2.6 Structure and function of the heart
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Q: What is cardiac output (CO)?
A: Cardiac output is the volume of blood pumped through each ventricle per minute.
Q: What is the equation for calculating cardiac output?
A: CO = Stroke Volume (SV) × Heart Rate (HR).
Q: What are the units for cardiac output, stroke volume, and heart rate?
A: * CO: ml/min or l/min * SV: ml or l * HR: beats per minute (bpm)
Q: What is stroke volume (SV)?
A: Stroke volume is the volume of blood pumped out of each ventricle each time the heart beats.
Q: What is heart rate (HR)?
A: Heart rate is the number of beats per minute, equal to the pulse rate.
Q: How does an increase in heart rate or stroke volume affect cardiac output?
A: An increase in either heart rate or stroke volume will increase cardiac output.
Q: How can stroke volume (SV) or heart rate (HR) be calculated from cardiac output (CO)?
A: * SV = CO / HR * HR = CO / SV
Q: What is the cardiac cycle?
A: The cardiac cycle is the pattern of contraction and relaxation of the heart during one complete heartbeat.
Q: What are the three stages of the cardiac cycle?
A: 1. Atrial and Ventricular Diastole - Chambers are relaxed and filling with blood. 2. Atrial Systole - Atria contract, pushing remaining blood into ventricles. 3. Ventricular Systole - Ventricles contract, pushing blood out through the aorta and pulmonary artery.
Q: What causes the ‘lubb dubb’ sounds heard in the heart?
A: These sounds are from the opening and closing of the atrioventricular (AV) and semilunar (SL) valves.
Q: What is the role of the sino-atrial node (SAN) in the heart
A: The SAN, located at the top of the right atrium, sets the heart’s contraction rate by sending out electrical impulses, causing atrial systole.
Q: How does the atrioventricular node (AVN) function in the cardiac conduction system?
A: The AVN, located in the lower right atrium, receives impulses from the SAN and sends them to conducting fibers, leading to simultaneous ventricular contraction (ventricular systole).
Q: What are the two pathways of the autonomic nervous system (ANS) that regulate heart rate?
A: * Sympathetic Pathway: Releases noradrenaline, increasing heart rate. * Parasympathetic Pathway: Releases acetylcholine, decreasing heart rate.
Q: What is the role of the medulla in controlling heart rate?
A: The medulla regulates the sino-atrial node’s rate through the antagonistic actions of the ANS.
Q: How does blood pressure change during the cardiac cycle?
A: Blood pressure increases during ventricular systole and decreases during diastole.
Q: What tool is used to measure blood pressure, and what values does it measure?
A: A sphygmomanometer measures blood pressure, recording systolic (heart squeezing) and diastolic (heart relaxing) values.
Q: What is considered average blood pressure for an adult?
A: 120/80 mmHg.
Q: What is hypertension, and why is it significant?
A: Hypertension is high blood pressure, a major risk factor for many cardiovascular diseases