CVR 5

Question 1

Define the cardiac cycle?

Answer 1

The relationship between electrical mechanical and valvular events during one complete heartbeat

Question 2

Two types of cells that have single cell potentials?

Answer 2

pacemaker (AV/SA) and non pacemaker (ventricular myocyte)

Question 3

Differences in AP between the two?

Answer 3

No plateau in pacemaker and easier to generate in pacemaker.

Tendency to depolarise in pacemaker, they are automatic.

Question 4

What fast conductance is missing in the nodal cells?

Answer 4

Sodium

Question 5

Whats high on the inside of cell?

Answer 5

Potassium, calcium.

Sodium on the outside.

Question 6

Whats high on the inside of cell?

Answer 6

Potassium

Sodium calcium on the outside.

Question 7

Potassium wanting to move out does what?

Answer 7

Re-polarization…makes the membrane more negative.

Question 8

Calcium moving into the cell causes?

Answer 8

Membrane to get less negative.

Question 9

What phase is the balance achieved by calcium and potassium in equilibrium?

Answer 9

Phase 2

Question 10

What is the main transfer conductance that causes the major upstroke?

Answer 10

Fast movement of sodium

Question 11

What is the funny current?

Answer 11

Sodium current through different channels than are present in the non nodal cells.
These are different from the fast AP’s.

i litte f

Question 12

Which of the following ions is not involved in the automaticity of nodal cells?

Answer 12

Calcium
Sodium
Potassium
(other)

Question 13

What does nor adrenaline do to the AP

Answer 13

shifts to the left and makes it easier to achieve

Question 14

What is tetany?

Answer 14

summation of AP’s

Question 15

Why does the heart not get tetany?

Answer 15

Refractory period. Sodium channels are deactivated. Followed by relative refractory period where many but not all sodium channels open.

Question 16

What fibres have the longest refractory period?

Answer 16

Pukinje Fibres have long plateau and prolonged absolute refractory.

Question 17

What fibres have the longest refractory period?

Answer 17

Pukinje Fibres have long plateau and prolonged absolute refractory.

Question 18

What is functional synctium?

Answer 18

AP’s spread themselves, freely between communicating cells. Allows rapid synchronous depolarization of myocardium.

Question 19

As far as electrical velocities go which is the odd one out?

Answer 19

AV node - to funciton mechanically you need a slowing down. If there is a problem with conductance it wil likely be here.

Question 20

Characteristics of the AV node?

Answer 20

narrow muscle fibre diameter
low density gaps
lack of fast NA
low amp AP
ANS effects

Question 21

What is Wolff Parkinson White Syndrome

Answer 21

Bypass tract called Bundle of Kent. Re entry back in the direction of the SA node. Global AV re-entry.
Supraventricular tachyarrhythmias.
Tx: sync cardioversion. Destruction of path via radiofrequency catheter ablation. - mutation in 5-AMP activated protien kinase subunit gamma.

0.1 % of the population.
PRKAG2

Question 22

What is Wolff Parkinson White Syndrome

Answer 22

Bypass tract called Bundle of Kent. Re entry back in the direction of the SA node. Global AV re-entry.
Supraventricular tachyarrhythmias.
Tx: sync cardioversion. Destruction of path via radiofrequency catheter ablation. - mutation in 5-AMP activated protien kinase subunit gamma.

0.1 % of the population.
PRKAG2

Question 23

What is atropine?

Answer 23

PNS antagonist to cholinergic muscarinic receptors

Question 24

What keeps the heart at a regular heart rate?

Answer 24

PNS keeps it regular at rest

SNS controls it in stress

Question 25

What are beta blockers?

Answer 25

SNS antagonists to adrenergic receptors

Question 26

When you examine a patient you may describe the normal pulse as being in sinus rhythm?

Answer 26

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