A cross section of a bundle of nerve fibers. Axons (orange) are wrapped in myelin (purple); an extension of the membrane of glial cells. Myelin has high lipid content, and acts to insulate the axons, causing them to transmit nerve impulses much faster.
frontal-cortex: Scanning electron microscope picture of a nerve ending that has been broken open to reveal the synaptic vesicles beneath the cell membrane. Image by Tina Carvalho. The Cell: An Image Library
The image is a coloured scanning electron micrograph (SEM) of a single dust mite among skin scales in house dust. Dust mites feed on flakes of shed human skin and are a common cause of asthma and allergic symptoms worldwide.