This thread is bullshit, startle response exists in all animals and anyone with any martial arts training or military background will tell you that having a startle response is a good thing. In a survival situation the animal part of your brain "the amygdala" takes over and the startle is actually because of a sudden flood of adrenaline in your body, this flood can cause the fight, flight or freeze response.
During this time your nose will flare to allow more oxygen to enter the body and supply your muscles the burst needed, your heart will pump faster in order to get all that oxygen rich blood to the muscle groups that need them, your eyes will tunnel vision, your hearing becomes acute and in certain scenarios you may lose control of your bowls as your body sheds excess fluids and "weight" in order to become faster in case you need to retreat!
Examples:
Auditory
Visual Stimuli
You will see that in both videos there are extreme response and delayed responses depending on the persons "Situational Awareness" at the time. In extreme responses the person will flinch backwards, close their eyes, their nostrils will flare to allow more air to enter the body, their hands will automatically retract to the chest ready to protect the vital parts of the body and in micro seconds their eyes will track the perceived threat, this all happens in seconds!
In animals:
Another example:
Here you can see people who had "situational awareness" at the time, saw the bat coming and their bodies took action to avoid the threat, this ranges from ducking 0.5 seconds to 2 seconds, primal flinch "hands covering head/face" 0.3 to 0.5 seconds and no response, bat to the face.
Another example of ZERO situational awareness vs. someone with awareness of his or her surroundings!
Martial Artist Tony Blaur did a fascinating study on startle response and create a tactical response program for Law Enforcement called SPEAR: Spontaneous Protection Enabling Accelerated Response. He talks about his findings in this video:
Too much stimuli and adrenaline can actually be toxic and open up calcium receptors in the hearts muscle tissues which in turn stop the heart from contracting correctly which leads to Ventricular Fibrillation in which the heart stops contracting and just dances around your body like jelly on a plate: See video for example
Point being that yes, you can die from too much excitement. It's not about being a coward, it's about being an animal and having natural limits!