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## Neuron Structure - **Cell body (soma)**: The **control center** of the neuron and contains the **nucleus**. - **Dendrites:** Look like the bare branches of a tree. They **receive signals** from other neurons and **conduct information** to the cell body. - **Axon:** It **carries nerve signals awa...

## Neuron Structure - **Cell body (soma)**: The **control center** of the neuron and contains the **nucleus**. - **Dendrites:** Look like the bare branches of a tree. They **receive signals** from other neurons and **conduct information** to the cell body. - **Axon:** It **carries nerve signals away** from the cell body. Nerve cells have only one axon. **Myelin sheath:** - Axons of many neurons are encased. - Consisting mostly of lipid, the myelin acts to **insulate the axon**. - In the peripheral nervous system Schwann cells form the myelin sheath. **Nodes of Ranvier:** - Gaps in the myelin sheath, where *action potentials are generated*. **Synaptic knob:** - The end of the axon branches **extensively** with each axon terminal ending. **Myelin:** - Helps speed impulse conduction. - Nerve fibers stimulate skeletal muscles where speed is more important. **Unmyelinated:** - Conducts nerve impulses more slowly. - Perform functions in which speed isn't essential. **Although myelination begins during the fourteenth week of fetal development, it is not complete until late adolescence** ## Life lesson: Multiple Sclerosis - MS is a disease in which the myelin sheaths surrounding the nerves of the CNS deteriorate and are replaced by hard scar tissue called Plaques.