During a lecture today, there was a video displayed in which a heart was cut surgically and parts were carefully removed. (I have some -rational- fear of said surgery, due to the possibility of myself having to undergo the operation in the future).

After viewing the video, extreme nausea quickly came over me, a pronounced ringing in my ears got louder and louder until i could not hear anything other than that ringing and i began to sweat profusely, my vision blurred and became blotched with spiraling patterns. All that lasted perhaps 3 minutes.   --This might be otherwise described as my body going into shock?, as a friend guessed--
Normally I am not queasy during presentation of cadavers, or any sort of thing. 

I have not had experience with seizures, but there has been some situations in the past where I would black out for no particular reason and then wakeup with no recollection.
Most of the time it was while walking around (luckily on carpet). It would last a few seconds to a few minutes on those occasions.
 I hope this never happens again, but I fear it will.

Can anyone give an explanation to why this event may have occurred? Also, no medications -legal or not- have been used for two weeks.

Mind you, most people are uncomfortable with seeing blood especially if you're not used to it. Watching the Budd Dwyer video made me feel kinda faint when I first saw it.
http://www.youtube.com/watch?v=3xqQ5g1tgho

Not entirely sure, my diet has never been very large, i eat healthy small portions, and at the time this occurred I had eaten only a few hours previous.
An altered mental state has been imprinted, one of panic and dispare. I suppose it will go away eventually, but it is not pleasant -to say the least- That, on the other hand, might have to do with something entirely different. Related to a sharp possibility of getting beaten (killed?) by drunken frat boys this weekend... why they gotta go after the nerd? -I sure as hell won't be in town this weekend.
That is more so a supposed happening, and not a reality, but is altogether possible if the perceived attitude of enemies was real.
Maybe I've said too much... I will edit this eventually.

Hey matey I just saw your problem from a different pov

 do you stop breathing under stress? Lots of people hold their breath when first "shocked" maybe as the procedure progressed you slowly started breathing less

 Maybe you just became feint!

"Is it possible that cannabis (THC) lowers the seizure threshold in those susceptible to them?"

In a word, yes.  it is known to cause hypotension (low/ered blood pressure) It's fair to think that someone with 'low' blood pressure, when combined with pot, could see it drop further...

as to whether it causes seizures, IME, no,,--are you 'sure' you are having seizures, or maybe you are just feinting, or have other peeps seen you seizing up?

"Would slightly lowered oxygen levels to the brain be something to note ? --a certain medical condition limits, albeit slightly, efficient oxygen use by the heart / lungs / brain"

Yep, the body 'shuts down' to save the brain, after all, ones brain consumes the lions share of the O2 we breathe, and will gladly shut the body down, to maintain itself! Also, insufficient Fe in the blood,(anemia) affects the ability of the blood to carry O2, but can be easily rectified, with some dietary supplements, once diagnosed

All these factors in 'concert' can most certainly result in the symptoms you discuss, and pot, especially when eaten,(and in large amounts) becoz two things occur during eating it--it lasts longer, and can also be stronger, as the HCl in ones stomach, can, and will isomerize cannabinols and cannabadiols, into various THC's...hence why, eating, hash, which when smoked has a heavy body stone, will sometimes become really 'trippy' when eaten with a longer duration

Breathing is the 'key' here..many folks dont breathe "well" and consequently dont 'realize' the affect this can/does have on many aspects of their health..

We can go without food for weeks, and water for days, but we cant go without a breath, for more than a few minutes...breathing IS ones "connection" to the life force....which is why, breathing 'properly' is so important in martial arts, yoga or meditation, to name a few practices, which emphasize the importance of breathing correctly.

It never fails to surprise me, just how Many people dont breathe well. Its almost as if we take it for granted. IMO, breathing properly, should be 'taught' to kids at school, along with a number of things which seem to be "overlooked" e.g. "critical thinking" which IMO should be taught from the get go! 

f1

I may need to start on some supplements, thanks a bunch.