The spinal cord - the link between the brain and the body - is a band of nervous tissue about the thickness of your little finger that runs through the backbone. Nerve cells called motor neurons convey electric impulses that travel from the brain to the spinal cord, branching off at the appropriate point and passing to the various parts of the body. Similarly, sensory neurons transmit messages from organs and tissues via the spinal cord to the brain. But the spinal cord also functions without the brain having to intervene; it alone controls those actions called spinal reflexes that need to be carried out very fast in response to danger.