Quiz: Nervous System Physiology — 24 questions

1. Which comparison accurately distinguishes nervous and endocrine system signaling?

A. The nervous system acts rapidly and briefly through nerve impulses, while the endocrine system acts slowly and sustainably through hormones in blood.

B. The nervous system acts slowly and sustainably through hormones, while the endocrine system acts rapidly through nerve impulses.

C. Both systems act rapidly through nerve impulses, but the nervous system affects fewer organs than the endocrine system.

D. Both systems act slowly through blood-borne signals, but the endocrine system produces more precise responses than the nervous system.

Answer: (A)

Explanation

Nervous signaling uses nerve impulses for rapid, brief, precise effects, whereas endocrine signaling uses blood-carried hormones for slower, more sustained effects. The second choice reverses the signaling mechanisms and time courses of the two systems.

2. Which activity illustrates the nervous system's role in maintaining homeostasis?

A. Interpreting the emotional meaning of a conversation with another person

B. Detecting the color and brightness of objects in the surrounding environment

C. Producing long-term memories about a familiar route through a city

D. Adjusting heart rate and body temperature as internal conditions change

Answer: (D)

Explanation

Regulating heart rate and body temperature helps keep internal conditions stable, which is homeostasis. Memory, emotion, and sensory detection are nervous system functions, but they do not directly represent the listed homeostatic regulation.

3. Which pair best represents nervous system functions that extend beyond detecting environmental stimuli?

A. Sweating and digestion

B. Memory and reasoning

C. Heart rate and blood pressure

D. Skeletal muscle contraction and respiration

Answer: (B)

Explanation

Memory and reasoning are higher nervous system functions in addition to sensory connection with the environment. The other pairs primarily describe physiological regulation or motor and visceral control.

4. A person touches a hot surface and quickly withdraws the hand; which sequence best describes nervous system function in this event?

A. An effector receives external information, the receptor processes it, and hormones produce the movement.

B. The brain creates a memory first, glands release enzymes, and sensory impulses then reach the receptor.

C. A receptor detects the stimulus, the information is integrated, and motor impulses activate an effector.

D. A motor effector detects the stimulus, the spinal cord releases hormones, and a receptor contracts the hand.

Answer: (C)

Explanation

Nervous system pathways proceed from reception by a receptor to integration and processing, followed by motor impulses acting on an effector. The other choices confuse the roles of receptors, effectors, hormones, and processing centers.

5. Which structures make up the central nervous system?

A. All nerves outside the brain and spinal cord

B. Sensory receptors and skeletal muscles

C. The brain and spinal cord

D. Glands and nerves controlling internal organs

Answer: (C)

Explanation

The central nervous system consists of the brain and spinal cord, which analyze, process, and coordinate information. Nervous tissue outside these structures belongs to the peripheral nervous system.

6. A sensory receptor detects pressure in the skin; in which direction does the resulting afferent information travel?

A. From the central nervous system toward a muscle

B. From a gland toward the central nervous system

C. From the receptor toward the central nervous system

D. From the spinal cord toward a sensory receptor

Answer: (C)

Explanation

Afferent sensory pathways carry information from receptors toward the central nervous system. Signals traveling from the central nervous system to tissues and organs are carried by efferent motor pathways.

7. Which response is primarily controlled by the autonomic nervous system?

A. Choosing to bend the elbow with a skeletal muscle

B. Writing a word by intentionally moving the fingers

C. Lifting a bag through a deliberate arm contraction

D. Changing the contraction of cardiac muscle

Answer: (D)

Explanation

The autonomic nervous system involuntarily regulates cardiac muscle, smooth muscle, and glands. Deliberate skeletal muscle movements are controlled by the somatic nervous system.

8. What is the approximate cellular composition of nervous tissue?

A. Neurons make up 10% and glial cells make up 90%.

B. Neurons make up 90% and glial cells make up 10%.

C. Neurons and glial cells each make up about 50%.

D. Neurons make up 10% and muscle cells make up 90%.

Answer: (A)

Explanation

Neurons compose about 10% of nervous tissue, while glial cells compose about 90%. The second choice reverses these proportions, and the remaining choices identify incorrect cell types or distributions.

9. Which function is characteristic of glial cells rather than neurons?

A. Generating the main electrical signals that communicate with effectors

B. Forming myelin sheaths that support and insulate neurons

C. Transmitting sensory information from receptors to the central nervous system

D. Carrying messages through nerve impulses between nervous system regions

Answer: (B)

Explanation

Glial cells support, isolate, and protect neurons and form myelin sheaths; they also contribute to cerebrospinal fluid production. The other choices describe message transmission through nerve impulses, a primary role of neurons.

