Q1. Imagine that you are doing an experiment on the movement of ions across neural membranes. Which of the following plays a role in determining the equilibrium concentration of ions across these membranes?
Correct Answer: (d)
The electrochemical gradient is the combined force of the chemical concentration gradient and the electrical gradient (charge difference) across a membrane. Together, these factors determine the direction and equilibrium of ion movement.
Q2. A fight-or-flight response in the body is controlled by the
Correct Answer: (a)
The sympathetic division is the part of the autonomic nervous system that prepares the body for stressful or emergency situations by increasing heart rate and blood flow to muscles while inhibiting non-essential functions like digestion.
Q3. Inhibitory neurotransmitters
Correct Answer: (a)
Inhibitory neurotransmitters typically open ligand-gated Cl– or K+ channels. This results in the membrane potential becoming more negative (hyperpolarization), which makes it more difficult for the postsynaptic neuron to reach the threshold for an action potential.
Q4. During an action potential
Correct Answer: (d)
Depolarization (the rising phase) is driven by the opening of voltage-gated Na+ channels, allowing sodium to enter the cell. Repolarization (the falling phase) occurs when these channels close and voltage-gated K+ channels open, allowing potassium to leave the cell (efflux).
Q5. The ____ cannot be controlled by conscious thought.
Correct Answer: (c)
The autonomic nervous system regulates involuntary physiological processes such as heart rate, blood pressure, respiration, and digestion. In contrast, the somatic nervous system is associated with the voluntary control of body movements via skeletal muscles.
Q6. Botox, a derivative of the botulinum toxin that causes food poisoning, inhibits the release of acetylcholine at the neuromuscular junction. How could this strange-sounding treatment produce desired cosmetic effects?
Correct Answer: (c)
Acetylcholine is the primary neurotransmitter that signals skeletal muscles to contract. By blocking its release, Botox induces a temporary paralysis of the facial muscles responsible for creating frown lines and wrinkles, resulting in smoother skin.
Q7. A functional reflex requires
Correct Answer: (a)
The simplest functional reflex arc is monosynaptic, consisting of a single sensory neuron and a single motor neuron. While many reflexes involve interneurons, the brain (cerebral cortex or thalamus) is not required for the basic execution of a reflex action.
Q8. Which of the following best describes the electrical state of a neuron at rest?
Correct Answer: (a)
The resting membrane potential of a neuron is approximately –70 mV, meaning the intracellular environment is more negatively charged relative to the extracellular fluid. This state is maintained by the Na+/K+ pump and the differential permeability of the membrane to ions.
Q9. As you sit quietly reading this sentence, the part of the nervous system that is most active is the
Correct Answer: (c)
The parasympathetic nervous system is the 'rest and digest' division of the autonomic nervous system. It predominates during periods of relaxation and low stress, maintaining homeostatic functions and conserving energy.
Q10. G protein–coupled receptors are involved in the nervous system by
Correct Answer: (d)
G protein–coupled receptors (metabotropic receptors) act as postsynaptic receptors that, upon binding neurotransmitters, initiate complex intracellular signaling cascades. These are distinct from ionotropic receptors, which are ligand-gated ion channels themselves.
Q11. Suppose that you stick your finger with a sharp pin. The area affected is very small and only one pain receptor fires. However, it fires repeatedly at a rapid rate (it hurts!). This is an example of
Correct Answer: (a)
Temporal summation occurs when a single presynaptic neuron (or receptor) fires multiple action potentials in rapid succession, resulting in the additive effect of postsynaptic potentials at the same location over time.
Q12. The following is a list of the components of a chemical synapse. A mutation in the structure of which of these would affect only the reception of the message, not its release or the response?
Correct Answer: (a)
Membrane proteins on the postsynaptic cell include the receptors that specifically bind to neurotransmitters. A mutation here would specifically block the 'reception' of the chemical signal from the cleft, without preventing the presynaptic cell from releasing the neurotransmitter or the postsynaptic cell from responding internally once a signal is received.
Q13. The Na+/K+ ATPase pump is
Correct Answer: (b)
While action potentials rely on the passive flow of ions through gated channels, the Na+/K+ ATPase pump is essential for maintaining the concentration gradients of sodium and potassium over the long term, ensuring the cell remains excitable.
Q14. White matter is ________, and gray matter is ________.
Correct Answer: (d)
White matter consists primarily of myelinated axons, giving it a white appearance. Gray matter consists of neuronal cell bodies, dendrites, and unmyelinated axons. Both are essential components of the central nervous system (CNS).
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