What are the parts of the nervous system in AP Psychology?
The nervous system is your body's communication network, and it splits into two main parts: the central nervous system (brain and spinal cord) and the peripheral nervous system (the nerves that connect the CNS to the rest of your body). The peripheral nervous system further divides into the somatic system (voluntary movement) and the autonomic system (involuntary processes like heartbeat), with the autonomic system splitting again into the sympathetic ("fight or flight") and parasympathetic ("rest and digest") divisions.
Why This Matters for the AP Psychology Exam
This topic is your foundation for understanding the biological bases of behavior, which makes up a big chunk of the course. On the AP Psychology exam, you will be asked to differentiate among the subsystems of the nervous system and connect each one to behavior and mental processes. The focus is on function, not memorizing structures, so you need to know what each system does and how to apply that to real scenarios.
You can expect multiple-choice questions that describe a behavior or body response and ask you to identify which subsystem is responsible. This topic also gives you the vocabulary you will use throughout Unit 1 when you study neurons, the brain, sleep, and sensation.
Key Takeaways
- The central nervous system (CNS) includes the brain and spinal cord and interacts with all processes in the body.
- The peripheral nervous system (PNS) relays messages between the CNS and the rest of the body, and it contains the autonomic and somatic systems.
- The somatic nervous system governs voluntary processes, like choosing to move your arm.
- The autonomic nervous system governs involuntary processes, like heart rate and digestion.
- The autonomic system splits into the sympathetic division (prepares the body for action) and the parasympathetic division (calms the body and restores balance).
- For the exam, focus on what each system does and how it connects to behavior, not on diagram labeling.
The Central Nervous System (CNS)
The CNS is the main control hub. It is made up of two parts: the brain and the spinal cord. The brain handles thinking, sensing, deciding, and feeling, while the spinal cord carries messages between the brain and the rest of the body. The CNS interacts with all processes in the body.
Core jobs of the CNS:
- Receives and interprets sensory input (sight, sound, touch, and more)
- Sends commands out to muscles
- Handles thought, memory, emotion, and awareness
- Coordinates reflexes and automatic reactions
The Peripheral Nervous System (PNS)
The PNS connects the brain and spinal cord to the rest of the body. Its job is to relay messages from the CNS to the body and back. Every time you move a finger or feel a cold breeze, the PNS is carrying those signals.
The PNS has two branches: the somatic nervous system and the autonomic nervous system.
Somatic Nervous System
- Governs voluntary processes, like walking, talking, or picking up a book
- Carries sensory information from your skin, muscles, and joints to your CNS
- Sends motor signals from your CNS to your skeletal muscles
Autonomic Nervous System
- Governs involuntary processes, the things your body does automatically
- Regulates internal organs like the heart, lungs, and stomach
- Splits into two opposite divisions that keep your body balanced
| Division | Main Function | Nickname |
|---|---|---|
| Sympathetic Nervous System | Prepares the body for action and stress | "Fight or Flight" |
| Parasympathetic Nervous System | Calms the body and restores balance | "Rest and Digest" |
The sympathetic division gets you going when you are in danger or excited. It increases heart rate, dilates pupils, and slows digestion.
The parasympathetic division brings you back to normal. It lowers your heart rate, restarts digestion, and conserves energy.
Helpful Memory Trick: PARA = Parachute
If you mix up sympathetic and parasympathetic, think of the parasympathetic system like a parachute. It helps you slow down and return to a calm, balanced state, just like a parachute brings you gently back to the ground after stress.
- Sympathetic = speeds you up (stress, action, alertness)
- Parasympathetic = slows you down (relaxation, recovery, rest)
How They Compare: Somatic vs Autonomic
Both the somatic and autonomic systems are part of the peripheral nervous system, but they do very different jobs.
| System | Voluntary? | Controls... | Example |
|---|---|---|---|
| Somatic | Yes | Skeletal muscles and sensory info | Choosing to kick a ball |
| Autonomic | No | Internal organs and automatic processes | Heart rate increases during anxiety |
The somatic system is about conscious movement and sensation. The autonomic system runs quietly in the background, keeping your body alive and balanced.
