Low intracellular Ca2+ concentration is sensed by a class of Ca2+ -binding proteins known as guanylate cyclase–activating proteins.

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#Id: 5431

#Unit 7. System Physiology – Animal

Two types of potentials are produced:

Nonpropagated potentials (local), depending on their location, synaptic, generator, or electrotonic potentials

Propagated potentials, the action potentials (or nerve impulses)

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#Id: 5432

#Unit 7. System Physiology – Animal

Action potentials are the primary electrical responses of neurons and other excitable tissues, and they are the main form of communication within the nervous system.

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#Id: 5433

#Unit 7. System Physiology – Animal

Important factors in the establishment of the normal resting membrane potential:

Na+-K+ pump

K+ “leak” channels

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#Id: 5434

#Unit 7. System Physiology – Animal

In response to a depolarizing stimulus, some of the voltage-gated Na+ channels open and Na+ enters the cell and the membrane is brought to its threshold potential (approximately −55 mV)

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#Id: 5435

#Unit 7. System Physiology – Animal

The entry of Na+ causes the opening of more voltage- gated Na+ channels and further depolarization, setting up a positive feedback loop .

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#Id: 5436

#Unit 7. System Physiology – Animal

The membrane potential moves toward the equilibrium potential for Na+ (+60 - +65mV) but does not reach it during the action potential, because the increase in Na+ conductance is short-lived.