Some asexuals can get aroused, some can't (but from my observation, it seems that most can). Some asexuals masturbate frequently, some don't at all.
I can get aroused, but also always through physical stimulation. I can't get turned on by attractive people, porn, or fantasies (but some asexuals can - the asexual spectrum is complicated!). And when I'm aroused, I don't feel the urge to have sex. I can just masturbate, or do nothing.
Some asexuals do feel having sex is like poking needles in their eyeballs, but some may just feel it's like picking their nose, and some can enjoy it physically and/or emotionally.
Heteroromantic asexual female, sex-positive, childfree, relationship anarchist.
Married to G, and in a partially non-romantic, completely non-sexual and long-distance triad with A and L.