16.4:
Neurons: The Cell Body and the Dendrites
Neurons, excitable nervous system cells, generally consist of three main parts: the cell body, the dendrites, and the axon.
The cell body, also known as the perikaryon, is the metabolic center of a neuron. It comprises the nucleus surrounded by cytoplasm containing other organelles, including mitochondria. Its cytoskeleton includes neurofibrils, bundles of intermediate filaments that support neurons, and neurotubules, along which materials are transported to the axon.
The cell body also has Nissl bodies, clusters of ribosomes and rough endoplasmic reticulum that give the characteristic gray color to gray matter.
Groups of cell bodies in the central nervous system are called nuclei, but in the peripheral nervous system, they are called ganglia.
Dendrites are slender cellular processes that emerge from the cell body. They are highly branched and are often covered with short dendritic spines that form synapses with neighboring neurons.
Dendrites contain receptors that bind to chemical messengers released by the surrounding cells and relay this information to the cell body through short-distance impulses called graded potentials.
16.4:
Neurons: The Cell Body and the Dendrites
A typical nerve cell comprises three main components: the cell body, dendrites, and the axon. The cell body, also known as the soma or perikaryon, serves as the central biosynthetic hub housing a nucleus surrounded by cytoplasm containing organelles commonly found in most cells. Notably, Nissl bodies, clusters of the rough endoplasmic reticulum and free ribosomes responsible for protein synthesis, are distinctive features of the neuronal cell body. As neurons age, aggregates of a brown pigment called lipofuscin, which is a product of lysosomes, accumulate. The cytoskeleton of the neurons consists of networks of intermediate filaments and microtubules called neurofilaments and microtubules, respectively. Microtubules are important for the transport of materials between the cell body and the axon. Neurofilaments form bundles called neurofibrils that provide structural support.
Dendrites, the short and branching extensions from the cell body, function to receive signals from other neurons, transforming them into short-distance electrical impulses known as graded potentials. Adorned with dendritic spines, tiny protrusions enhancing surface area for signal reception, dendrites have a plasma membrane rich in receptors for neurotransmitters—chemical messengers released by neighboring neurons upon stimulation.