Change permeability of selected ions , thereby altering the membrane potential and conditions are right, produce an electrical current.

ion-channel-coupled receptors.

Explanation:

These channels are mainly involved with the fast transmission. These receptors are organized into the membrane and regulating or ion-flow channels according to their internal diameter and the predominant electrical charge of their constituent amino acids.

Ion channels can be activated either by membrane potential variation (VOC´S - tension-operated channels), as well as interaction with an agonist (ionotropic receptors), as well as mechanical stimulation or via intracellular agents such as calcium ions, cyclic nucleotides, inositol triphosphate, and G protein.  This group includes the nicotinic cholinergic receptor, the GABA receptor, and the glutamate receptor.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

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