ECG And Excitable Tissue

Question 1

The rate of depolarization in phase 0 within ______ is slow while in ____ is rapid

Answer 1

AV node

Purkinji fibers

Cause in Av node diameter is smaller and less gapjunction and the oppiste in purkinji

Question 2

Spountouns depolarization (contraction) happens in

Answer 2

Cardiac muscle mayocytes and they conduct elctrical impulses

Question 3

High resteing K conductance is due to

Answer 3

Ungated k channles : leak

Inward K rectifying channels: open while rest and close while depolarization: عكس ال normal

Question 4

Torsade de pointes

Answer 4

Ventricular tachycardia due to prolonged QT interval

Question 5

Class I antiarrytmic works on which channel ?

Answer 5

Na fast channel reaulting in change in phase 0

Question 6

Class II antiarrythmic blocks which channel ?

Answer 6

K
Resulting in prolonged QT intervals

Like beta blockers

Question 7

What causes plateau in phase 2

Answer 7

Inward Ca and outward K

Question 8

In phase 2 long action potentials what does it prevents?

Answer 8

Tetany

Question 9

Whats the difference in action potentials between nodal and non-nodal cardiac cella ?

Answer 9

Nodal lack of Na channels and the action potentials is mediated by Ca current

Absent phase 1&2 in nodal

Starts as following in nodal

4———–>0—-——>3

Question 10

Funny channles function

Answer 10

They are in nodal cells action potentials and they are inward Na channles , invilved in HCN channles

In phase 4

Question 11

Ca channel blockers ?

Answer 11

Class IV antiarrythimics

Reduce automaticty and conduction in AV node

Really good to use in tacharrhythmias

Question 12

When beta blockers fail what do we use ?

Answer 12

Ivanradine which works on funny channles and reduce their current

Works on SA node
Usefull in tachycardia

Question 13

What controls the Nodal excitablity ?

Answer 13

1-Calecholmines: NE -Epi- beta~1receptors which stimulates the opneing of HCN and Ca channles

+ chronotropy SA node
+dromotropy AV node

2- parasympathetic
ACH
M2 receptors :open k channels,and inhibits funny channels or HCN

• chronotropy
• dromotropy

Question 14

How to read ecg steps

Answer 14

1- rythm
2 -HR 
3- wave check 
4-PR interval 
5-MEA

Question 15

What would u see in first degree heart block ?

Answer 15

Normal rythem
Normal HR
Normal waves
Prolonged p-R interval more than one big box

Question 16

Second degree heart block

Answer 16

Mobitz1 (wenkebach) : 
Rythm maybe normal 
Rate normal 
Pr interval progrissve prolonged 
Missed QRS 

Mobits 2: 
Rythm normal 
Rate normal 
PR interval normal 
Missed QRS

Question 17

Third degree heart block

Answer 17

Rythem normal
HR very slow
Waves abnormal and no consistancy

Question 18

Atrial flutter

Answer 18

Chain saw appearnce 
Tachycardia 
Appearnes of waves between QRS 
Cant descrimnate T waves 
Normal rythem

Question 19

A fib

Answer 19

Rythem abnoraml
HR unsteady
Absent p wave

Question 20

Wolf -parkinson-white-syndrom

Answer 20

Normal rythem and rate
Delta in R wave
QRS complex wide
Sometimes can cause accessory pathway and tachycardia

Question 21

What happens in ecg with
Hypercalcemia
Hypocalcemia

Hyper kalemia
Hypokalemia

Answer 21

Hypercalcemia& hypercalcemia : QT interval short due to increase rate of repolariszation

Hypo: prolonged QT interval cause it decreases repolarization

In hypokalemia may have U wave

Question 22

ST segment elevation

And depression

Answer 22

ST elevation :
Trnasmural infarct (unstable )
Prinzmetal angaina (coronary vasoapasm) 

ST depression : 
subendocardial ischemia 
Exerctional angina ( stable)