How the Autonomic Nervous System Works (2022)

Your nervous system helps you regulate your voluntary and involuntary actions, as well as thinking, communicating, and memory. Your autonomic nervous system is the aspect of the nervous system that controls all of your vital functions, like breathing, digestion, and heart rate—many of which you aren't consciously aware of. In short, it keeps you alive.

How the Autonomic Nervous System Works (1)

It's probably a good thing that your autonomic nervous system is out of your conscious control. If you fall when learning to walk, you may temporarily injure yourself, but you generally learn how to pick yourself up and start again. Can you imagine if you had to learn how to speed up your heart whenever you needed to? Or if you stopped breathing every time you forgot to breathe?

While few diseases attack the autonomic nervous system alone, almost all medical disorders have some impact on autonomic functions.

Autonomic Nervous System Anatomy

Your autonomic nervous system includes a craniosacral parasympathetic portion and a thoracolumbar part sympathetic portion. These are sometimes thought of as being opposite to each other, ultimately striking a balance within the body.

(Video) The Autonomic Nervous System: Sympathetic and Parasympathetic Divisions

The sympathetic and parasympathetic functions:

  • The parasympathetic is associated with rest and digestion. Its main function is to conserve the body’s energy and to help you sleep or break down and absorb the food you eat.
  • The sympathetic is responsible for the "fight or flight" response that helps you quickly use your body's energy in an emergency situation—like running away from danger.

The nerves of the autonomic nervous system synapse in a clump of nerves called a ganglion before the message is transmitted to the target organ, such as a salivary gland. This allows for another level of communication and control.

Function of the Autonomic Nervous System

The autonomic nervous system has many functions. The parasympathetic system performs basic housekeeping and controls things when you are at rest. The sympathetic system is the emergency system and helps you carry out life-saving flight or fight responses.

The Parasympathetic

Many nerves of the parasympathetic portion of the autonomic nervous system begin in the nuclei in your brainstem. From there, they travel through cranial nerves such as the vagus nerve, which slows the heart rate, or the oculomotor nerve, which constricts the pupil of the eye. Parasympathetic stimulation also causes your eyes to tear and your mouth to salivate.

Other parasympathetic nerves terminate in the walls of thoracic and abdominal organs like the esophagus, gastrointestinal tract, pharynx, heart, pancreas, gallbladder, kidney, and ureter. The sacral parasympathetic nerves synapse in ganglia in the walls of the colon, bladder, and other pelvic organs.

The Sympathetic

Sympathetic fibers of the autonomic nervous system exit the lateral (side) part of your spinal cord. They receive information from parts of the brain such as the brainstem and the hypothalamus.

(Video) Autonomic Nervous System: Crash Course Anatomy & Physiology #13

Fibers run from synapses in ganglia just outside the spinal column to their targets, usually along blood vessels. For example, the sympathetic nerves that dilate your pupils exit the spinal cord in your neck and synapse in the ganglion called the superior sympathetic ganglion, they then run along the carotid artery to your face and eye. The sympathetic nervous system supplies nerves to the abdominal and pelvic visceral organs, as well ashair follicles, sweat glands, and more.

Autonomic Neurotransmitters

The nervous system communicates through chemical messengers called neurotransmitters. Neurotransmitters like acetylcholine and norepinephrine are primarily responsible for communication in your autonomic nervous system.

  • In both the parasympathetic and sympathetic parts of the autonomic system, acetylcholine is released at the level of the ganglia.
  • Acetylcholine receptors in ganglia are nicotinic and may be blocked by drugs such as curare.
  • In the parasympathetic nervous system, postganglionic receptors in organs such as the gastrointestinal tract are called muscarinicand are susceptible to drugs such as atropine.
  • The post-ganglionic sympathetic neurons release norepinephrine. The norepinephrine released by the post-ganglionic neurons binds to adrenergic receptors. There are two main categories of adrenergic receptors, alpha, and beta, each of which has subcategories with their own unique properties and can be manipulated by different types of medication.

Neurotransmitters of the autonomic nervous system mediate important functions of the body, and these actions can also be regulated by medications that inhibit or stimulate these actions.

