Exam 1 Review Flashcards
What are the different types of cardiac cells?
Pacemakers - set the pace of the heart thru repeated, spontaneous depolarization influenced by ANS (sympathetic/epi + vagal stimulation) + CO. Major pacemaker cell = sinus node (60-100bpm, 5-10mcm)
Conduction cells - helps conduct current through heart. Major conduction pathway = Purkinje fibers. Bachmann’s bundle helps R–>L conduction across atria
Cardiac myocytes - (50-100mcm) majority of heart, resp. for major work of contracting/relaxing heart, contains many actin/myocin fibers + slow conduction of depolarization.
Define depolarization.
Movement of (+) charge into cell causing increased (+) charge w/in cell. Wave of depolarization represents flow of electricity detected by electrodes.
Define repolarization.
Movement of (+) charge into cell to restore normal resting potential. Also detected by electrodes
Define polar + nonpolar.
Polar = molecule in which the bond dipoles present do not cancel each other out
Nonpolar = molecule in which electrons are distributed more symmetrically
How do AP work?
AP = cycle of depolarization and non-depolarization caused by movement of current (ions) across the cell membrane.
- Stimulus causes movement of Na+ into cell through various channels depending on the situation.
- When internal charge passes threshold (-55mV), voltage-gated Na+ channels (many in cell) open allowing large inflow of Na+ across membrane –> +40mV
- Depolarization travels down axon, enhanced by myelin
- Repolarization occurs when voltage-gated K+ channels open, causing outflow of K+ often leading to hyperpolarization
What are the different types of AP?
Typical AP: (http://tinyurl.com/pnupdrq)
Pacemaker AP: leaky Na+ (and K+) channels that allow Na+ to drift in –> gradual increase in membrane potential towards threshold. Doesn’t require stimulus + occurs at regular pace. (http://tinyurl.com/qhxw4tt)
What does a cardiac myocyte look like? (Label important information - actin, myosin, relaxed vs. not)
Cardiac myocytes have many actin + myosin filaments as well as mitochondria to provide energy for contraction. They are also connected by gap junctions + intercalated discs. (http://tinyurl.com/qxpnjcx, http://tinyurl.com/9lg5f6)
Draw a pressure volume loop. (Understand how it works)
(http://tinyurl.com/qgou2cr)
Label cardiac cycle / Wigger’s diagram.
(http://tinyurl.com/paeermp)
How does the blood flow from IVC to the Aorta? (Draw + include chambers, valves, arteries, veins, direction to/from the lungs)
SVC/IVC –> RA –> tricupsid valve –> RV –> pulmonary valve –> pulmonary artery –> pulmonary circuit –> pulmonary vein –> LA –> bicuspid/mitral valve –> LV –> aortic valve –> aorta –> systemic circulation (http://tinyurl.com/pps824d)
What are the coronary arteries? Draw where are they located.
Right side: R coronary, R marginal, posterior descending
Left side: L coronary, L circumflex, L marginal, anterior descending (http://tinyurl.com/qbbt7un)
What is a PFO?
Patent foramen ovale = hole in the septum between R + L atria present in children, which usually closes with first breath after birth.
Don’t want bubbles in IV, esp for child –> venous air embolism (at least 30-40cc for adult but as little as a few cc’s for pedi)
What percentage of adults may have PFO?
30%
Can’t tell until in OR and pt gets venous air embolism from too much air in IV…
Describe + draw the pathway of electricity through the heart.
SA –> (R–>L atrium via Bachmann’s bundle; RA starts + fin. before LA) anterior/middle/posterior internodal tract –> (atrial deploy is pre. from comm. w ventricles by fibrous heart valves) forced conduction along inter ventricular septum thru AV node –> Bundle of His –> L + R bundle branches (L bundle branch has divides into septal, anterior + posterior fascicles) –> Purkinje fibers –> myocardium (http://tinyurl.com/qbkoxox)
What are components of a typical EKG wave?
P wave = atrial depolarization (0.08-0.10s). First half of wave reps RA depol, second half reps. LA depol.
QRS complex = ventricular depol (0.06-0.10s).
Q wave = septal depol, ↓ deflection, has to be first
R wave = first ↑ deflection following negative deflection
R’ (R-prime) = second ↑ deflection
S wave = first ↓ deflection following ↑ deflection
T wave = ventricular repol (atrial repeal hidden by QRS complex)
What are the units of an EKG graph paper?
Horizontal axis (time): Sm box = 0.04s Lg box (5 sm) = 0.2s
Vertical axis (voltage): Sm box = 0.1mV Lg box = 0.5mV
What is resting potential?
Resting state of cell (-70mV) maintained by Na-K pumps along cell membrane, which pumps 2K+ in and 3Na+ out of cell –> negatively charged inside relative to outside. At resting state, all ion channels are closed.
Explain Excitation-contraction Coupling.
- Depolarization down axon of nerves, which causes Ca++ channels to open in axon terminal
- Ca++ enters axon terminal, causing synaptic vesicles containing Ach to undergo exocytosis into synaptic cleft
- Ach binds to acetylcholine receptors along postsynaptic cleft (Ach receptors = ion channels) + allows flow of ions into muscle cell
- Depolarization occurs across myocyte membrane + down T-tubules, parallel to SR
- AP stimulates sarcoplasmic reticulum (SR) to release stored Ca++ ions (Ca2+ allows interaction of actin myosin fibers)
- Contraction
List the different segments + intervals common to describe an EKG.
Segment = straight line conn. two waves Interval = wave(s) + conn. line
PR interval PR segment QRS interval ST segment QT interval
What is the normal ranges of PR interval + what part of the cardiac cycle does it correspond to?
0.12-0.2s
Start of atrial depol –> start of ventricular depol (incl. delay in conduction at AV node) = time taken for electrical activity to move from atria to ventricles
What part of the cardiac cycle does PR segment correspond to?
End of atrial depol –> start of ventricular depol = delay/pause in conduction at AV node –> allows atria to fully empty before ventricles contract
What is the normal ranges of QRS interval + what part of the cardiac cycle does it correspond to?
0.06-0.10s
Ventricular depolarization
What is the normal ranges of ST segment + what part of the cardiac cycle does it correspond to?
0.08-.12s
Isoelectric section b/w ventricular depol + repol, elevation/depression highly indicative of myocardial ischaemia or infarction
What is the normal ranges of QT interval + what part of the cardiac cycle does it correspond to?
0.2-0.4s depending on HR
Q-Tc (corrected)
Describe placement of the 12-lead EKG.
Limb leads:
2 electrodes on arms
2 electrode on legs
Precordial leads:
V1 - 4th intercostal space, R of sternum
V2 - 4th intercostal space, L of sternum
V3 - b/w V2 + V4
V4 - 5th intercostal space, midclavicular line
V5 - b/w V4 + V6
V6 - 5th intercostal space, midclavicular line
What are the 12 vectors of a 12-lead EKG?
Limb leads (frontal):
Standard: I (0), II (60), III (120)
Augmented: avL (-30), avR (-150), avF (90)
Precordial leads (horizontal): V1, V2, V3, V4, V5, V6
Describe the direction of the limb lead vectors.
I - (+) LA (-) RA II - (+) legs (-) RA III - (+) legs (-) LA avL - (+) LA avR - (+) RA avF - (+) legs
Describe the positioning of the heart within the body cavity.
RV - anterior + medial
LV - posterior + lateral
