Podcast
Questions and Answers
What proportion of the cardiac cycle is approximately dedicated to diastole?
What proportion of the cardiac cycle is approximately dedicated to diastole?
During which phase of the cardiac cycle do the atrioventricular valves open?
During which phase of the cardiac cycle do the atrioventricular valves open?
Which part of the autonomic nervous system increases heart rate?
Which part of the autonomic nervous system increases heart rate?
What is the formula for calculating cardiac output?
What is the formula for calculating cardiac output?
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Which factor does not affect cardiac output?
Which factor does not affect cardiac output?
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What is the primary function of the sinoatrial node?
What is the primary function of the sinoatrial node?
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What is the role of the bundle of His?
What is the role of the bundle of His?
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What is the term for the amount of blood pumped by the heart per minute?
What is the term for the amount of blood pumped by the heart per minute?
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What is the approximate duration of atrial contraction during the cardiac cycle?
What is the approximate duration of atrial contraction during the cardiac cycle?
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What triggers the depolarization of the ventricles?
What triggers the depolarization of the ventricles?
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What nerves regulate heart rate and contractility during cardiac output regulation?
What nerves regulate heart rate and contractility during cardiac output regulation?
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What is the primary function of baroreceptors in the aorta and carotid sinus?
What is the primary function of baroreceptors in the aorta and carotid sinus?
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What is the characteristic of systole in terms of blood pressure?
What is the characteristic of systole in terms of blood pressure?
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During which phase of the cardiac cycle are the atrioventricular valves closed?
During which phase of the cardiac cycle are the atrioventricular valves closed?
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What is the approximate duration of systole during the cardiac cycle?
What is the approximate duration of systole during the cardiac cycle?
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What is the characteristic of diastole in terms of ventricular pressure?
What is the characteristic of diastole in terms of ventricular pressure?
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Study Notes
Cardiac Cycle
Diastole
- Period of cardiac cycle when heart muscle relaxes and chambers fill with blood
- Lasts approximately 2/3 of the cardiac cycle
- Atria and ventricles relax, and atrioventricular valves open
- Blood flows from atria to ventricles through open valves
- Ventricular pressure decreases, and volume increases
Systole
- Period of cardiac cycle when heart muscle contracts and pumps blood out of the heart
- Lasts approximately 1/3 of the cardiac cycle
- Atria and ventricles contract, and atrioventricular valves close
- Blood is pumped out of the heart through semilunar valves
- Ventricular pressure increases, and volume decreases
Heart Rate Regulation
- Heart rate regulated by autonomic nervous system (ANS)
- Sympathetic nervous system (SNS) increases heart rate
- Parasympathetic nervous system (PNS) decreases heart rate
- Baroreceptors in blood vessels detect changes in blood pressure and send signals to the brain
- Brain sends signals to the heart to adjust heart rate accordingly
Cardiac Output
- Amount of blood pumped by the heart per minute
- Calculated by multiplying heart rate and stroke volume
- Factors affecting cardiac output:
- Heart rate
- Stroke volume
- Preload (venous return)
- Afterload (blood pressure)
- Contractility (heart muscle strength)
Electrical Conduction
- Electrical signals control the heartbeat
- Sinoatrial (SA) node: natural pacemaker, generates electrical impulses at a rate of 60-100 bpm
- Atrioventricular (AV) node: relays impulses from SA node to ventricles
- Bundle of His: group of specialized fibers that carry impulses from AV node to ventricles
- Purkinje fibers: branch off from bundle of His, stimulate ventricular contraction
Cardiac Cycle
Diastole
- Heart muscle relaxes, and chambers fill with blood during diastole
- Diastole lasts approximately 2/3 of the cardiac cycle
- Atria and ventricles relax, and atrioventricular valves open, allowing blood to flow from atria to ventricles
- Ventricular pressure decreases, and volume increases during diastole
Systole
- Heart muscle contracts, and pumps blood out of the heart during systole
- Systole lasts approximately 1/3 of the cardiac cycle
- Atria and ventricles contract, and atrioventricular valves close, pumping blood out of the heart through semilunar valves
- Ventricular pressure increases, and volume decreases during systole
Heart Rate Regulation
- Autonomic nervous system (ANS) regulates heart rate
- Sympathetic nervous system (SNS) increases heart rate
- Parasympathetic nervous system (PNS) decreases heart rate
- Baroreceptors in blood vessels detect changes in blood pressure, sending signals to the brain to adjust heart rate accordingly
Cardiac Output
- Cardiac output is the amount of blood pumped by the heart per minute
- Calculated by multiplying heart rate and stroke volume
- Factors affecting cardiac output include heart rate, stroke volume, preload, afterload, and contractility
Electrical Conduction
- Electrical signals control the heartbeat
- Sinoatrial (SA) node generates electrical impulses at a rate of 60-100 bpm
- Atrioventricular (AV) node relays impulses from SA node to ventricles
- Bundle of His and Purkinje fibers carry impulses from AV node to ventricles, stimulating ventricular contraction
Cardiac Cycle
Atrial Contraction
- Atrial contraction lasts for approximately 0.1 seconds
- Triggered by the sinoatrial (SA) node, which depolarizes the atria
- Atria contract, pumping blood into the ventricles, contributing to 20-30% of total ventricular filling
Ventricular Contraction
- Ventricular contraction lasts for approximately 0.3 seconds
- Triggered by the atrioventricular (AV) node, which depolarizes the ventricles
- Ventricles contract, pumping blood out of the heart and into the circulatory system
- Responsible for the majority of cardiac output
Cardiac Output Regulation
- Regulated by the autonomic nervous system (ANS) and hormone signals
- ANS regulates heart rate and contractility through sympathetic and parasympathetic nerves
- Hormones such as epinephrine and norepinephrine increase cardiac output during stress or exercise
- Baroreceptors in the aorta and carotid sinus help regulate blood pressure and cardiac output
Systole
- The period of ventricular contraction, lasting approximately 0.3 seconds
- Characterized by:
- Increased blood pressure
- Increased ventricular pressure
- Closed atrioventricular valves
- Open semilunar valves
Diastole
- The period of ventricular relaxation, lasting approximately 0.4 seconds
- Characterized by:
- Decreased blood pressure
- Decreased ventricular pressure
- Open atrioventricular valves
- Closed semilunar valves
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Description
Test your knowledge of the cardiac cycle, including diastole and systole, and their roles in the heart's functioning.
