Cardiac Physiology & Electrocardiography (ECG) (9/8) w/Smith (unfinished)

Question 1

What is electrocardiography (ECG)?

Answer 1

provides a record of the net cardiac electrical activity measure between two points on the body surface as it changes with time during the cardiac cycle.

*Records the net voltage difference between two points on the body surface, which is the product of the summation of many weak APs in the individual cardiac cells of the heart.

Question 2

What allows the propagation of cardiac action potentials?

Answer 2

Gap junctions allow cell-to-cell propagation of cardiac action potentials.

Question 3

ECG is the primary clinical tool for:

Answer 3

• detection and diagnosis of arrhythmieas and myocardial injury
• disturbances in heart rate, rhythm, and wave-front propagation.

Question 4

What does the mnemonic TPMA stand for?

Answer 4

The path of blood flow though valves in the heart:
TP My Ass

Tricuspid
Pulmonary
Mitral (bicuspid)
Aortic

Question 5

T/F: Valves are structurally designed to allow flow in only one direction and passively open and close.

Answer 5

True.

Question 6

Diastole:

Answer 6

is the part of the cardiac cycle when the heart refills with blood following systole, or contraction.

Question 7

Ventricular filling:

Answer 7

mid-to-late ventricular diastole (includes atrial systole, P-Q interval)

Question 8

Ventricular systole:

Answer 8

isovolumetric contraction and ejection phase (Q-T interval)

Question 9

Quiescent phase:

Answer 9

isovolumetric relaxation in early ventricular diastole until atrial contraction (end of T wave to beginning of next P wave)

Question 10

What do the heart sounds reflect?

Answer 10

The heart sounds reflect the turbulence created when the heart valves snap shut.

“lub-dub”

Question 11

What is the first heart sound? What produces it?

Answer 11

(S1) “LUB”- is produced by the closure of the atiroventricular valves at the beginning of ventricular contraction, or systole.

Question 12

What is the second heart sound? What produces it?

Answer 12

(S2) “DUB”- is produced by the closing of the semilunar valves at the end of ventricular systole and the beginning of ventricular diastole.

Question 13

What are the 2 types of heart cells?

Answer 13

• Specialized (pacemaker) cells

- Working myocardial cells

Question 14

What do specialized cells do? What parts of the conduction system do they include?

Answer 14

responsible for the initiation and conduction of electrical signals (APs) through the heart.

Includes:
SA node
AV node
His bundle (common bundle)
Purkinje fiber network

Question 15

T/F: The Specialized (pacemaker) cells insure the heart beat is rhythmic and coordinated.

Answer 15

True.

Question 16

T/F: Due to their small size relative to the working myocardium, the specialized cells contribute significantly to the strength of contraction of the whole heart.

Answer 16

False. Due to their small size, the specialized cells DO NOT significantly contribute to the strength of contraction.

Question 17

What is the role of the working myocardial cells?

Answer 17

they are responsible for contraction and relaxation; these make up the majority of the mass of the heart muscle.

Question 18

What is the sequence of normal activation of the electrical conduction system of the heart?

Answer 18

SA node
Atria
AV node
His bundle
Bundle branches
Purkinje Fibers
Ventricles

Question 19

What is the function of the SA node?

Answer 19

pacemaker and initiation of action potential

Question 20

What is the function of the AV node?

Answer 20

contains slowly conducting cells that normally function to create a slight delay between atrial and ventricular contraction.

Question 21

What is the function of the Purkinje fibers?

Answer 21

specialized for rapid conduction and ensure that all ventricular cells contract at nearly the same instant.

Question 22

T/F: heart rate is normally controlled by the electrical activity of the AV node,

Answer 22

FALSE. Heart rate is controlled by the SA node.

The rest of the conduction system provides backup in case the SA node fails or is injured.

Question 23

Fast-response action potentials involve which cells?

Answer 23

Most cardiac cells.

Question 24

Slow-response action potentials involves what structures?

Answer 24

SA node
AV node
Bundle branches
Purkinje fibers

Question 25

Name the 5 phases of cardiac action potential and what occurs:

Answer 25

Phase:
0- upstroke, rapid depolarization
1- rapid repolarization following the peak
2- depolarized plateau
3- rapid repolarization following the plateau
4- period between max negativity (aka resting potential)

Question 26

T/F: Specialized cells slowly depolarize throughout phase 4, whereas working myocardium do not depolarize in phase 4.

Answer 26

True. Working myocardium (fast-response) do not depolarize in phase 4, but rely on pacemaker stimulus instead.

Question 27

What is automaticity?

Answer 27

a property of the specialized cardiac cells to spontaneously fire APs.

Question 28

T/F: The SA node has the fastest fate and is therefore the latent pacemaker.

Answer 28

False. The SA node is the dominant pacemaker.

Question 29

T/F: The specialized cells are latent pacemakers.

Answer 29

True.

Question 30

What happens if the SA node fails?

Answer 30

The next fastest latent pacemaker (AV node) becomes the dominant and the heart continues to beat.

Question 31

What happens if the slower pacemakers cannot maintain normal cardiac output and blood pressure?

Answer 31

An artificial pacemaker must be implanted.

Question 32

T/F: Cardiac APs are the result of transient changes in the ionic permeability of the cell membrane which are triggered by an initial depolarization in the pacemaker (SA node).

Answer 32

True. APs are a result in the change of permeability of the cell membrane.

Question 33

What is the absolute refractory period?

Answer 33

time frame when the working myocardial cells cannot be stimulated to fire another AP.

Question 34

What is the relative refractory period?

Answer 34

during this period, the myocardial cell can fire an AP, but it requires a greater than normal stimulus.