Yes, IMPULSE is a Scrabble word!

Letter values in Scrabble US: I 1, M 3, P 3, U 1, L 1, S 1, E 1.

Is it a valid word?

IMPULSE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

an instinctive motive
a sudden desire
the electrical discharge that travels along a nerve fiber
(electronics) a sharp transient wave in the normal electrical state (or a series of such transients)
the act of applying force suddenly
an impelling force or strength

Also: nerve impulse, nervous impulse, neural impulse.