Question

PART A: Discuss how buffers, ventilation, and the kidneys all work together to regulate blood pH.

PART B: Discuss the changes that occur in heart rate, stroke volume, and cardiac output from rest to maximal exercise. Why do they occur, and how do they interact with each other to maintain adequate cardiovascular support for exercise?

Answer 1

1. The most important way that the pH of the blood is kept relatively constant is by buffers dissolved in the blood. Other organs help enhance the homeostatic function of the buffers such as kidneys, which help remove excess chemicals from the blood. The kidneys remove H+ ions and other components of the pH buffers that build up in excess.
The lungs provide a faster way to help control the pH of the blood. The increased-breathing response to exercise helps to counteract the pH-lowering effects of exercise by removing CO2, a component of the principal pH buffer in the blood.

2.

At rest HR is between 60-80 BPM, just before the start of exercise the anticipatory response cause the HR to increase above RHR. Heart rate increases directly proportional to exercise intensity(up to a point when you reach max HR) . During max exercise SV doubles due to increase in preload(end diastolic ventricular stretch), increase in contractility(from NE/E) and decrease in afterload (VD= decrease it total peripheral resistance). Cardiac output increase with increase intensity but platues near VO2 max. Higher the stroke volume the larger the cardiac output. When the body shifts from reclining to sitting, to standing, gravity causes the blood to pool in the legs, which reduces the volume of blod returning to heart which reduces SV. To compensate for this HR increase to maintain cardiac output. From rest to walking HR increases, from 60-90BPM than again to 140BPM with jogging and 180BPM with running. The initial HR increase is due to withdrawl in vagal tone, furthu increases are due to sympathetic nervous system. When beginning to exercise increase in cardiac output is cause by an increase in HR and SV. As intensity increases SV either plateus or slows down. Increase in cardiac output from this point would be from an increase in HR.