Everyone loves to picture themselves as the captain of their own ship, steering every decision and, at the very least, every twitch of their own flesh. The idea of bodily autonomy is as common as a morning coffee—people agree you have the right to choose what you do with your own body. You can opt out of a medical procedure, you can ink your skin, you can style your hair, you can pick out the outfit you feel most confident in. In short, you’re in the driver’s seat… most of the time. Except when you aren’t.
There are whole systems inside you that run on autopilot, completely out of your conscious reach. Think about the relentless thump of your heart or the way your stomach churns after a big meal. While you can practice calming techniques to mellow a racing pulse, you can’t simply decide to start or stop the heart on a whim—thankfully, that’s a good thing. You can hold your breath for a while, but you can’t push it to the point of passing out without your body forcing a gasp for air. Digestion, blood circulation, hormone release—these processes happen without you having to think about them. So why does the brain hand over some jobs to the unconscious, while keeping others under direct command? And what about those borderline abilities—like breath control or bathroom timing—that feel like a gray area? Let’s dive into the astonishingly intricate machine that is you, focusing especially on the nervous system that pulls the strings.
5 Nervous Systems In General
Technically, you house two major nervous systems. The first is the central nervous system (CNS), comprising the brain and spinal cord, which acts as the command center, receiving and processing every bit of sensory data that streams in. The second is the peripheral nervous system (PNS), a sprawling network that extends beyond the CNS to reach every corner of your body. The PNS can be sliced further into the autonomic nervous system (ANS) and the somatic nervous system (SNS). Even deeper, the autonomic branch splits into the sympathetic, parasympathetic, and enteric subsystems. While we won’t unpack every single branch here, we’ll start with the sympathetic system, then glide over the autonomic and somatic portions to see how they dictate what you can consciously steer and what runs on its own.
Your CNS—brain and spinal cord—receives and reacts to all sensory input. The enteric nervous system, a specialized network governing digestion, is technically autonomous and largely out of your conscious reach, so we’ll set it aside for now. Let’s keep our focus on the peripheral system and see how its branches influence the tug‑of‑war between control and surrender.
4 Peripheral Nervous System
If the CNS is the hard‑drive of a computer, the peripheral nervous system is every peripheral device—cables, cameras, keyboards—that plugs into it. This is the conduit that shuttles information back and forth between the brain and the rest of the body. The signals traveling through the PNS dictate everything that happens without your conscious say‑so.
In plain terms, anything that isn’t the brain or spinal cord lives in the peripheral arena. Those are the actual nerves threading through muscles, skin, and organs, plus the sensory receptors that detect temperature, pressure, and pain. The PNS splits into two main crews: the autonomic nervous system, which runs the behind‑the‑scenes processes, and the somatic nervous system, which handles the actions you choose to perform. Together, they cover all your senses—touch, smell, sight—as well as every movement, whether you’re deliberately reaching for a coffee mug or your body is silently regulating blood pressure.
3 Autonomic Nervous System
The autonomic nervous system (ANS) is the invisible bridge linking your brain to the majority of your internal organs—heart, lungs, liver, and more. Most of its work happens under the radar, without you needing to think about it. Even functions that seem under your conscious eye, like pupil dilation, are governed by the ANS once the eyes are open.
The ANS further divides into three sub‑systems: the sympathetic (the famed “fight‑or‑flight” response), the parasympathetic (the “rest‑and‑digest” side), and the enteric system (the gut’s own nervous network). The sympathetic branch cranks up heart rate, blood pressure, sweating, digestion, and even urination when you’re under stress. The parasympathetic does the opposite, calming the heart, relaxing airways, and promoting digestion when you’re at ease.
While the theory sounds straightforward, the real‑world coordination is a symphony of signals keeping you alive and functional. Take the enteric system, for instance: it kicks off digestion the moment you taste food, prompting salivation, then orchestrates a cascade of muscle contractions that move food through the stomach and intestines—much like an assembly line in a factory.
A star player in the ANS is the vagus nerve, a massive bundle of roughly 100,000 fibers that shuttles information between the brainstem and organs. This nerve influences digestion, heart rate, breathing, blood pressure, skin sensations, urination, speech, immune responses, and even taste. It taps into about 37 different sensory neuron types, sensing pressure, toxins, nutrients, and stretch, and relays this data to brain regions that handle memory, emotion, and self‑awareness. In short, these “automatic” processes are far more intertwined with our conscious mind than you might think.
2 Somatic Nervous System
The somatic nervous system (SNS) is the part you interact with daily. While the autonomic system runs behind the curtains, the somatic system is the spotlight on stage—everything you consciously decide to move or feel. Walking, scrolling through your phone, waving hello—these are all somatic actions.
Your body houses ten cranial nerves sprouting from the brainstem, which control most head movements, plus 31 pairs of spinal nerves and 12 pairs of cranial nerves that together manage the muscles of your arms, legs, torso, and face. All voluntary movements, even reflexes, are coordinated through this network, translating your intentions into actual motion.
1 Can You Consciously Control Autonomic Functions?
Why does the somatic system answer to you, while the autonomic system seems to ignore your commands? The answer lies in evolutionary design: the body delegated life‑supporting tasks to an automatic pilot so you could focus mental energy on more complex problems. Yet, humans have discovered clever ways to peek behind that curtain.
Holding your breath is a classic example of conscious influence over an automatic rhythm. Meditation practitioners can deliberately slow their heart rate, and some monks have been shown to raise the temperature of their fingers by more than 8 °C (over 46 °F) through focused practice. Wim Hof, the “Iceman,” can intentionally trigger his sympathetic nervous system, releasing epinephrine and dampening immune responses to survive extreme cold—an ability that isn’t genetic but trainable.
Biofeedback technology offers a modern shortcut. Sensors track breathing, heart rate, and muscle tension in real time, displaying the data on a screen. When a participant sees a spike in heart rate during a painful stimulus, they can consciously relax, slowing their pulse and easing tension. This method has helped people manage conditions like diabetes—lowering blood glucose—and ADHD, by teaching them to regulate physiological responses.
Even something as simple as voluntarily producing goosebumps—a reflex usually reserved for cold or fear—has been demonstrated with focused attention. While mastering such feats often requires extensive meditation or training, everyday techniques can grant modest control. Deep, deliberate breathing, systematic muscle relaxation, and vivid imagination (think of a calm, happy place) can shift the balance from sympathetic “fight‑or‑flight” to parasympathetic “rest‑and‑digest.”
A practical breathing routine might look like this: inhale slowly through the nose, hold for five seconds, then exhale through the mouth, pausing ten seconds before the next breath. For muscle relaxation, tense a group of muscles—say, your shoulders—for five seconds, then release for ten, moving through each major region. Pair these with a mental visualization of a serene scene, and you’ll notice a gentle dip in heart rate and a calmer mind.
Full mastery over autonomic functions isn’t realistic—or necessarily desirable. Forgetting to salivate or to urinate would be disastrous. However, with dedication, you can nudge these processes in beneficial directions, improving health, performance, and overall wellbeing.