Question

Heart rate is controlled by a pacemaker-an area within the heart that initiates contractions of the heart muscles. If left

alone, the pacemaker would set an unchanging beat. When you exercise, your heart needs to pump more blood
through your body. Why is this necessary? (1 point)
O Blood contains too much carbon dioxide and too little oxygen.
O Blood contains too much oxygen and too little carbon dioxide.

Answer 1

Answer: Blood contains too much carbon dioxide and too little oxygen

Explanation: I took the assignment

Answer 2

Blood contains too much carbon dioxide and too little oxygen.

Step-by-step explanation: