Why does my heart pound?

I'm doing an experiment write up about the affects of caffeine on a daphnia's heart rate. Apparently, one reason for this, is that caffeine blocks adenosine receptors on heart muscle cells, which causes the heart to pound. What exactly is adenosine and...

When I stand up or bend over I feel my heart pound really hard in my chest and I can hear the heart beat "wooshing" in my ears, and I start to go dizzy. I also sometimes feel my heart beat or thump one really hard beat, and I feel a rush of...

Its been going on for a couple months now but i can just be at home watching tv and out of no where i feel my heart pound so hard that it keeps me from catching the breath i was just about to take. It feels like someone knocked the wind out of me. What...

My heart pounded so fast everytime i saw my old crush.. But that was before i moved. I moved to a new school in a new state and i have a few crushes here but my heart doesnt pound as fast! Why is that?

I live in Florida and it hits 90's I like to lay in the sun once in awhile. Whats been happening to me is my heart starts to pound so hard I have to come inside before I faint. It beats so hard it feels like I ran a race! I keep hydrated with an ice...

I have noticed that when i eat subway sandwiches, i had a garlic footlong bread with chicken parmesan yestersay with cheese, after a few minutes I start to feel my heart pounding, its like when i put my hand on my chest i can feel it pounding harder...

Why does my heart race and my blood pound when I wake up from a nap? This doesn't happen when I wake up from a regular sleep session, but if I nap during the day, I almost always wake up with the really unpleasant sensation of my blood racing through...

This is really confusing me. I'm quite skinny, well very skinny, my bmi is 13.2 You can see my heart a little all the time but sometimes, for no reason it pounds really hard and it looks like it's leaping out of my chest. When it does this, it's quite...

I am a farily healthy 32 year old. My heart suddenly starts to pound and i get dizzy on the rare occasion (once a year) i go up north to my friends cottage or to an outdoor event surrounded by farmland. I believe it only happens late evening. It never...