PHYS20090 Principles of Physiology Cardiac Muscle and Conduction System Quiz

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Questions and Answers

Which of the following is NOT a key structural feature of cardiac muscle?

Lack of striations (correct)

Intercalated discs

T-tubules and sarcoplasmic reticulum

Branching

What is the primary function of the intercalated discs found in cardiac muscle?

To store calcium for release during muscle contraction

To allow for the passage of nutrients and oxygen to the muscle fibers

To facilitate rapid and coordinated contraction of the cardiac muscle (correct)

To provide structural support to the muscle fibers

What is the primary function of the cardiac conduction system?

To monitor and maintain the electrical activity of the heart

To distribute oxygenated blood throughout the body

To regulate the heart rate

To coordinate the contraction of the cardiac chambers (correct)

Which of the following imaging techniques is most commonly used to assess the structure and function of the heart?

Echocardiography Signup and view all the answers

What is the primary role of the cardiac valves in the cardiovascular system?

To prevent the backflow of blood during the cardiac cycle Signup and view all the answers

What is the function of the SA Node in the cardiac conduction system?

Coordinating and providing rhythm to the heartbeat Signup and view all the answers

Which part of the cardiac conduction system has the lowest conduction speed?

Atrioventricular (AV) node Signup and view all the answers

What role do pacemaker cells play in the heart's functioning?

Coordinating and providing rhythm to the heartbeat Signup and view all the answers

Which structure ensures there is no summation of cardiac muscle contractions?

Long-lasting refractory period Signup and view all the answers

What is the primary role of the AV node in the cardiac conduction system?

Delaying electrical impulse transmission to allow atrial contraction Signup and view all the answers

Which statement accurately describes Purkinje fibers' function in the heart?

Rapidly conducting action potentials to the myocardium Signup and view all the answers

What is the primary mechanism that allows for the coordinated contraction of cardiac muscle tissue?

The presence of gap junctions between adjacent cardiac myocytes, forming a functional syncytium Signup and view all the answers

Which of the following sequences correctly represents the excitation-contraction coupling process in cardiac myocytes?

Action potential → Increase in intracellular calcium → Opening of L-type calcium channels → Release of calcium from sarcoplasmic reticulum → Myofilament contraction Signup and view all the answers

Which structure is responsible for the rapid and coordinated conduction of electrical signals throughout the heart?

The sinoatrial node Signup and view all the answers

Which statement best describes the role of the fibrous skeleton in cardiac muscle contraction?

It serves as an electrical insulator between the atria and ventricles Signup and view all the answers

Which of the following structures is responsible for the release of calcium ions from the sarcoplasmic reticulum during excitation-contraction coupling?

Ryanodine receptors Signup and view all the answers

Which of the following statements accurately describes the role of the intercalated discs in cardiac muscle contraction?

They allow for the propagation of action potentials across cardiac muscle tissue Signup and view all the answers

Study Notes

Cardiac Muscle Structure and Features

Cardiac muscle features striations similar to skeletal muscle but is involuntary and unique to the heart.
Intercalated discs connect individual cardiac muscle cells, allowing for rapid electrical signal transmission and synchronized contractions.
The structural arrangement of cardiac muscle cells prevents summation of contractions, ensuring effective heartbeats.

Intercalated Discs

Intercalated discs primarily facilitate communication between cardiac muscle cells.
They contain gap junctions that allow ions and electrical impulses to pass freely, promoting coordinated contraction.

Cardiac Conduction System

The cardiac conduction system is responsible for the heart's rhythm and pace, coordinating heartbeats.
Functions include initiating electrical impulses and spreading them throughout cardiac muscle to trigger contractions.

Imaging Techniques

Echocardiogram (ultrasound) is the most commonly used imaging technique to assess heart structure and function.

Cardiac Valves

Cardiac valves direct blood flow through the heart chambers and prevent backflow, ensuring efficient circulation.

SA Node

The SA Node, known as the heart's natural pacemaker, initiates electrical impulses influencing heart rate and rhythm.

Conduction Speed

The AV Node has the lowest conduction speed in the cardiac conduction system, allowing a brief delay for ventricular filling.

Pacemaker Cells

Pacemaker cells in the SA Node generate spontaneous action potentials, leading to rhythmic heart contractions.

Fibrous Skeleton

The fibrous skeleton of the heart provides structural support and maintains the integrity of valves while electrically isolating atria and ventricles.

Purkinje Fibers

Purkinje fibers rapidly conduct electrical signals to ensure synchronized contraction of the ventricles.

Excitation-Contraction Coupling

The coordinated contraction of cardiac muscle relies on the influx of calcium ions, crucial for excitation-contraction coupling.
The process begins with electrical impulses, leading to calcium release from the sarcoplasmic reticulum, facilitating muscle contraction.

Overview of Structures

The sarcoplasmic reticulum is responsible for the release of calcium ions during excitation-contraction coupling.
Intercalated discs provide mechanical and electrical connectivity, essential for the coordinated contraction of the heart.

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Description

Test your knowledge on cardiac muscle classification, contraction mechanisms, coordination of contraction, organization of cardiac chambers and valves, and the cardiac conduction system. This quiz covers learning objectives from Associate Prof. Stuart Bund and Dr. Marie-Victoire Guillot-Sestier at UCD School of Medicine.