Tetrodotoxin is a poison found in pufferfish and some other animals. most cases of human tetrodotoxin poisoning occur when a person eats cooked or uncooked pufferfish. the most strongly toxix parts are the liver and ovaries; muscle and testes are weakly toxic. the lethal dose (LD50) for humans is less than 10 ug/kg (1-2mg total for most people). there is no known antidote, and death can occur from respiratory failure if the diaphragm is unable to contract

tetrodotoxin acts by blocking sodium channels. how does it lead to a loss of excitatory conduction in neurons?

-membrane potential approaches +20 mV
-the membrane cannot depolarize
-it blocks Na+ ions from flowing out of the cell
-membrane repolarization is slowed
-the membrane cannot repolarize