The EKG is nothing more than a recording of the heart’s electrical activity, and it is through (a)   in the normal electrical patterns that we are able to diagnose many different cardiac disorders.

The electrical activity of the heart is governed by?

(a)  

Sinoatrial (SA) node, a microscopic structure located in the ______ ______.

(a)  

The electrical activity of the heart is governed by the sinoatrial (SA) node, a microscopic structure located in the right atrium, at the junction between the?

(a)  

SA node is made of what cells?

(a)  

SA node is made of pacemaker cells, which are intrinsically capable of generating rhythmic electrical impulses at rates that normally range from __ to ___ beats per minute (bpm).

(a)  

The electrical current that originates here is propagated to the?

(a)  

Internodal tracts:

Which includes a branch for the left atrium.

(a)  

Internodal tracts:

Other name of Middle Internodal Tract?

(a)  

Internodal tracts:

Other name of posterior internodal tract?

(a)  

From the atria, the depolarization wave spreads to the (a)   the second fundamental station in the heart’s electrical conduction system.

AV node is located in the ______________ _________ of the interatrial septum near the opening of the coronary sinus and represents the only normal connection between the atria and the ventricles. It is therefore the obligatory point of passage for impulses travelling to the ventricles.

(a)  

Propagation of the electrical impulses from the (a)   themselves occurs through a specialized conduction system.

The proximal portion, which is known as the (a)   , begins at the AV node and then divides within the ventricular septum to form the right and left bundle branches.

The two bundle branches continue to divide, forming a densely ramified subendocardial system known as the (a)   , which propagates the depolarization current throughout the ventricular myocardium.

In their resting state, are electrically polarized, that is, their insides are negatively charged with respect to their outsides.

(a)  

This electrical polarity is maintained by ___________ ________ that ensure the appropriate distribution of ions necessary to keep the insides of these cells relatively electronegative.

(a)  

IONS:

(a)  

Cardiac cells can lose their internal negativity in a process called? Is the fundamental electrical event of the heart.

(a)  

Depolarization is propagated from ____ to ____, producing a wave of depolarization that can be transmitted across the entire heart. This wave of depolarization represents aflow of electricity , an electrical current, that can be detected by electrodes placed on the surface o f the body .

(a)  

After depolarization is complete, the cardiac cells are able to restore their resting polarity through a process called? This, too, can be sensed by recording electrodes.

(a)  

All of the different waves that we see on an EKG are manifestations of these two processes:

(a)  

The normal electrical power source of the heart is the?

(a)  

Pacemaker cells are small cells approximately how long?

(a)  

TRUE OR FALSE:

Pacemaker cells are able to depolarize spontaneously over and over again, at a particular rate.

(a)  

The dominant pacemaker cells in the heart are located high up in the?

(a)  

This group of pacemaker cells is called the sinoatrial (SA) node, or _____ _____ for short.

(a)  

The hard wiring of the heart; are long, thin cells. Like the wires of an electrical circuit, these cells carry current rapidly and efficiently to distant regions of the heart.

(a)  

The electrical conducting cells o f the ventricles join to form?

(a)  

The conducting pathways in the atria have more anatomic variability; prominent among these are fibers at the top o f the intra-atrial septum in a region called _________ _______ which allow for rapid activation of the left atrium from the right.

(a)  

The contractile machinery o f the heart. by far the major part of the heart tissue. They are responsible for the heavy labor of repeatedly contracting and relaxing, thereby delivering blood to the rest of the body.

(a)  

Myocardial cells are about __ to ___ μm in length

(a)  

Myocardial cells are about 50 to 100 μm in length and contain an abundance of the contractile proteins?

(a)  

When a wave of depolarization reaches a myocardial cell, calcium is released within the cell, causing the cell to contract. This process, in which calcium plays the key intermediary role, is called?

(a)  

The SA node has an intrinsic discharge rate (normal range: __ to ___ bpm) that is higher than those of other parts of the myocardium.

(a)  

The AV node, which is the most important subsidiary station in the conduction system, emits impulses at a

slightly lower rate (__ to __ bpm).

(a)  

Under normal and pathological conditions, other portions of the conduction system or even the ordinary working myocardium are capable of firing at rates ranging from __ to __ bpm.

(a)  

The electrical and contractile activities of the heart are mediated by the constant flow of ions (mainly sodium, calcium, and potassium) through lipoprotein structures in the cardiomyocyte cell membrane known as?

(a)  

The potential reflects the existence of ion concentration gradients across the membrane characterized by high levels of ________ outside the cell and high _______ levels in the intracellular compartment.

(a)  

The resting action potential of the cell membrane is modified by a rapid influx of sodium ions from the extracellular compartment, an event referred to as?

(a)  

The electrical phenomena that occur when the cell is activated in this manner are referred to collectively as the?, and they can be recorded.

(a)  

Characterized by a rapid phase-0-upstroke and is typical of the cells in the His-Purkinje system and those of the atrial and ventricular myocardium.

