Podcast
Questions and Answers
What is the term for the series of events that occur from the beginning of one heartbeat to the beginning of the next?
What is the primary function of the cardiovascular system?
What is the term for the amount of blood pumped by the heart per minute?
What is the primary factor that regulates heart rate during exercise?
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What is the effect of exercise on venous return?
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What is the term for the theory that proposes that the cardiovascular system is regulated by a central nervous system mechanism during exercise?
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What is the average blood pressure during a cardiac cycle called?
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What is the pacemaker of the heart?
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What is the formula for cardiac output?
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Which of the following can increase blood pressure?
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What is the effect of beta-blockers on the heart?
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Which nervous system slows the heart rate?
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What is the Frank-Starling mechanism?
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What factor increases with increased end-diastolic volume?
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What is the main function of the venous return?
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What is the name of the recording of the electrical activity of the heart during the cardiac cycle?
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What is the primary function of the right side of the heart?
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What is the term for the contraction phase of the cardiac cycle?
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What is the benefit of regular exercise on the heart?
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What is the formula for calculating mean arterial pressure (MAP)?
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What is the term for blood pressure above 140/90 mmHg?
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What is the role of the kidneys in blood pressure regulation?
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What is the term for the heart's electrical stimulation?
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What is the purpose of the atrioventricular node (AV node)?
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What is the term for the difference between systolic and diastolic pressure?
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What is the term for the heart's ability to adapt to increased blood volume during exercise?
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Study Notes
Heart: Myocardium and Cardiac Cycle
- The pacemaker of the heart is the SA node.
- The average blood pressure during a cardiac cycle is called mean arterial pressure.
Cardiac Output
- Cardiac output is the amount of blood pumped by the heart each minute.
- It is the product of heart rate and stroke volume (Q = HR x SV).
- It depends on training state and gender.
Regulation of Heart Rate
- The parasympathetic nervous system slows heart rate by inhibiting the SA and AV nodes via the vagus nerve.
- The sympathetic nervous system increases heart rate by stimulating the SA and AV nodes via cardiac accelerator nerves.
- Low resting heart rate is due to parasympathetic tone.
Regulation of Stroke Volume
- End-diastolic volume (EDV) is the volume of blood in the ventricles at the end of diastole.
- Average aortic blood pressure is the pressure the heart must pump against to eject blood.
- The strength of ventricular contraction (contractility) is enhanced by circulating epinephrine and norepinephrine, and direct sympathetic stimulation of the heart.
Clinical Applications
- Beta-adrenergic blocking drugs (beta-blockers) reduce heart rate and contractility by competing with epinephrine and norepinephrine for beta-adrenergic receptors in the heart.
- Regular exercise is cardioprotective and reduces the incidence of heart attacks.
Myocardium
- The heart wall is composed of epicardium, myocardium, and endocardium.
- Myocardial infarction (MI) is caused by blockage in coronary blood flow, resulting in cell damage.
- Exercise training protects against heart damage during MI.
The Cardiac Cycle
- Systole is the contraction phase, where ~2/3 of blood is ejected from ventricles per beat.
- Diastole is the relaxation phase, where the heart fills with blood.
- At rest, diastole is longer than systole, but during exercise, both systole and diastole are shorter.
Arterial Blood Pressure
- Arterial blood pressure is expressed as systolic/diastolic (e.g., 120/80 mmHg).
- Systolic pressure is generated during ventricular contraction, and diastolic pressure is the pressure in the arteries during cardiac relaxation.
- Mean arterial pressure (MAP) is the average pressure in the arteries, calculated as MAP = DBP + 0.33(SBP – DBP).
Factors that Influence Arterial Blood Pressure
- Determinants of mean arterial pressure include cardiac output and total vascular resistance (MAP = cardiac output x total vascular resistance).
- Short-term regulation involves the sympathetic nervous system and baroreceptors in the aorta and carotid arteries.
- Long-term regulation involves the kidneys, which control blood volume.
Electrical Activity of the Heart
- Contraction of the heart depends on electrical stimulation of the myocardium.
- The conduction system includes the sinoatrial node (SA node), atrioventricular node (AV node), bundle branches, and Purkinje fibers.
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Description
Explore the heart's pacemaker, cardiac cycle, and factors that influence blood pressure, including heart rate, blood volume, and peripheral resistance.
