Cardiac Output Control Quiz

Questions and Answers

What is the role of β1 receptors on ventricular cells in cardiac contraction?

They reduce cross-bridge formation.

They inhibit noradrenaline activity.

They facilitate calcium release and influx. (correct)

They decrease the force of contraction.

How does increased afterload affect stroke volume (SV)?

It increases SV by lowering systemic resistance.

It decreases SV due to the heightened load on the heart. (correct)

It has no effect on SV.

It increases SV by reducing pulmonary pressure.

What characterization differentiates the left ventricle (LV) from the right ventricle (RV)?

RV ejects blood against higher resistance than LV.

LV has a larger chamber volume than RV.

LV has thinner muscle than RV.

LV has a thicker muscle than RV. (correct)

Which pressure is considered afterload for the left ventricle?

Aortic pressure. Signup and view all the answers

What effect does an increase in cross-bridge formation have on heart function?

It decreases end-systolic volume (ESV). Signup and view all the answers

Which factors primarily influence the afterload for the right ventricle?

Pulmonary pressure and vascular resistance. Signup and view all the answers

What is the relationship between end-diastolic volume (EDV) and stroke volume (SV) according to the Frank-Starling Law?

An increase in EDV leads to an increase in SV. Signup and view all the answers

How does increasing EDV enhance the force of ventricular contraction?

Through greater stretching of the sarcomeres which increases cross-bridge formation. Signup and view all the answers

What parameters define cardiac output (CO)?

Heart rate (HR) multiplied by stroke volume (SV). Signup and view all the answers

What is the term for the volume of blood in the ventricles at the end of contraction?

End-systolic volume (ESV). Signup and view all the answers

Which statement accurately describes the length-tension relationship in cardiac muscle?

It supports the idea that increased muscle length results in increased force of contraction. Signup and view all the answers

What effect does preload have on cardiac performance?

Increased preload leads to improved cardiac output. Signup and view all the answers

What is the formula to calculate cardiac output?

CO = HR x SV Signup and view all the answers

How do intrinsic properties of cardiac muscle cells contribute to heart function?

They allow rhythmic depolarization and contraction without external stimulation. Signup and view all the answers

Which node is primarily responsible for initiating the heartbeat?

Sino-atrial (SA) node Signup and view all the answers

What role do veins play in determining cardiac output?

Veins help in regulating blood volume returning to the heart. Signup and view all the answers

Which statement accurately describes the function of the autonomic nervous system in heart rate regulation?

It regulates heart rate through both sympathetic and parasympathetic pathways. Signup and view all the answers

An increase in cardiac output can occur through what combination of factors?

Increased heart rate and increased stroke volume. Signup and view all the answers

Study Notes

Overview of Cardiac Output Control

Cardiac output (CO) is determined by the equation CO = Heart Rate (HR) x Stroke Volume (SV).
Stroke Volume can be further defined as SV = End-Diastolic Volume (EDV) – End-Systolic Volume (ESV).

Factors Influencing Cardiac Output

Variables that control CO vary with physiological states; at rest, they maintain a baseline, while during stress or exercise, they adjust to increase or decrease CO.

Heart Rate Control

Cardiac muscle cells exhibit myogenic rhythmicity, allowing them to depolarize and contract without neuronal input.
Significant to heart rhythm is the Sino-atrial (SA) node, located in the right atrium, acting as the natural pacemaker.

Autonomic Nervous System's Role

The Autonomic Nervous System (ANS) regulates HR.
Sympathetic stimulation increases HR through β1 adrenergic receptors, enhancing contractility and cardiac efficiency.

Frank-Starling Mechanism

The relationship between EDV and SV is articulated by Starling’s Law, stating that increased EDV leads to enhanced stroke volume.
Increased preload (stretch of cardiac muscle) results in more effective heart contractions due to length-dependent increases in calcium (Ca²⁺) sensitivity.

End-Systolic Volume Control

ESV is controlled primarily by the sympathetic nervous system, which increases calcium release in ventricular cells.
Increased sympathetic activity results in higher force of contraction, reducing ESV and boosting SV.

Afterload and Stroke Volume

Afterload is the resistance the heart must overcome to eject blood; for the left ventricle, it is influenced by aortic pressure, while for the right ventricle, it relates to pulmonary pressure.
A higher afterload reduces SV; thus, the left ventricle must generate greater force than the right ventricle, leading to thicker muscular walls in the left ventricle compared to the right.

Summary

Cardiac output is vital for effective circulation, modulated through heart rate, stroke volume, and various physiological parameters, including vascular resistance and muscle properties.

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Description

Test your understanding of cardiac output control mechanisms, including the factors influencing heart rate and stroke volume. Explore the roles of the autonomic nervous system and the Frank-Starling mechanism in regulating heart function.