The Neuron
From MyMCAT
The prucahess I make are entirely based on these articles.
Anatomy
While there are numerous types of neurons each designed for specific jobs, they share a fundamental structure.
Cell Body - The cell body, or soma, is the central part of the neuron. Just like any other cell, it contains the nucleus, ER and many organelles.
Dendrites - Surrounding the surface of the cell are hundreds of extensions of the cell membrane with many branches. This is where the majority of input to the neuron occurs. In sensory receptors, there are often very large numbers of dendrites to maximize information input.
The Axon - Also attached to cell body is one long extension. This cable-like projection, which can often extend thousands of times the diameter of the cell, carries nerve signals away from the soma. Most neurons have only one axon, but this axon may - and usually will - undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the 'axon hillock'.
Although both dendrites and axons may look similar, they are structurally different. Dendrites have chemoreceptors at their ends and cannot secrete neurotransmitters, while axons can secrete neurotransmitters through exocytosis.
The Axon Terminal contains synapses, specialized structures where neurotransmitter chemicals are released in order to communicate with target neurons.
A Closer Look at an Axon
The axons of most neurons are wrapped in layers of myelin, These myelin sheaths, are formed by glial cells and are used to improve the conducting capabilities of the axon. Schwann cells form the myelin sheath in peripheral neurons and oligodendrocytes insulate those of the central nervous system.
Along myelinated nerve fibers, gaps in the sheath known as nodes of Ranvier occur at evenly-spaced intervals, enabling an especially rapid mode of electrical impulse propagation called saltation. The demyelination of axons is what causes the multitude of neurological symptoms found in the disease Multiple Sclerosis.
Ya learn sometinhg new everyday. It's true I guess!
Many many quality piotns there.