Blood Pressure Control

Blood pressure is a good example of how the sympathetic and parasympathetic components of the nervous system work together within the body. In general, there are two main things that cause blood pressure to go up: The speed and force of your pumping heart, and the narrowness of the blood vessels in your body.

  • When sympathetic nervous system activity dominates, your heart pumps hard and quickly, your peripheral blood vessels are narrow and tight, and your blood pressure will be high.
  • The parasympathetic system slows the heart and widens peripheral blood vessels, causing the blood pressure to fall.

Imagine that you stand suddenly after having been in a seated position for a long time. Receptors in blood pressure walls at the carotid sinus and aortic archsense the change in pressure and send messages to the brainstem, which responds appropriately by increasing your blood pressure.

(Video) Autonomic Nervous System: Sympathetic vs Parasympathetic, Animation

In other cases, you may need your blood pressure to rise because you are, say, terrified by an angry bear and you need quick energy to be able to run away. Even before you start to run, your brain has recognized the bear and sent messages to your hypothalamus to prepare your body to spring into action. Sympathetics are activated, the heart starts pounding, and the blood pressure begins to rise, providing you with oxygen and glucose to power your muscles so you can run as fast as possible.

While there are other systems that can control blood pressure, such as hormones, these tend to be gradual and slow, not immediate like those controlled directly by your autonomic nervous system.

Control of the Autonomic Nervous System

Most of the time, your autonomic nervous system works very well. However, the fight or flight response may become activated with small everyday stresses, releasing a lot of the stress hormone cortisol and driving your blood pressure and heart rate up unnecessarily.

For most of us, the autonomic nervous system is generally out of our conscious control. In the brainstem, the nucleus tractus solitarius is the main command center for the autonomic nervous system, sending input largely through cranial nerves IX and X.

The cerebral cortex of your brain, normally associated with conscious thought, can change your autonomic nervous system to some degree—usually involuntarily, but sometimes voluntarily. In the cerebral cortex, the insula, anterior cingulate cortex, substantia innominata, amygdala, and ventromedial prefrontal cortex are areas that help you understand the events that are going on around you, as well as your emotions. These regions communicate with your hypothalamus to impact the actions of your autonomic nervous system.

(Video) The Autonomic Nervous System and Why It’s Important

Voluntary Control of the Autonomic Nervous System

Because the cerebral cortex is linked to the autonomic nervous system, you may be able to control your autonomic nervous system through conscious effort, especially with some practice. Practices like yoga, mindfulness, and meditation can help you manage your physical autonomic nervous system activity.

Highly trained people, such as advanced yoga practitioners, may be able to intentionally slow their heart rate or even control their body temperature. Mindfulness and meditation can have similar effects.

For most of us, though, focusing on things that are relaxing rather than stressful, or just taking a slow, deep breath when you notice that you're feeling anxious or your heart is racing can bring your autonomic nervous system back into a degree of control.

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FAQs

How does the autonomic nervous system works? ›

The autonomic nervous system is a component of the peripheral nervous system that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. It contains three anatomically distinct divisions: sympathetic, parasympathetic, and enteric.

How does autonomic nervous system work quizlet? ›

What is the function of the autonomic nervous system? a control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.

How does the autonomic nervous system work to regulate the body's homeostasis? ›

The ANS regulates the internal organs to maintain homeostasis or to prepare the body for action. The sympathetic branch of the ANS is responsible for stimulating the fight or flight response. The parasympathetic branch has the opposite effect and helps regulate the body at rest.

What does the autonomic nervous system control Brainly? ›

The autonomic nervous system (ANS) is the division of the PNS that governs the internal activities of the human body, including heart rate, breathing, digestion, salivation, perspiration, urination, and sexual arousal.

What activates the autonomic nervous system? ›

The autonomic nervous system is one of the major neural pathways activated by stress. In situations that are often associated with chronic stress, such as major depressive disorder, the sympathetic nervous system can be continuously activated without the normal counteraction of the parasympathetic nervous system.

Why is autonomic nervous system important? ›

The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing. This system works automatically (autonomously), without a person's conscious effort. Disorders of the autonomic nervous system can affect any body part or process.

