This unit is ≈16% of the Psychology, across 10 lessons. Full syllabus
AP Psychology · Lesson 2 of 10 · Unit 1
Overview of the nervous system
3 quick checks ≈1% of the test6 min read · about 45 min with practicePreview
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The nervous system is the body’s rapid electrochemical communication network, and on the AP Psychology exam it appears constantly in scenario-based multiple-choice questions and as a biological concept you can apply in the Evidence-Based Question (EBQ). You must be able to trace a real-world action—like jumping at a loud noise or typing an essay—to the exact subsystem governing it.
By the end you’ll be able to
Differentiate the central nervous system (brain and spinal cord) from the peripheral nervous system and explain how they interact.
Differentiate the somatic nervous system, which governs voluntary processes, from the autonomic nervous system, which governs involuntary processes.
Explain the roles of the sympathetic (arousing) and parasympathetic (calming) divisions of the autonomic nervous system in scenarios such as stress responses.
What the exam asks
Scenario application (Section I MCQ): Given an everyday situation (e.g., an athlete preparing for a race, a pianist moving their fingers, or a student calming down after a pop quiz), identify which specific branch of the nervous system is most active.
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Pathway tracing (Section I MCQ): Explain how sensory information travels from the body to the brain and how motor commands travel back out, including the role of the spinal cord in automatic reflexes.
Concept application in the EBQ (Section II): Use the sympathetic or parasympathetic division as the outside psychological concept in part B(ii) or C(ii) to explain why study participants showed physiological changes like elevated heart rate or slowed breathing.
Core ideas
The big split: Central vs. Peripheral
The human nervous system is divided into two main parts that work together continuously:
Central Nervous System (CNS): Consists solely of the brain and the spinal cord. It is the body’s command and integration center.
The brain processes complex sensory information, initiates voluntary actions, and houses cognition and emotion.
The spinal cord is the two-way information highway connecting the brain to the rest of the body. It also governs simple reflexes—automatic, inborn responses to stimuli (like pulling your hand back from a hot pan) that are processed directly in the spinal cord via interneuronsbefore pain signals even reach the brain.
Peripheral Nervous System (PNS): Consists of all the sensory and motor nerves that branch out from the brain and spinal cord to the rest of the body (extremities, skin, muscles, and organs).
How they interact: The PNS gathers information from the environment and inside the body via sensory (afferent) neurons and sends it to the CNS. The CNS processes that input and sends instructions back out through the PNS via motor (efferent) neurons to tissues, muscles, and glands.