Chapter 17 pt. 2

Place the following parts of the cardiac conduction system in the order in which they transmit the action potential. 1. atrioventricular (AV) bundle 2. Purkinje fibers 3. sinoatrial (SA) node 4. right and left bundle branches 5. contractile cells of cardiac muscle tissue 6. atrioventricular (AV) node

3, 6, 1, 4, 2, 5

Which wave on the electrocardiogram (ECG) represents ventricular depolarization?

QRS wave

The main pacemaker of the heart is the __________

SA Node

The concentration gradient for calcium ions has the same direction

as sodium ions

Certain drugs used to treat dysrhythmias, called local anesthetics, work by blocking voltage gated sodium ion channels and slowing the entry of sodium ions into the cell during an action potential. What effects would you see?

Decrease depolarization of the cell

What is best defined as an influx of positive charges, causing the resting membrane potential to become less negative, i.e., more positive?

Depolarization

A damaged atrioventricular (AV) bundle or atrioventricular (AV) node will primarily affect the length of the:

P wave.

A damaged right bundle branch will prevent the passage of the action potential to the:

Purkinje fibers in the right ventricle.

Which of the following can be used to measure heart rate?

R-R Interval

Determine the impact if the connection between the sinoatrial (SA) node and the atrioventricular (AV) node becomes blocked.

The ventricles will contract more slowly.

According to the Frank-Starling law, a bigger preload will result in __________.

a stronger contraction

What is not an effect of the sympathetic nervous system?

decrease in heart rate

How would a decrease in blood volume affect both stroke volume and cardiac output?

decreased stroke volume and no change in cardiac output

Which of the following would increase heart rate?

epinephrine and norepinephrine

How would an increase in the sympathetic nervous system increase stroke volume?

increased contractility

By what mechanism would an increase in venous return increase stroke volume?

increased end diastolic volume

What would increase cardiac output to the greatest extent?

increased heart rate and increased stroke volume

What ion movement changes the membrane potential in a contractile cell from negative to positive during the rapid depolarization phase?

influx of sodium ions

The cells that rhythmically and spontaneously generate action potentials in the heart are called __________.

pacemaker cells

Which of the following is NOT a population of pacemaker cells in the heart? - Purkinje fiber system - papillary muscles - atrioventricular (AV) node - sinoatrial (SA) node

papillary muscles

What do pacemaker cell action potentials lack?

plateau phase

Which of the following pacemaker cell populations has the fastest intrinsic rate of depolarization at about 60-70 times or more per minute?

sinoatrial (SA) node

How will the cardiac output change if you double the heart rate but reduce the stroke volume by one-half?

It will not change.

Which of the following happens immediately after the P wave?

The atria relax.