The Nervous System: Somatic vs. Autonomic
The human nervous system is a complex communication network that manages everything from our voluntary movements to the involuntary processes that keep us alive.
At the heart of this system are two critical divisions: the somatic nervous system and the autonomic nervous system. In this blog, we’ll break down how these systems operate, their unique functions, and how they work together to maintain our health.
Article Recap:
To summarize the Somatic vs. Autonomic Systems
Somatic Nervous System: Controls voluntary actions, such as moving muscles and responding to sensory inputs.
Autonomic Nervous System: Governs involuntary processes, such as heart rate and digestion, through its two divisions—sympathetic and parasympathetic.
Together, these systems enable the nervous system to regulate both our conscious movements and the essential functions that sustain life.
Jenna Fair, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Learn more at mcat.kingofthecurve.org.
Overview: The Peripheral Nervous System (PNS)
The peripheral nervous system (PNS) connects the central nervous system (CNS)—which includes the brain and spinal cord—to the rest of the body. The PNS acts as a bridge, relaying sensory information to the CNS and transmitting motor commands from the CNS to muscles and glands.
The PNS is divided into two main functional systems:
Somatic Nervous System: Controls voluntary movements.
Autonomic Nervous System: Manages involuntary functions.
Fun Fact: The peripheral nervous system contains 43 pairs of nerves connecting the CNS to various parts of the body!
1) The Somatic Nervous System: Voluntary Control
The somatic nervous system is responsible for controlling voluntary movements and conscious sensations. This system primarily manages skeletal muscles, allowing us to perform deliberate actions like walking, lifting, or typing.
Sensory Input: Sensory information from external stimuli (such as touch or temperature) is sent to the CNS via afferent neurons.
Motor Response: The CNS processes this information and sends signals back to muscles through efferent neurons, enabling us to respond appropriately.
Through this system, we consciously interact with our environment, controlling our movements and responding to sensory inputs.
2) The Autonomic Nervous System: Involuntary Control
In contrast to the somatic system, the autonomic nervous system (ANS) manages all involuntary functions—activities that occur without conscious effort. These include heart rate, digestion, breathing, and metabolism.
The ANS ensures that our body maintains homeostasis (internal balance), keeping vital processes running smoothly in the background.
2a) Divisions within the Autonomic Nervous System
The autonomic nervous system is further divided into two opposing systems:
Sympathetic Nervous System:
Parasympathetic Nervous System:
These systems work in harmony to balance the body’s responses to various stimuli.
2a-1) Sympathetic Nervous System
The sympathetic nervous system activates during stressful or emergency situations, preparing the body for rapid action. This is often referred to as the fight or flight response.
When the sympathetic system is activated, it:
Increases heart rate
Dilates pupils to improve vision
Redirects blood flow to muscles
Releases adrenaline (epinephrine) to boost energy and alertness
These physiological changes equip the body to respond quickly to danger or stress.
2a-2) Parasympathetic Nervous System: Rest and Digest
The parasympathetic nervous system takes over during periods of relaxation, promoting processes that restore and conserve energy. This system is often called the rest and digest system.
When the parasympathetic system is active, it:
Slows heart rate
Stimulates digestion
Supports urination and reproductive functions
This system allows the body to recharge, focusing on maintenance and repair rather than immediate action.
Fun Fact: The vagus nerve plays a major role in parasympathetic control, regulating the heart, lungs, and digestive system.
Coordinated Functions: Balancing Action and Rest
The sympathetic and parasympathetic systems work together to keep the body balanced. One common example is in sex, where parasympathetic activation is required for libido and a sympathetic surge causes an orgasm.
Why Understanding These Systems Matters
The somatic and autonomic nervous systems work in tandem to manage both our voluntary actions and the involuntary processes that keep us alive. By understanding these divisions, we gain insight into how our bodies maintain balance, respond to stress, and support overall health.
Learn More with King of the Curve
If you’re interested in exploring the complexities of the nervous system and other critical MCAT topics, check out the King of the Curve app. Our platform is designed to help you master challenging concepts in neuroscience, biology, and beyond. Download the app or visit kingofthecurve.org to start your learning journey today!
-
Here is a breakdown of our platform.
Study Modes:
Roadmap, Summary Diagrams, Lecture Videos, AI Tutor
Training Modes:
Adaptive Question Bank, Anki Flashcards, Custom Quiz, Passage Mode
Review Modes:
Past Games, Review Theory, Questions of the Day, Review Flagged Questions
Compete Modes:
Endless Mode, Timed Mode, Blitz Facts Mode, Multiplayer (Friends or Global), and Leaderboards
-
The bulk of your score is based on your responses to practice questions, normalizing for question difficulty.
Your accuracy on the adaptive Q-bank and custom quiz modes are directly fed into the scaled scoring model for your specific exam. While your accuracy on gamified questions (endless, blitz, timed, multiplayer) is compared with a machine learning model that contains the data of past KOTC students, including their ultimate scores and how they've interacted with the platform.
-
The KOTC algorithm tracks your predicted score. If the time remaining until your exam + your rate of improvement do not meet your exam goal (or at least a 50th percentile score), an automated alert system will flag.
The system explains the situation to the student and gives them an opportunity to increase alerts, incentivizing changed study habits. Moreover, institutional partners are alerted if any of their students find themselves in this scenario, and their students are offered tutoring and personalized guidance.
