Final answer:
Increased K+ in the interstitial fluid would not increase stroke volume, as high potassium levels can decrease heart functionality. Other listed factors such as increased Ca²+, epinephrine, increased venous return, and a slow resting heart rate can all contribute to increasing stroke volume.
Step-by-step explanation:
Stroke Volume Factors
Stroke volume refers to the amount of blood ejected by the left ventricle of the heart in one contraction. Several factors can influence stroke volume, positively or negatively. To answer the student's question, increased K⁺ in the interstitial fluid would not increase stroke volume. It is well-established that decreased potassium levels can lead to an increase in stroke volume by influencing cardiac output, whereas elevated potassium levels can have a negative effect on the heart's functionality, potentially leading to arrhythmias and a decrease in the efficiency of cardiac contractions.
On the other hand, factors such as increased Ca²⁺ in the interstitial fluid, the presence of epinephrine, an increase in venous return, or a slow resting heart rate can all lead to an increase in stroke volume. Increased calcium ions and epinephrine both enhance the strength of heart contractions, venous return increases the preload on the heart which can enhance contraction, and a slow resting heart rate allows more time for the heart to fill with blood between contractions, potentially increasing the volume of blood ejected per beat.
Therefore, when looking at these options, increased K⁺ would be the choice that does not contribute to an increase in stroke volume.