Cardiac Output and Regulation exam study with answers

Cardiac Output and Regulation Exam Study with Answers

Cardiac output (CO) represents the volume of blood the heart ejects per minute, serving as a critical determinant of overall circulatory efficiency. Understanding its regulation, influencing factors, and clinical implications is essential for students preparing for examinations in cardiovascular physiology. This guide provides an in-depth study of cardiac output and its regulation, along with key exam-style questions and answers to enhance comprehension.

Understanding Cardiac Output and Its Regulation

Cardiac output is calculated as:

where heart rate is the number of beats per minute, and stroke volume is the amount of blood ejected per beat. Typically, a healthy adult exhibits a cardiac output of approximately 5 liters per minute at rest. This parameter fluctuates based on metabolic demands, making its regulation vital for maintaining homeostasis.

Several intrinsic and extrinsic factors influence cardiac output, including:

• Preload: The initial stretching of cardiac myocytes prior to contraction, influenced by venous return.

• Afterload: The resistance the ventricles must overcome to eject blood, primarily determined by arterial pressure.

• Contractility: The intrinsic strength of cardiac muscle contraction, independent of preload and afterload.

• Heart Rate: Regulated by autonomic innervation and hormonal control.

Which Nerve Provides Parasympathetic Supply to the Heart?

The vagus nerve (cranial nerve X) provides parasympathetic innervation to the heart. It primarily acts on the sinoatrial (SA) and atrioventricular (AV) nodes to decrease heart rate via the release of acetylcholine, which hyperpolarizes pacemaker cells and slows conduction.

The Frank-Starling Law of the Heart States

The Frank-Starling law of the heart posits that the greater the end-diastolic volume (EDV), the greater the force of contraction, and thus, the greater the stroke volume. This phenomenon occurs due to the length-tension relationship of cardiac muscle fibers: increased sarcomere length enhances actin-myosin cross-bridge formation, leading to a more forceful contraction. However, excessive stretching may diminish contractility, as seen in heart failure.

Which is the Correct Sequence of Events of the Cardiac Cycle?

The cardiac cycle consists of sequential mechanical and electrical events that ensure unidirectional blood flow. The correct sequence is:

1. Atrial Systole – Atria contract, forcing blood into the ventricles.

2. Isovolumetric Contraction – Ventricles contract with closed valves, increasing pressure but without volume change.

3. Ventricular Ejection – Ventricles continue contracting, surpassing arterial pressure, and ejecting blood.

4. Isovolumetric Relaxation – Ventricles relax, pressure falls, and semilunar valves close.

5. Ventricular Filling – Atrioventricular (AV) valves open, and blood passively fills the ventricles.

This cycle repeats with every heartbeat, ensuring continuous circulation.

The Second Heart Sound is Heard During Which Phase of the Cardiac Cycle?

The second heart sound (S2), commonly described as "dub," is heard during isovolumetric relaxation. It results from the closure of the aortic and pulmonary semilunar valves following ventricular systole. This event signifies the transition from the ejection phase to diastole and is crucial for maintaining pressure gradients within the heart.

During Isovolumetric Relaxation

Isovolumetric relaxation occurs immediately after ventricular systole when the ventricles begin to relax but all heart valves remain closed. This phase marks a rapid decline in ventricular pressure while volume remains unchanged. Once ventricular pressure drops below atrial pressure, the AV valves open, initiating ventricular filling.

Which of the Following Would Cause a Decrease in Cardiac Output?

Several factors can lead to a decrease in cardiac output, including:

• Bradycardia: A reduced heart rate diminishes overall blood flow.

• Decreased Venous Return: Less preload results in lower stroke volume.

• Increased Afterload: Higher arterial resistance impedes ventricular ejection.

• Myocardial Infarction: Impaired contractility reduces cardiac efficiency.

• Hypovolemia: Low blood volume diminishes preload and stroke volume.

• Heart Failure: The heart’s inability to pump effectively lowers CO.

Cardiac Output and Regulation Exam Study with Answers PDF & Quizlet

For students seeking additional study materials, numerous resources, including Cardiac Output and Regulation Exam Study with Answers PDFs and Quizlet flashcards, provide structured learning tools. These materials contain multiple-choice questions (MCQs), case studies, and interactive quizzes to reinforce core concepts.

Sample Exam Questions and Answers

1. Which of the following correctly describes cardiac output?

A) Stroke volume divided by heart rate
B) Total blood volume in the heart at any time
C) Volume of blood pumped per minute
D) Volume of blood pumped per stroke
Answer: C

2. Which factor primarily determines stroke volume?

A) Peripheral resistance
B) Blood viscosity
C) Preload, afterload, and contractility
D) Respiratory rate
Answer: C

3. The second heart sound is associated with which event?

A) AV valve closure
B) Semilunar valve closure
C) Ventricular contraction
D) Atrial systole
Answer: B

4. Which phase of the cardiac cycle immediately follows ventricular systole?

A) Ventricular filling
B) Isovolumetric relaxation
C) Atrial contraction
D) Ventricular ejection
Answer: B

Conclusion

Mastering the regulation of cardiac output is pivotal for understanding cardiovascular physiology. Key topics such as the Frank-Starling law, autonomic control, and the phases of the cardiac cycle provide a framework for analyzing cardiac efficiency. Utilizing resources like Cardiac Output and Regulation Exam Study with Answers PDFs and Quizlet quizzes can significantly enhance retention and exam performance. By systematically reviewing these concepts and practicing questions, students can develop a robust understanding of cardiac physiology and its clinical significance.

Below are sample Questions and Answers:

1.Cardiac Output (CO): The amount of blood pumped by the heart per
minute, calculated as the product of heart rate (HR) and stroke volume
(SV)
2.Heart Rate: The number of heartbeats per minute, controlled by the
autonomic nervous system (ANS)
3.Sympathetic Branch: Part of the autonomic nervous system that increases
heart rate through ²1-adrenergic receptors in the sinoatrial (SA) node
4.Parasympathetic Branch: Part of the autonomic nervous system that
decreases heart rate through muscarinic receptors in the SA node, with
impulses reaching the heart through the vagus nerve
5.Stroke Volume: The amount of blood ejected by the left ventricle of the
heart in one contraction, largely determined by myocardial contractility,
cardiac afterload, and cardiac preload
6.Preload: degree of stretch of the cardiac muscle fibers at the end of
diastoles (filling of the ventricles)
7.Afterload: the load a muscle must overcome in order to contract
8.Cardiac after load is determined primary by: degree of peripheral resistance
9.starling law: the greater the volume of blood inside the heart during
diastole, the stronger the heart contraction force during the systole.
10.systemic filling pressure: force that returns blood to the heart