Which of the following statements regarding neurotransmitters is TRUE?
A. Acetylcholine is broken down by enzymes present on postsynaptic cell membranes.
B. Acetylcholine that is released at synapses binds to adrenergic receptors in the postsynaptic cell membrane.
C. Catecholamines are the most abundant neurotransmitters in the central nervous system.
D. Opiate drugs, such as morphine, are antagonists of a class of neurotransmitters called endorphins.
E. Gamma-aminobutyric acid (GABA) is a major excitatory transmitter in the central nervous system.
(
Question 2) Which is TRUE about the initial segment of an axon?
A. Its membrane potential at threshold is more positive than that of the cell body and dendrites.
B. Its membrane potential at threshold is more negative than that of the cell body and dendrites.
C. Synapses far from the initial segment are more effective in influencing whether an action potential will be generated in the axon than are synapses close to the initial segment.
D. It is the region where neurotransmitter vesicles are docked and ready to be released by exocytosis.
E. It can only conduct graded potentials because it lacks voltage-gated Na+ channels.
(
Question 3) Neuron X makes inhibitory axon-axon synaptic contact with neuron Y at the synapse of Y and neuron Z. Which will occur when action potentials are stimulated in neuron X?
A. Neuron Y will be inhibited from reaching the threshold to fire an action potential.
B. The release of neurotransmitter by neuron Y will be inhibited.
C. The synapse between neurons Y and Z will be changed from an excitatory synapse to an inhibitory one.
D. Neurons Y and Z will both be more likely to reach threshold and fire an action potential.
E. Neurons Y and Z will both be less likely to reach threshold and fire an action potential.
(
Question 4) A presynaptic synapse:
A. is a synapse between an axon terminal and a dendrite that can be either excitatory or inhibitory.
B. is a synapse between an axon terminal and another axon's terminal that can be either excitatory or inhibitory.
C. is any synapse onto a cell body, and they can be either stimulatory or inhibitory.
D. is a synapse between an axon terminal and a dendrite of the same cell, which is always inhibitory.
E. is a synapse between an axon terminal and another axon's terminal that is always inhibitory.
(
Question 5) A postsynaptic neuron has three presynaptic inputs - from neurons X, Y, and Z. When X and Y are stimulated simultaneously and repeatedly, the postsynaptic neuron reaches threshold and undergoes an action potential.
When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. The simultaneous stimulation of X and Y is an example of
A. temporal summation.
B. presynaptic inhibition.
C. spatial summation.
D. neuronal divergence.
E. presynaptic facilitation.
(
Question 6) A postsynaptic neuron has three presynaptic inputs - from neurons X, Y, and Z.
Stimulation of neuron X causes the postsynaptic neuron to depolarize by 0.5 mV. When X and Y are stimulated simultaneously, the postsynaptic neuron depolarizes by 1 mV. When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. What is most likely true about presynaptic neurons Y and Z?
A. They are both excitatory.
B. They are both inhibitory.
C. Y is excitatory and Z is inhibitory.
D. Z is excitatory and Y is inhibitory.
(
Question 7) Which best describes temporal summation?
A. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated.
B. It only refers to addition of EPSPs.
C. Two synapses on different regions of a cell are stimulated at the same time.
D. It always brings a postsynaptic cell to threshold.
E. The size of an EPSP depends on the size of the stimulus.
(
Question 8) Which of the following statements about EPSPs is FALSE?
A. They are produced by the opening of ligand-gated sodium channels.
B. They transmit signals over relatively short distances.
C. They depolarize postsynaptic cell membranes.
D. They are able to summate.
E. They are always the same amplitude.
(
Question 9) An EPSP:
A. is a direct result of the opening of ligand-gated channels permeable to both Na+ and K+ ions.
B. is a direct result of the opening of voltage-gated channels permeable to both Na+ and K+ ions.
C. stabilizes the membrane to remain at its resting potential.
D. opens voltage-gated Ca2+ channels in the presynaptic membrane.
E. occurs when voltage-gated Cl- channels open in a postsynaptic cell membrane.
(
Question 10) Which is FALSE about interneurons?
A. They receive synaptic input from other neurons in the CNS.
B. They sum excitatory and inhibitory synaptic inputs.
C. They deliver synaptic input on other neurons.
D. They make synapses on effector organs in the PNS.
E. They can transmit information between afferent neurons and efferent neurons.
Quick Reply
