52 Questions
What is the primary function of atrial systole in the cardiac cycle?
To preload the ventricles with additional blood
During which phase of the cardiac cycle do the pulmonic and aortic valves open?
Systole
What is the main purpose of understanding the cardiac cycle?
To evaluate heart sounds and read electrocardiographs
What percentage of additional blood does atrial systole provide to the ventricles?
20 to 25 percent
During which phase of the cardiac cycle do the ventricles fill with blood?
Diastole
What is the sequence of contractions in the cardiac cycle?
Atria contract first, followed by ventricles
What is the primary function of the natriuretic peptides?
To counteract the effects of the sympathetic nervous system and the renin–angiotensin–aldosterone system
Which of the following electrolytes is NOT involved in myocardial depolarization?
Chloride
What is the effect of hypercalcemia on myocardial contractility?
Increased contractility
What is the role of intercalated disks in cardiac muscle fibers?
To conduct electrical impulses quickly from one muscle fiber to the next
What is the effect of BNP on blood pressure?
Decrease blood pressure
What is the difference between the contraction of atrial and ventricular syncytia?
Atrial syncytium contracts from superior to inferior, whereas ventricular syncytium contracts from inferior to superior
What is the effect of hypokalemia on cardiac function?
Increased irritability
What is the function of the sympathetic nervous system in response to left ventricular dysfunction?
To increase heart rate and cardiac contractile force
What is the difference between ANP and BNP?
ANP is secreted by the atria, whereas BNP is secreted by the ventricles
What is the effect of Nesiritide (Natrecor) on cardiac function?
It decreases cardiac output and blood pressure
What percentage of the blood it contains at the end of systole does the normal ventricle eject?
50 to 70 percent
What is the term for the pressure in the filled ventricle at the end of diastole?
Preload
According to Starling's law of the heart, what happens when the myocardial muscle is stretched?
It contracts with greater force
What is the term for the volume of blood that the heart pumps in 1 minute?
Cardiac output
What is the average heart rate in beats per minute?
60 to 100
What is the result of an increase in peripheral vascular resistance on stroke volume?
It decreases
What is the sympathetic nervous system's role in regulating the heart?
It speeds up the heart rate
What is the term for the amount of blood ejected from the ventricle during each contraction?
Stroke volume
What is the result of a decrease in stroke volume on blood pressure?
It remains the same
What is the average cardiac output in liters per minute?
5 L/min
What is the primary function of the AV junction in the cardiac conduction system?
To slow the impulse and allow the ventricles time to fill
What is the term for the ability of conductive system cells to depolarize without an outside impulse?
Automaticity
Which component of the cardiac conduction system has the slowest intrinsic rate of self-excitation?
Purkinje system
What is the purpose of the internodal atrial pathways in the cardiac conduction system?
To transmit the impulse to the atrial muscle mass
Which of the following is NOT a property of conductive system cells?
Pacemaker potential
What is the name of the bundle that divides into the right and left bundle branches in the ventricles?
Bundle of His
What is the primary function of the fibrous structure that separates the atria from the ventricles?
To physically separate the atria from the ventricles
What is the characteristic of cardiac muscle function that ensures complete depolarization of the atria or ventricles?
The 'all-or-none' principle of depolarization
What is the approximate millivolt difference between the inside and outside of a myocardial cell in its resting state?
-70mV
What is the purpose of the sodium-potassium pump in a myocardial cell?
To regulate the ionic difference across the cell membrane
What is the effect of the influx of sodium ions into a myocardial cell during depolarization?
The inside of the cell becomes more positively charged
What is the function of the cardiac conduction system in terms of ventricular depolarization?
To stimulate the ventricles to depolarize from inferior to superior
What is the reason why the ventricles would be ineffective if the depolarization impulse originated in the atria and spread passively to the ventricles?
The ventricles would contract from superior to inferior
What is the role of the intercalated disks in the cardiac muscle?
To transmit depolarization throughout the entire syncytium
What is the effect of the calcium ions influx through the calcium channels during depolarization?
The positive charge inside the cell is increased
What is the duration of the sodium influx through the sodium channels during depolarization?
A fraction of a second
What is the primary function of alpha receptors in the sympathetic nervous system?
Regulate vasoconstriction in peripheral blood vessels
What is the effect of norepinephrine on the heart rate?
Increases heart rate and cardiac contractile force
What is the primary function of the vagus nerve in terms of heart control?
Decrease heart rate and slow atrioventricular conduction
What is the term for the autonomic control of heart rate?
Chronotropy
What is the effect of a negative chronotropic agent on the heart?
Decreases heart rate
What is the primary difference between a native heart and a transplanted heart in terms of nervous system connections?
A transplanted heart has less nervous system connections
What is the effect of a transplanted heart on the patient's ability to feel chest pain?
Decreases the patient's ability to feel chest pain
What is the primary function of beta1 receptors in the sympathetic nervous system?
Increase heart rate and contractility
What is the primary function of the cardiac plexus?
Innervate the atria and ventricles
What is the effect of the sympathetic nervous system on the heart rate?
Increases heart rate and cardiac contractile force
Learn about the sequence of events that occurs between the heartbeats, including the contraction and relaxation of the atria and ventricles, and the opening and closing of heart valves. Understand how the heart's right and left sides work together to pump blood through the body. Test your knowledge of the cardiac cycle and its components.
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