Spinal Reflex Pathways
Muscle Stretch Reflex. Parts A and B show some of the connections made by groups Ia and II (not shown) afferent fibers from muscle spindle receptors. These afferent fibers are…
Intramedullary Course
DISORDERS OF THE HYPOGLOSSAL NUCLEUS AND NERVE Supranuclear lesions affecting the corticobulbar fibers above their decussation result in weakness of the contralateral half of the tongue. Bilateral upper motor neuron…
Accessory (XI) Nerve
The cranial root is the smaller of the two portions of the accessory nerve. Although it is discussed in this section, it is often considered as a part of the…
Spinal Effector Mechanisms
Motor Neurons. Except for muscles innervated by the cranial nerves, each somatic muscle receives its motor supply from a column of motor neurons arranged longitudinally in the anterior horn of…
Central Versus Peripheral Facial Paralysis
The facial nerve can be damaged at any level along its course (Plate 1-27). Facial musculature paralysis is the hallmark of seventh cranial nerve lesions. The presence or absence of…
Oculomotor (III), Trochlear (IV), and Abducens (VI) Nerves
Oculomotor Nuclei. The somatic and parasympathetic efferent fibers in the oculomotor nerve are the axons of cells located in the complex oculomotor nuclei situated anterolateral to the upper end of…
Control of Eye Movements—Pathology (Continued)
NEUROLOGIC DEFICITS Eye movement disorders from brainstem involvement of the pathways subserving horizontal and vertical gaze are usually exquisitely localizing. For example, a lesion in the right abducens nucleus will…
Pupillary Light Reflex and the Accommodation Reflex
The deeper collicular layers are the source of several efferent projections. One group of fibers crosses the midline and runs caudally, sending terminals to the brainstem reticular formation and then…
Spinal Membranes and Nerve Roots
The external, tough, fibrous dura mater continues downward as far as the second sacral vertebra, where it ends blindly. It is separated from the wall of the vertebral canal by…
