At the cellular level, cardiac muscle cells respond to an increase in ventricular volume to the point of overload by: Select all that apply

Question

A) Elongating the cardiac muscle cells
B) Thickening of the individual myocytes
C) Replicating the myofibrils
D) Decreasing the ventricular wall thickness
E) Symmetrically widening and lengthening the hypertrophy

Answer 1

Ans: A, D
Feedback:
At the cellular level, cardiac muscle cells respond to stimuli from stress placed on the ventricular wall by pressure and volume overload by initiating several different processes that lead to hypertrophy. With ventricular volume overload, the increase in wall stress leads to replication of myofibrils in series, elongation of the cardiac muscle cells, and eccentric hypertrophy. Eccentric hypertrophy leads to a decrease in ventricular wall thickness or thinning of the wall with an increase in diastolic volume and wall tension. Production of a symmetric hypertrophy occurs with a proportionate increase in muscle length and width, as occurs in athletes; concentric hypertrophy with an increase in wall thickness, as occurs in hypertension; and eccentric hypertrophy with a disproportionate increase in muscle length, as occurs in dilated cardiomyopathy. When the primary stimulus for hypertrophy is pressure overload, the increase in wall stress leads to parallel replication of myofibrils, thickening of the individual myocytes, and concentric hypertrophy. Concentric hypertrophy may preserve systolic function for a time, but eventually the work performed by the ventricle exceeds the vascular reserve, predisposing to ischemia.