The nervous system is the body's communication system. It sends information to and from the brain and allows the control of the rest of the body in response. And the nervous system is divided into two parts. We have the central nervous system, which is our brain and our spinal cord, and the peripheral nervous system. This tutorial will focus specifically on:
The peripheral nervous system is the part of the nervous system that extends out from the brain and spinal cord to the rest of our body. Carrying things like motor and sensory information, it controls voluntary as well as involuntary behaviors and actions in the body. And the peripheral nervous system is divided into two parts, so we have the somatic and the autonomic nervous systems.
The somatic nervous system includes all the nerves that connect to the sense organs and the skeletal muscles within our body. It controls all of the voluntary behavior and all of the motor neurons, things that help to move the body. They allow for actions, like drawing, jumping, running, anything that we control directly.
Motor neurons can also control involuntary reactions. And these are things that we called the reflex arc, which are simple, automatic responses to stimuli in the world.
When you go to the doctor's office and they hit your knee to see if your knee reacts very quickly, that's not something you necessarily control.
The stimuli, the hitting of the knee, sends a reaction, not directly to your brain, but rather just to your spinal cord. The spinal cord is where reflex arcs are controlled. And then that response is sent right back to your leg more quickly than if it has to go directly to your brain and allows your knee to give a quick jerk.
Sensory neurons are controlled in the somatic system, which is responsible for smell, taste, sight, as well as our skin for touch. So as you can see, the somatic system covers quite a lot of ground.
The autonomic nervous system includes all the nerves within the rest of our body that connect to our internal organs. They control all of the internal involuntary body functions like breathing, which we can control voluntarily but generally is outside of our control, and it's something we just do automatically. Also, things like heart rate, digestion, anything that's happening with the organs within our body.
The name itself, "autonomic," it looks a little bit like "automatic", which may help you remember that this system is responsible for automatic, involuntary reactions.
The autonomic nervous system is further subdivided into two different parts:
The sympathetic branch of the autonomic nervous system controls any kind of body responses that are related to flight or fight. This is a protective response that kicks in when you feel like you're in danger. Perhaps your heart beats faster or your palms sweat. This is a result of the sympathetic nervous system.
Sympathetic Branch: Increases heart rate, dilates pupils, releases adrenaline, stops digestion. It also releases the bladder.
When people get so excited they might throw up or accidentally urinate themselves. This is the sympathetic nervous system in action.
Parasympathetic Branch: Constricts pupils, stimulates digestion to get you back on track, slows the heart rate, and makes you feel more calm.
Someone is driving too close behind you and honking the horn. Once they turn off, you take a deep breath and your hands are no longer sweaty.
Whereas the sympathetic nervous system excites the body, the parasympathetic nervous system keeps it at a normal level. It decreases from an excited state to a lesser level and helps to maintain the body or bring it down after danger has passed.
This tutorial covered the breakdown of the peripheral nervous system. It is broken into somatic and autonomic systems. The somatic nervous system handles all the actions we do with direct control such as drawing or jumping, and the autonomic nervous system is the involuntary reaction, such as the knee jerk and breathing. The autonomic system is further broken down into the sympathetic branch, which is responsible for exciting the body, and the parasympathetic branch, which calms the body down.
Source: This work is adapted from Sophia author Erick Taggart.
Nerves connected to the sense organs and skeletal muscles, which control voluntary movement, reflexes, and sensory neurons.
Controls body responses related to “flight or fight” response, when feel like in danger.
Nerves connected to internal organs, which control internal, involuntary body functions (like breathing, heart rate, and digestion).
Helps to maintain normal body functions and calm it down when excited by the sympathetic nervous system.
Simple, automatic responses to stimuli.
Neurons that send information to brain from sense organs.