Principal Fiber Tracts of Spinal Cord
The schematic cross section in the lower part of the illustration shows the location of the principal fiber tracts within the spinal white matter. As indicated by the colors, the…
Pathologic Causes of Vertigo
The eighth cranial nerve is vulnerable to fractures involving the petrous part of the temporal bone and by tumors affecting the brainstem or cerebellum. Vertigo may be caused by central…
Spinal Origin or Termination of Major Descending Tracts and Ascending Pathways
The descending pathways shown in parts A, B, C, and D have a variety of actions on spinal circuitry, including the modulation of somatosensory input and the production of motor…
Arteries of Spinal Cord
The radicular arteries arise from the lateral spinal arteries, which traverse the intervertebral foramina at each vertebral segment. Regardless of their origin, the many small radicular arteries pass medially to…
Olfactory Receptors
Olfactory receptor cells may be considered specialized, primitive-type, bipolar neurons. Their nuclei are located at the base of the epithelial layer. Basal stem cells located along the basement membrane differentiate…
Nerves of Orbit and Cavernous Sinus
TROCHLEAR NERVE The trochlear nerve is slender, and its nucleus of origin is located in the midbrain just caudal to the oculomotor nuclei. The trochlear fibers curve posterolaterally and slightly…
Reticulospinal and Corticoreticular Pathways
Pontine reticulospinal fibers project to the spinal cord via the medial reticulospinal tract only. This tract traverses the anterior funiculus ipsilaterally and extends along the entire length of the spinal…
Disorders of Hypoglossal Nucleus and Nerve
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Clinical Findings in Cranial Nerve XI Damage
DISORDERS Proximal spinal accessory nerve lesions cause weakness of the sternocleidomastoid and the trapezius muscles. Damage within the posterior triangle of the neck spares the sternocleidomastoid, resulting in trapezius weakness….
