Cardiac Cycle Sounds and Stethoscope Placement Quiz

Cardiovascular System

• The cardiovascular system consists of a network of vessels that circulate blood throughout the body, driven by the action of the heart.
• The circulatory system has two main divisions: pulmonary circulation (between heart and lungs) and systemic circulation (between heart and all other body parts).

Heart Structure and Function

• The heart has four chambers: right atrium, left atrium, right ventricle, and left ventricle.
• Atrioventricular valves (AV valves) are found between the atria and ventricles, preventing blood from flowing back into the atria.
• Semilunar valves are found at the base of the pulmonary trunk and aorta, preventing blood from flowing back into the ventricles.
• Blood flow through the heart follows this path: pulmonary artery → pulmonary semilunar valve → heart → AV valves → heart → semilunar valves → aorta.

Heart Sounds and Murmurs

• Heart sounds are created by the closure of the AV valves and semilunar valves.
• The "lub" sound is caused by the closure of the AV valves, while the "dub" sound is caused by the closure of the semilunar valves.
• Heart murmurs are abnormal heart sounds caused by damaged valves, which can result in stenosis (narrowing) or regurgitation (backflow) of blood.

Cardiac Cycle and Output

• The cardiac cycle consists of ventricular systole (contraction) and diastole (relaxation).
• Cardiac output (CO) is the amount of blood pumped by each ventricle per minute, calculated by multiplying heart rate (HR) and stroke volume (SV).

Regulation of Heart Rate

• The heart rate is regulated by the cardioacceleratory center (increases HR) and cardioinhibitory center (decreases HR).
• The sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) also play a role in regulating heart rate.

Conduction System of the Heart

• The conduction system consists of the sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje fibers.
• The SA node acts as the pacemaker, generating spontaneous action potentials that trigger the heartbeat.
• The AV node relays the signal to the ventricles, causing them to contract.

Electrocardiogram (ECG)

• An ECG is a recording of the electrical events of the cardiac cycle.
• The ECG is used to diagnose abnormalities of rhythm and conduction.
• A standard ECG consists of three leads: lead I (right arm to left arm), lead II (right arm to left leg), and lead III (left arm to left leg).
• The ECG waveforms include the P-wave (atrial depolarization), QRS complex (ventricular depolarization), and T-wave (ventricular repolarization).

Blood Pressure and Pulse

• Systemic arterial blood pressure is the pressure exerted by the blood on the walls of the aorta and arteries.
• Blood pressure is highest during left ventricular ejection and lowest during diastole.
• Pulse is the rhythmic expansion and contraction of the arteries, corresponding to the heartbeat.

Test your ability to listen and distinguish the sounds of the cardiac cycle ('lub' and 'dub') at different locations on the anterior thorax using a stethoscope. Understand concepts related to stroke volume, cardiac output, and heart rate.