As you are walking home from studying at the library late one evening, you get startled by a strange sound behind you. This activates your sympathetic nervous system. What affect does this change have on stroke volume? Group of answer choices Stroke volume will increase due to an increase in contractility. Stroke volume will decrease due to reduced blood pressure. Stroke volume will increase due to increased blood pressure. Stroke volume decreases due to an increase in contractility. Stroke volume will increase due to a decrease in contractility.

Stroke volume will increase due to an increase in contractility.

Explanation:

When the individual is going through a stressful situation, the sympathetic nervous system, in conjunction with the hypothalamic-pituitary-adrenal (HPA) system, sends signals to prepares the body for stressful situations.

The body gets ready to respond to stress by increasing heart biting frequency and strength, contractibility, blood pressure, stimulating respiration and dilating respiratory tracts.

Stroke volume refers to the blood volume ejected from the ventricles as a result of the heart contraction. As said before, stressful situations increase heart bitting frequency and strength, as well as contractibility. Contractibility also influences stroke volume.

Stroke volume is determined by the difference in values of the end-diastolic volume and the end-systolic volume → SV = EDV - ESV

Contractility is one of the main factors that influence stroke volume, by affecting the end-systolic volume. It does not alter the diastolic volume. Consequently, there is an increase in stroke volume.

The central factor of systolic ejection is the myocardium sarcomere contractibility. The sarcomere´s contractile capability generates strength to become shorter after myosin heads join to the uncovered actin-binding points forming cross-bridges.

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