The sympathetic nervous system is one of the two branches of the autonomic nervous system, which controls all the things we do unconsciously, like keeping our heart rate stable and digesting food.
This system is responsible for what's known as our "fight or flight" response - it kicks in when we're stressed, in danger or physically active. The effects of this system can be pretty dramatic - it can increase our heart rate and breathing ability, improve our eyesight and even slow down processes like digestion. In this article, we will discuss in detail the anatomy and function of the sympathetic nervous system!
What is the sympathetic nervous system (SNS)?
The sympathetic nervous system is one of two divisions of the autonomic nervous system. The autonomic nervous system controls the body's involuntary actions, such as heart rate and digestion. The sympathetic nervous system is responsible for the "fight-or-flight" response. This response is a natural reaction that helps us to deal with dangerous or stressful situations. It works by releasing adrenaline and other hormones that cause an increase in heart rate, blood pressure, and blood sugar levels. This can give us the extra energy and strength we need to deal with a threat.
In most cases, the sympathetic nervous system works automatically and we are not aware of it. However, we can also consciously activate the sympathetic nervous system by getting angry, scared, or feeling stressed out. Once the threat has passed, the sympathetic nervous system slowly returns to its normal state.
Structure of the sympathetic nervous system
The sympathetic nervous system (SNS) is a branch of the autonomic nervous system and is made up of a network of neurons, or nerve cells. These neurons are located all over the central nervous system (CNS) and the peripheral nervous system.
The CNS is composed of the brain and the spinal cord. The peripheral nervous system is made up of all the nerves that branch off from the CNS and extend to the rest of the body.
The sympathetic nervous system is made up of two types of neurons: preganglionic neurons and postganglionic neurons. Preganglionic neurons originate in the brainstem or spinal cord and send their axons, or nerve fibers, to the sympathetic ganglia. Sympathetic ganglia are clusters of neurons located near the major organs of the body, such as the heart, lungs, and stomach.
Postganglionic neurons are found outside of the central nervous system in the sympathetic ganglia. They receive input from the preganglionic neurons and send their axons to affect the function of organs such as the heart or lungs.
The sympathetic nervous system works with the parasympathetic nervous system to maintain homeostasis, or balance, in the body. The sympathetic and parasympathetic nervous systems are sometimes referred to as the "gas" and "brake" of the autonomic nervous system. The sympathetic nervous system is responsible for increasing heart rate and blood pressure while the parasympathetic nervous system has the opposite effect.
Functions of the sympathetic nervous system
The main function of the sympathetic nervous system is to control and regulate the cardiovascular system which is activated in response to fear and anxiety, stress, danger, or physical activity. When this happens, it releases hormones that increase heart rate and blood pressure. It also helps to maintain homeostasis by stimulating organs and systems that keep the body functioning properly. Some functions include:
Regulation of blood sugar
The SNS regulates blood sugar levels by stimulating the release of glucose from energy stores in the liver. This release of glucose provides the body with quick energy in times of stress. It also regulates blood sugar when you are hungry.
Regulation of blood pressure
The SNS helps to increase blood pressure by constricting (narrowing) the arteries and veins, also known as blood vessels. This provides the body with extra blood and oxygen in times of stress.
Pupil dilation to improve vision
The SNS increases blood flow to the eyes, which helps to enlarge or dilate the pupils. This allows us to see better in times of stress or danger.
Slowing down digestion
The SNS slows down digestion by decreasing blood flow to the digestive organs. This allows the body to redirect blood and oxygen to muscles that may be needed for the fight-or-flight response. This decrease in blood flow is what makes you feel "butterflies" in your stomach when you're nervous.
Regulating body temperature
To help keep your body at a comfortable temperature, the SNS regulates blood flow and sweating. When your body temperature rises, the SNS kicks in to cool your body down by increasing blood flow to the skin and making you sweat.
On the other hand, when your body temperature drops, the SNS kicks in by constricting blood vessels to preserve heat, makes your body shiver, and sends signals to release fatty acids to keep you warm.
What happens to your body during the Fight or Flight Response
As you can see, the sympathetic nervous system is responsible for a lot of different functions in the body which are involved in the fight or flight response as well.
The stress response starts when any of your five senses perceive a potential threat. For example, let's say you see a big dog coming your way; the message received through your eyes is sent to the visual cortex and processed by the brain which in a fraction of a second will assess the threat and determine how to react.
If the brain determines that the big dog is a threat, it will send an electrical signal to the amygdala, which is part of the brain that generally processes thoughts and emotions related to fear. The amygdala will then send a message to the hypothalamus to start releasing stress response hormones which will travel to the adrenal glands by activating the sympathetic nervous system. The adrenal glands will then release three main stress hormones: adrenaline, cortisol, and norepinephrine. These hormones will prepare your body for the fight or flight response by increasing your heart rate, blood pressure, and respiration. In addition, they will divert blood from your digestive system to your skeletal muscles so you can either run away from the big dog or stay and fight if a loved one is in danger.
As you can see, the stress response is a very complex process that happens in a fraction of a second. And it is designed to help us survive in life-threatening situations. Once the threat is gone, the parasympathetic nervous system kicks in to help our body return to its normal state.
