Compare the size of the nucleolus in the motor neuron with the nuclei in the surrounding support cells. The motor neuron in the ventral horn is easily identifiable by its large size, polygonal shape and extension from the cell body. Fibers leading to the spinal cord travel through the dorsal root.Ī motor neuron innervates one or many muscle fibers to control muscle contraction. Fibers heading toward the periphery leave the ganglion through the spinal nerve, where they run together with motor fibers. These neurons are pseudounipolar and contain an axon-like process that bifurcates with one branch extending toward the periphery and the other branch heading toward the grey matter of the spinal cord. The dorsal root ganglion contains the cell bodies of sensory neurons that bring information from the periphery to the spinal cord. The ventral and dorsal roots come together to form a spinal nerve. The ventral root contains efferent motor axons. The dorsal root contains afferent sensory fibers that transmit signals from the periphery, through the dorsal root ganglion, to the dorsal horn. The central canal lies in the center of the cord and contains cerebrospinal fluid. The gray matter, which contains cell bodies, is located in the center of the cord and is easily identified by its color and butterfly shape. The white matter is composed of nerve fibers carrying ascending and descending information and makes up the outer regions of the cord. Many important features of the spinal cord are visible in this cross section.
This lab will be limited to the study of the basic features of neurons and glial cells - specific organs composed of neurons, including the retina of the eye and the organ of Corti of the inner ear, will be studied in the Sensory Systems lab, in conjunction with the Neuroanatomy course. The nervous system is extraordinarily complex, and it is therefore impossible to cover it in its entirety in a single laboratory.
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