10. Which neuronal structure contains the nucleus, cytoplasm, mitochondria, and other organelles while synthesizing neurotransmitters?

A. The cell body

B. The terminal button

C. The dendritic tree

D. The axon hillock

Answer: (A)

Explanation

The cell body houses the nucleus and other organelles and synthesizes neurotransmitters. The axon hillock instead marks the region where the axon begins and does not perform this complete set of functions.

11. A neuron receives incoming messages through which highly branched structure that forms part of its receptive region?

A. The dendrite

B. The axon

C. The terminal corpuscle

D. The synapse

Answer: (A)

Explanation

Dendrites are highly branched structures that receive messages together with the cell body. The axon carries messages away from the cell body toward terminal corpuscles.

12. What is the primary direction of information flow through an axon?

A. From the axon hillock toward the terminal corpuscles

B. From the terminal buttons toward the dendrites

C. From the cell body toward the axon hillock

D. From the synapse toward the cell body

Answer: (A)

Explanation

An axon carries a message from the axon hillock toward the terminal corpuscles, where terminal buttons transmit information onward. Dendrites, rather than axons, receive incoming messages.

13. What occurs at a synapse?

A. A receptor cell sends electrical signals directly into the nucleus.

B. An axon converts all incoming signals into a permanent membrane change.

C. A neuron communicates with another neuron or an effector cell through neurotransmitters.

D. A dendrite produces organelles and stores them inside the cell body.

Answer: (C)

Explanation

A synapse is the meeting point between an axon terminal and a target cell, allowing communication through neurotransmitters. The other choices describe functions that are not defining features of synapses.

14. Which classification correctly matches neuronal types with their common examples?

A. Unipolar neurons include some special-sense neurons, bipolar neurons include most sensory neurons, and multipolar neurons include motor neurons and most interneurons.

B. Unipolar neurons include all motor neurons, bipolar neurons include most interneurons, and multipolar neurons include some special-sense neurons.

C. Unipolar neurons include most sensory neurons, bipolar neurons include all motor neurons, and multipolar neurons include receptor cells.

D. Unipolar neurons include most interneurons, bipolar neurons include all motor neurons, and multipolar neurons include most sensory neurons.

Answer: (A)

Explanation

Some special-sense neurons are unipolar, most sensory neurons are bipolar, and all motor neurons with most interneurons are multipolar. The alternatives interchange these classifications, especially the common confusion between bipolar sensory neurons and multipolar motor neurons.

15. A neuron carrying sensory information from a receptor would most commonly belong to which structural class?

A. A bipolar neuron

B. A terminal neuron

C. A unipolar neuron

D. A multipolar neuron

Answer: (A)

Explanation

Most sensory neurons are classified as bipolar neurons. Multipolar neurons are associated with all motor neurons and most interneurons, while unipolar neurons include some special-sense neurons.

16. Which description best defines the resting potential of a neuron?

A. A temporary local membrane change produced when sodium enters through chemically gated channels

B. A rapid membrane event that follows depolarization past the excitation threshold

C. A membrane potential of approximately $-70\,\text{mV}$, with the cytoplasm more negative than the extracellular environment

D. A membrane potential of approximately $-55\,\text{mV}$, with the cytoplasm more positive than the extracellular environment

Answer: (C)

Explanation

The resting potential is the polarized membrane potential of a resting neuron, approximately $-70\,\text{mV}$, with a more negative cytoplasm. The value $-55\,\text{mV}$ represents the excitation threshold, not the resting potential.

17. What is a graded potential?

A. A temporary, localized membrane change caused by a stimulus, often involving sodium entry through chemically gated channels

B. A membrane state maintained by the sodium-potassium pump during neuronal rest

C. A full membrane response that occurs after depolarization reaches the excitation threshold

D. A signal that travels from the axon hillock to terminal buttons without local variation

Answer: (A)

Explanation

A graded potential is a temporary and localized change that can result when neurotransmitters open chemically gated sodium channels. An action potential is the threshold-dependent response that differs from this local graded change.

