- One heartbeat lasts about 0.85 seconds and includes atrial contraction, ventricular contraction, and relaxation of all chambers.
- The first sound "LUBB" is caused by the closure of tricuspid and bicuspid valves at the start of ventricular contraction.
- The second sound "DUP" is due to the closure of semilunar valves at the start of ventricular relaxation.
- Smaller animals and newborns have faster heart rates because of higher metabolism and heat loss.
- The full sequence of contraction and relaxation in a heartbeat is called the cardiac cycle.
Definitions [7]
Define the Circulatory system.
The circulatory system is a transport system moving substances throughout our body with the help of blood.
Define the Veins.
Veins are the blood vessels that carry deoxygenated (impure) blood from the body cells to the heart.
Define the Arteries.
Arteries are the blood vessels in which oxygenated blood is going away from the heart to all parts of the body.
Define the following term:
Blood
Blood is a fluid that circulates in the heart, arteries, capillaries, and veins of vertebrate animals. It transports nutrients and oxygen throughout the body and removes waste.
Definition: Serum
The plasma from which the protein fibrinogen has been removed is called serum.
Define portal vein.
A portal vein is one that starts with capillaries and also ends in capillaries.
Definition: Cardiac Cycle
The complete sequence of events that occurs during one heartbeat, including contraction and relaxation of the atria and ventricles, is called the cardiac cycle.
Key Points
Key Points: Circulation of Blood in the Heart
- The cycle begins with atrial contraction (atrial systole) while the ventricles are relaxed; blood flows easily from atria into ventricles through open cuspid valves.
- As ventricles contract (ventricular systole) and atria relax, pressure closes the cuspid valves, preventing blood from flowing back into the atria.
- Chordae tendinae, attached to papillary muscles, hold the cuspid valve flaps in place and prevent their inversion during ventricular contraction.
- Blood is pushed out of the ventricles into the pulmonary artery and aorta through semilunar valves, which open under pressure from below.
- When ventricles relax again, blood tends to return, but the semilunar valves fill and close, preventing backflow into the heart.
Key Points: Heart Beat
