How dangerous (in general) are spiders to cats?

Tonight when I got home from grocery shopping and dinner with my Mom (I know, I know, my life is too exciting) I called the cats into the bedroom to give them some treats. (I always give them a few treats before bed, so I was keeping things consistent with the location.) When my boy cat Bruno jumped up on the bed, he suddenly jumped as if startled and jumped off the bed. I figured something just freaked him out for a second (my cats have always been jumpy since I brought them home from the shelter last February.)

Except this was more severe. He was so spooked that he didn’t want to get back up on the bed…and to say he loves treats, etc. would be putting it mildly. His favorite activity is eating, lol! He kept acting as if something was on the blanket, and would not get back up. Finally, his love of treats won out, and I coaxed him back up on the bed and he had some treats. When we were done, I shook out the blankets, but didn’t see anything.

I was carrying two pieces of clothing that had been on the bed into the other room to do laundry. Suddenly I saw a medium size spider on the floor, with its legs sort of gathered up. (It wasn’t moving). I don’t know where it came from, although I wonder if it had fell out of the clothes. I sucked it up with the vacuum cleaner and kept an eye on my cat for a little bit. He seems fine, and was chasing the laser pointer around like normal, but it got me to thinking…

All spiders are venomous, but of course the majority are no threat to humans (except maybe giving us heart attacks when they appear out of nowhere). I would assume the more dangerous species (the widows and recluses, etc.) would also be harmful to pets, and, given their relatively smaller size, any ill effects would probably act sooner. But if a run-of-the-mill spider bites a cat or dog, that should be okay, right?

(Sorry for the long story).