Cardiovascular system reading 3 Flashcards
List in order the events of the cardiac conduction system, starting with the first at the top.
- The SA node fires.
- Excitation spreads through the atrial myocardium.
- AV node fires
- Excitation spreads down the AV bundle.
- Purkinje fibers distribute excitation through the ventricular myocardium
The structure that relays excitation from the atria to the ventricles is known as the _____.
atrioventricular node
The electrical pathway by which signals leave the AV node to move to the interventricular septum is the atrioventricular _______.
bundle
The sinoatrial node is located in the wall of the ______.
right atrium
True or False: Action potentials from the SA node travel to all cells in the atria and the AV node at the same rate.
False
Purkinje fibers _____.
are terminal branches of the cardiac conduction system
What is the importance of the action potential delay at the AV node?
Allows the completion of atrial contraction before ventricular contraction
The terminal branches of the conduction system that distribute the electrical signals throughout the ventricles are called ______.
Purkinje fibers
Where does ventricular contraction begin?
Apex
The resting membrane potential primarily depends on the plasma membrane permeability of all of the following ions EXCEPT ______.
chloride
The membrane potential when a cardiac muscle cell is relaxed is the resting ______.
membrane potential
Which occurs during the repolarization phase of a cardiac muscle cell but not in a skeletal muscle cell?
Calcium channels begin to open
At rest, what ion is abundant inside of the cardiac cell membrane, helping to establish the resting membrane potential?
Potassium
How is action potential propagation different in cardiac muscle cells than in skeletal muscle cells?
Action potentials are conducted from one cardiac cell to another.
The action potential of a cardiac muscle has a plateau due to the opening of ______ channels.
calcium
What is the first step in an action potential in a cardiac muscle cell?
Sodium channels open
Initial depolarization of a cardiac muscle cell is due to the opening of ______ channels.
sodium
The action potential of a cardiac muscle has a plateau primarily due to the diffusion of _____ the cell.
calcium into
Electrical changes across the membrane cause the opening and closing of what-gated ion channels.
voltage
Repolarization of a cardiac muscle cell is due primarily due to the diffusion of ______ the cell.
potassium out of
Depolarization of the cardiac muscle cell is primarily due to the diffusion of ______ the cell.
sodium into
What controls the opening of the ion channels in cardiac muscle cells during phases of the action potential?
Electrical changes
The movement of calcium into a cardiac muscle cell through the membrane results in calcium release from the ______.
sarcoplasmic reticulum
Calcium-induced calcium release occurs when ______.
calcium entering through the plasma membrane stimulates release of calcium from sarcoplasmic reticulum
The cardiac muscle cells are described as ______ because individual cells can depolarize on their own without outside stimulation.
autorhythmic
A spontaneously developing local potential that generates action potentials in the SA node is called the _____ potential.
pacemaker
The pacemaker potential of SA node cells is due to the influx of what ions through special non-gated channels?
sodium or Na
The depolarization of the SA node (from threshold to peak) is mainly due to the inflow of ______ ions.
calcium
A pacemaker potential and an action potential are the same thing.
False
Calcium-induced calcium release occurs when ______.
calcium entering through the plasma membrane stimulates release of calcium from sarcoplasmic reticulum
What ions cause the depolarization of the SA node (from threshold to peak) through their movements into the cell?
Sodium
Calcium
If another region of the heart other than the SA generates a heartbeat, this region is called a(n) what focus?
ectopic
The strongest stimulus will not cause muscle contraction during the ______ refractory period.
absolute
What is a normal firing rate of the SA node for a healthy person at rest?
75
What causes the long refractory period in cardiac muscle cells?
Plateau phase
The frequency of action potential generation in the SA node is ______ than in other foci of the heart.
higher
What is an ECG?
A recording of cardiac action potentials measured at the body’s surface
An ectopic focus is a region of the heart that generates a heartbeat other than the ______.
SA node
The what is a composite recording of all cardiac action potentials?
electrocardiogram, ECG, or EKG
The QRS complex is the ECG recording of depolarization of the ______.
ventricles
Why does atrial repolarization not appear as a separate wave on an ECG?
It is obscured by ventricular contraction.
