The penis is a complicated contraption, and getting an erection involves cooperation between the heart, lungs, blood vessels, hormones, nerves, and brain. So a problem in any of those areas can contribute to erectile dysfunction (ED). The source of ED could be heart disease, diabetes, high blood pressure, low testosterone, nerve damage, depression, COPD, or side effects from medication — Can you run as fast as you did when you were 20 years old? Hit a baseball as far as you once could? Bash a tennis ball with the same speed and spin? Probably not. But even as we age, there are still plenty of ways to stay in the…