The nervous system
The nervous system
Michael is out and about. Hi Michael! - Shhh! - Oh, good music? -- Alright, we won't interrupt. -- Hmm, what's going on inside Michael right now? He is seeing a group of musicians, with his eyes, of course. He is hearing the music they're playing, with his ears. And he is thinking about what he is experiencing, with his brain.
This means, the eyes and the ears must be in contact with the brain in some way. They communicate. But how? What does that communication look like? Let's have a closer look at that. -- The body consists of cells, and all cells have their particular tasks.
This cell is a bit special, with a unique appearance... almost like a star. The tentacles function a bit like antennae. They can catch a signal from the eye, for instance. The signal is passed on, through a cord for outgoing signals.
This signal is detected by the adjacent cell, which in turn passes it on. The cells in a row form a long thread. And this is where the communication takes place. The thread is a nerve, and these cells that look like stars are nerve cells. Throughout our bodies, there are nerves forming a network that transmits signals back and forth.
Signals about what we see and hear, for example. In the spine, there is a collection of nerves grouped together. This is the spinal cord, and it is in direct contact with the brain. The nerves, the spinal cord and the brain, together constitute the nervous system of the body. -- The brain and the spinal cord form the central nervous system. The nerves out in the body form the peripheral nervous system. -- When somebody touches your arm, specialised sensory cells are activated.
They register the touch and convert it to nerve signals, which are transmitted into the body. The signals move in a flash, first to the spinal cord, and then on to the brain. This is when we really feel the tap on the arm: when the brain interprets and analyses. And this is exactly what happens in Michael's brain when he is standing in the city square. Lots of signals about the music and the people in the square have been sent to his brain.
The brain interprets, and analyses. And now Michael notices another thing. The trumpet girl is quite cute. Yes, in fact very cute. Oh, Michael gets a bit shy, and blushes… … but he still chooses to approach the trumpet girl and talk with her.
When Michael decides to do that, the brain transmits a signal to the muscles in the legs. The muscles respond to the signal, and start to move. The blushing in the face, though, is not a decision made by Michael. It just happened. But it is the brain that transmits the signal to the body, to increase the blood flow and make the cheeks redden.
What can we learn from all this? For one, that there are two kinds of nerve function. One that you can control consciously, for instance to do with moving or talking. This is the somatic nervous system. The other function we can not always control, and we don't need to.
We breathe without thinking about it; and it's the same thing with the heart. It beats without us deciding about it. This function is called the autonomous nervous system. The other thing to learn is that nerve signal go in two directions. Information about what we see, hear, and feel go to the brain.
Signals controlling the muscles go from the brain. The nervous system is active in all parts of the body, and involved in many of the body's functions. When you hear music, the hearing nerves are activated. If you start to dance, the nerves make the body move. And that nice feeling you can get in the body when you hear music you like, is controlled by the nerves.
But nothing of this matters to Michael right now. He's just grooving...