THE NERVOUS SYSTEM [ IN HARMONY ( MANY PARTS/HEAD & BODY ) ]
Much of what goes mto making music takes place without thought. Professional musicians don’t stop to ask themselves, How do I playa C major chord? Instead, their actions have become automatic. Likewise, some learned actions are so routinely processed that they pass out of the conscious thoughts of the cortex and are pushed deeper into the rote performance of the cerebellum.
The similarities continue. The noise of some instruments may be drowned out by the trumpets and drums, but those sounds are still there, just as the brain’s control of breathing and heartbeat continues regardless of whether they register on the mind. The conductor may step down from the podium and lower his arms; the brain rests and the body falls asleep. Or the pianist may have injured an arm and play badly or not at all, just as the signals to or from the brain may fail, and the body consequently suffers.
HEAD & BODY
The human body has been shaped through cephalization, an evolutionary force that concentrates nervous and sensory tissue at one end of the body. Animals under- going this process enjoy advantages in natural selection. When vision, hearing, smell, and other faculties work with a nearby brain, they provide a rich picture of the world. Specifically, having a head improves efficiency in locating food and avoiding predators.
A narrow gap between brain and sensory organs, such as eyes, creates the shortest pathways for information to move back and forth between the two. That reduces reaction time. Imagine the alternative: if you had organs of vision in your toes, it would take a moment longer for any images they register to reach a brain at the other end of your body, and another moment or two for the brain to send them feedback. That’s a long delay when the eyes detect a potential threat. There’s not typically a lot of variation from one head to another.
Each brain lies encased within a hard, bony skull, a series of 22 fused bones that protect it. Inside the skull is a series of protective membranes called meninges that cover the brain tissue and blood vessels, and a shock-absorbing liquid called cerebrospinal fluid. The average man’s brain weighs about 3.5 pounds; the average woman’s, 3.2. Taken as a pure ratio between brain size and body mass, that’s not a significant difference.
Like a captain on the bridge of a ship, the brain issues commands atop the spinal cord, which also lies within protective membranes, a column of bones called vertebrae, and cerebrospinal fluid. The brain communicates with most of the body through nerves that pass through the thumbwide bundle of the spinal cord inside the vertebrae, and branch out in 31 pairs of spinal nerves, each serving its own region. A few nerves, such as those that serve the face, connect directly to the brain.