Introduction to the Autonomic Nervous System - Online Tutor, Practice Problems & Exam Prep

The autonomic nervous system (ANS) consists of two main divisions: the sympathetic and parasympathetic systems. The sympathetic division activates the fight or flight response during stress, increasing heart rate and mobilizing energy. In contrast, the parasympathetic division promotes rest and digestion, lowering heart rate and facilitating homeostasis. Both divisions innervate the same organs but typically have opposing effects, crucial for maintaining physiological balance. Understanding these systems is essential for grasping how the body responds to various stimuli and maintains homeostasis.

Somatic vs. Autonomic Nervous System

Hey, everyone, and welcome to the autonomic nervous system. So we're going to begin this chapter by doing a quick review of the divisions of the peripheral nervous system because I know that there's a lot of divisions to keep track of here. As a quick reminder, our peripheral nervous system can be divided into 2 major subsystems. First, we have our somatic nervous system. The somatic nervous system innervates skeletal muscle and is going to be in charge of voluntary movement. There are a couple of reflexes thrown in there too, but mainly our voluntary movement. In our somatic nervous system, the efferent pathway, the motor pathway, consists of 1 neuron.

Now we also have our autonomic nervous system, and the autonomic nervous system innervates smooth muscle as well as cardiac muscle and glands, so more of those like visceral systems. And here the autonomic pathways are involuntary. This nervous system basically covers all of the bodily systems that keep you alive and help your body maintain homeostasis, all those things that you never have to consciously think about. And in our autonomic nervous system, the efferent pathway, the motor pathway, consists of 2 neurons. So you can see here in this figure we have our PNS divided into these 2 subsystems, our somatic nervous system and our autonomic nervous system. You can see that the somatic nervous system is covering that skeletal muscle and we covered a lot of that in detail in our chapter on the peripheral nervous system. So if you want a review of the somatic nervous system, go check out that chapter. From this point on, we'll be focusing entirely on the autonomic nervous system. So I'll see you in our upcoming videos. Bye bye.

Introduction to the Autonomic Nervous System Example 1

Alrighty. So for this one, we're going to be figuring out whether each of these movements is coordinated by our somatic nervous system or our autonomic nervous system. So remember, with the somatic nervous system, we're thinking about skeletal muscles, either voluntary movements or reflexes involving skeletal muscles. And our autonomic nervous system is about viscera and glands, things we have no conscious control over. Right? So looking here, we have heart rate increasing, and that is definitely autonomic. Right? No skeletal muscle involved there, and it's all involuntary. And the same for pupils dilating. Right? That's an involuntary response. That is our autonomic nervous system. Our knee jerk reflex involves skeletal muscles. Right? That's a reflex that we have in our somatic nervous system. And then secreting insulin, that is autonomic. Right? That is an involuntary process that does not involve skeletal muscles. Then e, we have a sudden jump in response to a loud sound, a startle reflex that involves skeletal muscles; that is somatic. And then throwing a ball, that is a voluntary action involving our skeletal muscles, which is again a somatic action. Alright? So there you have it.

Which of the following is the primary functional difference between the somatic nervous system (SNS) and autonomic nervous system (ANS)?

• A. The SNS controls glands, the ANS controls muscles.
• B. The SNS controls involuntary muscle, the ANS controls voluntary muscle.
• C. The SNS controls voluntary muscle, the ANS controls involuntary muscle.
• D. The SNS sends signals from the CNS, the ANS sends signals from the PNS.

Divisions of the ANS

In this video, we're going to be talking about the divisions of the autonomic nervous system. Our autonomic nervous system can be organized into two divisions. We have our sympathetic division or the sympathetic nervous system, and we have our parasympathetic division or the parasympathetic nervous system. These two divisions are working in some kind of balance usually, which is called autonomic tone, but they also respond to environmental cues or emotionally salient stimuli in your environment. When that happens, one system will become more dominant, and one will get suppressed temporarily. Our sympathetic division is going to become activated when we are engaged with a stimulus, when we are feeling threatened, or when we're feeling stressed. So, basically, if we're feeling some kind of strong emotional arousal, either positive or negative, this division will kind of kick in and become more dominant. This division is responsible for our fight or flight response, which I'm sure you've heard of, which is our body's attempt to mobilize energy resources to help us either encounter a threat or potentially run away from one. Here we have this kind of quintessential evolutionary example of a fight or flight response kicking in when, for instance, a lion is chasing you. But to be clear, anything that stresses you out is going to activate this division. So, for example, if you have a huge presentation coming up in your anatomy and physiology class and you're really stressed out about it, your fight or flight response is going to kick in. It's the exact same physiological process. Our sympathetic division will also help us maintain homeostasis when we are engaged in physical activity. So, for example, if you're playing a soccer game or a basketball game and you have to maintain a physiologically aroused state for a good hour or two, you need that increased heart rate, blood pumping to your muscles, your lungs taking in lots of oxygen, this system will help you maintain homeostasis during that. Now, on the flip side, we have our parasympathetic division, and this becomes activated when we are relaxed and calm and at rest. In contrast to fight or flight, this system is sometimes called our rest and digest system. As we will see in some upcoming videos, this system is very important for healthy digestion in particular, but it basically helps us maintain homeostasis when we are at rest. It lowers the heart rate, slows down the breathing, and helps your body focus on more homeostatic activities like digestion. These two systems by and large innervate the same organs; they innervate the same effectors. However, they usually have opposite effects. For example, if one division stimulates an effector, the other division usually inhibits it. We're going to be covering both of these systems in a lot more detail in upcoming videos. Alright. So I will see you there. Bye bye.

