Controlling heart rate

Is it possible to control your heart rate with your mind?  I know that I can be sat down and if i wonder what my rate is I start to feel it, I can feel it pounding, whether at normal rate or fast.  Then when it goes up i struggle to get the heart rate back down even with breathing exercises.  Is it possible that I am causing it to still be high subconciously?

Last night it went up fast after climbing the stairs and didn't go back down, I took half a beta blocker, because that usually works, but it didn't, it remained fast all night, I woke up with it fast this morning.  Then when I was talking on the phone to my mother about half an hour later it was down to normal, then it raced up again.  

What can I do to slow it down successfully?

This morning I took a beta blocker and I had an appointment at the Dr's this afternoon about 2 hours after taking the beta blocker, the Dr took my bp and pulse and they were both quite normal, the bp being 116/80 and the pulse being 64bpm.  But then I walked home and was hot and tired so I laid down on the sofa and my pulse was about 90+ resting and did not slow down.  I found that it would slightly slow down on exhaling, but went up on inhaling but the rate remained fast.  

I only took the beta blocker 5 hours ago and my rate has gone up and it won't come down.  Yesterday I was fine with my heart rate until about 4am after climbing the stairs but it had been fine all day until that point.  When I climbed the stairs I was out of breath, I ached all over and it was fast and would not slow down.  And yet during the day when I go for a walk it will come down fine.

Does this mean it's psychological?  Is my mind controlling the rate?

[Jon10]

You cant control you heart rate with your mind in terms of management. For example you cant say "right heart, i want you to beat 70 times a minute" but your heart rate does change with your emotions i.e if you are feeling particually anxious your heart rate will increase. Which is im sure what happens in your case.