Which is true of drugs that decrease membrane permeability to sodium ions? some are used as local. they may block nerve impulses from moving along the axon. they may prevent the perception of pain. they work by blocking sodium channels in the cell membrane. all of these are true?

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.