Which best describes autonomic nervous system control? ›

The correct answer is (c) Controls and maintains homeostasis. The autonomic nervous system consists of the sympathetic and parasympathetic nervous systems, which control the unconscious processes that help maintain homeostasis, or stable, internal conditions.

Which of the following is correct about the autonomic nervous system ANS quizlet? ›

Which of the following is correct about the autonomic nervous system (ANS)? The ANS is part of both the CNS and the PNS. ANS functions are involuntary. ANS motor neurons innervate cardiac muscle fibers, smooth muscle fibers, and glands.

Which of the following is controlled by the autonomic nervous system quizlet? ›

Autonomic nervous system controls smooth muscle, cardiac muscle, and glands.

How can autonomic nervous system be improved? ›

Autonomic Dysfunction Treatment

taking medication to help stabilize blood pressure; taking medication to control other symptoms, such as intolerance to hot temperatures, digestion issues, and bladder function; consuming fluids that are fortified with electrolytes; getting regular exercise; and.

What affects the autonomic nervous system? ›

Autonomic nervous system disorders can occur alone or as the result of another disease, such as Parkinson's disease, cancer, autoimmune diseases, alcohol abuse, or diabetes.

Where is the autonomic nervous system? ›

Where is it located? Your autonomic nervous system includes a network of nerves that extend throughout your head and body. Some of those nerves extend directly out from your brain, while others extend out from your spinal cord, which relays signals from your brain into those nerves.

What is the main purpose of the nervous system? ›

The nervous system transmits signals between the brain and the rest of the body, including internal organs. In this way, the nervous system's activity controls the ability to move, breathe, see, think, and more.

How does the autonomic nervous system control breathing? ›

The nervous system

Your breathing usually does not require any thought, because it is controlled by the autonomic nervous system, also called the involuntary nervous system. The parasympathetic system slows your breathing rate. It causes your bronchial tubes to narrow and the pulmonary blood vessels to widen.

Which brain structure controls the autonomic nervous system? ›

The hypothalamus is the key brain site for central control of the autonomic nervous system, and the paraventricular nucleus is the key hypothalamic site for this control. The major pathway from the hypothalamus for autonomic control is the dorsal longitudinal fasciculus.

Can stress cause autonomic? ›

Chronic real-life stress in humans appears associated to increased arterial pressure and to impaired autonomic regulation of cardiovascular functions.

How stress affects the autonomic nervous system? ›

In the male anatomy, the autonomic nervous system, also known as the fight or flight response, produces testosterone and activates the sympathetic nervous system which creates arousal. Stress causes the body to release the hormone cortisol, which is produced by the adrenal glands.

Is the autonomic nervous system under conscious control? ›

The autonomic nervous system is included in the peripheral system and is largely unconscious. It controls vital body functions such as heart rate, swallowing, breathing, digestion, and arousal. Although primarily unconscious, many aspects of the autonomic nervous system can come under conscious control.

What happens if the autonomic nervous system is damaged? ›

Autonomic neuropathy occurs when there is damage to the nerves that control automatic body functions. It can affect blood pressure, temperature control, digestion, bladder function and even sexual function.

Is the autonomic nervous system voluntary? ›

Although most of the autonomic nervous system responses are involuntary, they can integrate with the somatic nervous system, which is responsible for the voluntary movements. For example, in the case of defecation, there is an interplay between voluntary and involuntary movements.

Which part of the autonomic system is most likely to be dominant? ›

The 2 divisions of the ANS are dominant under different conditions. As stated previously, the sympathetic system is activated during emergency “fight-or-flight” reactions and during exercise. The parasympathetic system is predominant during quiet conditions (“rest and digest”).

Where do the autonomic nerves lead from and go to? ›

Innervation. Autonomic nerves travel to organs throughout the body. Most organs receive parasympathetic supply by the vagus nerve and sympathetic supply by splanchnic nerves. The sensory part of the latter reaches the spinal column at certain spinal segments.

What is it called when your body does something automatically? ›

A reflex is an involuntary movement to a stimulus.

Which neurotransmitter is important to the autonomic system of the PNS? ›

As mentioned, acetylcholine is the primary neurotransmitter of the PNS. Acetylcholine acts on cholinergic receptors known as muscarinic and nicotinic receptors.

