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Questions and Answers
What is referred to as systolic pressure?
What is referred to as systolic pressure?
Which valve prevents backflow of blood into the right atrium during ventricular contraction?
Which valve prevents backflow of blood into the right atrium during ventricular contraction?
During which phase does blood fill the ventricles?
During which phase does blood fill the ventricles?
Which structure initiates the electrical signal for heart contractions?
Which structure initiates the electrical signal for heart contractions?
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What type of blood pressure is measured when the ventricles are relaxed?
What type of blood pressure is measured when the ventricles are relaxed?
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What is the primary purpose of ventricular contraction during systole?
What is the primary purpose of ventricular contraction during systole?
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Which of the following statements is true regarding the pressures in the ventricles?
Which of the following statements is true regarding the pressures in the ventricles?
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What mechanism ensures one-directional flow of blood through the heart?
What mechanism ensures one-directional flow of blood through the heart?
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What is the primary function of the sinoatrial (SA) node in the cardiac conduction system?
What is the primary function of the sinoatrial (SA) node in the cardiac conduction system?
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Which structure is responsible for transmitting impulses six times faster than normal cell-to-cell connections?
Which structure is responsible for transmitting impulses six times faster than normal cell-to-cell connections?
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What characteristic of the atrioventricular (AV) node contributes to the delay in impulse transmission to the ventricles?
What characteristic of the atrioventricular (AV) node contributes to the delay in impulse transmission to the ventricles?
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Where is the bundle of His located in relation to the atrioventricular node?
Where is the bundle of His located in relation to the atrioventricular node?
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Which substance is primarily responsible for vasodilation and can form anywhere in the circulatory system?
Which substance is primarily responsible for vasodilation and can form anywhere in the circulatory system?
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What is the effect of increased extracellular Ca2+ on the heart?
What is the effect of increased extracellular Ca2+ on the heart?
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What is the typical duration of normal P-waves in an electrocardiogram?
What is the typical duration of normal P-waves in an electrocardiogram?
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How do the right and left bundle branches function after the impulse leaves the bundle of His?
How do the right and left bundle branches function after the impulse leaves the bundle of His?
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Which hormone acts as a potent vasoconstrictor and also regulates fluid volume by controlling water reabsorption?
Which hormone acts as a potent vasoconstrictor and also regulates fluid volume by controlling water reabsorption?
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What is the significance of the relatively weak transmission of the depolarization wave through the AV node?
What is the significance of the relatively weak transmission of the depolarization wave through the AV node?
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How do chemoreceptors in the brain and carotids respond to decreased O2 levels?
How do chemoreceptors in the brain and carotids respond to decreased O2 levels?
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What aspect of the SA node's depolarization is noteworthy in electrocardiography?
What aspect of the SA node's depolarization is noteworthy in electrocardiography?
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Which of the following substances is NOT a vasodilating agent?
Which of the following substances is NOT a vasodilating agent?
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What is the primary function of angiotensin in the body?
What is the primary function of angiotensin in the body?
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Which chemical would likely cause local edema due to increased capillary permeability?
Which chemical would likely cause local edema due to increased capillary permeability?
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A decrease in arterial pressure triggers which of the following responses?
A decrease in arterial pressure triggers which of the following responses?
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What mechanism allows the cardiac conduction cells to respond to an electrochemical stimulus?
What mechanism allows the cardiac conduction cells to respond to an electrochemical stimulus?
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During which phase of the cardiac cycle does blood begin to flow out of the ventricles?
During which phase of the cardiac cycle does blood begin to flow out of the ventricles?
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What is the role of the Sinoatrial (SA) node in the heart?
What is the role of the Sinoatrial (SA) node in the heart?
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What is the approximate change in membrane potential required for an action potential in ventricular muscle?
What is the approximate change in membrane potential required for an action potential in ventricular muscle?
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Which node receives the electrical impulse after it is generated by the SA node?
Which node receives the electrical impulse after it is generated by the SA node?
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What happens to the pressure in the ventricles during early diastole?
What happens to the pressure in the ventricles during early diastole?
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Which ions primarily flow into the cardiac conduction cells during electrochemical stimulation?
Which ions primarily flow into the cardiac conduction cells during electrochemical stimulation?
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What initiates the contraction of the cardiac muscle tissue?
What initiates the contraction of the cardiac muscle tissue?
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What does a prolonged P-R interval indicate?
What does a prolonged P-R interval indicate?
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Which of the following describes the QRS complex?
Which of the following describes the QRS complex?
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How is stroke volume calculated?
How is stroke volume calculated?
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What is the normal duration of a QRS complex?
What is the normal duration of a QRS complex?
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What does the S-T segment represent?
What does the S-T segment represent?
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Which of the following factors does not decrease cardiac output?
Which of the following factors does not decrease cardiac output?
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What percentage of blood volume is typically ejected from a healthy heart during contraction?
