control breathingphrenic nuceus
Where is the phrenic nucleus located?in ventral horn from C3-C7 (mostly C3-C5)
What is the function of the phrenic nucleus?contains neurons which innervate diaphragm and control breathing
Located in ventral portion of ventral horn at S1-S3; innervates sphincter and erectile musculature Onuf's nucleus
Where is Onuf's nucleus located?in the ventral portion of the ventral horn at S1-S3
What is the function of Onuf's nucleus?innervates sphincter and erectile musculature
What are important components of cervical enlargement (2)?upper limb motor neurons, phrenic nucleus
What are important components of T1-L2 (2)?intermediolateral cell column, Clarke's nucleus
What is the imporant component in lumbar enlargement?lower limb motor neurons
What are the important components of sacral gray matter (2)?Onuf's nucleus, parasympathetic neurons
How are ascending tracts organized?in a somatotropic manner - sacral origin - medial most, cervical origin lateral most
What is significant about second order neurons in major ascending systems?they cross the midline
What is the modality of fascilculus gracilis?discriminative touch, vibration, and proprioception for lower body
What is the location of fasciculus gracilis? medial dorsal funiculus throughout spinal cord
What is the origin of fasciculus gracilis?cell bodies located in DRGs from T6 - coccygeal levels
What is the projection of fasciculus gracilis axons?Enter dorsal columns and project to ipsilateral brainstem nucleus (nucleus gracilis), axons from brainstem cross midline (2nd order neurons) and ascend to thalamus, thalamus axons project to primary somatosensory cortex
What is the modality of fasciculus cuneatus?discriminative touch, vibration, and proprioception for upper body
What is the location of fasciculus cuneatus?lateral dorsal funiculus from upper thoracic to cervical spinal cord
What is the origin of fasciculus cuneatus?cell bodies located in DRGs from C1-T5
What is the projection of fasciculus cuneatus axons?DRG axons enter dorsal colums and project to ipsilateral brainstem nucleus (nucleus cuneatus); axons from brainstem neurons cross the midline, ascend to contralateral thalamus; thalamus axons project to the primary somatosensory cortex
What is the modality of the spinothalamic tract/anterolateral tract?pain, temperature, and crude touch for entire body
What is the location of the spinothalamic tract/anterolateral tract?Anterolateral white matter throughout spinal cord
What is the origin of the spinothalamic/ anterolateral tract?Dorsal horn neurons that receive pain and temp information from small diameter sensory neurons
What is the projection of axons from the spinothalamic/ anterolateral tract?Spinal neurons (which are second order because signal started in DRG sensory neuron) sends axons across the midline through the anterior white commissure; axons ascend as the spinothalamic tract to the thalamus; thalamus axons project to primary somatosensory cortex
Which ascending tracts are ipsilateral in the spinal cord, and which are contralateral?Fasciculus gracilic and fasciculus cuneatus are ipsilateral, Spinothalamic tract is contralateral
What sensory deficits exist if there is a lesion on the right side of the cord?Lose fine touch and vibration from from right side of body; lose pain and temp from left side of body
Major descending systems (4)Lateral corticospinal tract, Rubrospinal tract, Vestibulospinal tracts, Reticulospinal tracts
What is the origin of the lateral corticospinal tract? contralateral cerebral cortex
What is the pathway of the lateral corticospinal tract?Axons descend through the brain --> brainstem pyramids --> cross at the pyramidal decussation --> dorsolateral funiculus
Where do lateral corticospinal tract axons synapse?mostly on interneurons, but also some direct projections to the motor neurons
What is the function of the lateral corticospinal tract?major influence on distal musculature, particulary for skilled/rapid use of digit
What is the ventral corticospinal tract?some of the axons from the corticospinal tract which do not cross in pyramids and remain ipsilateral in the spinal cord
What is the pathway of the ventral corticospinal tract?axons descend through brain --> brainstem pyramids --> do not cross --> tracts run in ventral white matter
What is the function of the ventral corticospinal tract?innervates medial motor neurons to control trunk muscles
What is the origin of the rubrospinal tract?red nuclues
What is the pathway of the rubrospinal tract?axons exit nucleus --> cross --> descend through brain/brainstem --> lateral funiculus
What is the function of the rubrospinal tract?mainly controls the tone of flexor muscles, especially upper limb - excitation of flexor, inhibition of extensor
What is the origin of the vestibulospinal tracts?Lateral (Dieter's) and medial vestibular nuclei
What is the pathway of the lateral vestibulospinal tract?ventral funiculus throughout entire cord
What is the pathway of the medial vestibulospinal tract?ventral funiculus only through cervical levels
What is the function of the vestibulospinal tracts?primary route by which vestibular system causes postural changes to compensate for tilts and movments of the body; excite muscles to oppose motion - decrease undesired movement
What is the origin of the reticulospinal tracts?Reticular formation in the pons (Pontine RST) and medulla (Medullary RST)
What is the pathway of reticulospinal tracts?Ventral and ventrolateral funiculus - both tracts contact medial motor neurons, interneurons, and propriospinal neurons
What is the function of reticulospinal tracts?Influence trunk and proximal limb muscles for postural adjustments and locomotion
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