--- title: "Peripheral Nervous System — AP Psych Definition & Guide" description: "The peripheral nervous system (PNS) carries signals between your brain/spinal cord and the rest of your body. Learn how it splits into somatic and autonomic branches for AP Psych Unit 2." canonical: "https://fiveable.me/ap-psych-revised/key-terms/peripheral-nervous-system" type: "key-term" subject: "AP Psychology" unit: "Unit 2" --- # Peripheral Nervous System — AP Psych Definition & Guide ## Definition The peripheral nervous system (PNS) is the part of the nervous system made up of all the nerves outside the brain and spinal cord. It links the central nervous system (CNS) to your limbs, organs, and senses, and divides into the somatic and autonomic nervous systems. ## What It Is Your nervous system has two big halves. The **[central nervous system](/ap-psych-revised/unit-1/3-the-neuron-and-neural-firing/study-guide/AVvPhAH234j4u83J "fv-autolink") (CNS)** is the brain and [spinal cord](/ap-psych-revised/key-terms/spinal-cord "fv-autolink"), your command center. The **peripheral nervous system (PNS)** is everything else: all the nerves and ganglia that branch out from the CNS to the rest of your body. Think of the CNS as the headquarters and the PNS as the entire network of cables running out to every limb, organ, and sense receptor. The PNS splits into two branches. The **[somatic nervous system](/ap-psych-revised/key-terms/somatic-nervous-system "fv-autolink")** handles voluntary movement, like deciding to raise your hand or kick a ball, by carrying signals to your skeletal muscles. The **autonomic nervous system** runs the automatic stuff you don't consciously control, like heart rate, digestion, and breathing. So the PNS is both your "I chose to do that" wiring and your "this happens without me thinking" wiring, all bundled together outside the brain and spinal cord. ## Why It Matters This term lives in **[Unit 2](/ap-psych-revised/unit-2 "fv-autolink"): Cognition**, specifically topic 2.3, the overview of the nervous system and the neuron. Before you can understand how [neurons](/ap-psych-revised/key-terms/neurons "fv-autolink") fire, how the brain processes memory, or how stress floods your body, you need the basic map of where signals travel. The PNS is half of that map. Understanding the PNS sets up later [concepts](/ap-psych-revised/unit-2/2-thinking-problem-solving-judgments-and-decision-making/study-guide/gHqqU9CdMYyy4lPn "fv-autolink") in biological psychology. The autonomic branch, for example, is the foundation for the fight-or-flight response you'll see again when studying stress, emotion, and anxiety disorders. Get the nervous-system organization down cold here and the more complex topics later in the course slot right into place. ## Connections ### [Somatic Nervous System (Unit 2)](/ap-psych-revised/key-terms/somatic-nervous-system) The somatic nervous system is one of the two branches of the PNS. It's the part that controls voluntary skeletal muscle movement, so any time you choose to move, that signal travels through the somatic branch of the PNS. ### [Autonomic Nervous System (Unit 2)](/ap-psych-revised/key-terms/autonomic-nervous-system) The [autonomic nervous system](/ap-psych-revised/key-terms/autonomic-nervous-system "fv-autolink") is the PNS's other branch, the one running your automatic functions like heartbeat and digestion. It further splits into sympathetic (arousal, fight-or-flight) and parasympathetic (calming, rest-and-digest) divisions. ### Ganglia (Unit 2) Ganglia are clusters of nerve cell bodies found outside [the brain](/ap-psych-revised/unit-1/4-the-brain/study-guide/zffu0vU5m7HwEMsU "fv-autolink") and spinal cord. Because they sit outside the CNS, they're part of the PNS, which is why the PNS definition specifically mentions nerves AND ganglia. ### [Anxiety Disorders (Unit 5)](/ap-psych-revised/key-terms/anxiety-disorders) The autonomic branch of the PNS drives the physical symptoms of anxiety, like racing heart and sweaty palms. When you study anxiety disorders and treatments like exposure therapy later, you're seeing the PNS's fight-or-flight response in action. ## On the AP Exam Expect this on multiple-choice questions that test whether you can sort the nervous system into its parts. A classic stem asks which system controls voluntary movement of skeletal muscles (the somatic, a PNS branch) or asks what the nervous system comprises. You need to correctly place the PNS as everything outside the brain and spinal cord, then identify its somatic and autonomic subdivisions. Questions often work by elimination, so knowing that the CNS is brain plus spinal cord lets you label everything else as PNS. No released FRQ uses this term verbatim, but the nervous-system framework underlies biological-basis questions throughout Unit 2. ## Peripheral Nervous System vs Central Nervous System (CNS) The CNS is the brain and spinal cord. The PNS is everything else. They're easy to mix up because they work together constantly, but the line is simple: if it's the brain or spinal cord, it's central; if it's a nerve branching out to the body, it's peripheral. ## Key Takeaways - The peripheral nervous system (PNS) is all the nerves and ganglia outside the brain and spinal cord. - The PNS connects the central nervous system (CNS) to your limbs, organs, and senses. - The PNS has two branches: the somatic nervous system (voluntary movement) and the autonomic nervous system (automatic functions). - The autonomic branch further divides into sympathetic (arousal) and parasympathetic (calming) divisions. - If a question asks about voluntary skeletal muscle control, the answer is the somatic nervous system, a PNS branch. ## FAQs ### What is the peripheral nervous system in AP Psych? It's the part of the nervous system made up of all nerves and ganglia outside the brain and spinal cord. It links the central nervous system to the rest of your body and splits into the somatic and autonomic nervous systems. ### Does the peripheral nervous system include the brain? No. The brain and spinal cord make up the central nervous system (CNS). The PNS is everything else, all the nerves branching out from the CNS to your body. ### What's the difference between the peripheral and central nervous systems? The CNS is the brain and spinal cord, your processing center. The PNS is all the nerves outside it that carry signals to and from your muscles, organs, and senses. Simple rule: brain or spinal cord means central, everything else means peripheral. ### What are the two branches of the peripheral nervous system? The somatic nervous system, which controls voluntary movement of skeletal muscles, and the autonomic nervous system, which controls automatic functions like heart rate and digestion. The autonomic branch then splits into sympathetic and parasympathetic divisions. ### Which nervous system controls voluntary movement? The somatic nervous system, which is a branch of the PNS. So if an AP question asks about controlling skeletal muscles on purpose, the answer is somatic, not autonomic or central. ## Related Study Guides - [2.3 Overview of the Nervous System and the Neuron](/ap-psych-revised/unit-2/review/study-guide/6LIggXCKrR2TfcynGNdN) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/ap-psych-revised/key-terms/peripheral-nervous-system#resource","name":"Peripheral Nervous System — AP Psych Definition & Guide","url":"https://fiveable.me/ap-psych-revised/key-terms/peripheral-nervous-system","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/ap-psych-revised/key-terms/peripheral-nervous-system#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-06-11T00:58:34.572Z","isPartOf":{"@type":"Collection","name":"AP Psychology Key Terms","url":"https://fiveable.me/ap-psych-revised/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/ap-psych-revised/key-terms/peripheral-nervous-system#term","name":"Peripheral Nervous System","description":"The peripheral nervous system (PNS) is the part of the nervous system made up of all the nerves outside the brain and spinal cord. 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