Introduction to the Autonomic Nervous System Example 2

Okay. So this one asks us, which of the following is true of the sympathetic and parasympathetic divisions of our ANS? So looking through them, I see a reads that our sympathetic division is responsible for an increase in heart rate and that's true. Right? We got it in 1. So our sympathetic division is also our fight or flight response. Right? So if something in your environment is threatening or stressful or causing you some kind of major emotional arousal, even a positive arousal, it's going to kind of help your body gear up to deal with that. And that involves things like increasing your heart rate. So a is our answer. I can see here that both b and c would involve our parasympathetic division increasing heart rate and that's just not what it would do. Right? Our parasympathetic division is our rest and digest. It helps your body maintain homeostasis when things are calm. It's not going to be increasing your heart rate. And then d here claims that neither division would be responsible but both of these divisions do indeed innervate our heart just in opposite ways. So our answer here is a, and there you go.

Ruby has just eaten a large meal and is now laying down on the couch to relax. Her _________________ nervous system becomes active, allowing her to digest her meal. She decides to watch a horror movie, which causes her ___________________ nervous system to take over as her heartbeat _________________ and sweat glands become active.

• A. Parasympathetic, sympathetic, decreases.
• B. Parasympathetic, sympathetic, increases.
• C. Sympathetic, parasympathetic, decreases.
• D. Sympathetic, parasympathetic, increases.

Here’s what students ask on this topic:

What are the main divisions of the autonomic nervous system?

The autonomic nervous system (ANS) is divided into two main divisions: the sympathetic and parasympathetic systems. The sympathetic division is responsible for the 'fight or flight' response, which activates during stress or perceived threats, increasing heart rate and mobilizing energy. On the other hand, the parasympathetic division promotes 'rest and digest' activities, lowering heart rate and facilitating digestion and other homeostatic functions. Both divisions innervate the same organs but usually have opposing effects to maintain physiological balance.

How does the sympathetic nervous system affect the body during stress?

During stress, the sympathetic nervous system activates the 'fight or flight' response. This leads to several physiological changes: increased heart rate, dilation of airways, and mobilization of energy stores. Blood flow is redirected to essential muscles, and non-essential functions like digestion are temporarily suppressed. These changes prepare the body to either confront the threat or flee from it, ensuring survival in stressful situations.

What is the role of the parasympathetic nervous system in maintaining homeostasis?

The parasympathetic nervous system plays a crucial role in maintaining homeostasis by promoting 'rest and digest' activities. It lowers the heart rate, reduces blood pressure, and stimulates digestive processes. This system helps the body conserve energy and perform essential maintenance functions, such as digestion and waste elimination, when at rest. By counterbalancing the sympathetic nervous system, it ensures that the body can recover and maintain a stable internal environment.

How do the sympathetic and parasympathetic nervous systems interact to regulate heart rate?

The sympathetic and parasympathetic nervous systems interact to regulate heart rate through opposing actions. The sympathetic nervous system increases heart rate by releasing norepinephrine, which binds to receptors on the heart, enhancing its activity. Conversely, the parasympathetic nervous system decreases heart rate by releasing acetylcholine, which binds to different receptors, slowing down the heart's activity. This dynamic balance ensures that the heart rate is appropriately adjusted based on the body's needs, whether during stress or relaxation.

What is autonomic tone and how does it affect the balance between the sympathetic and parasympathetic systems?

Autonomic tone refers to the continuous level of activity maintained by both the sympathetic and parasympathetic nervous systems. It represents the baseline level of activity that keeps the body's physiological functions in balance. Autonomic tone ensures that neither system is completely dominant, allowing for quick adjustments in response to environmental or internal changes. For example, during stress, the sympathetic tone increases, while the parasympathetic tone decreases, and vice versa during relaxation. This balance is crucial for maintaining homeostasis and responding appropriately to various stimuli.