Larger diameters are typical of invertebrates and are nonmylenated
Cuttlefish (Sepia sp.) 200 micron Large central fibers
Squid (Loligo sp.) 400 micron Large central fibers
(Both used in early nerve research)
Crab 100 to 250 micron Central fiber
Lobster 60 to 90 micron Leg axons
Earthworms 40 to 90 micron
Cockroach 50 micron Central fiber
Carp 20 micron Lateral neuron
Human 10 to 20 micron Mylenated - to/from skeletal muscle
0.3 to 1.3 Nonmylenated - deep pain
Data from Rainer Flindt, Amazing Numbers in Biology,2003. (More specific citations within.)
Unmyelinated fibers typically have smaller diameters than myelinated fibers.
Axons send information away from a cell body.
A motor neurone connects the central nervous system (CNS) with an effector, which is to say either a muscle or a gland. The length of the neurone depends on the size of the animal. In a human, some of the longest neurones extend from the base of the spine to the foot. The longest must be in the largest animals. Think of a giraffe. Not to mention a blue whale!
an axon terminal
what is the axon made of
An axon hillock is a special cell body that connects an axon to a neuron. It is the last place where propagated membrane potentials are transmitted to the axon.
Dendrites, Axon, Axon Terminal, and Cell Body
The larger (wider) the axon's diameter, the faster the conduction. This is because resistance to the flow of electrical current is inversely proportional to the cross-sectional area of a conductor (such as a wire or an axon). page 1020, chapter 48.3, unit seven Biology AP, Campbell/Reece
axon hillock = where cell body meets the axon axon bulb = end of the axon...lies very close to the dendrites of another neuron so impulses can pass over the synapse. AP Biology student *