Which is an example of an autonomic reflex? ›

Everyday examples include breathing, swallowing, and sexual arousal, and in some cases functions such as heart rate.

Which division of the autonomic nervous system is activated during the stress response? ›

The sympathetic nervous system directs the body's rapid involuntary response to dangerous or stressful situations.

Which of the following is not controlled by the autonomic system? ›

So, the correct answer is 'Memory and learning'

What are the two types of cells found in the nervous system? ›

Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the "conducting" cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell.

Which part of your nervous system helps you to conserve energy as it calms you down after a stressful event? ›

Your parasympathetic nervous system makes sure things are balanced. It works to relax you and helps conserve and restore energy. You need both systems to run properly. “Think of your sympathetic nervous system and your parasympathetic nervous system like your car's gas and breaks,” explains Dr.

Where is autonomic nervous system? ›

Where is it located? Your autonomic nervous system includes a network of nerves that extend throughout your head and body. Some of those nerves extend directly out from your brain, while others extend out from your spinal cord, which relays signals from your brain into those nerves.

What is an example of autonomic nervous system? ›

It operates automatically, and is generally considered to be outside the realm of voluntary control. Examples of the types of functions controlled by the ANS are salivating, sweating, changing pupil size, managing heart rate, crying, and secreting hormones.

What are the 4 nerves within the autonomic nervous system? ›

These are the preganglionic neurons, which synapse with postganglionic neurons in these locations: Parasympathetic ganglia of the head: Ciliary (Cranial nerve III), Submandibular (Cranial nerve VII), Pterygopalatine (Cranial nerve VII), and Otic (Cranial nerve IX)

Which of the following is an example of the autonomic nervous system at work? ›

Peristalsis of the intestines is the example of the action of the autonomous nervous system. The organs of our body (viscera), the heart, intestines and stomach, are regulated by a branch of the nervous system known as the autonomic nervous system.

Can we control the autonomic nervous system? ›

Because the cerebral cortex is linked to the autonomic nervous system, you may be able to control your autonomic nervous system through conscious effort, especially with some practice. Practices like yoga, mindfulness, and meditation can help you manage your physical autonomic nervous system activity.

What affects the autonomic nervous system? ›

Autonomic nervous system disorders can occur alone or as the result of another disease, such as Parkinson's disease, cancer, autoimmune diseases, alcohol abuse, or diabetes.

Can stress cause autonomic? ›

Chronic real-life stress in humans appears associated to increased arterial pressure and to impaired autonomic regulation of cardiovascular functions.

What are the two main functions of the autonomic nervous system? ›

The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing.

Which organ is not controlled by autonomic nervous system? ›

The organs that are not controlled by the autonomic nervous system are the skeletal muscles.

What happens if the autonomic nervous system is damaged? ›

Autonomic neuropathy occurs when there is damage to the nerves that control automatic body functions. It can affect blood pressure, temperature control, digestion, bladder function and even sexual function.

What is the opposite of autonomic nervous system? ›

The autonomic nervous system controls internal organs and glands, while the somatic nervous system controls muscles and movement.

Which part of the autonomic system is most likely to be dominant? ›

The 2 divisions of the ANS are dominant under different conditions. As stated previously, the sympathetic system is activated during emergency “fight-or-flight” reactions and during exercise. The parasympathetic system is predominant during quiet conditions (“rest and digest”).

Where does the autonomic nervous system originate from? ›

The first set, called preganglionic neurons, originates in the brainstem or the spinal cord, and the second set, called ganglion cells or postganglionic neurons, lies outside the central nervous system in collections of nerve cells called autonomic ganglia.

What part of the autonomic nervous system calms you down after an exciting event? ›

The parasympathetic nervous system (PSNS) is part of your autonomic nervous system, which regulates your automatic body functions, such as heart rate, metabolism, and body temperature. Your PSNS is all about slowing your body down, helping it to relax and rebalance, especially after anything stimulating has occurred.

Which branch of the autonomic nervous system helps return the body to homeostasis? ›

The parasympathetic division is responsible to maintain homeostasis when the body is at rest. Parasympathetic ganglia are located near or within the effector organs.

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