Nervous System Overview Table
| System | Function | Includes |
|---|---|---|
| Central Nervous System | Processes info, sends commands | Brain and spinal cord |
| Peripheral Nervous System | Communicates between CNS and body | Nerves connecting CNS to the body |
| Somatic Nervous System | Voluntary movements and sensory input | Skeletal muscles, skin, joints |
| Autonomic Nervous System | Involuntary control of internal processes | Heart, lungs, stomach, glands |
| Sympathetic Division | Prepares for action | Increases heart rate, slows digestion |
| Parasympathetic Division | Calms the body | Slows heart rate, restores digestion |
How to Use This on the AP Psychology Exam
MCQ
Most questions on this topic give you a scenario and ask which subsystem is at work. Use these quick decision steps:
- Is the action voluntary (you chose to do it)? That is the somatic nervous system.
- Is the process automatic (heartbeat, digestion, sweating)? That is the autonomic nervous system.
- Is the body gearing up for stress or excitement (racing heart, dilated pupils)? That is the sympathetic division.
- Is the body calming down and recovering (slowed heart rate, digestion restarting)? That is the parasympathetic division.
Concept Application
When a question describes a behavior, connect the subsystem to its function. For example, if someone hears a loud noise and their heart starts pounding, the sympathetic division is responsible. After they realize it was nothing and relax, the parasympathetic division takes over. Practice linking the system to the behavior, since the exam rewards function over labels.
Common Trap
Watch for questions that try to get you to pick the somatic system for an internal organ response, or the autonomic system for a chosen movement. Slow down and ask whether the action is voluntary or automatic before you answer.
Common Misconceptions
- The sympathetic system is not the "good" one and the parasympathetic the "bad" one. Both are necessary, and they work together to keep your body balanced.
- The autonomic system does not only mean stress. It includes both the sympathetic and parasympathetic divisions, so it handles both speeding up and calming down.
- The peripheral nervous system does not make decisions. It relays messages, while the central nervous system does the processing.
- The spinal cord is part of the central nervous system, not the peripheral nervous system. Only the brain and spinal cord make up the CNS.
- Sympathetic activation is not always about danger. It also kicks in during excitement, like before a big game or performance.
Related AP Psychology Guides
Vocabulary
The following words are mentioned explicitly in the College Board Course and Exam Description for this topic.Term | Definition |
|---|---|
autonomic nervous system | The division of the peripheral nervous system that governs involuntary processes such as heart rate and digestion. |
brain | The central organ of the central nervous system that processes information and controls body functions. |
central nervous system | The part of the nervous system consisting of the brain and spinal cord that processes information and coordinates responses. |
parasympathetic nervous system | The division of the autonomic nervous system responsible for the 'rest and digest' response that helps reduce anxiety and promote relaxation. |
peripheral nervous system | The part of the nervous system outside the brain and spinal cord that connects the central nervous system to the rest of the body. |
somatic nervous system | The division of the peripheral nervous system that governs voluntary processes and skeletal muscle control. |
spinal cord | The bundle of nerves extending from the brain through the vertebral column that is part of the central nervous system. |
sympathetic nervous system | The division of the autonomic nervous system responsible for the 'fight or flight' response that contributes to feelings of anxiety. |
Frequently Asked Questions
What are the main parts of the nervous system in AP Psychology?
The nervous system divides into the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which connects the CNS to the rest of the body.
What is the central nervous system?
The central nervous system, or CNS, includes the brain and spinal cord. It processes information, coordinates responses, and interacts with all body processes.
What is the peripheral nervous system?
The peripheral nervous system, or PNS, relays messages between the central nervous system and the rest of the body. It includes the somatic and autonomic nervous systems.
What is the difference between somatic and autonomic nervous systems?
The somatic nervous system controls voluntary movement and sensory input. The autonomic nervous system controls involuntary processes such as heart rate, digestion, and breathing.
What is the difference between sympathetic and parasympathetic systems?
The sympathetic division prepares the body for action or stress, often called fight or flight. The parasympathetic division calms the body and restores balance, often called rest and digest.
How is the nervous system tested on the AP Psychology exam?
AP Psychology questions often give scenarios and ask which subsystem is responsible. Decide whether the process is voluntary or automatic, then connect the system to its function.