Exam Review (Part 1)
• Know as S1 (lub) & S2 (Dub)- lub-dub you hear
• S1 (first sound): is when the AV close
o Which is correlated with isovolumetric contraction phase
▪ This is the first step of ventricular systole
• S2 (second sound): is when the semilunar valves close
o Which is correlated with Isovolumetric relaxation
▪ This is also early diastole
Sounds of Heart when you put a Stethoscope to Listen
• Aortic Valve sounds: heard in 2nd intercostal space at right sternal margin
o Listening to the aorta valves
• Pulmonary valve sounds: heard in 2nd intercostal space at left sternal margin o Listening to the pulmonary valves If you want to learn more check out A sole proprietorship means what?
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• Mitral valve sounds: heard over heart apex (in 5th intercostal space) in line with middle of clavicle (collar bone)
o Listening to mitral valve (also known as bicuspid valve)
• Tricuspid Valve sounds: typically heard in right sternal margin of 5th intercostal space o Listening to the Tricuspid Valve
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Age related changes on the heart
• Valve flaps thicken & become sclerotic (stiff)
o Occurs where the stress of blood flow is greatest (mitral valve). For this reason heart murmurs are more common in elderly people
• Cardiac reserve decline
o Aging causes little change in resting heart rate, the aged heart is less able to respond to both sudden & prolonged stressors that demand increase output. The maximum heart We also discuss several other topics like Who explores the louisiana purchase lands?
rate declines as sympathetic control of the heart becomes less efficient. This is less of a problem in physically active seniors If you want to learn more check out What is a veneer?
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• Cardiac muscle become fibrosed (scarred)
o More cardiac cells die & are replaced with fibrous tissue. As a result the heart stiffens & fills less efficiently, reducing stroke volume. The nodes of the heart’s conduction system may also become fibrosed which increases the incidence of arrhythmias & other condition problems
o Insidious progress of atherosclerosis begins in childhood but inactivity, smoking & stress accelerate it. Most serious consequence to the heart are hypertensive heart disease & coronary artery occlusion, both of which increase risk of heart attack & stroke. It’s found that diet is single most important contributor to cardiovascular disease and now aging (lower risk by eating less animal, fat, sugar & salt)
Focus Figure 18.2 The cardiac Cycle
Pressure & Valves
• Blood flows from high to low pressure, but only if valves are open. When lines cross on the pressure curve, valves either open or close.
• See Image on page 696 for more detail if needed
1. Atrioventricular (AV) valves: close when the ventricular pressure exceeds the atrial pressure 2. Semilunar (SL) valves: open when the ventricular pressure exceeds the aortic pressure 3. Semilunar valves: close when the ventricular pressure drops below the aortic pressure.
(Blood in the aorta rebounds against the closed valve, causing the pressure to rise briefly at the dicrotic notch)
4. AV valves: open when the ventricular pressure drops below the atrial pressure Electrical events and volume changes in the heart (continuation of Fig. 18.2)
• P wave: atrial depolarization)
o Precedes atrial contraction
• QRS complex: ventricular depolarization
o Precedes ventricular contraction
• T wave: ventricular repolarization)
o Precedes ventricular relaxation
• Rise in pressure caused by atrial contraction
• Pressure changes caused volume changes (if valves are open)
• Volume of blood in ventricle is greatest at the end of diastole.
o This is EDV- end diastolic volume
• Amount of blood ejected from each ventricle is the SV (stroke volume)
• Volume of blood in the ventricle is smallest at the end of systole
o This is ESV- end systolic volume
• Blood enters heart from Superior and Inferior Vena Cava
• AV valves are open, blood passively flows into the Ventricles
• Atrium Contract squeezing remaining blood into the Ventricles during Atrial Systole • The AV valves snap shut as the Isovolumetric (early Ventricular Systole) contraction phase occurs
• As pressure builds during Ventricular Systole the Semi-lunar valves burst open causing the ventricles to eject the blood into the Aorta and Pulmonary Artery.
• Beyond this point Isovolumetric relaxation phase occurs as the heart prepares for the next beat. ECG Tracing (See slide 7 for image)
1. Atrial depolarization = P wave
• Initiated by SA node
2. With atrial depolarization complete, impulse is delayed at the AV node
• (Hence the flat line after the P wave)
3. Ventricular depolarization = QRS complex
• Ventricular depolarization begins at apex
• Atrial repolarization occurs
4. Ventricular depolarization is complete
• (Hence flat line again after QRS complex)
5. Ventricular repolarization = T wave
• Ventricular repolarization begins at apex
6. Ventricular repolarization is complete
• (Hence flat line after the T wave)
Action potential of Contractile Cardiac Muscle cells
1. Depolarization is due to Na+influx through fast voltage-gated Na+channels • A positive feedback cycle rapidly opens many Na+channels. Reversing the membrane potential. Channel inactivation ends this phase.
2. Plateau phase: due to Ca2+ influx through slow Ca2+ Channels.
• This keeps the cell depolarized because few K+channels are open
3. Repolarization: due to Ca2+ channels inactivating and K+channels opening
• Allows K+ efflux, which brings the membrane potential back to its resting voltage Cardiac Output
• Cardiac Output= Heart Rate x Stroke Volume
• Cardiac Output= the amount of blood pumped out by each ventricle in 1 minute. • Stroke volume= the volume of blood pumped out by one ventricle with each beat. • Direct relationship between Heart Rate and Cardiac Output.
o (If HR goes up then CO goes up)
o (If SV goes up then CO goes up)