What percentage of blood volume is typically ejected from a healthy heart during contraction?
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What is the average cardiac output for a resting person?
What is the average cardiac output for a resting person?
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What is the correct formula used to calculate cardiac output?
What is the correct formula used to calculate cardiac output?
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Under sympathetic control, which effect is NOT observed on the heart?
Under sympathetic control, which effect is NOT observed on the heart?
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Which of the following statements regarding parasympathetic control is accurate?
Which of the following statements regarding parasympathetic control is accurate?
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What determines the stroke volume of the heart?
What determines the stroke volume of the heart?
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Which factor is NOT listed as an extrinsic regulator of the heart?
Which factor is NOT listed as an extrinsic regulator of the heart?
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What is the primary neurotransmitter released by most postsynaptic sympathetic nerve endings?
What is the primary neurotransmitter released by most postsynaptic sympathetic nerve endings?
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What is the expected stroke volume for a resting college student with a cardiac output of 5 L/min and a heart rate of 72 beats/min?
What is the expected stroke volume for a resting college student with a cardiac output of 5 L/min and a heart rate of 72 beats/min?
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Which condition correlates with sympathetic stimulation in terms of blood flow?
Which condition correlates with sympathetic stimulation in terms of blood flow?
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Study Notes
Cardiac Physiology
- The heart's pumping action involves two phases: systole and diastole.
- Systole is the contraction of the ventricles, forcing blood into the arteries. Systolic pressure is the increased pressure during this contraction.
- Diastole is the relaxation of the ventricles, allowing them to fill with blood from the atria. Diastolic pressure is the lower pressure during relaxation.
- Heartbeat is a two-part process. The first part, diastole, involves the filling of the atria and ventricles with blood.
- The second part of the heartbeat is systole. It involves the contraction of the ventricles, forcing blood out into the lungs and body.
Normal Cardiovascular Pressures
- Various locations in the cardiovascular system have different pressure levels.
- These pressures—measured in mmHg—vary based on the specific location and normal ranges.
- See the table in the supplemental material for a detailed breakdown.
Cardiac Conduction System
- Electrical impulses originating at the Sinoatrial (SA) node initiate cardiac contraction.
- The SA node is the natural pacemaker, located in the upper wall of the right atrium.
- The electrical signal moves through the atria to stimulate contraction.
- Then, the signal passes to the Atrioventricular (AV) node.
- Next, the signal goes down the bundle of His, causing the ventricles to contract.
- The signal then branches into the right and left bundle branches.
- Special pathways or bundles, called interatrial pathways and internodal pathways, expedite the movement of the electrical signal through the conduction system.
Electrocardiography (ECG/EKG)
- ECG measures the electrical activity of the heart over time.
- Specific waveforms or segments on the ECG, such as the P wave, P-R interval, QRS complex, and T wave each represent different stages of the cardiac cycle.
- Different parts of the electrocardiogram correspond to atrial and ventricular depolarization and repolarization.
- See the included images for examples of these traces.
Stroke Volume
- The stroke volume is the amount of blood ejected from the heart during each beat (systole)
- Stroke volume is calculated as the difference between the end-diastolic volume (EDV) and the end-systolic volume (ESV).
- Stroke volume is directly linked to ventricular contraction force and plays a prominent role in determining cardiac output.
Cardiac Output
- Cardiac output (CO) is the amount of blood pumped by the heart per minute.
- Cardiac output is calculated by multiplying stroke volume by the heart rate.
- Both resting and exercising cardiac output values are provided.
- Normal cardiac output varies depending on an individual's exertion level.
Extrinsic Regulation of the Heart
- The heart is regulated by both neural (nervous) and humoral (chemical) factors.
- Sympathetic nervous system stimulation increases heart rate, force of contraction, and therefore cardiac output, associated with the "fight-or-flight" response.
- Parasympathetic nervous system stimulation (vagus nerve) reduces heart rate and force of contraction.
- Blood pressure, body temperature and other factors all affect heart rate in extrinsic control pathways.
Humoral Regulation of Circulation
- Chemical substances in the bloodstream regulate blood circulation.
- Vasoconstricting agents, like epinephrine and norepinephrine, and angiotensin, constrict blood vessels.
- Vasodilating agents, like bradykinin, histamine, and others, widen blood vessels.
- These humoral factors affect blood flow, pressure and other aspects of circulation.
Effect of Specific Factors on Heart Rate/Contraction
- Chemoreceptors and other systems monitor various factors like pH, CO2, and oxygen in the blood.
- Ion concentrations (K+ and Ca2+) influence heart rate and contractility.
- Blood pressure is monitored by baroreceptors.
- Body temperature alters heart rate.
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Description
Test your knowledge on cardiac physiology, including the heart's pumping action, phases of heartbeat, and normal cardiovascular pressures. This quiz covers key concepts such as systole, diastole, and the cardiac conduction system.
