Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Cell growth wikipedia , lookup
Tissue engineering wikipedia , lookup
Node of Ranvier wikipedia , lookup
Chemical synapse wikipedia , lookup
Cell culture wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cellular differentiation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Programmed cell death wikipedia , lookup
Nerve Cells (Human) 1 Neurons Structure Nerve cells are called neurons. They do not go through the process of reproducing themselves (mitosis). They are said to be amitotic: if destroyed, they cannot be replaced. Ganglia are collections of nerve-cell bodies outside the central nervous system. All neurons contain the same elements: a Cell body This includes a nucleus (control center) and fibers called processes extending out. b Axon This is a long, slim “trunk” that transmits information from the cell body to other cells via junctions known as synapses. Some axons are only a few millimeters long; others are more than a yard long. Axons are sheathed in a fatty substance called myelin which helps with the conduction of electrical impulses. c Dendrites These are networks of short fibers that branch out from the axon or cell body and link the ends of axons from other neurons. Dendrites are the cell’s receivers of information, bringing signals to their neuron’s own cell body. Each neuron might have hundreds of dendrites. Functions Neurons communicate electrochemically with one another to transmit impulses throughout the body. a cell body c dendrites b axon 1 2 Neuroglia The nervous system also contains neuroglia cells. These do not conduct nerve impulses. Instead, they support and protect neurons. They are capable of mitosis (so if damaged can be replaced). There are four types of neuroglia within the central nervous system: a star-shaped astrocytes cling to neurons and help protect them; b smaller microglia are spider shaped and help get rid of dead brain cells and bacteria; c ependymal cells line the ventricles of the spinal cord and brain, and their cilia (hairlike fronds) help circulate cerebrospinal fluid; and d long-extensioned oligodendrocytes wrap around and protect nerve fibers. 2 a astrocytes b microglia c ependymal cells d oligodendrocytes Sometimes, Schwann cells and satellite cells, found in the peripheral nervous system, are considered neuroglia. © Diagram Visual Information Ltd.