Podcast
Questions and Answers
What is the term used to describe the contraction of heart muscle?
What is the name of the valves that close at the beginning of ventricular diastole?
What is the formula for calculating cardiac output (CO)?
What is the term used to describe the amount of blood pumped out by a ventricle with each beat?
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What is the term used to describe the difference between resting and maximal cardiac output?
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What is the term used to describe the amount of blood collected in a ventricle during diastole?
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What is the term used to describe the back pressure exerted by blood in the large arteries leaving the heart?
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What is the term used to describe the increase in contractile strength, independent of stretch and end-diastolic volume?
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What is the nervous system that opposes the sympathetic nervous system and slows heart rate?
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What is the hormone that increases heart rate?
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Study Notes
Heart Sounds and Valves
- Heart sounds (lub-dup) are associated with the closing of heart valves
- First sound occurs when AV valves close, signaling the beginning of systole
- Second sound occurs when SL valves close at the beginning of ventricular diastole
Cardiac Cycle
- Cardiac cycle refers to all events associated with blood flow through the heart
- Systole: contraction of heart muscle
- Diastole: relaxation of heart muscle
- Ventricular filling: mid-to-late diastole
Phases of Cardiac Cycle
- Heart blood pressure is low as blood enters atria and flows into ventricles
- AV valves are open, then atrial systole occurs
- Ventricular systole: atria relax, rising ventricular pressure results in closing of AV valves
- Isovolumetric contraction phase
- Ventricular ejection phase: opens semilunar valves
Cardiac Output (CO)
- CO is the amount of blood pumped by each ventricle in one minute
- CO is the product of heart rate (HR) and stroke volume (SV)
- Formula: CO (ml/min) = HR (beats/min) x SV (ml/beat)
- Example: CO = 5250 ml/min (5.25 L/min) = 75 beats/min x 70 ml/beat
Cardiac Reserve and Stroke Volume
- Cardiac reserve is the difference between resting and maximal CO
- SV = end diastolic volume (EDV) minus end systolic volume (ESV)
- Factors affecting SV: preload, contractility, and afterload
Factors Affecting Stroke Volume
- Preload: amount ventricles are stretched by contained blood
- Contractility: cardiac cell contractile force due to factors other than EDV
- Afterload: back pressure exerted by blood in the large arteries leaving the heart
- Increase in preload: slow heartbeat and exercise
- Decrease in preload: blood loss and extremely rapid heartbeat
- Increase in contractility: sympathetic stimuli, certain hormones, Ca2+, and some drugs
Autonomic Nervous System
- Sympathetic nervous system (SNS) stimulation: increases heart rate, activated by stress, anxiety, excitement, or exercise
- Parasympathetic nervous system (PNS) stimulation: mediated by acetylcholine, slows heart rate, and causes vagal tone
- Hormones: epinephrine and thyroxine increase heart rate
Ion Concentrations and Heart Function
- Intra- and extracellular ion concentrations must be maintained for normal heart function
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Description
This quiz covers the basics of heart sounds, including the lub-dup sounds associated with the closing of heart valves, and the cardiac cycle, including systole and diastole. It also touches on ventricular filling and blood pressure in the heart.
