The Platelet Quiz

Platelets

• Platelets are associated with characteristics such as small size, anucleate, and short lifespan.
• The main role of platelets in hemostasis is to form a platelet plug to stop bleeding.

Cardiac Cycle

• The two major events in the cardiac cycle are diastole and systole.
• The phase of the cardiac cycle characterized by the contraction of the atria and the opening of AV valves is atrial systole.
• During atrial systole, SL valves prevent backflow of blood into the atria.
• Isovolumetric ventricular contraction occurs in the cardiac cycle when the ventricles contract and the AV valves are closed.
• There are 8 phases or steps in the cardiac cycle.

ECG and Cardiac Output

• The QRS complex in the ECG coincides with the onset of ventricular systole.
• The main purpose of measuring blood flow, pressure changes, and blood volume throughout the phases of the cardiac cycle is to evaluate cardiac function.
• Cardiac output can be calculated using the formula: CO = HR x SV.

Heart Structure and Function

• The autonomic nervous system relays information derived from blood pressure through the medulla oblongata.
• The outermost layer of the heart wall is the epicardium.
• The AV valves ensure blood flows from the atria to the ventricles and prevent backflow.
• The SL valves prevent backflow of blood into the atria during ventricular systole.

Blood Pressure Regulation

• The law of Starling states that the longer or more stretched the heart fibers are at the beginning of contraction, the stronger the contraction.
• Baroreceptors are located in the walls of arteries and veins.
• The term for the amount of blood left in the ventricles after ejection is end-systolic volume.
• The term for the phase of ventricular diastole between the closure of the SL valves and the re-opening of the AV valves is diastasis.

Heart Layers

• The endothelium makes up the innermost layer of the heart wall.
• The endothelium lines the heart chambers and blood vessels.