30 Questions
Which of the following variables does NOT influence stroke volume?
Heart rate
What is the typical end-diastolic volume (EDV) in a resting adult?
130 mL
What is the typical end-systolic volume (ESV) in a resting adult?
60 mL
What is the formula for calculating stroke volume (SV)?
SV = EDV - ESV
Which of the following factors influences end-diastolic volume (EDV)?
Venous return
Which of the following factors influences end-systolic volume (ESV)?
Afterload
What is the primary mechanism by which sympathetic stimulation increases heart rate?
Increasing the firing rate of the SA node by opening Ca2+ channels
What is the role of thyroid hormone (TH) in increasing heart rate?
TH increases the number of β1-adrenergic receptors on SA nodal cells, making them more responsive to NE and EPI
How do certain chemical compounds, such as nicotine, cocaine, and caffeine, increase heart rate?
They increase the release of NE and EPI from the adrenal medulla
What is the role of Ca2+ influx in the SA nodal cells during sympathetic stimulation?
Ca2+ influx is responsible for the depolarization of the SA nodal cells, increasing their firing rate
How do drugs that act on this pathway increase heart rate?
They directly open Ca2+ channels in SA nodal cells
What is the role of the AV node in the increase in heart rate during sympathetic stimulation?
The AV node is inhibited by sympathetic stimulation, decreasing the conduction delay
Which of the following best describes the term 'systole'?
Contraction of a heart chamber
What initiates the contraction of the ventricular muscles?
The Purkinje fibers of the conduction system
What is the primary driving force that ensures the unidirectional movement of blood through the heart and the opening and closing of heart valves?
Ventricular contraction and relaxation
During the initial phase of ventricular contraction, what happens to the atrioventricular (AV) valves?
They are forced closed to prevent backflow into the atria
Which of the following statements accurately describes the relationship between pressure changes and the movement of blood in the heart?
Blood moves along a pressure gradient, from an area of greater pressure to an area of lesser pressure
What is the purpose of the tendinous cords and papillary muscles in relation to the AV valves?
To brace and prevent the AV valves from bulging into the atria
During the initial phase of ventricular contraction, what is the state of the semilunar valves?
They are closed to prevent backflow from the arterial trunks
Which of the following statements accurately describes the action of heart valves during ventricular contraction?
The atrioventricular valves close, and the semilunar valves open
During the initial phase of ventricular contraction, what happens to the blood volume within the ventricular chambers?
It remains the same as no blood enters or leaves the ventricles
Which of the following statements accurately describes the relationship between the opening and closing of heart valves?
As the atrioventricular valves close, the semilunar valves open
What event marks the beginning of the ventricular ejection phase?
The semilunar valves open due to increased ventricular pressure
Which of the following analogies best describes the action of heart valves during the cardiac cycle?
It's like a pair of swinging doors, where one door closes as another opens
Which of the following statements about venous return is accurate?
During exercise, venous return can approximately double compared to its rate at rest.
What is the primary factor that determines balanced ventricular output?
The inherent ability of the heart to contract more forcefully in response to increased venous return.
What happens when you start to exercise and venous return from the body into the right side of the heart increases?
Both the right and left ventricles contract more forcefully, increasing stroke volume and cardiac output.
What is the relationship between stroke volume and inotropic agents?
Stroke volume is altered by external factors, including inotropic agents.
What is the effect of a low resting heart rate on venous return?
A low resting heart rate increases venous return.
What is the consequence of low blood volume or an abnormally high heart rate?
It decreases venous return, end-diastolic volume, preload, and ultimately stroke volume.
Test your knowledge on the processes that occur within the heart due to pressure changes and the phases of the cardiac cycle. Understand the concepts of systole and diastole, and how they impact the atria and ventricles during contraction and relaxation.
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