Quiz 6: Synaptic Transmission

At electrical synapses: A)There is a synaptic delay as the signal travels from the presynaptic element to the postsynaptic element. B)Release of neurotransmitter is required. C)There is a low-resistance pathway for flow of current between cells. D)Electrical potentials can be transmitted in only one direction.

At gap junctions,the intercellular space: A)Widens and is filled by electron-lucent material. B)Widens and is filled by electron-dense material. C)Narrows and is filled by electron-lucent material. D)Narrows and is filled by electron-dense material.

Chemical synapses are typically characterized by: A)Unidirectional and instantaneous transmission of electrical signals. B)Unidirectional transmission of electrical signals after a short delay. C)Bidirectional and instantaneous transmission of electrical signals. D)Bidirectional transmission of electrical signals after a short delay.

Calcium entry into the presynaptic terminal is greatest: A)During the rising phase of the action potential. B)At the peak of the action potential. C)During the falling phase of the action potential. D)During the afterhyperpolarization that follows an action potential. E)When the action potential is in its resting phase.

The quantal nature of chemical synaptic transmission is best supported by observation of: A)Spontaneous miniature end plate potentials (mEPPs). B)Discrete jumps in end plate potential (EPP)amplitude when [Ca⁺⁺] is normal. C)EPPs that vary smoothly in amplitude. D)A constant EPP amplitude. E)Evoked EPPs that are smaller than mEPPs.

The kiss-and-run method of vesicle recycling is most important for maintaining synaptic transmission at: A)An axon with a high firing rate and small presynaptic terminals. B)The neuromuscular junction. C)A large central nervous system (CNS)synapse. D)A presynaptic terminal with a low probability of release.

Temporal summation refers to the fact that: A)Excitatory postsynaptic potentials (EPSPs)generated by synapses on different dendrites will add linearly. B)EPSPs generated by synapses on the same dendrite will add linearly. C)Two EPSPs generated at slightly different times will produce a larger overall response. D)Two EPSPs generated at the same time will shunt each other.

The neurotransmitter gamma-aminobutyric acid (GABA): A)Is stored in large electron-dense vesicles. B)Is the major excitatory transmitter in the brain. C)When released,acts mainly at the immediate postsynaptic membrane. D)Binds to only ionotropic receptors.

Ionotropic receptors: A)Activate second messenger cascades. B)Trigger EPSPs that are longer than those of metabotropic receptors. C)Are a common receptor type for neuropeptides. D)Underlie fast synaptic transmission.

Metabotropic receptors: A)Trigger EPSPs whose time course is mainly determined by the resistor-capacitor (RC)circuit (i.e.,passive electrical)properties of the cell membrane. B)Trigger EPSPs that last approximately 10 msec. C)Are coupled to a G protein. D)Have only one significant action,which is to cause voltage changes (postsynaptic potentials [PSPs]).