In: Anatomy and Physiology
1. Sympathetic innervation of the heart results in the following adaptations (check all that apply)
a. Enhanced Heart Contractility
b. Arterial Vasodilation
c. Increased Ejection Fraction
d. Increased Heart Rate
e. Decreased Heart Rate
f. Increased End-systolic Volume
g. Increased End-distolic volume
2. What is the main Cardiovascular adaptation when someone goes from lying down to a standing position?
a. Increase in stroke volume
b. Vasodilation of vascular
c. Increase in Heart Rate
d. Decrease in Heart Rate
3. Gap Junctions
Ans 1.
a. Enhanced heart contractility C. Increased ejection faraction d. Increased heart rate g.increased end diastolic volume The heart rate increases because of a decrease in parasympathetic activity of SA node combined with increased sympathetic activity. The stroke volume increases because of increased ventricular contractility, manifested by an increased ejection fraction and mediated by sympathetic nerves to the ventricular myocardium. End-diastolic volume increase slightly. Because of this increased filling, the Frank-Starling mechanism also contributes to the increased stroke volume (stroke volume increases when end-diastolic volume increases). Ans 2. Increased heart rate When a person stands up, baroreceptor reflexes are rapidly activated to restore arterial pressure so that mean arterial pressure normally is not reduced by more than a few mmHg when a person is standing compared to lying down. However, in order to maintain this normal mean arterial pressure, the person who is standing upright has increased systemic vascular resistance (sympathetic mediated), decreased venous compliance (due to sympathetic activation of veins), decreased stroke volume (due to decreased preload), and increased heart rate (baroreceptor-mediated tachycardia). Ans3. B. Allow the conduction of electric signals to adjacent muscle cells. Gap junctions are a specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells. |