Beginning with all chambers of the heart in the "relaxed" phase, describe the cardiac cycle in mammals, with systole and diastole of the atria and ventricles
For each time point in the cycle you select, state the following:
? Whether the atria and ventricles are contracting or relaxing
? Whether the AV valves and semilunar valves are closed or open
? Whether the pressure in the atria and ventricles is high or low
Answer: i. The heart begins with all chambers relaxed. The AV valves are open and the semilunar valves are closed. Low pressure in the heart causes the blood to flow passively into the atria and ventricles.
ii. The atria contract. The ventricles are relaxed. Additional blood flows into the ventricles. Semilunar valves are closed. AV valves are open.
iii. The ventricles contract. The atria relax. The AV valves close. The semilunar valves are still closed. Pressure rises within the ventricles.
iv. High pressure within the ventricles causes the semilunar valves to open. Blood is ejected from the ventricles into circulation.
v. The ventricles relax. The atria are still in diastole. The semilunar valves close. Pressure is low in the atria and ventricles.
vi. The low pressure allows blood from circulation to flow into the atria and ventricles, and the cycle begins anew.
You might also like to view...
Unencapsulated receptors for light touch and pressure on the skin are called __________ discs.
Fill in the blank(s) with the appropriate word(s).
What chemical binds free hydrogen ions in solution?
What will be an ideal response?
Which of the following major events of prenatal development happens first?
A) Bone calcification begins B) The central nervous system begins to form C) Meconium accumulates in the intestines D) The eyes are fully open E) The body is covered with lanugo
The pituitary gland is located in the
A. cribriform plate. B. mandibular fossa. C. sphenoidal sinus. D. sella turcica.