Source: Video and Images Created by Amanda Soderlind
Welcome to this lesson today on the central and peripheral nervous system. Today, we will be discussing the structure and function of both the central and peripheral nervous systems. So we are going to be starting out by discussing the central nervous system, also sometimes abbreviated CNS for central nervous system.
So the central nervous system is composed of the brain and the spinal cord, and contains all of the inner neurons of the nervous system. So all the inner neurons of the nervous system can be found within the central nervous system. And the central nervous system contains both afferent and efferent nerves.
So afferent nerves are nerves that carry info to the CNS while efferent nerves are nerves that carry info away from the CNS. So afferent nerves are carrying information towards the central nervous system, and efferent nerves are carrying information away from the central nervous system.
The other division of the nervous system is the peripheral nervous system, sometimes abbreviated PNS. So the peripheral nervous system is composed of 31 pairs of spinal nerves and 12 pairs of cranial nerves. So if you take a look at a diagram right here, the central nervous system is in this brown color, has the brain and spinal cord. And the peripheral nervous system is in green. So we have the cranial nerves, and then we also have the spinal nerves. And ganglia, which are clusters of neurons, can also be found in the peripheral nervous system.
So the peripheral nervous system is divided into two divisions. We have the somatic division and the autonomic division. So somatic nerves are nerves that carry signals to the head, the trunk, and the limbs. So the effectors for somatic nerves would be skeletal muscle, for example. And autonomic nerves are nerves that carry signals to your internal organs. So the effectors in this case, then, would be like smooth muscles or glands. So somatic and autonomic are the two divisions of the peripheral nervous system.
From there, we can actually break the autonomic division into two more divisions. So we have the sympathetic and parasympathetic division of the autonomic system. So sympathetic nerves are nerves that dominate at times of danger, stress, excitement. And basically, they increase the force and the rate of your heartbeat, increase your blood pressure, and increase your breathing. So what this does is it primes the body to respond to an emergency. So that's the sympathetic division.
Parasympathetic nerves are nerves that dominate during quiet, low-stress situations. So basically, what they do is slow the body down and divert energy to things like digestion or other housekeeping items. So sympathetic and parasympathetic nerves are actually antagonistic to one another. So the acts of one are opposite of the acts of the other. So the sympathetic and parasympathetic work antagonistically with each other.
So we're going to take a look at a diagram right here and fill this out just so you can kind of see how the nervous system is broken down a little bit more visually. So we're going to label this the nervous system. And then the nervous system, as we mentioned, is broken down into two divisions. We have the central nervous system and we have the peripheral nervous system.
And then, as we said, the peripheral nervous system can be broken down even farther into the autonomic division and the somatic division. And then the autonomic division can be broken down even further into sympathetic and parasympathetic nerves. So this just gives you kind of more of a visual of how the nervous system can be broken down into the different divisions and different nerves. So this lesson has been an overview on the central and peripheral nervous systems.