or cotton-wool patches. Since the axon depends on axoplasmic transport for vital proteins and materials, injury, such as diffuse axonal injury, which interrupts the transport, will cause the distal axon to degenerate in a process called Wallerian degeneration. Cancer drugs that interfere with cancerous growth by altering microtubules (which are necessary for cell division) damage nerves because the microtubules are necessary for axonal transport. Infection The rabies virus reaches the central nervous system by retrograde axoplasmic flow. The tetanus neurotoxin is internalised at the neuromuscular junction through binding the nidogen proteins and is retrogradely transported towards the soma in signaling endosomes. Neurotropic viruses, such the herpesviruses, travel inside axons using cellular transport machinery, as has been shown in work by Elaine Bearer's group. Other infectious agents are also suspected of using axonal transport. Such infections are now thought to contribute to Alzheimer's disease and other neurodegenerative neurological disorders. See also Intraflagellar transport References Neurophysiology