AP Psychology: Overview of the Nervous System (Drill 2)

Question 1. A doctor taps a patient's knee with a reflex hammer. The patient's leg kicks forward without any conscious thought or deliberate movement. Which part of the nervous system is primarily responsible for producing this response?

• A) The parasympathetic nervous system, which governs automatic bodily functions
• B) The cerebral cortex, which integrates sensory information and generates motor commands
• C) The spinal cord, which can process simple reflex arcs without input from the brain ✓
• D) The somatic nervous system's motor pathways, which require conscious activation

Explanation: A knee-jerk reflex is a spinal reflex arc: sensory neurons carry the signal from the knee to the spinal cord, interneurons process it there, and motor neurons send the response to the muscle, all without waiting for the brain. "Automatic" does not mean "autonomic": this reflex is automatic in the everyday sense, but it runs through the somatic nervous system, not the autonomic. (B) is wrong because the cerebral cortex is not involved in simple reflexes; cortical involvement would make the response too slow and require conscious effort. (A) is a true-but-irrelevant distractor: the parasympathetic system does regulate automatic functions like heart rate and digestion, but spinal reflexes are a distinct somatic mechanism. (D) contains a misconception, spinal reflexes do use somatic motor neurons, but those neurons do not require conscious activation for reflex arcs. [Practice 1]

Question 2. After finishing a large meal, Marcus notices that his heart rate has slowed, his digestion feels active, and he feels calm and relaxed. Which division of the nervous system best accounts for Marcus's current state?

• A) The somatic nervous system, which controls voluntary muscle activity under these conditions
• B) The sympathetic nervous system, which prepares the body for action
• C) The central nervous system, which coordinates all bodily responses
• D) The parasympathetic nervous system, which promotes rest and digestion ✓

Explanation: The parasympathetic division is active during restful, low-demand states; it slows heart rate, stimulates digestion, and conserves energy. Marcus's post-meal calm is a textbook parasympathetic response. (B) is the classic misconception here: the sympathetic system does the opposite; it accelerates heart rate and diverts blood away from digestion for fight-or-flight situations. (A) is wrong because the somatic system governs voluntary, conscious muscle movement, not the autonomic states Marcus is experiencing. (C) is a true-but-irrelevant distractor: the CNS does coordinate all nervous system activity at a broad level, but the specific mechanism for these rest-and-digest responses is the peripheral autonomic division, not the CNS as a category. [Practice 1]

Question 3. A neuroscientist suspects that a patient's loss of hand sensation is caused by damage to the peripheral nervous system rather than the brain. She runs a nerve conduction test on the affected arm and a brain imaging scan while the hand is stimulated. Which result would most strongly support her hypothesis that the problem is peripheral rather than central?

• A) The patient performs normally on a cognitive reasoning task that requires use of both hands.
• B) The brain imaging scan shows normal activity in the somatosensory cortex, but the nerve conduction test shows impaired signal transmission in the arm. ✓
• C) The patient reports no sensation in the hand but can move her fingers voluntarily when asked.
• D) The nerve conduction test shows normal transmission, but the patient still reports no sensation.

Explanation: If peripheral nerves are transmitting signals poorly but the brain's somatosensory cortex is intact, the evidence points directly to the peripheral nervous system as the site of the problem, the fault lies in the wiring before the signal reaches the brain. (D) is the key foil: if nerve conduction is normal but sensation is still absent, that would point toward a central problem, making it the opposite of what the hypothesis predicts. (A) is a true-but-irrelevant distractor: intact cognitive reasoning suggests broad cortical function is preserved, but it does not specifically localize a sensory deficit to the PNS. (C) tells us motor pathways are intact, which does not address where the sensory deficit originates. [Practice 2]

Question 4. A researcher studying stress responses measures participants' heart rate and pupil dilation during two conditions: (1) resting quietly and (2) preparing to give a surprise speech in front of an audience. Results are shown below: Mean heart rate (bpm), Resting: 68 | Pre-Speech: 97 Mean pupil diameter (mm), Resting: 3.1 | Pre-Speech: 6.4 Which conclusion is best supported by these data?

• A) The parasympathetic nervous system was more active during the pre-speech condition than during rest.
• B) Heart rate and pupil dilation are controlled by different branches of the nervous system and therefore cannot be compared.
• C) The sympathetic nervous system produced measurable physiological changes in preparation for a stressful situation. ✓
• D) The central nervous system directly controlled pupil dilation in response to the threat of social evaluation.

Explanation: Both elevated heart rate and increased pupil dilation are hallmark sympathetic nervous system responses, the body mobilizing resources in anticipation of a demanding situation. The data show both measures increased from rest to the pre-speech condition, supporting sympathetic activation. (A) is the opposite of what the data show: parasympathetic dominance is associated with decreased heart rate and pupil constriction. (D) is a true-but-irrelevant distractor: the CNS does play a coordinating role at a higher level, but the specific mechanism for these autonomic changes is the sympathetic division of the peripheral autonomic nervous system, not the CNS as a category. (B) is factually incorrect: both measures are influenced by the autonomic nervous system and are routinely compared in stress research. [Practice 3]

Question 5. A peripheral nerve bundle serving a patient's right arm is severed. She can no longer feel touch or pain in the arm, and the arm is completely limp; she cannot move it at all. A medical student says: "This injury must have affected the central nervous system, because both sensation and movement are lost." Which of the following best evaluates the student's reasoning?

• A) The student is incorrect; the symptoms are consistent with damage to the peripheral nervous system, which carries both sensory and motor signals. ✓
• B) The student is correct; only CNS damage can produce combined sensory and motor deficits.
• C) The student is incorrect; loss of movement indicates CNS damage while loss of sensation indicates PNS damage.
• D) The student is correct; spinal cord lesions are, by definition, central nervous system injuries.

Explanation: The peripheral nervous system carries both afferent (sensory) and efferent (motor) fibers, severing a peripheral nerve bundle can eliminate both sensation and voluntary movement without any CNS involvement. The medical student's error is assuming that combined sensory-motor loss must implicate the CNS. (D) is a true-but-irrelevant distractor: it is accurate that spinal cord lesions are CNS injuries, but the stem specifies a severed peripheral nerve bundle, not a spinal cord lesion, a student reading quickly may select (D) because it contains a true statement while missing that it does not apply here. (C) is false: both sensory and motor functions are served by peripheral nerves, and either or both can be disrupted by peripheral damage alone. [Practice 2]