I learn that the nerves from the Peripheral Nervous System can carry signals from and to other organs of the body.

I'm wondering if A Single Nerve carries

1) Only chemical signals

2) Only physical signals

3) Both of them at the same time

4) It can occur either of the case below, either (1), (2), or (3) Thank you!

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When you say "nerve" this refers to a bundle of axons from many different neurons, but I suspect what you actually mean is a single neuron.

Synapses occur at the ends of axons. Almost all axons branch to some degree, so there are many of these endings, and they fairly exclusively end in chemical synapses.

However, the actual propagation of the signal down the axon is electrical.

Electrical synapses ("gap junctions") also occur in vertebrate nervous systems, but they do not necessarily involve the ends of axons contacting dendrites of other cells. Rather, electrical synapses tend to be between dendrites of different cells, or between a dendrite and the somatic region of another cell, or between axons of two different cells.

The neurons that make electrical synapses also typically make chemical synapses in other places - sometimes they make these electrical synapses with the same cells they make chemical synapses with.

Note that these rules are different in invertebrates, and in general the distinction between axons and dendrites in invertebrates is more complicated.

There are other places besides the CNS with gap junctions/electrical synapses as well, including in the enteric nervous system and in the heart.

Draguhn, A., Traub, R. D., Schmitz, D., & Jefferys, J. G. R. (1998). Electrical coupling underlies high-frequency oscillations in the hippocampus in vitro. Nature, 394(6689), 189.

Galarreta, M., & Hestrin, S. (2001). Electrical synapses between GABA-releasing interneurons. Nature Reviews Neuroscience, 2(6), 425.

Traub, R. D., Bibbig, R., Piechotta, A., Draguhn, R., & Schmitz, D. (2001). Synaptic and nonsynaptic contributions to giant IPSPs and ectopic spikes induced by 4-aminopyridine in the hippocampus in vitro. Journal of Neurophysiology, 85(3), 1246-1256.


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