Science

Differences between Electrical and Chemical Synapses

In principle, the synapse can be defined as a specialized intercellular functional approximation between neurons, either between two association neurons, a neuron and a receptor cell, or between a neuron and an effector cell. In this approach, the transmission of the nerve impulse is carried out. Thus, the synapse can be electrical or chemical according to the secretion of neurotransmitters and the number of nerve impulses involved in the process.

That said, to clarify this terminology a little more, we are going to specify each of these synapse processes to later present the differences that exist between them.

electrical synapse

Briefly, the electrical synapse is a synapse in which the transmission between the first neuron and the second is not produced by the secretion of a neurotransmitter but by the passage of ions from one cell to another, through gap junctions (small channels formed by the coupling of protein complexes, based on connections, in closely adherent cells).

In the electrical synapse, the space between the pre- and post-synaptic elements is much smaller. Such junctions are common in some invertebrates, such as sponges, molluscs, and annelids. In them, the information is transmitted through local currents that are symmetrical and bidirectional, therefore, there is no synaptic delay (time it takes for the synaptic connection to occur).

chemical synapse

Basically, the chemical synapse is produced by the release of neurotransmitters with the arrival of a nerve impulse and through a very rapid process of cellular secretion where, in the pre-synaptic nerve terminal, they remain anchored and prepared next to the synaptic membrane. In the chemical synapse, the nerve impulse passes from one neuron to another through chemical transmitters. Chemical synapses occur between cells that are separated from each other by a gap of about 20-30 nm, the so-called synaptic cleft.

Thus, in chemical synapses, information is transmitted by means of neurotransmitters, being asymmetric and unidirectional (the postsynaptic neuron cannot transmit information to the presynaptic), therefore, the synaptic delay is greater.

In attention to the definitions presented, the differences between electrical synapses and chemical synapses are the following:

  • In electrical synapses information is transferred through local currents while in chemical synapses it is transmitted through neurotransmitters.
  • In electrical synapses there is practically no synaptic delay (time it takes for the synaptic connection to occur) while in chemical synapses this delay is greater.
  • Electrical synapses are symmetric while chemical synapses are asymmetric.
  • Electrical synapses are bidirectional while chemical synapses are unidirectional (the postsynaptic neuron cannot transmit information to the presynaptic).
  • Electrical synapses have low plasticity (information is always translated in the same way, that is, when an action potential is produced in one neuron it is produced in the other) while chemical synapses show high plasticity that allows adaptation to changes in the environment.
  • Chemical synapses are more evolved than electrical synapses.
  • Electrical synapses are more common in invertebrates while chemical synapses are more common in vertebrates.

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