Nervous System

The nervous system is made up of the brain and spinal cord (the central nervous system or CNS) and the all the other nerves of the body (the peripheral nervous system or PNS).

The nervous system works along side the endocrine system to communicate information between organs and tissues and from the sensory organs to the brain. Most nerves are white in appearance because they are covered in a layer of fat called the myelin sheath. Much like the insulation on electrical wires, myelin acts as an insulator to prevent electrical signals from leaving the nerve. In contrast with the endocrine system, nerve impulses can travel very fast. Knowing that electrical impulses can travel at 225 miles per hour and a blue whale can be 100 feet long, can you calculate how long it would take a signal to travel from the brain of a blue whale to its tail?


Detailed annotated images of the nervous system in a California Sea Lion are shown below.  CLICK on an image to see an enlarged view.