Processes in the Autonomic Nervous System

The human body consists of countless complex systems that work and interact seamlessly, many of which automatically carry out vital functions. These automatic, meaning involuntary, functions are crucial for human survival, health, and overall well-being. The process of unconsciously keeping humans alive and functioning properly is homeostasis.

Homeostasis:

Homeostasis comes from ancient Greek words “homo” and “stasis,” which respectively mean “equal” and “hold still.” Homeostasis, likewise, is a self-regulating process where biological systems maintain and regulate their internal systems to reach a stable environment while adjusting to external conditions. Homeostasis explains how an organism can maintain relatively constant internal conditions with the ability to adapt to survive challenging external environments (Billman, 2020). While homeostasis’s main function is maintaining the overall balance of everything the body needs, it also helps the body adjust to conditions and recover from injuries and illnesses. A maintained balance is when the body's internal environment, including oxygen levels throughout the respiratory system and temperature, is just right. While water and oxygen are crucial, drinking too much water can cause hyponatremia, a condition where the concentration of sodium in the blood is dangerously low, and breathing pure oxygen for a long period can result in oxygen toxicity, both of which are deadly conditions (Cleveland Clinic, 2025).

Homeostatic processes are automatically conducted by the hypothalamus in the brain through positive and negative feedback. Negative feedback means your body senses an unwanted change and will try to reverse it. Most homeostatic processes rely on negative feedback, such as blood flowing against the pull of gravity to your head, sweating to cool down, shivering to generate heat, fluid balance to extricate extra fluid, and respiratory homeostasis with increased activity as the demand for oxygen increases. Positive feedback means the processes add to themselves and strengthen until the initial cause is gone. An example is the cervix beginning to stretch during childbirth, which triggers nerve signals to the brain that work with the hormone oxytocin to cause contractions. In another case, blood clots may form to seal a wound, or the immune system may cause inflammation at the site of infection or injury (Cleveland Clinic, 2025).

Human survival is dependent on homeostasis and the processes that drive it. When an individual is injured or sick, the body adjusts its homeostatic processes to recover, such as a fever accompanying infections or blood clots sealing a bleeding wound. However, chronic conditions occur when something goes wrong, and the homeostatic processes cannot adjust sufficiently to make up for it. For example, high blood pressure and hypertension occur when the human body cannot keep the pressure within a healthy range, and osteoporosis happens when bones lose calcium faster than the body can replace it (Cleveland Clinic, 2025).

Respiration:

Human beings are powered by breathing approximately 22,000 times a day; however, it is regulated subconsciously. Breathing does not normally require any thought as it is controlled by the autonomic nervous system, otherwise known as the involuntary nervous system (NIH, n.d.). As the lungs breathe in air, they remove the oxygen and pass it through the bloodstream. The oxygen is then carried off to the tissues and organs, creating energy that allows humans to walk, talk, and move. The medulla oblongata links the cardiovascular and respiratory systems together into one that controls vital signs, including heart rate, breathing, blood pressure, and so forth (Cleveland Clinic, 2022). Activities will change vital signs when the cardiovascular system follows neural instructions. For example, when exercising, the brain sends signals to the lungs to work faster, but when sleeping or resting, the lungs slow down (NIH, n.d.).

The lungs are like sponges; they cannot enlarge by themselves. When inhaling, the muscles in the chest and abdomen contract to create a small vacuum around the lungs, which causes air to flow. When exhaling, the muscles relax, and the lungs deflate, which is similar to a balloon deflating if the air is left in for too long (NIH, n.d.).

Blood Pressure:

Blood pressure is the force of the blood moving through the arteries. When the heart beats, it generates pressure to pump oxygen-filled blood into the arteries, which carry blood, oxygen, and nutrients throughout the body’s cells and tissues. The heart uses the contractile force of the myocardium to pump blood. As the heart muscles contract, pressure forces blood into the arteries, which creates blood pressure. The power of the contraction determines the amount of blood pumped with the heartbeat and the pressure on the walls of the arteries. Although this functions automatically, the beating during this vital process occurs between 60 and 100 times a minute, 24 hours a day (Better Health Channel, n.d.).

Blood pressure fluctuates according to the body’s needs. It responds to the body’s position, breathing, emotional state, exercise, and sleep. What is considered healthy blood pressure varies for everyone. Nevertheless, blood pressure should be checked regularly by a physician because high blood pressure, or hypertension, is a major risk factor for failures in body systems and usually has no symptoms (Better Health Channel, n.d.).

Gastrointestinal System:

The Gastrointestinal System, otherwise known as the GI system, GI tract, and digestive system, supports a healthier body. The GI tract is essential for the human body’s responsibility for breaking down food into nutrients that the body can absorb and utilize for energy, growth, and cell repair. Not only is it responsible for the entry and exit of food, water, and other liquids, but the gastrointestinal system is also a major component of immune function, supporting blood flow, energy production, and the maintenance of overall immune homeostasis (Weill Cornell Medical Center, n.d.).

Each of the many parts of the digestive system aids in moving and breaking down food and liquid into smaller parts throughout the GI tract. Once completed, the small intestine absorbs most of the nutrients, and the circulatory system transports the nutrients to other parts of the body either to store or to utilize them. Special cells aid the absorbed nutrients to cross the intestinal lining into the bloodstream to the liver, where simple sugars, amino acids, glycerol, vitamins, and salts are stored, processed, or delivered when needed (NIH National Institute of Diabetes and Digestive and Kidney Diseases, 2017).

Conclusion:

Autonomic body functions are crucial for survival and maintaining the body’s proper functioning. These compulsory processes ensure that humans can carry out their daily activities without having to consciously regulate them. They work continuously in the background, adjusting to changes in an individual’s internal and external environments. The body’s ability to self-regulate is a testament to the remarkable complexity and intricacy that enable human beings' existence, sustain life, and overall support human health.

References

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     from https://www.nyp.org/monahancenter/about-gi-system.html.

Billman, G. E. (2020). Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology. Frontiers in physiology, 11, 200. https://doi.org/10.3389/fphys.2020.00200

Blood Pressure. (n.d.). Better Health Channel. Retrieved March 2, 2025, from

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Homeostasis. (2025, March 11). Cleveland Clinic. Retrieved March 2, 2025, from

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Medulla Oblongata. (2022, May 15). Cleveland Clinic. Retrieved March 11, 2025,

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Your Digestive System & How it Works. (2017, December). NIH National Institute

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