Question

Which of the following statements about the composition of a complete homomeric heterotypic gap junction channel is TRUE?

a. It contains two different heteromeric connexons

b. It contains only one type of connexin

c. It contains at least two different types of connexins

d. None of the above

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If two neurons were connected by both chemical and electrical synapses, which of the following statements would be TRUE?

	a.	When an action potential occurs in the presynaptic neuron, a spikelet in the postsynaptic neuron would begin before an EPSP in the postsynaptic neuron
	b.	When an action potential occurs in the presynaptic neuron, a spikelet would not affect the membrane potential of the postsynaptic neuron
	c.	Neurons cannot be connected via electrical and chemical synapses at the same time

Answer 1

Q1. c is true

Homomeric connexons have a single type of connexin in them and heterotypic gap junctions are made of different types of connexon hemichannels/ connexons. So, Heterotypic homomeric gap junctions would have at least two homomeric connexons each made of a different type of connexin.

Q2. Two neuronal synapses cannot ctransfer signal via chemical and electrical methods at the same time. Neurons act by chemical or electrical pulses. electrical synapses are attached to each other through gap junctions and they transfer ions in both directions. chemical synapses have synaptic gaps through which neurotransmitters amplify and transfer signals. Spikelets happen after EPSP in postsynaptic neurons, not before. And an action potential in neurons with chemical signaling has been reported to appear as a spikelet in postsynaptic cells.