Human Anatomy and Physiology : Help with Cardiac Muscle Physiology

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

Example Question #1 : Help With Cardiac Muscle Physiology

Which of the following is NOT characteristic of cardiac muscle?

Possible Answers:

Composed of sarcomeres

Multinucleated cells

Involuntarily controlled

Attached to other cells by intercalated discs

Correct answer:

Multinucleated cells

Explanation:

Skeletal muscle is the only muscle type that is multinucleated. Both cardiac and smooth muscle cells have only one nucleus.

Smooth muscle is under involuntary control, innervated by the autonomic nervous system, and contains mononucleated cells. Skeletal muscle is striated, multinucleated, and under voluntary control. Cardiac muscle is striated, mononucleated, and under involuntary control.

Cardiac muscle also uses intercalated discs, specialized cellular junctions, to facilitate electrical conduction between cardiomyocytes. This helps coordinate the contraction of the heart.

Example Question #2 : Help With Cardiac Muscle Physiology

Three muscle cells are placed side by side.

In muscle cell 1, striations are clearly visible.

In muscle cell 2, striations are also present, with sharp discs periodically found along muscle fibers. Further examination shows gap junctions between adjacent cells.

In muscle cell 3, no striations are present.

Which of the above types of muscle cell is most likely to be found in the myocardium?

Possible Answers:

Muscle cell type 2

Muscle cell types 2 and 3

Muscle cell type 1

Muscle cell type 3

Muscle cell types 1 and 3

Correct answer:

Muscle cell type 2

Explanation:

Cardiac muscle is physiologically and morphologically distinct from skeletal and smooth muscle. Instead of using myosin light chain kinase (like smooth muscle), cardiac muscle uses the same sarcomere pattern of skeletal muscle. This explains the presence of striations in both types of tissue.

Cardiac muscle is unique, however, in that it has gap junctions that allow the exchange of ions between individual cells. This allows the myocardium, or muscular portion of heart tissue, to beat in a coordinated fashion, as cells are depolarizing alongside one another. Additionally, intercalated discs are present at the ends of sarcomeres, but are not present in skeletal muscle.

These two characteristics allow us to conclude that muscle cell type 2 is cardiac muscle, and will be found in the myocardium.

Example Question #3 : Help With Cardiac Muscle Physiology

Which of the following cellular structures allows the heart to operate as a functional syncytium?

Possible Answers:

None of these

Sodium-potassium pumps

Gap junctions

Desmosomes

Adherens junctions

Correct answer:

Gap junctions

Explanation:

The presence of gap junctions within the intercalated discs of contractile cardiac myocytes allows for the rapid passage of ions from one cell to another. Once pacemaker cells in the sinoatrial node of the heart spontaneously generate action potentials, this wave of depolarization spreads into neighboring contractile myocytes via gap junctions. These gap junction connections are crucial to the heart operating in a unified and coordinated fashion, and are responsible for the characteristic wavelike contraction of the heart from the apex to the base. 

Example Question #4 : Help With Cardiac Muscle Physiology

What is the pericardial membrane?

Possible Answers:

The tissue that surrounds the thoracic cavity

The tissue that surrounds the blood vessels in the neck

The tissue that surrounds the aorta

The tissue that surrounds the heart

Correct answer:

The tissue that surrounds the heart

Explanation:

The pericardial membrane is the tissue that surrounds the heart. The easiest way to determine the answer in this problem is to understand that "cardial" indicates pertinence heart and that "peri" is a prefix meaning "around."

Example Question #5 : Help With Cardiac Muscle Physiology

What is the correct sequence of the cardiac impulse as it transverses through the heart?

Possible Answers:

Sinoatrial node, atrioventricular node, purkinje fibers, bundle of His, ventricles

Ainoatrial node, atrioventricular node, atria, bundle of His, Purkinje fibers, ventricles

Atrioventricular node, bundle of His, Purkinje fibers, sinoatrial node, ventricles, atria

Sinoatrial node, atria, atrioventricular node, bundle of His, Purkinje fibers, ventricles 

Correct answer:

Sinoatrial node, atria, atrioventricular node, bundle of His, Purkinje fibers, ventricles 

Explanation:

Cardiac contraction begins in the sinoatrial node. The impulse travels through both atria then followed by arriving at the atrioventricular node, which slows the impulse to allow for complete atrial contraction and ventricular filling. Then the impulse travels through the bundle of His, which branches into the right and left bundle branches and through the Purkinje fibers in the walls of both ventricles generating a strong contraction.

Example Question #5 : Help With Cardiac Muscle Physiology

A patient is shown to have a cardiac output of  and a stroke volume of . What is his pulse (in beats per minutes)?

Possible Answers:

 

Correct answer:

Explanation:

Cardiac output (CO) is defined as:

Rearrange to solve for heart rate.

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