Cardiac Electrophysiology Muscle Structure/Function

The conduction block phenomenon characterized by slow conduction and unidirectional block is known as:

A re-entry block.

Which of the following statements is false regarding preload?

An overstretched sarcomere will result in excessive force.

One of the consequences of ischemic myocardium is coronary artery disease (CAD). This can lead to dysrhythmia because it:

Depolarizes myocardium.

Which of the following events occurs first during mechanical contraction of the myocardium?

NOT - Myosin crossbridges attach to actin, possibly CA entry into sarcoplasm?

Which of the following is a unique feature of action potentials in atria?

The plateau phase is not as prominent as fast response cells.

Contraction of cardiac cells occurs as a consequence of filament sliding and binding. Which of the filaments is anchored onto Z bands of the sarcomere?

Actin

The force that the myocardium must develop for the cells of the ventricle to shorten is called:

Afterload.

Which ion is not generally regarded to be a factor in fast response action potentials?

Cl-

Cardiac contraction occurs when calcium channels open and calcium influx occurs. What is the stimulus that opens calcium channels?

Depolarization from Na+ influx

The primary difference between fast response and slow response cardiac action potentials is that:

Fast response potentials are approximately 300 msec in duration.

The term "inward rectifier" is another name for:

K+ channels open at rest.

Parasympathetic stimulation of rate-setting tissue results in:

K+ channels opening.

Rate-setting slow response cardiac tissue will depolarize independent of autonomic influence. However, in the presence of sympathetic stimulation, what is the physiologic process that increases heart rate?

Lower depolarization threshold

After an electrical stimulus is generated by the atrioventricular (AV) node, which ion channels open to affect the depolarization stage 0?

Na+

Open ___ channels are responsible for maintaining voltage in resting state.

Potassium (K+)

Among the variety of tissue types found in cardiac muscle, which type has the greatest ability to beat autonomously?

Sinoatrial (SA) node tissue

According to the Frank-Starling Performance Curve, all of the following are indices of cardiac performance except:

Sympathetic nervous system.

The specialized rapid conduction tissue that is important to ventricular muscle contraction is known as:

The His-Purkinje System.

In contractile cells, what is happening to Na+ channels in phase 3?

h gates recover.