Neuroscience Practice Questions

Lectures 11-20

Connexin

Individual subunit.

Connexon

Multimer forming one half of the channel.

Extracellular Domain

Forms bond between two halves of the channel.

Transmembrane Domain

Surrounds the channel pore.

Which of the following is NOT a function of gap junctions?

Amplify signals.

An electrical synapse between two neurons can be recognized by all of the following evidence, EXCEPT:

All of the above would provide evidence of an electrical synapse.

Electrical synapses differ from chemical synapses in that:

Electrical synapses are less common than chemical synapses.

Suppose two neurons are connected by gap junctions. Which of the following would you NOT predict to occur?

All of the above would be predicted to occur.

Suppose two cells are connected by gap junctions. If positive current is injected into cell #1, what would be observed in cell #2?

depolarization

Suppose two neurons are normally connected by gap junctions, but you are studying them in an animal with Cx36 knocked out. How would you expect their behavior to change?

Action potentials in the two neurons would not be synchronized.

Electrical synapses are more common than chemical synapses because of all of the following, EXCEPT:

None of the above. Chemical synapses are more common than electrical.

A complete gap junction channel is:

Two hexamers in two cells.

The extracellular domain of the gap junction channel mediates:

Attachment between two half-channels.

Suppose two neurons are normally connected by gap junctions. What would be the most likely effect of a pharmacological agent that blocks the gap junction channel?

Spikes in the two cells would be desynchronized.

What is the structure of a complete gap junction channel?

Two hexamers, where each cell expresses the six subunits that form one hexamer.

Synapses formed by gap junctions are fast, because of which of the following?

Current travels directly from one cell to the other.

Two cells are connected by an electrical synapse. If one cell fires an action potential, which of the following is a possible response in the other cell?

An excitatory postsynaptic potential and an action potential with a smaller peak depolarization.

Two cells are normally connected by an electrical synapse, but a mutation has been introduced that disrupts their formation. How would you expect the function of the neurons to change?

Action potentials in the two neurons would become desynchronized.

The two halves of a gap junction channel join together at which of the following?

Through the extracellular domains.

What is a connexon?

A hexamer, composed of six subunits.

Which of the following domains of connexin forms the pore of the gap junction channel?

The transmembrane domains.

How do electrical synapses allow signals to travel bidirectionally?

Gap junction channels allow currents to flow in both directions.

Which of the following is a feature of gap junction channels, but not of voltage-gated ion channels?

Only gap junction channels require subunits expressed in more than one cell.

Why are electrical synapses so much faster than chemical synapses?

Because currents in one cell pass directly to the next.

The pore of the gap junction allows which of the following to pass through?

Ions.

Which of the following is an important function of gap junctions in neurons?

To enhance synchronous firing of neurons.

Number of subunits per connexon:

6

Number of subunits per channel:

12

Number of genes in the family:

21