CVR 5 Flashcards
Define the cardiac cycle?
The relationship between electrical mechanical and valvular events during one complete heartbeat
Two types of cells that have single cell potentials?
pacemaker (AV/SA) and non pacemaker (ventricular myocyte)
Differences in AP between the two?
No plateau in pacemaker and easier to generate in pacemaker.
Tendency to depolarise in pacemaker, they are automatic.
What fast conductance is missing in the nodal cells?
Sodium
Whats high on the inside of cell?
Potassium, calcium.
Sodium on the outside.
Whats high on the inside of cell?
Potassium
Sodium calcium on the outside.
Potassium wanting to move out does what?
Re-polarization…makes the membrane more negative.
Calcium moving into the cell causes?
Membrane to get less negative.
What phase is the balance achieved by calcium and potassium in equilibrium?
Phase 2
What is the main transfer conductance that causes the major upstroke?
Fast movement of sodium
What is the funny current?
Sodium current through different channels than are present in the non nodal cells.
These are different from the fast AP’s.
i litte f
Which of the following ions is not involved in the automaticity of nodal cells?
Calcium
Sodium
Potassium
(other)
What does nor adrenaline do to the AP
shifts to the left and makes it easier to achieve
What is tetany?
summation of AP’s
Why does the heart not get tetany?
Refractory period. Sodium channels are deactivated. Followed by relative refractory period where many but not all sodium channels open.
What fibres have the longest refractory period?
Pukinje Fibres have long plateau and prolonged absolute refractory.
What fibres have the longest refractory period?
Pukinje Fibres have long plateau and prolonged absolute refractory.
What is functional synctium?
AP’s spread themselves, freely between communicating cells. Allows rapid synchronous depolarization of myocardium.
As far as electrical velocities go which is the odd one out?
AV node - to funciton mechanically you need a slowing down. If there is a problem with conductance it wil likely be here.
Characteristics of the AV node?
narrow muscle fibre diameter low density gaps lack of fast NA low amp AP ANS effects
What is Wolff Parkinson White Syndrome
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
What is Wolff Parkinson White Syndrome
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
What is atropine?
PNS antagonist to cholinergic muscarinic receptors
What keeps the heart at a regular heart rate?
PNS keeps it regular at rest
SNS controls it in stress
What are beta blockers?
SNS antagonists to adrenergic receptors
When you examine a patient you may describe the normal pulse as being in sinus rhythm?
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