Signals called impulses are sent through nerve cells. These impulses flash along neurons. Neurons contain three parts: dendrites, a cell body, and an axon. Impulses can race at speeds of up to 120 meters per second. The gap between neurons is a fraction of an inch wide. The axon releases chemical droplets, which connect the neurons. Sensory neurons collect information from stimuli and send it to the brain and spinal cord. Motor neurons carry commands to the glands and muscles. Others help transport food through the intestines and speed up the heartbeat. Associative neurons pass impulses from sensory to motor neurons.