vels when they fall too low by releasing glucose from the liver, where it is stored as glycogen.
2. (a) Describe the composition and function of the cell body. (b) How are axons and dendrites alike? In what ways (structurally and functionally) do they differ?
(a) The cell body of a nerve, known as the perikaryon, is the large, dilated region of the cell containing a large, euchromatic nucleus and a prominent nucleolus (Ross, Romwell and Kaye, 1995, 257). Nerve cell bodies also contain inclusions known as Nissl bodies, which correspond to a stack of rough endoplasmic reticulum. The cell body contains many mitochondria, a large perinuclear Golgi apparatus, lysosomes, microtubules, neurofilaments, vesicles, and other inclusions. The Nissl bodies, free ribosomes, and sometimes the Golgi apparatus, extend into the dendrites, but not into the axon. The combination of a euchromatic nucleus, large nucleolus, prominent Golgi apparatus, and Nissl bodies indicates a high level of anabolic activity, which is needed to maintain the large cell bodies of nerves.
Neurons do not replicate, but there is a large turnover of subcellular components (Ross, Romrell and Kaye, 1995, 258). There is a constant need to replace enzymes, transmitter substances, membrane components, and other complex molecules which necessitates the high level of synthetic activity in the nerve cell bodies. Newly synthesized molecules also need to be transported to different areas of the neuron by axonal transport.
The cell body is therefore the synthetic center for the whole neuron.
(b) Dendrites are neuronal processes that receive stimuli from other nerve cells and from the environment (Ross, Romrell and Kaye, 1995, 258-259). They are generally located near the cell body. Dendrites have a larger diameter than axons, and are not myelinated. They are usually tapered in shape, and form extensive arborizations known as dendritic trees. These dendriti...