Chapter 20 Flashcards: Heart Anatomy and Cardiac Muscle

Flashcards covering internal anatomy of the heart and cardiac muscle tissue.

Pectinate Muscles

Located predominantly in the right atrium and may increase force of contraction without increasing size and thickness.

Trabeculae carneae

Found in both ventricles in a weaving-like pattern; help the papillary muscles with valve stability.

What is the Fossa Ovalis?

Scar from the closing of the Foramen Ovale in the interatrial septum during fetal development

Why is the right ventricular wall thinner than the left?

The right side pumps to the pulmonary circuit (lungs) which are right next to the heart, requiring less force.

Why does the left ventricle need to be thicker than the right ventricle?

The left side pumps to the systemic circuit (the entire body) and needs more force.

What are the three layers of the heart wall?

Epicardium, Myocardium, Endocardium

Epicardium

Outer surface layer covering the heart

Is the epicardium the same as the visceral pericardium?

Yes, the epicardium is also called the visceral pericardium.

What is the mesothelium?

Single layer simple squamous epithelium that makes up the epicardium

Endocardium

The innermost layer lining the heart chambers.

What is the function of the endothelium produced by the endocardium?

Reduces friction between blood cells and chamber wall and prevents clotting of cells inside the ventricles

Myocardium

Middle, muscular layer forming atria and ventricles

What tissues are found in the myocardium?

Cardiac muscle tissue, blood vessels, and nerves

How do the muscle contractions of the myocardium eject blood?

The muscle contractions squeeze the heart like twisting a wash rag to get out the water.

Where is Cardiac Muscle Tissue found?

Only in the heart

What are Intercalated Discs?

Specialized intercellular connections that stabilize relative positions of adjacent cells

What are the components of Intercalated Discs?

Desmosomes and Gap junctions

What is the function of gap junctions in cardiac muscle?

Allow ions and molecules to move directly between cells creating a direct electrical connection, allowing an action potential to pass directly between cells

How do cardiac muscle cells function?

All cells function as one (functional syncytium)

What are some structural or functional differences between cardiac muscle cells and skeletal muscle fibers?

Cardiac muscle cells are smaller, have typically one nucleus, have short T tubules and abundant mitochondria, and rely on aerobic metabolism. Skeletal muscle fibers are larger, have multiple nuclei, long T tubules, less abundant mitochondria, and can function anaerobically.

What is the stimulus for contraction in cardiac muscle cells?

Autorhythmicity of pacemaker cells generates action potentials

What is the stimulus for contraction in skeletal muscle fibers?

Activity of somatic motor neuron generates action potentials in sarcolemma

What is the trigger for contraction in cardiac muscle cells?

Calcium entry from the ECF and calcium release from the sarcoplasmic reticulum

What is the trigger for contraction in skeletal muscle fibers?

Calcium release from the sarcoplasmic reticulum

What is a key difference between the action potential in skeletal and cardiac muscle?

Cardiac muscle shows a plateau phase due to the opening of voltage-gated Ca2+ channels, which slows repolarization.

How does the refractory period affect tension in cardiac muscle?

Cardiac muscle contracts and relaxes almost completely during the refractory period.

What changes in ion permeability occur during the pacemaker potential?

A small number of Na+ channels are open, voltage-gated K+ channels are closing, and voltage-gated Ca2+ channels begin to open.

From superficial to deep, name the layers of the heart wall.

Epicardium, Myocardium, Endocardium

What is a function of the epicardium?

The epicardium's primary function is to protect the inner heart layers and assist in the production of pericardial fluid, which lubricates the heart.

Why is it important that cardiac tissue be richly supplied with mitochondria and capillaries?

Mitochondria produce the energy for contractions, and capillaries supply oxygen; cardiac tissue needs a lot of both.

List five differences between cardiac and skeletal muscle

1. cardiac muscle cells are smaller, 2. typically have one nucleus, 3. have short T tubules and abundant mitochondria, 4. rely on aerobic metabolism, 5. have intercalated discs.

What is the function of the intercalated discs?

Intercalated discs help anchor cells together and allow free passage of ions.

Do you have a foramen ovale in your right atrium? Why or why not.

Hopefully not; the foramen ovale closes after birth. The depression that remains is called the fossa ovalis.

What is a functional syncytium?

A functional syncytium is when many cells function as one large cell.