Cardiac Physiology & Electrocardiography (ECG) (9/8) w/Smith (unfinished) Flashcards
What is electrocardiography (ECG)?
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.
What allows the propagation of cardiac action potentials?
Gap junctions allow cell-to-cell propagation of cardiac action potentials.
ECG is the primary clinical tool for:
- detection and diagnosis of arrhythmieas and myocardial injury
- disturbances in heart rate, rhythm, and wave-front propagation.
What does the mnemonic TPMA stand for?
The path of blood flow though valves in the heart:
TP My Ass
Tricuspid
Pulmonary
Mitral (bicuspid)
Aortic
T/F: Valves are structurally designed to allow flow in only one direction and passively open and close.
True.
Diastole:
is the part of the cardiac cycle when the heart refills with blood following systole, or contraction.
Ventricular filling:
mid-to-late ventricular diastole (includes atrial systole, P-Q interval)
Ventricular systole:
isovolumetric contraction and ejection phase (Q-T interval)
Quiescent phase:
isovolumetric relaxation in early ventricular diastole until atrial contraction (end of T wave to beginning of next P wave)
What do the heart sounds reflect?
The heart sounds reflect the turbulence created when the heart valves snap shut.
“lub-dub”
What is the first heart sound? What produces it?
(S1) “LUB”- is produced by the closure of the atiroventricular valves at the beginning of ventricular contraction, or systole.
What is the second heart sound? What produces it?
(S2) “DUB”- is produced by the closing of the semilunar valves at the end of ventricular systole and the beginning of ventricular diastole.
What are the 2 types of heart cells?
- Specialized (pacemaker) cells
- Working myocardial cells
What do specialized cells do? What parts of the conduction system do they include?
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
T/F: The Specialized (pacemaker) cells insure the heart beat is rhythmic and coordinated.
True.
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.
False. Due to their small size, the specialized cells DO NOT significantly contribute to the strength of contraction.
What is the role of the working myocardial cells?
they are responsible for contraction and relaxation; these make up the majority of the mass of the heart muscle.
What is the sequence of normal activation of the electrical conduction system of the heart?
SA node Atria AV node His bundle Bundle branches Purkinje Fibers Ventricles
What is the function of the SA node?
pacemaker and initiation of action potential
What is the function of the AV node?
contains slowly conducting cells that normally function to create a slight delay between atrial and ventricular contraction.
What is the function of the Purkinje fibers?
specialized for rapid conduction and ensure that all ventricular cells contract at nearly the same instant.
T/F: heart rate is normally controlled by the electrical activity of the AV node,
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.
Fast-response action potentials involve which cells?
Most cardiac cells.
Slow-response action potentials involves what structures?
SA node
AV node
Bundle branches
Purkinje fibers
