Which subdivision of the PNS is involved in increasing your heart rate?

The sympathetic division of the autonomic nervous system (ANS) is involved. The ANS is the visceral motor subdivision of the PNS, and its sympathetic division mobilizes body systems during activity, which includes increasing heart rate.

The peripheral nervous system (PNS) includes the autonomic nervous system (ANS), which has two functional subdivisions: the sympathetic division and the parasympathetic division. These divisions generally work in opposition, with the sympathetic division mobilizing body systems during activity. Increasing the heart rate is a sympathetic response because it prepares the body for activity, unlike the parasympathetic division, which conserves energy and promotes resting functions.