(a)  

Is typical of the cells of the SA and AV nodes and of ischemic myocardial cells.

(a)  

The rapid inward current of sodium ions.

(a)  

The influx of Sodium ions slows, the transmembrane action potential is about 0 millivolts (mV), and there is a transient outflow of potassium.

(a)  

A slow inward-directed flow of calcium ions that triggers the release of intracellular stores of calcium, which bind to the contractile proteins of the cardiomyocytes.

(a)  

Which marks the beginning of repolarization, is produced by a biphasic (initially rapid, then slow) outflow of potassium ions, which continues until the resting electrical potential of the membrane has been restored.

(a)  

During which the resting negative polarity is maintained by an outward flow of sodium ions and an inward flow of potassium ions.

(a)  

(1856–1922), a British physiologist, used a crude mercury capillary electrometer to record the first human electrocardiogram in 1887 (1,2). He initially labeled the waves V1 and V2 because he knew they were ventricular events. As new waves were discovered with the use of improved mercury capillary electrometers, he switched to the letters ABCD.

(a)  

(1860–1927), a Dutch physician–scientist, improved the galvanometer and made many contributions to the field of electrocardiography. He invented the bipolar extremity leads and created Einthoven’s law. He named the waves in the electrocardiogram PQRST.

(a)  

(1881–1945), a British physician-scientist, studied the use of the electrocardiogram in deciphering arrhythmias and was one of the first electrophysiologists.

(a)  

(1890–1952), an American, studied with Lewis. He later worked at the University of Michigan, in Ann Arbor, and became the foremost electrocardiographerin the world. He contributed to the mathematical understanding of the electrocardiogram and invented the unipolar.

(a)  

(1915–1966; see Fig. 2-1E), working at Emory University in Atlanta, Georgia, developed and taught the use of vector concepts in the interpretation of every electrocardiogram.

(a)  

The electrode is placed in the fourth intercostal space, on the right sternal border.

(a)  

Electrode in the fourth intercostal space, on the left sternal border.

(a)  

Electrode placed midway between V2 and V4.

(a)  

Electrode placed in the fifth intercostal space, on the anterior midclavicular line.

(a)  

Electrode is horizontally aligned with V4, on the anterior axillary line.

(a)  

Electrode placed on the midaxillary line and aligned horizontally with V4.

(a)  

Is a galvanometer calibrated to produce a deflection with an amplitude of 1 cm for every millivolt (mV) of voltage.

(a)  

The electrocardiogram (ECG) is recorded on graph paper divided into small?

(a)  

At the standard paper speed of (a)   , each small square corresponds to 40 ms.

Is the graphic representation of atrial electrical activation. It normally has a duration of 50–120 msand a maximum amplitude of 2.5 millimeters (generally recorded in lead II).

(a)  

Atrial depolarization normally proceeds downward from the SA node and from right to left. The mean electrical axis in the frontal plane thus ranges from?

(a)  

The P wave is (a)   in the inferior leads.

The P wave is (a)   in lead aVR

The P wave is positive in all the precordial leads except V1, where it is?

(a)  

Deviations from these norms are suggestive of an?

(a)  

Represents the time needed for atrioventricular conduction.

(a)  

PR interval is measured from the beginning of atrial activation to the beginning of ventricular activation, and its normal duration is from

(a)  

Ventricular myocardial depolarization—and, hence, ventricular contraction—is marked by a new deflection on the EKG called the?

(a)  

TRUE OR FALSE:

The amplitude o f the QRS complex is much greater than that of the atrial P wave because the ventricles have so much more muscle mass than the atria.

(a)  

Ventricular repolarization inscribes a third wave on the EKG, the?

(a)  

If the first deflection is downward, it is called a?

(a)  

The first upward deflection is called an?

(a)  

If there is a second upward deflection, it is called?

(a)  

The first downward deflection following an upward deflection is called an?

(a)  

TRUE OR FALSE:

Therefore, if the first wave o f the complex is an R wave, the ensuing downward deflection is called an S wave, not a Q wave. A downward deflection can only be called a Q wave if it is the first wave o f the complex . Any other downward deflection is called an S wave.

(a)  

If the entire configuration consists solely of one downward deflection, the wave is called a?

(a)  

includes the P wave and the straight line connecting it to the QRS complex . It therefore measures the time from the start of atrial depolarization to the start of ventricular depolarization.

(a)  

Is the straight line running from the end of the P wave to the start of the QRS complex . It therefore measures the time from the end of atrial depolarization to the start of ventricular depolarization.

(a)  

The straight line connecting the end o f the QRS complex with the beginning of the T wave. It measures the time from the end of ventricular depolarization to the start of ventricular repolarization.

(a)  

Includes the QRS complex , the ST segment, and the T wave. It therefore measures the time from the beginning o f ventricular depolarization to the end of ventricular repolarization.

(a)  

Is used to describe the duration of the complex alone without any connecting segments. Obviously , it measures the duration of ventricular depolarization.

(a)