Our body is broken down into the autonomic and somatic nervous system. For this post, we are going to focus just on the autonomic nervous system. With that being said, everything within this post will be about the sympathetic and parasympathetic nervous system.
Our body is incredible. We are able to control almost every part of our body and our body is able to "run" on its own. For example, our heart, is able to beat without us telling it to beat. This is our autonomic nervous system (ANS). Within the ANS, it is divided up into two categories: sympathetic (SNS) and parasympathetic nervous system (PSNS). Our SNS acts on a concept known as the "fight-or-flight" response. With this response, if something triggers our body, such as we get scared, our heart rate will increase, or bronchi will dilate, convert glycogen to glucose, stimulate the release of adrenaline, and contract our bladder. By doing this, our body is preparing to "fight." It is up to our brain to decide whether or not we stay and "fight" or "flee" the event.
When our body is triggered to just relax, we have stimulated our PSNS. This allows for us to rest, digest our food, urinate/defecate, cry, salvage, and a few more. After we eat a meal, our body goes into the PSNS to allow our body to digest out food and move it throughout the GI tract.
Let's think about this for a second. Say you are walking down the road, and someone comes up to and wants to fight. Our body has two phases to choose form: stay and fight, or run away. If our body decides that it wants us to stay and fight, we have put our body into a sympathetic state. Whereas if we run away, and I mean run fast, because we are scared like no-other, than we have put our body into a parasympathetic state. Now, let's look at this. You are given a patient, who is in critical condition. What is the best state to be in? Parasympathetic or sympathetic? In all reality, both. The reason is because we want our body to do what we can to help this patient, but at the same time we need our body to be relaxed.
Overall, our body is a piece of art, that no matter how much we study it, we continue to learn new things involving our autonomic nervous system.
What drug do we give to a patient who is bradycardic, and what is the pharmacodynamic of the drug?
-Atropine. This drug works by blocking our PSNS, thus allowing the SNS to take over, thus increasing our heart rate.