cardiac physiology

Question 1

resting poteintial of potassium calcium and sodium concentraitons

Answer 1

potassium high in the cell, calcium and sodium high outside the cell

Question 2

resting membrane potential

Answer 2

-60–80

Question 3

frquency of the SA, AV, and purkinje

Answer 3

SA: 60 b/min AV: 40 b/min purkinje: 20 b/min since SA is highest frequency, it sets the heart rate

Question 4

innervation of SA node

Answer 4

sympathetic: vagus nerve parasympathetic: T1-T4

Question 5

phases of SA node action potentials

Answer 5

phase 4: spontaneous depolarization (K+ out, Na+ in) phase 0: rapid depolarization (Ca+ in) phase 3: repolarization (K+ in)

Question 6

phases of ventricular action potentials

Answer 6

phase 4: resting phase 0: upstroke of AP rapid depolarization (Na+ in) 1: rapid repolarization (K+ out) 2: plateau phase (K+ out, Ca+ in) 3: repolarization (K+ out)

Question 7

how does acetylcholine affect heart rate

Answer 7

acetylcholine is released by parasympathetic nervous system through the vagal nerve decreases the rate of depolarization by decreasing funny current decreases maximum diastolic potential (start from more negative) by increasing K1 activity increase threshold potential by decreasing Ca activity

Question 8

class I antiarrythmic drugs

Answer 8

sodium channel blockers reduce phase 0 peak and slope of depolarization

Question 9

class III antiarrythmic drugs

Answer 9

potassium channel blockers increase action potential duration and effective refractory period, delay repolarization

Question 10

class IV antiarrythmic drugs

Answer 10

calcium channel blockers L-type Ca, slows rate in SA and AV node

Question 11

class V antiarrythmic drugs

Answer 11

Miscellaneous, various effects ex. funny channel blockers HCN selective blocker

Question 12

class II antiarrythmic drugs

Answer 12

beta blockade block sympathetic activity, reduce rate of of conduction

Question 13

What two mechanisms must antiarrythmic drugs meet in order to have desired effect

Answer 13

supress ectopic/abnormal pacemakers more than the SA node increase the ratio of the ERP/APD (effective refractory period/action potential duration)

Question 14

time per small box in EKG

Answer 14

.2 seconds

Question 15

mV per small box in EKG

Answer 15

.5 mV

Question 16

norm value for PR interval

Answer 16

.12-.2

Question 17

QRS duration norm

Answer 17

.08-.1

Question 18

QT interval norm

Answer 18

.4-.43

Question 19

RR interval norm

Answer 19

.6-1

Question 20

angle of lead AVF

Answer 20

90 degrees (straight up is negative and straight down is positive)

Question 21

angle of lead I

Answer 21

0 degrees (horizontal axis, to the left of the patient’s heart is towards 0 and to the rigth of the patients heart is towards 180)

Question 22

finding heart rate on EKG strip

Answer 22

find an R wave that falls on or nearly on a heavy line and count number of square until next R wave, determine bPM by 300/# large squares between R waves

Question 23

what will leads I and AVF look like in normal, left axis deviation, right axis deviation, and extreme right axis deviation

Answer 23

normal: I: + AVF : + left axis deviation: I: +, AVF: - right axis deviation: I: -, AVF: + extreme right deviation: I: -, AVF: -

Question 24

sinus origin arrhythmias

Answer 24

originated either too slow or too fast

Question 25

ectopic origin arrhythmias

Answer 25

AP originates from site other than SA node

Question 26

electrical looping

Answer 26

reentrant, anatomical boundaries keep current bouncing back and forth rather than progressing to next phase

Question 27

conduction block

Answer 27

sinus AP is originated normally but stops unexpectedly

Question 28

electrical shortcuts

Answer 28

electrical conduction follws an accessory pathway which bypass normal ones, “preexcitation syndromes”