Exam 1 Review

Question 1

What are the different types of cardiac cells?

Answer 1

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.

Question 2

Define depolarization.

Answer 2

Movement of (+) charge into cell causing increased (+) charge w/in cell. Wave of depolarization represents flow of electricity detected by electrodes.

Question 3

Define repolarization.

Answer 3

Movement of (+) charge into cell to restore normal resting potential. Also detected by electrodes

Question 4

Define polar + nonpolar.

Answer 4

Polar = molecule in which the bond dipoles present do not cancel each other out

Nonpolar = molecule in which electrons are distributed more symmetrically

Question 5

How do AP work?

Answer 5

AP = cycle of depolarization and non-depolarization caused by movement of current (ions) across the cell membrane.

1. Stimulus causes movement of Na+ into cell through various channels depending on the situation.
2. When internal charge passes threshold (-55mV), voltage-gated Na+ channels (many in cell) open allowing large inflow of Na+ across membrane –> +40mV
3. Depolarization travels down axon, enhanced by myelin
4. Repolarization occurs when voltage-gated K+ channels open, causing outflow of K+ often leading to hyperpolarization

Question 6

What are the different types of AP?

Answer 6

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)

Question 7

What does a cardiac myocyte look like? (Label important information - actin, myosin, relaxed vs. not)

Answer 7

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)

Question 8

Draw a pressure volume loop. (Understand how it works)

Answer 8

(http://tinyurl.com/qgou2cr)

Question 9

Label cardiac cycle / Wigger’s diagram.

Answer 9

(http://tinyurl.com/paeermp)

Question 10

How does the blood flow from IVC to the Aorta? (Draw + include chambers, valves, arteries, veins, direction to/from the lungs)

Answer 10

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)

Question 11

What are the coronary arteries? Draw where are they located.

Answer 11

Right side: R coronary, R marginal, posterior descending

Left side: L coronary, L circumflex, L marginal, anterior descending (http://tinyurl.com/qbbt7un)

Question 12

What is a PFO?

Answer 12

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)

Question 13

What percentage of adults may have PFO?

Answer 13

30%

Can’t tell until in OR and pt gets venous air embolism from too much air in IV…

Question 14

Describe + draw the pathway of electricity through the heart.

Answer 14

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)

Question 15

What are components of a typical EKG wave?

Answer 15

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)

Question 16

What are the units of an EKG graph paper?

Answer 16

Horizontal axis (time):
Sm box = 0.04s
Lg box (5 sm) = 0.2s

Vertical axis (voltage): 
Sm box = 0.1mV
Lg box = 0.5mV

Question 17

What is resting potential?

Answer 17

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.

Question 18

Explain Excitation-contraction Coupling.

Answer 18

1. Depolarization down axon of nerves, which causes Ca++ channels to open in axon terminal
2. Ca++ enters axon terminal, causing synaptic vesicles containing Ach to undergo exocytosis into synaptic cleft
3. Ach binds to acetylcholine receptors along postsynaptic cleft (Ach receptors = ion channels) + allows flow of ions into muscle cell
4. Depolarization occurs across myocyte membrane + down T-tubules, parallel to SR
5. AP stimulates sarcoplasmic reticulum (SR) to release stored Ca++ ions (Ca2+ allows interaction of actin myosin fibers)
6. Contraction

Question 19

List the different segments + intervals common to describe an EKG.

Answer 19

Segment = straight line conn. two waves
Interval = wave(s) + conn. line

PR interval
PR segment
QRS interval
ST segment
QT interval

Question 20

What is the normal ranges of PR interval + what part of the cardiac cycle does it correspond to?

Answer 20

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

Question 21

What part of the cardiac cycle does PR segment correspond to?

Answer 21

End of atrial depol –> start of ventricular depol = delay/pause in conduction at AV node –> allows atria to fully empty before ventricles contract

Question 22

What is the normal ranges of QRS interval + what part of the cardiac cycle does it correspond to?

Answer 22

0.06-0.10s

Ventricular depolarization

Question 23

What is the normal ranges of ST segment + what part of the cardiac cycle does it correspond to?

Answer 23

0.08-.12s
Isoelectric section b/w ventricular depol + repol, elevation/depression highly indicative of myocardial ischaemia or infarction

Question 24

What is the normal ranges of QT interval + what part of the cardiac cycle does it correspond to?

Answer 24

0.2-0.4s depending on HR

Q-Tc (corrected)

Question 25

Describe placement of the 12-lead EKG.

Answer 25

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

Question 26

What are the 12 vectors of a 12-lead EKG?

Answer 26

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

Question 27

Describe the direction of the limb lead vectors.

Answer 27

I - (+) LA (-) RA
II - (+) legs (-) RA
III - (+) legs (-) LA
avL - (+) LA
avR - (+) RA
avF - (+) legs

Question 28

Describe the positioning of the heart within the body cavity.

Answer 28

RV - anterior + medial

LV - posterior + lateral