What occurs when the autonomic nervous system is stimulated by stressors?

sympathetic nervous system, division of the nervous system that functions to produce localized adjustments (such as sweating as a response to an increase in temperature) and reflex adjustments of the cardiovascular system. Under conditions of stress, the entire sympathetic nervous system is activated, producing an immediate widespread response called the fight-or-flight response. This response is characterized by the release of large quantities of epinephrine from the adrenal gland, an increase in heart rate, an increase in cardiac output, skeletal muscle vasodilation, cutaneous and gastrointestinal vasoconstriction, pupillary dilation, bronchial dilation, and piloerection. The overall effect is to prepare the individual for imminent danger.

The actions of the sympathetic nervous system occur in concert with other neural or hormonal responses to stress, including increases in corticotropin and cortisol secretion. In humans, chronic stress results in long-term stimulation of the fight-or-flight response, which leads to constant production and secretion of catecholamines (e.g., epinephrine) and hormones such as cortisol. Long-term stress-induced secretion of these substances is associated with a variety of physiological consequences, including hyperglycemia (high blood glucose levels), which can lead to type 2 diabetes mellitus, and hypertension (high blood pressure), which can lead to cardiovascular disease.

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Anatomically, the sympathetic preganglionic neurons, the cell bodies of which are located within the central nervous system, originate in the lateral horns of the 12 thoracic and the first 2 or 3 lumbar segments of the spinal cord. (For this reason the sympathetic system is sometimes referred to as the thoracolumbar outflow.) The axons of these neurons exit the spinal cord in the ventral roots and then synapse on either sympathetic ganglion cells or specialized cells in the adrenal gland called chromaffin cells.

The sympathetic nervous system is one of two antagonistic sets of nerves of the autonomic nervous system; the other set constitutes the parasympathetic nervous system.

A new manager at work. A child’s book report that’s due tomorrow (and of course, you find this out the night before). Driving in bumper-to-bumper traffic. When stressful thoughts consume your day, it’s easy to feel overwhelmed—and label this stress as strictly a mental problem.

But the reality is, stress manifests outside of your racing thoughts and intrusive thoughts. In fact, stress materializes as both emotional and physiological systems. After all, your brain and body are inseparable (yup, that’s the “mind-body connection” you’re always hearing about).

Whether you’re running from a lion or preparing for a presentation at work, your brain and body share a single response system for all stressors—the autonomic nervous system (ANS). Knowing how your body uses the ANS to react to different situations can help you build awareness. Then, you can identify practices that transform your stress reaction into a reasoned response.

Ready to tame your stress? Here’s what you should know about the autonomic nervous system.

What is the autonomic nervous system?

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Within your body, you have two overarching components of the nervous system: the central nervous system (consisting of your spinal cord and your brain) and the peripheral nervous system.

The is part of the peripheral nervous system, and it functions like a tug-of-war game between two subsystems: your activation (sympathetic nervous) system and your rest (parasympathetic nervous) system. Your sympathetic nervous system is well known as the driver of your activating, fight-or-flight response, while the parasympathetic nervous system kicks in during calmer moments as your rest-and-digest network

Both the sympathetic and parasympathetic systems regulate essential body functions like heart rate, respiratory rate, and digestion. Similarly, both systems dial their activity up or down, based on messages from your brain and spinal cord. These systems can be active at the same time, or one can take over and dominate the other.

What happens when your parasympathetic and sympathetic nervous systems are stimulated?

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When activated, these systems trigger a cascade of changes in your body.

When your fight-or-flight system starts to dominate, your resting heart rate increases and your heart rate variability decreases. Respiration speeds up (ever notice your breath quicken when you feel anxious?). Blood flow increases to muscles and lungs and simultaneously decreases to deprioritized areas. Finally, stress hormone levels rise, and some rest-and-digest functions scale back or stop altogether.

That last part is important to note. After all, your rest-and-digest system includes your heart, lungs, and liver; when those organs change how they’re functioning, it affects the rest of the body and brain. For example, when you’re running, your digestion naturally pauses. Or, when warming up for a jog, your body will shift its temperature-regulating strategy and reroute blood from your internal organs to your skin in an effort to shed heat.

Once your fight-or-flight response has played out, your rest-and-digest system can come back into balance. That means your resting heart rate decreases and heart rate variability increases. Your breathing slows, and your blood flow increases back to the digestive system and other organs so they can resume functioning. Finally, your stress hormone levels fall and you’re able to breathe that sigh of relief.

Finding balance between the two systems

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Life’s stress levels naturally fluctuate. When your body remains in a stressed-out, fight-or-flight mode, it can take a serious toll on your health by slowing your recovery time, weakening your immune system, and impacting your mental state.

Our ANS was designed to help us deal with brief episodes of high-intensity stress (like running from that lion). However, our modern lifestyle contains multiple chronic stressors that rarely shut off—job pressure, balancing childcare and work, sleep deprivation, and constant device stimulation, just to name a few.

So, how do we counteract these constant stresses invading our health? It’s all about balance. You don’t want your fight-or-flight system to be in a constant state of activation, but you also don’t want it to remain inactive. It is essential for your survival ability to respond to stress and maintain your body’s equilibrium.

How to manage your stress

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Chances are, you’re not aware of the tug-of-war we talked about earlier—the one between your fight-or-flight and rest-and-digest systems. These power struggles happen involuntarily and reflexively, without you even knowing. However, becoming more in tune with the physiological effects of stress can help you regulate your response or deploy strategies to bring you back into balance.

Try these tips to identify and reverse imbalances sooner:

• Become more self-aware: Techniques like meditation can help you become more in touch with how activated or relaxed your body is. Taking a moment during the day also offers an opportunity to reset imbalances when you sense them and may even improve your sleep.
• Sense imbalances sooner: Consider how wearables, like Oura, can give you the opportunity to follow patterns of stress within your body and measure their impact more objectively. You can even see your body’s ANS balance and reduce stress by monitoring your heart rate variability.
• Improve your resilience: Increasing your fitness level and improving your sleep both boost your body’s ability to bounce back from stressful periods. If you’re looking for ways to rest and restore, consider these ideas.
  

While every human being has an autonomic nervous system, the ways it activates and responds to stress can vary from person to person. To get the most effective advice on managing stress, look to precision healthcare. Not only will your healthcare professional ask about your lifestyle, but they’ll also look at your personal genomics, lab results, and biometrics to determine your specific risk factors for chronic stress. That way, you’ll be able to optimize your response to stress instead of relying on generalized advice.

What happens when the autonomic nervous system is stimulated?

What occurs when the autonomic nervous system is stimulated by stressors resulting in a fight or flight reaction?

Which autonomic nervous system is activated during stress?

Which part of autonomic nervous system turns on when you encounter stressors?