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25 Cards in this Set

  • Front
  • Back

What allows AP to travel from cell to cell? This allows for what to occur?

Gap junctions. syncytium (functioning as a whole).

What does it mean to have pacemaker activity? How long is the AP in the sinuatrial node?
Spontaneous AP.
AP in sinuatrial is about 200 to 300 ms

What are the different phases in the sinoatrial node?

Pre potential/ Pacemaker potential/ spontaneous diastolic depolarization.


Upstroke potential.


Repolarization.


Maximal diastolic repolarization.

What happens during the Pre potential/ pacemaker potential?

There is cationic non-specific current= Sodium entering is greater then Potassium leaving => slow depolarization => slowly getting to Ca channel activation

What happens during the upstroke potential?

Calcium channels open and depolarize (Ca influx)

What happens during repolarization?

Potassium Efflux

What happens during maximal diastolic repolarization?

The most negative membrane potential and where pacemaker potential begins. This is the resting membrane potential.

What does it mean to be the nomotropic rhythm generator?

It is caused by the sinoatrial node which are the primary pacemaker cells.

What are the parts of the heart responsible for electrical conducting system?

Sinoatrial node. Internodal branches. Thorel branch. AV node. HIS bundles. Purkinje fibers (from here it will spread to myocardial cells).

Which other parts of the electrical conducting system can produce spontaneous AP?

AV node. HIS bundle. Thorel branch. Purkinje Fibers.

What determines the pacemaker activity? What is the order from greatest to least?

The highest frequency of AP. Highest at sinoatrial node to AV node to HIS bundles

What does it mean to have Heterotropic rhythm generator?

When sinoatrial node not controlling pacemaker activity.

What has the fastest conduction in the heart? What has the slowest conduction in the heart?

Fastest are the purkinje fibers and the thorel branches and the slowest is the AV node.

What does the sinoatrial node fire at? What is characteristic of this? What controls parasympathetic nervous system?

It is SUPPOSED to fire 100 AP/ minute, but does not because parasympathetic system inhibits it, resulting in an AP of 60-70 AP/minute.


Vagus n

What controls the heart at rest and what stimulates the heart?

The parasympathetic heart controls at rest and the sympathetic innervates the heart

How can we change the heart rate?

By adjusting the slope. By adjusting the activation threshold for Calcium. By adjusting the maximal diastolic repolarization.

What does it mean to Adjust the slope of the heart rate?

In sympathetic we make it steeper to reach activation of the calcium threshold quicker to increase AP.


In parasympathetic we make it flatter to increase the time to activate calcium channels to decrease AP.

What does it mean to adjust the activation threshold for Calcium?

In sympathetic we make it more negative to reach activation earlier to increase AP (-90 mV vs -80 mV).


In parasympathetic we make it less negative so that the AP is decreased. (-70 mV vs -80 mV).

What does it mean to adjust the maximal diastolic repolarization?

In sympathetc we make it more positive so that the calcium activation is reached earlier.


In parasympathetic we make it more negative so that the calcium activation is reached later.

Where is the AV node located?

Between right atria and right ventricle

Why does the AV node have the slowest conducting velocity?

To delay the depolarization between the atria and ventricle. This will lead to atria contracting before ventricle to improve filling of the ventricle.

How does the AV node act as a semiconductor?

It prevents any AP from travelling back to the sinoatrial node.

What does the AV node do to the Sinoatrial node AP?

Filters it from 300 AP/min to a lower AP.

What is the ratio of diastole to systole? What happens during the diastole and systole?

2:1. Diastole is when the ventricles relax and the systole contract pushing the blood out.

When do the ventricles fill?

Ventricles fill during the diastole.