Do you think you can control your heartbeat, making it faster or slower whenever you want? Are cardiac muscles voluntary or involuntary in their function? Also name an activity that makes your heart beat faster?

Why can you move your lower jaw and not the upper jaw?

No we cannot control our heartbeat. Cardiac muscles are involuntary.
Running or exercising makes our heartbeat faster.
We can move the lower jaw and not the upper jaw at our will as they are voluntary muscles. They both are separate muscles and can be moved without the movement of other.