[somebody]

Why does my heart rate increase when someone jumps out of nowhere and scares the heck out of me? When attacks like these increase your heart rate does that necessarily mean that you start breathing faster?

please help is needed, i been wondering about this all night!

[InfiniteNow]

Originally Posted by somebody

Why does my heart rate increase when someone jumps out of nowhere and scares the heck out of me? When attacks like these increase your heart rate does that necessarily mean that you start breathing faster?

please help is needed, i been wondering about this all night!

The easy answer is natural selection. We were all prey to some predator, and our ancestors which managed to get away from predators were the ones who passed on their genes and made us what we are today.

The “thing” jumping out of the shadows could be trying to eat you. If you were to lie there lazily, you’d be dinner. If you get a surge of energy and ability to move, you run away or fight the predator off sucessfully, you survive and live another day (to fornicate and pass on your genes).

The response is due in large part to a release of adrenaline, which is like a jumper cable for your heart… BOOOM! It's the "on switch" which has evolved, and animals which didn't have it didn't last long.

Adrenaline

The heart is called into action to push blood through the body as quickly as possible to the muscles, and that blood feeds oxygen to the body’s muscles which are essentially being asked to “wake up!” and run. As the oxygen gets consumed quickly by these muscles in the running process, it needs to be replaced and your rate of breathing increases also.

Through time, those organisms that did these things in parallel (multiple actions simultaneously) instead of one response/action… then the next… then the next… tended to survive more than those who did these things in serial (one action after another linearly), or not at all.

Fear -> adrenaline -> heart rate increase -> use of energy more quickly by the muscles -> need for more oxygen through respiration -> I’m not dinner today.

Curiously, it's pretty much the same mechanism when you're the predator chasing the prey.

[Johnson]

I wonder what gets depleted in your body and brain when you produce adrenaline?

[ronthepon]

Adrenaline is produced in the adrenal glands, and in pretty small quantities. So effectively, nothing significant is actually depleted during the production of the horomone.

But once adrenaline activates your body and icreases activity, your fuel- glucose is depleted. Of course, waste will also be produced. The net result will be depending on your activities. Wether you run or just stand there, all charged and terrified.

[ErlyRisa]

The best thing to do is to turn that relfex action into a skill ...eg Karate/Ninja etc. --> it will teach discipline regarding our reaction to everything... in effect the next time you get a fright, you won't instantly access your 'fright centres' , instead you will be first accesing your logic centres , eg. was it the shadow off a tree or a robber with a knife, and then instantiate your fright centres if you wich to do so.