What are the bundles of fibers that send messages between the brain and spinal chord and other parts of the body called?

What are bundles of neurons called?  What causes the brain to send messages?  What is the main purpose of body fibers?  How do nerves send messages to the brain?  Explain how brain send message to the parts of the body?  Important body tissue that transmit messages to the brain?  How does the brain send messages to other parts of the body?  Axons and dendrites are clustered into bundles of fibers called?  What is the nerve pathway between the brain and other parts of the body called?  Thick bundle of nerve fibers through which the brain communicates with the body?  What is made of the bundles of neurons that carry impulss from all parts of the body to the brain and from the brain toall the parts of your body?  What is the bundles of neurons that carry umpulses form all parst of the body to the brain and from the brain to all the parts of your body?  All 31 pairs of spnal nerves which carry messages to and from the brain spinal cord and all parts of the body are called?  A bundle of fibers that carries messages between the brain and the spinal cord and other parts of the body?  What are the 12 structures receive and send sensory and motor signals between the body and brain?  Through what structure does the earthworms brain send messages to other parts of the body?  Provides great strength through parallel bundles of collagenic fibers found in tendons?