Cardiac physiology and ECG

Question 1

What is the purpose of desmosomes in cardiac muscle cells

Answer 1

allows the cardiac myocyte to cope with mechanical stress, e.g stretching

Question 2

What is CICR?

Answer 2

Calcium-Induced-Calcium-Release

Question 3

What is the funny current activated by?

Answer 3

Hyperpolaristaion

Question 4

What is the resting potential of the cardiac myocyte cells?

Answer 4

-55mV

Question 5

What channels lead to repolarisation?

Answer 5

Potassium channels

Question 6

What is the refractory period?

Answer 6

A period where it is not possible to elicit a new action potential immediately regardless of how much the membrane is depolarised

Question 7

Why do we need a refractory period in the heart?

Answer 7

So that the heart has enough time to fill in between contractions

Question 8

What is the absolute refractory period?

Answer 8

The shortest possible time between two consecutive action potentials in a cell

Question 9

What is the latent period?

Answer 9

time between initiation of an AP and the succeeding
contraction

Question 10

What does the conduction system in the heart allow for?

Answer 10

Allows for propagation of a nervous impulse rapidly throughout the heart, also ensures there’s a delay in impulse conduction between the atria and ventricles

Question 11

What is annulus fibrosis?

Answer 11

An electrical insulator that slows down transmission from the atria to the ventricles

Question 12

What connects cardiac myocytes to eachother?

Answer 12

Intercalated discs

Question 13

Why are gap junctions important?

Answer 13

they ensure the velocity and safety of propagation of impulse

Question 14

What are some differences between the action potential of the SAN and a non-pacemaker cell?

Answer 14

Cardiac, -55mv, uses ‘funny channels’, slower rise

Question 15

What type of cells have a brief refractory period?

Answer 15

skeletal muscle cells

Question 16

Where would you place ECG’s?

Answer 16

Right and Left forelimb and Left hindlimb

Question 17

Describe a first degree atrioventricular block

Answer 17

P waves are still present but there is a longer time period between P and R, hence there is a delay in the AV- this can be missed on traces and is usually not a cause for concern

Question 18

Describe a second degree atrioventricular block

Answer 18

Multiple P waves fire without a QRS Complex, although the Pr interval still stays the same

Question 19

Describe a third degree atrioventricular block

Answer 19

The atria and ventricles do not communicate with each other so the P wave and QRS wave are independent of each other

Question 20

What is phase 0 of the cardiac action potential?

Answer 20

Depolaristaion of the membrane due to a strong but brief increase in the permeability of Na+

Question 21

What is phase 1 of the cardiac action potential?

Answer 21

Na+ channels quickly reactivate causing the membrane to quickly repolarise

Question 22

What is phase 2 of the cardiac action potential?

Answer 22

Repolarisation is halted due to the opening of voltage gated calcium channels which creates a plateau phase

Question 23

What is phase 3 of the cardiac action potential?

Answer 23

Repolarisation begins with the opening of K+ channels

Question 24

What is phase 4 of the cardiac action potential?

Answer 24

K+ channels are open and maintain a resting membrane potential

Question 25

Where are gap junctions found?

Answer 25

Within the intercalated discs

Question 26

What is the resting membrane potential?

Answer 26

The membrane is more negative on the inside in comparison to the outside

Question 27

What are the only cell types that funny channels exist in?

Answer 27

Funny channels only exist in pacemaker cells found in the SAN

Question 28

What is SA node autorythmicity?

Answer 28

When the cardiac cycle is repeated

Question 29

What kind of cells only have a brief refractory period?

Answer 29

Skeletal muscle cells

Answer 30

new contraction can be initiated
before the previous one has terminated.

Question 31

What is the Bundle of His?

Answer 31

Bundle of conducting muscle cells which penetrate the annulos fibrosus between the atria and ventricles in the septum

Question 32

What kind of fibres are purkinjie fibres?

Answer 32

conducting fibres

Question 33

How would you measure voltage difference?

Answer 33

It is the difference between two surface electrodes

Question 34

What is a mobitz type 1 2cd atrioventricular block?

Answer 34

PR complex gradually increases over time, then the QRS complex disappears