Lesson Notes

Lesson 2.2a  Central Nervous System (CNS): The Brain and Spinal Cord

In this lesson you will learn that the Central Nervous System (CNS) consists of the brain and spinal cord. Our CNS is what makes humans unique to other animals. The CNS is what controls our reflexes, even ones we have since birth. It allows us to process information quickly, learn, and adapt to our environment. Looking at the spinal cord, it is like a major highway leading to our brain. It carries messages to and from the brain and helps determine which messages get sent. Our brain is the main executive of our bodies. Damage to either of these areas can be severely dangerous, even lethal.

Lesson 2.2b  Peripheral Nervous System (PNS): Connecting the CNS to the Rest of the Body

This lesson talks about the peripheral nervous system (PNS), the system that is literally on the “periphery”. The main function of the PNS is to carry and send messages from the brain and spinal cord to the outside areas of the body. Whether that area be you fingers, nose, feet, or shoulders, messages to these areas start and end with help from the PNS. 

The PNS is also divided into separate divisions with unique responsibilities (the Somatic Nervous System and Autonomic Nervous System). The SNS controls voluntary actions like your eyes moving across the page and your fingers typing on the keyboard. While the ANS is in charge of involuntary functions, such as breathing or your heart beat.

The Autonomic Nervous System is further divided into two other branches: The Sympathetic Nervous System and the Parasympathetic Nervous System. The primary role of these branches is important to our basic survival. The Sympathetic system prepares us for “fight or flight”, while the Parasympathetic system’s role is to calm our bodies down. Let’s look at an example. Say you were in the woods and saw a bear. Upon seeing the bear your Sympathetic Nervous System is going to kick in. You will start to experience a shortness of breath, your blood flow will go to your legs and arms, and bodily functions like hunger will be suppressed. In other words, your body is getting ready to run (flight). Once you are long gone and safe from danger, your body Parasympathetic Nervous System starts to kick in to calm your body down and get you back to functioning normally. As you can see, these areas of the nervous system are vital to our survival.