Professor Diamond continues her discussion of the nervous system and begins by revisiting her discussion of the ascending path. She notes the presence of substantia gelatinosa in the area of the second neuron and describes the concept of homunculus, which is the upside-down representation of the body in the brain, and notes that this does not occur in the face for reasons unknown to neurologists. Professor Diamond then begins describing the descending paths of the spinal cord, the corticospinal tract and the corticobulbar tract. She begins at the telencephalon level, describing how the axons of pyramidal cells feed their way through various structures including the ventricles, putamen, lentiform nucleus, globus pallidus, and the corona radiata. She continues to the mesencephalon level, describing the superior colliculi, aqueducts, basal plates, and cerebral pinduncles before moving to the metencephalon to describe pyramids and ending at the myelencephalon to describe the decussation of pyramids. Professor Diamond concludes her explanation of the pathways of corticoaxons in the spinal cord, describing the lateral funiculus, lateral corticospinal tract, and anterior corticospinal tract, as well as how corticoaxons travel to the anterior horn cell. She applies this discussion to upper and lower motor neurons and discusses the symptoms of a upper motor neuron lesions noting the loss of the cremasteric reflex and a positive Babinski reflex, and the symptoms of a lower motor neuron lesion.
The functional anatomy of the human body as revealed by gross and microscopic examination.