Unfortunately, when fear or anxiety is so intense or continually experienced over a long period, the person’s sympathetic nervous system gets stuck in the fight-or-flight response causing the central nervous system and the brain to overload to the point of causing the neurons to stop working or even die. This is why most people end up developing mental illnesses or anxiety disorders.
In addition, the stress response can be triggered when there is no real threat present. For example, if you're constantly worried about bills or your job, your sympathetic nervous system will be activated more often than it should be. And this can lead to some serious health problems like anxiety, depression, cardiovascular disease, chronic stress, and more. That's why it's important to learn how to manage stress in your life.
Autonomic Dysfunction
This article will not be complete without mentioning autonomic dysfunction, which can damage the sympathetic nervous system.
Autonomic dysfunction is a condition that affects the autonomic nervous system. When CNS is not functioning properly, it can become erratic and out of control. Symptoms of autonomic dysfunction include dizziness, lightheadedness, fainting, fatigue, blurred vision, and difficulty swallowing.
The cause of this condition is often unknown, but it may be the result of an injury to the nervous system or a disease that affects the nerves. Treatment for autonomic dysfunction typically focuses on managing symptoms and improving quality of life. In some cases, medications may be prescribed to help control heart rate or blood pressure. In severe cases, surgery may be necessary to correct any damage to the nervous system.
So now that you know how the sympathetic nervous system works, what do you think? Are you going to be more mindful of the times when your "fight or flight" response is triggered? Let us know in the comments below!
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Frequently Asked Questions?
What is the autonomic nervous system (ANS)?
The autonomic nervous system function is to control the body's involuntary actions, such as heart rate, digestion, and respiration. The autonomic nervous system is divided into two parts: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNS). The SNS is responsible for the body's "fight-or-flight" response, while the PSNS promotes a sense of relaxation and well-being. Both systems work together to maintain homeostasis, or balance, in the body. The autonomic nervous system is controlled by the brainstem and the spinal cord. It receives input from sensors in the body and sends signals to the muscles and organs. In this way, the autonomic nervous system helps to keep the body functioning properly.
What is the parasympathetic nervous system?
The parasympathetic nervous system is a branch of the autonomic nervous system that helps to regulate the body's "rest and digest" functions. This includes activities like digestion, urination, and defecation. The parasympathetic nervous system is activated when the body is at rest or in a relaxed state. It works in opposition to the sympathetic nervous system, which is responsible for the body's "fight or flight" response.
While an overactive sympathetic nervous system increases heart rate and blood pressure, the parasympathetic nervous system decreases heart rate and blood pressure. The two systems work together to maintain a balance in the body. For example, when you are resting, your heart rate and blood pressure will be lower than when you are exercising. However, if you are in danger, your sympathetic nervous system will kick into gear to help you respond quickly. The two systems work together to keep your body functioning properly.
What is the spinal cord?
The spinal cord is a long, thin bundle of nerves that extends from the brain to the lower back. It is responsible for carrying messages between the brain and the rest of the body. The spinal cord is protected by the vertebral column, or spine. The spinal cord is divided into two main sections: the cervical and lumbar regions. The cervical region contains eight vertebrae, which protect the neck and support the head. The lumbar region contains five vertebrae, which protect the lower back. The spinal cord is also surrounded by a layer of tissue called the meninges, which helps to protect it from injury.
What are postganglionic neurons?
Postganglionic neurons are a type of nerve cell that transmits signals from the autonomic nervous system to specific organs or tissues. The autonomic nervous system controls involuntary actions, such as digestion and respiration. Postganglionic neurons are located in ganglia, which are collections of nerve cells outside of the central nervous system. There are two types of postganglionic neurons: sympathetic and parasympathetic. Sympathetic postganglionic neurons stimulate the "fight-or-flight" response, while parasympathetic postganglionic neurons promote rest and relaxation. Both types of postganglionic neurons use chemical signals, called neurotransmitters, to communicate with their target organs or tissues.
Postganglionic sympathetic nerves
The postganglionic sympathetic nerves are a network of nerves that originate from the sympathetic trunk and innervate various organs in the body. These nerves play an important role in the fight-or-flight response, as they help to increase heart rate and blood pressure. They also release adrenaline and noradrenaline, which help to prepare the body for action. In addition, the postganglionic sympathetic nerves help to constrict blood vessels and pupils, and they also stimulate sweat glands. As a result, they play a vital role in the body's response to stress.
What is sympathetic innervation?
Sympathetic innervation refers to the nerves that innervate (supply) the sympathetic nervous system. Sympathetic innervation plays an important role in mediating the fight-or-flight response and helps to ensure that the body has the resources it needs to deal with a stressful situation.
Please note: This article is for informational purposes only and should not be used as medical advice to treat mental health disorders or cure anxiety disorders. If you have any questions or concerns about your health, please speak with a doctor or other healthcare professional. Anxiety disorders and mental disorders can be serious, so it is important to seek medical help if you think you may be experiencing acute anxiety disorder symptoms. Always consult with a healthcare professional before starting any mental health treatment.