18. What happens when a neuron's depolarization reaches the excitation threshold of $-55\,\text{mV}$?

A. The membrane returns to its resting potential without producing a signal.

B. The sodium-potassium pump immediately prevents further membrane change.

C. A graded potential becomes more localized and remains below threshold.

D. An action potential occurs according to the all-or-none law.

Answer: (D)

Explanation

Reaching $-55\,\text{mV}$ triggers an action potential according to the all-or-none law. Depolarization that remains below this threshold does not produce an action potential.

19. Which sequence correctly describes the main ionic changes during an action potential?

A. Potassium enters and depolarizes the membrane, then sodium exits to repolarize and hyperpolarize it

B. Sodium exits and hyperpolarizes the membrane, then potassium enters to restore depolarization

C. Sodium enters and depolarizes the membrane, then potassium exits to repolarize and hyperpolarize it

D. Chloride enters and repolarizes the membrane, then sodium exits to produce sustained depolarization

Answer: (C)

Explanation

Voltage-gated sodium entry drives depolarization toward approximately $+30\,\text{mV}$, while potassium efflux produces repolarization and subsequent hyperpolarization near $-80\,\text{mV}$. The alternatives reverse the roles of sodium and potassium or assign these phases to chloride.

20. What distinguishes the absolute refractory period from the relative refractory period?

A. Both periods prevent a second action potential, but the relative period lasts longer than the absolute period

B. Both periods allow a second action potential, but the absolute period requires less stimulation than the relative period

C. A second action potential cannot occur during the absolute period, but a stronger stimulus may trigger one during the relative period

D. A second action potential requires a stronger stimulus during the absolute period, but cannot occur during the relative period

Answer: (C)

Explanation

The absolute refractory period prevents a response to any second stimulus, whereas the relative refractory period permits a response when the stimulus is stronger than normal. The other choices either reverse this distinction or incorrectly describe both periods as having the same effect.

21. How do excitatory and inhibitory neurotransmitters differ in their effects on a postsynaptic neuron?

A. An excitatory transmitter decreases the likelihood of an action potential, whereas an inhibitory transmitter increases it

B. An excitatory transmitter increases the likelihood of an action potential, whereas an inhibitory transmitter decreases it

C. Both transmitters decrease action-potential likelihood, but they differ in the duration of their effects

D. Both transmitters increase action-potential likelihood, but they act at different locations on the neuron

Answer: (B)

Explanation

Excitatory neurotransmitters produce excitatory postsynaptic potentials that make firing more likely, while inhibitory neurotransmitters produce inhibitory postsynaptic potentials that make firing less likely. The other choices confuse the direction of these effects or incorrectly treat both transmitter types as having the same influence.

22. A neuron opens sodium channels in its postsynaptic membrane, and the resulting depolarization exceeds threshold. What is the most likely outcome?

A. The membrane becomes hyperpolarized because sodium entry increases the distance from threshold

B. The membrane generates an action potential because sodium entry drives depolarization toward threshold

C. The membrane remains below threshold because potassium entry counteracts the sodium current

D. The membrane generates an action potential because chloride entry blocks repolarization

Answer: (B)

Explanation

Opening sodium channels causes depolarization, and an action potential can follow when that depolarization exceeds threshold. Chloride entry and additional potassium-channel opening instead promote hyperpolarization, while potassium does not enter to counteract sodium in this rule.

23. What does summation refer to in synaptic integration?

A. The movement of an action potential from one node of Ranvier to the next node

B. The conversion of one action potential into several neurotransmitters inside the presynaptic terminal

C. The insulation of an axon by glial cells to increase the speed of impulse conduction

D. The addition of excitatory and inhibitory postsynaptic potentials at the axon hillock or trigger zone

Answer: (D)

Explanation

Summation is the combination of excitatory and inhibitory postsynaptic potentials, either across time or across different synaptic inputs, at the axon hillock or trigger zone. The other options describe neurotransmitter release, myelination, or saltatory conduction rather than synaptic integration.

24. A motor neuron receives several synaptic inputs, and the excitatory postsynaptic potentials outweigh the inhibitory postsynaptic potentials. What will the neuron most likely do?

A. It will hyperpolarize because excitatory inputs reduce membrane potential

B. It will remain below threshold because inhibitory inputs prevent depolarization

C. It will depolarize beyond threshold and generate an impulse

D. It will generate an impulse only after the inhibitory inputs become stronger

Answer: (C)

Explanation

When excitatory postsynaptic potentials outweigh inhibitory ones, the motor neuron depolarizes beyond threshold and generates an impulse. The other choices describe outcomes expected when inhibitory influences dominate or incorrectly assign hyperpolarization to excitatory input.