Functional and Anatomical Organization of the Nervous Tissue
Objectives
By the end of this section the student will be able to:
- identify the anatomical and functional divisions of the nervous system
- list the basic functions of the nervous system
Divisions of the Nervous System
The nervous system has three major functions; sensory, integration, and motor. The sensory function is involved with detecting changes in the internal and external environment. The integration function involves processing the sensory information and formulating a response. The motor function is involved with controlling effectors such as muscles and glands.
These functions would be displayed if you ordered a pizza one night when you were very hungry. Simply anticipating the pizza would make your mouth water. When you heard the delivery person pull in the drive, your entire digestive system would kick into action. Your stomach would start to secrete gastric juice and increase its muscular activity. The way you smell and see the pizza would cause your digestive system to swing into full gear, and that first bite would be the culmination of your anticipation. The motor responses (salivation and increased gastric activity) would be appropriate for the sensory input of seeing, smelling, tasting, and anticipating the food.
Suppose you opened the door expecting the pizza delivery person but found an angry grizzly bear instead. You would see the bear, hear its growl, and smell its breath. Your entire body would instantly be prepared to fight or flee (I suggest the later). Your heart rate would increase, your breathing rate would increase, your pupils would dilate, and you would experience a massive rush of epinephrine from the adrenal glands. I suspect you would scream slam the door shut and run to another room in your house. Again, this would be an appropriate motor response to the given situation.
In both cases above, your nervous system detected these environmental factors, processed the sensory input (integration), and sent out the motor responses to your muscles and glands. Consider what might happen if we "had our wires crossed" and the grizzly bear was at the door, we would salivate, experience increased gastric activity, and try to hand the bear a check. Or we might scream, slam the door, and run from the pizza person with the pizza. Of course, we do not have "wires" to cross but it is an interesting way to demonstrate what might happen if integration did not work properly.
Although we do not have electrical "wires" that run through our body (normally); we do have several similarities to electrical devices. Think about an amplifier for a stereo system. The amplifier simply amplifies the sound that comes into it from its input devices such as CD players, cassette decks, DVD players, and video cassette players. The amplifier then sends signals to the speakers. There are wires that go into the amplifier and wires that come out of the amplifier. The wires that go in are input wires from the various sound-producing components. The wires that go out conduct the amplified sound information to the speakers. You can change the qualities of the sound with the amplifier such as volume, tone, left right balance, base and treble balance, etc.
