If you tend to jog at an even pace, then your heart rate probably stays pretty consistent as well. This is great for burning calories and of course you're definitely working the muscles in your lower body, but if you want to get your heart pumping a little faster then you've got to work sprints into your routine.
Since sprinting is tough on your muscles and your lungs, you'll want to ease into them. Before adding sprinting intervals throughout your run, try sprinting the last thirty seconds of your workout. It's easier to run at the end because you know that after the thirty seconds is up, you can stop and cool down. It feels amazing to push yourself, and I guarantee that you'll feel so strong and proud when you're done. I always pretend that I'm racing someone for first place, and that the thirty-second mark is the finish line. It may be childish, but it sure gets my legs moving.