Are four beats in a line of iambic pentameter?

There are 10 syllables in an iambic pentameter because iambic means the 1st syllable is not stressed but the 2nd one is stressed; kinda of like a heart beat (da-DUM da-DUM). pentameter comes from pentagon which is 5 so there would be 5 unstressed syllables and 5 stressed syllables (da-DUM da-DUM da-DUM da-DUM da-DUM).