Lab #4: Introduction to Cardiovascular Physiology
1. In reference to the “lubdub…lubdub…” sounds that are heard through a stethoscope when it is
placed over the heart, what cause the lub sound?
• During isovolumic ventricular contraction, the beginning of ventricular systole
• After ventricles have completely filled, they contract and the backflow of blood towards
the atria (because atria have lower pressure now) pushes AV valves close and bulge
backwards towards atria but does not create enough pressure to open semilunar valves
• The closing of the AV valves makes the lub sound
2. In the auscultatory method of measuring the blood pressure, what causes the first Korotkoff
• The first Korotkoff sound is heard when the pressure from the cuff gradually decreases to
the point at which the blood will squirt through the constricted artery with each systole of
• Causes a rhythmic rushing sound
• Referred to as the systolic pressure, highest pressure in the artery
3. What are intercalated disks in the heart muscle? What are their functions?
• Intercalated disks are regions where plasma membrane of adjacent cardiac cells interlock
• They contain desmosomes and gap junctions
• They support the rapid spread of APs and synchronised contraction of cardiac tissue
4. How do the valves within the veins of the arms and legs help blood return to the heart?
• The valves in veins ensure oneway flow back to the heart,