Here is a summary of the correct answers to this learning activity. a. Heart rate increases because of increased sympathetic input to the SA node. Remember that heart rate is the number of times the heart contracts and sends blood out into the arteries to be delivered to the working tissues. Increasing heart rate is one way to increase the delivery of oxygen. b. Stroke volume increases during aerobic exercise. The increase in sympathetic stimulation leads to increased contractility of the left ventricle. As a result, the volume of blood leaving the LV with each beat is greater. Obviously, this leads to an increase in the delivery of oxygen to the working tissues. c. Because cardiac output is a product of stroke volume and heart rate, it too will increase. The volume of blood pumped out each minute will increase during aerobic exercise. d. Remember that blood pressure includes both systolic and diastolic phases. Because cardiac output directly affects SBP, it increases during aerobic exercise. However, DBP reflects the peripheral resistance to blood flow. Because the capillaries and arterioles are opening in the working tissues by local, sympathetic, and hormonal influences, the resistance decreases. Thus, DBP will either stay the same or decrease during aerobic exercise. Therefore, there's the potential for blood pressure to both increase (SBP) and decrease (DBP) during aerobic exercise e. O2 extraction increases during aerobic exercise. As the blood travels through the working tissues, oxygen is taken up from the blood into the cells. The local signals resulting from the exercise (increased temperature, decreased pH, decreased O2, increased CO2) all act to increase the hemoglobin-oxygen dissociation, leading to greater availability of O2 to enter the cells. f. Tidal volume increases during aerobic exercise. Because the goal is to increase oxygen delivery to the working cells so that ATP can be made by the oxidative system, getting more air (and oxygen) into the lungs makes sense. Breathing more deeply (i.e., increasing tidal volume) will make more oxygen available and get rid of CO2 more quickly as the blood passes through the pulmonary circuit at an increased rate (due to increased heart rate). g. Breathing rate does increase during aerobic exercise. In addition to increasing the depth of breathing, the respiratory control center in the medulla oblongata also stimulates an increase in breathing rate. h. Minute ventilation also increases during aerobic exercise. Minute ventilation is the product of the depth and rate of breathing. Because both of these increase, the volume of air breathed per minute will increase during aerobic exercise. Click Next to continue.