BCR TBL 2: Electrical Properties of the Heart and Rhythm Disturbances

Are cardiomyocytes polarised or non polarised

Polarised

What does polarised mean

Contains electrical charge

What is the Na/K pump ion movement

2 K in 3 Na out

What are cardiomyocytes connected by

Gap Junctions

What does SAN stand for

Sinoatrial Node

What does AVN stand for

Atrioventricular node

What are the bundle of cells that start a heart beat

Pacemaker cells

Where are pacemaker cells

SAN

When an impulse travels from SAN to AVN what contracts

Atria

When the impulse reaches the AVN what happens before the AVN passes on the impules

Delay

Why is there a delay

All blood can flow of atria

Where does impulse travel after AVN

Bundle of His

Where does impulse travel after Bundle of His

Left and right Bundle fibres

Where does the impulse travel after bundle fibres

Purkinje Fibres

What does the impulse in the purkinje fibres cause contraction in

Ventricles

What percentage of the heart is conductive tissue

1%

What is happening at

Depolarisation of atria

What is the QRS complex showing

Depolarisation of ventricle and repolarisation of atria

What does the T show

Repolarisation of Ventricle

What is the PQ section

Delay

what is the ST section

End of Contraction

In a 12 Lead ECG what color is right arm lead

red

In a 12 Lead ECG what color is Left arm lead

Yellow

In a 12 Lead ECG what color is right leg lead

Green

In a 12 Lead ECG what color is left leg lead

Black

How many chest electrodes

6

Where is V1 Lead

Right side of 4th ICS space

Where is V2 lead

left of 4th ICS space

Where is V3 lead

On 5th left rib

Where is V4 5 6 lead

Laterally from 5th ICS moving Laterally

On ECG paper how much is 1mm in time

40ms

Name of receptor which detects voltage change for calcium channel in action potential

DHPR

What are calcium-activated calcium channels in sarcoplasmic reticulum called

Ryanodine

What are DHPR receptors attached to

Ryanodine Receptors

What kind of K+ channels in cell membrane

Inward Rectifier K+ channels

What is the Nernst Equation

• Vm= Membrane Potential
• R= gas constant = 8.316J K-1 mole-1

• T = absolute temperature (°K)

• F = Faraday’s constant = 96484 coulombs/mole

• z = valency of ion under consideration (z=1 for K+ )

Vm = RT / Zf ln([K+]o / [K+]i)

What is the equilibrium potential for K+

-95mv

What happens if u have an increase in [K+ ]o

Cardiac Arrhythmia or kidney disease

What is RMP(Resting membrane Potential)

-70mV

Why is RMP less than Calculated RMP

Leakage of ions

What does SERCA do (Sarcoendoplasmic Reticulum Calcium ATPase)

pumps calcium from cytoplasm to SR

What does calcium being pumped into SR do

End Contraction

What is blue line

Depolarisation

What is green line

Outward flow of K+

What is purple line

Opening of DHPR

What is Pink line

Calcium channels inactivate

8 Step approach to ECG

Rate Rhythm Axis P wave PR interval QRS complex ST segment T wave

What should ECG rate be roughly

60-100

What can changes in ST phase lead to

Angina

How much is a Small square in ECG in seconds

0.04

How much is a big square in seconds in ECG

0.2

How to work out BPM using RR interval

300/RR

For irregular heart rate how do you work out heart rate

QRSx6

Automaticity refers to

Cells ability to spontaneously depolarise

Conduction block refers to

Impulse encounters non excitable tissue

Re-entrant Circuits are when

Impulse circulates in loop due to non conducting tissue

Triggered Activity is when

Normal AP which triggers Abnormal AP

Is summation possible in cardiomyocytes

No

What are latent pacemakers

Backup pacemakers in lower conducting tissue

Early afterdepolarisation

Delayed afterdepolarisation

What is Tachycardia

More than 100BPM

What is BradyCardia

Less than 60BPM

What is the main kind of Conduction block

AV block

What happens in first degree AV block

PR interval is more than 200ms

What is happens in atrial fibrillation

Small Chaotic contractions no P wave narrow QRS complex arrhythmia

What Happens in atrial flutter

Narrow QRS complex sawtooth p wave

Atrial Flutter

Atrial Fibrillation

Ventricular Tachycardia

What happens in Ventricular Tachycardia

No p Waves Wide and regular QRS complex no T wave

Ventricular Fibrillation

What happens in Ventricular Fibrillation

Irregular peaks No complexed Varying amplitude

What does ICD do

Shock a heart during Ventricular Fibrillation

Myocardial Infarction

What happens during myocardial Infarction

ST elevation

Cardiac Ischaemai

What happens in Cardiac Ischaemia

ST Depression

what does the sum of cardiac vectors show

Mean Electrical Vector

If impulse travels to positive electrode which way is projection on ECG

Upwards

If you have Left axis Deviation which leads are inverted

II and III

If you have right axis deviation which leads are inverted

I

If you have extreme right axis deviation which leads are inverted

All of them