I. CONDUCTION: is reserved for the passage of an impulse along a axon or muscle fiber. Axonal conduction: stems largely from the work of Hodgkin and Husley: Energy-dependent active transport mechanism, Na+K+-ATPase. Transmembrane ionic currents produce local circuit currents around axons.
1. Tetradotoxins, puffer fish, selectively block axonal conduction; they do so by blocking the voltage-sensitive Na+ channel and preventing the increase in Na+ permeability associated with the rising phase of action potential.
2. Batrachotoxin, south American frog, an extremely potent steroidal alkaloid, produces paralysis through a selective increase in permeability of the Na+ channel, which induces a persistent depolarization.
3. Scorpion toxins are peptides that also cause persistent depolarization, but they do so by inhibiting the inactivation process.
1. Storage and release of transmitter.
2. Combination of the transmitter with post-junctional receptors and production of post-junctional potential.
3. Initiation of post-junctional activity.
4. Destruction or dissipation of the transmitter.
5. Non-electrogenic functions.
Nguồn: Goodman 11th edition, section III, chapter 6. p.137-180.