Question

1. While in a resting condition, most tissues only use about 25% of the oxygen carried in the blood stream. However, the heart uses as much as 65% during rest. During exercise, the heart demands huge quantities of oxygen to function however since it already uses 65% only 35% remains to be extracted for working heart muscle. Because 35% isn’t enough, what must the heart do in order to gain more oxygen in order to keep functioning under high stress exercise conditions?

Answer 1

In rest, heart tissue uses 65% of oxygen carried in the bloodstream. During exercise, demand for oxygen increases.

In order to attain the increases demand of oxygen, heart does certain adjustments.

* Heart rate increases

* Cardiac contractility increases

* Cardiac output increases

As a result of theses changes, heart tissue is able to draw more oxygen. Also, increased cardiac output increases perfusion of tissues and organs with blood thus increases oxygen delivery to tissues.