Electrical Potentials + ECG

Question 1

SAN/AVN AP goes from?

Answer 1

-65 mV to +10 mV

Question 2

Phase 4 of AVN/SAN?

Answer 2

Decreased K efflux
Na influx via HCN channel
Ca influx

Question 3

Phase 0 of AVN/SAN?

Answer 3

Ca influx

Question 4

Phase 3 of AVN/SAN?

Answer 4

K efflux

Question 5

What 2 things are HCN channels activated by?

Answer 5

Hyperpolarisation and cAMP

Question 6

Contractile myocyte AP goes from?

Answer 6

-90 mV to +20 mV

Question 7

Phase 4 of myocyte AP?

Answer 7

Na and Ca enter via gap junctions

Question 8

Phase 0 of myocyte AP?

Answer 8

Na influx

Question 9

Phase 1 of myocyte AP?

Answer 9

K efflux

Question 10

Phase 2 of myocyte AP?

Answer 10

Ca influx and CICR

K efflux

Question 11

Phase 3 of myocyte AP?

Answer 11

K efflux overrides Ca influx

Question 12

Skeletal/cardiac muscle contraction?

Answer 12

Adenylyl cyclase forms cAMP
cAMP activates PKA
PKA activates L-type Ca channel allowing CICR
Ca binds troponin C which shifts tropomyosin out actin cleft to form cross-bridge

Question 13

Skeletal/cardiac muscle relaxation?

Answer 13

PKA phosphorylates phospholamban which increases Ca pumping from SE and relaxation rate
L-type channels close and Ca efflux occurs
Ca-ATPase recruits Ca back into SR
Ca dissociates from troponin C and cross bridges break resulting in relaxation

Question 14

SR channels that allows Ca in and out?

Answer 14

Ryanodine (out) and SERCA (in)

Question 15

Direction leads “look” from?

Answer 15

+ve to -ve

Question 16

Limb leads are … and augmented leads are …?

Answer 16

Bipolar and unipolar

Question 17

Describe leads I, II and III?

Answer 17

I = right arm to left arm (+ve)
2 = right arm to left leg (+ve)
3 = left arm to left leg (+ve)

Question 18

2 septal leads?

Answer 18

V1 and V2

Question 19

4 lateral leads?

Answer 19

I, aVL, V5 and V6

Question 20

3 inferior leads?

Answer 20

II, III and aVF

Question 21

2 anterior leads?

Answer 21

V3 and V4

Question 22

P wave represents + duration?

Answer 22

Atrial depolarisation + 0.08-0.1 seconds

Question 23

QRS represents + duration?

Answer 23

Ventricular depolarisation + < 0.1 seconds

Question 24

PR duration + where the measurement it taken from?

Answer 24

0.12-0.2 seconds + start of P wave to start of QRS

Question 25

QT duration?

Answer 25

0.44 seconds

Question 26

Large box on ECG represents?

Answer 26

0.2 seconds

Question 27

Small box on ECG represents?

Answer 27

0.04 seconds

Question 28

How to calculate normal ECG HR?

Answer 28

300/number of squares between R peaks

Question 29

How to calculate irregular ECG HR?

Answer 29

Number of R peaks in 30 boxes X 10

Question 30

Left axis deviation?

Answer 30

QRS in I and II point away from eachother

Question 31

Right axis deviation?

Answer 31

QRS in I and III +/- II point towards eachother

Question 32

T wave represents?

Answer 32

Ventricular depolarisation

Question 33

Normal calibration of ECG paper?

Answer 33

25 mm/cm and 1 cm/mV

Question 34

Absent P waves and short QRS?

Answer 34

Atrial fib or flutter

Question 35

Saw tooth wave?

Answer 35

Atrial flutter

Question 36

Delta wave on QRS complex?

Answer 36

WPW syndrome

Question 37

Polymorphic VT?

Answer 37

Torsades des Pointes

Question 38

Reverse tick sign?

Answer 38

Digoxin toxicity

Question 39

ST elevation is caused by what 2 things?

Answer 39

MI or pericarditis

Question 40

ST depression is caused by which 3 things?

Answer 40

Ischaemia, angina and NSTEMI

Question 41

Tall tented T waves and wide QRS?

Answer 41

Hyperkalemia

Question 42

How does parasympathetic innervation slow heart rate?

Answer 42

Activates GIRKS which allow K influx

Question 43

M sign in V1 and deep S in V6?

Answer 43

RBBB

Question 44

Deep S in V1 and M sign in V6?

Answer 44

LBBB

Question 45

Inverted T wave and wide QRS?

Answer 45

Hypokalaemia