FMIS 105 Course: Weeks 3-4 Study Materials on 12 Lead ECG and Cardiac Physiology

Myocardial (M) cells are

working cells or mechanical cells that are Responsible for contraction

Pacemaker (P) Cells are Specialized:

conducting cells or automatic cells, responsible for generating (forming) spontaneous electrical impulses and can alter the speed of electrical conduction

Automaticity in cardiac cells is:

The ability of pacemaker cells to initiate an electrical impulse without being stimulated by another source

The Ability of a Cardiac cell to Receive an electrical stimulus and conduct that impulse to an adjacent cell is known as?

Conductivity

Contractibility is?

Ability of cardiac Cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus

SA Node is considered as?

Primary pacemaker of the heart- A normal SA node beats 60-100 beats/min

(T/F) The AV node helps prevent the Atria and Ventricles form contracting at the same time

TRUE--The conduction delay by the AV node allows both atrial chambers to contract and empty blood into the ventricles before the next ventricular contraction begins

When is a Cardiac Cell said to be Polarized?

When a Cardiac cell is at rest, the cell membrane's inner surface is covered by negatively charged ions while positively charged ions envelop the external surface.

What is Depolarization?

is the movement of ions across a cell membrane, causing the inside of the cell to become more positive. It propagates in a wave-like form

What is Repolarization?

the cell returns to its polarized (i.e., resting) state, contractile proteins in the working myocardial cells separate (i.e., relax)

What is the 1st wave seen in an EKG strip?

The P Wave

What does the P-Wave Represent?

atrial depolarization (contraction)

What is the 2nd Wave or complex seen in an EKG strip?

The QRS Complex

What does the QRS complex represent?

ventricular depolarization (contraction)

What wave represents Ventricular Repolarization?

The T Wave

(T/F) The cardiac cell's Action potential reflects the Voltage changes that occur across the cell Membrane during the electrical cardiac cycle

TRUE-

The period of Recovery that cells need after being discharged before they are able to respond to a stimulus is known as:

Refractoriness

In Action potential, Phase 0 is Rapid _____________, Phase 1 is initial _____________ and Phase 2 is the _____________ phase

Depolarization, Repolarization, Plateau

What is ERP?

The effective refractory period (ERP)- The interval from the beginning of the Action potential until the myocardial fiber is able to conduct another action potential

(True-False) A Cardiac Cell can contract /respond to further stimulation during ERP

FALSE- The cardiac cell may during RRP only.

What is RRP?

The relative refractory period. It begins at the end of ERP and can be stimulated to depolarize to a stronger than normal stimulus.

The Fast Response action potential occurs in?

-Atrial and Ventricular working myocardian cells

-His-Purkinje Fibers

What are the Standard Limb leads

I, II, and III they are Bipolar

(T/F) The Left leg electrode is always Negative?

False- IT IS ALWAYS POSITIVE

(T/F) Right arm electrode can be Positive or Negative?

False- The RT. arm electrode is always negative. Only the LEFT ARM electrode can be + or -

What are Bipolar Leads

Leads that consists of a positive and negative electrode

(T/F) All ECG leads are technically bipolar leads

TRUE-

(T/F) Leads I,II and III use 2 distinct electrodes

TRUE

This Lead views the Lateral wall of the Left Ventricle

Lead I- It records difference in electrical potential between LT arm (+) and RT arm (-).

aVR, aVL, and aVF are known as the:

augmented leads or unipolar leads

What are the chest leads?

V1, V2, V3, V4, V5, V6 Chest leads are denoted by the letter V in-front.

(T/F) The QRS Complex's Amplitude is equal among different leads in the EKG?

False- It is different between leads I, II or II

The ability of Cardiac cells to respond to an outside stimulus is know as?

Excitability or Irritability

What is the 6 second method when determining Ventricular or HR (Rule of 10)?

count the number of complete QRS complexes within 6 seconds, and multiply that number by 10 to find the number of complexes in 1 minute. Quick way to determine HR

A straight line on an EKG reading is recorded when NO electrical activity is detected is know as:

Baseline

(T/F) EKG paper normally records at 50mm/sec

FALSE- it normally records at 25mm/sec

(T/F) On an EKG paper there are smallest boxes are approximately 5mm^2

FALSE- The smallest boxes are 1mm^2

What is the TP segment of an EKG?

The portion of the EKG when a cardiac cycle ends (last wave) and a new one begins (1st wave). End of T wave to beginning of P wave

What is the ST Segment?

The portion of the ECG tracing between the QRS complex and the T wave

(T/F) The heart has multiple secondary pacemaker sites:

TRUE- Areas of the heart other than the SA node can initiate beats and assume pacemaker responsibility under special circumstances