Chapter 11: Conduction System of the Heart Flashcards
What initiates the electrical activity of the heat?
specialized muscle cells
wave of electrical activity
action potential
Where do impulses initiate?
SA (sinoatrial) node
What is the natural pacemaker of the heart?
SA node
Where is the SA node located?
In the R atrium, near the opening of the superior vena cava
True or false: Ability of the cardiac muscle to depolarize and contract depends on the nervous system.
False; it is intrinsic
What is the path of conduction through the heart?
SA node -> AV node -> AV bundle (bundle of His) -> R and L branches -> Purkinje fibers -> muscle fibers contract.
On average, how often does atrial systole occur?
every .85 seconds
What is one heartbeat comprised of?
1) Atrial systole
2) Ventricular systole
3) Diastole (heart relaxes)
How many heartbeats comprise one cardiac cycle?
1 heartbeat
What happens is the SA node is not working properly?
AV node takes over (slower HR: 40-60 bpm)
What happens if both the SA and AV nodes stop working?
Bundle of His takes over (30-40 bpm)
What does lack of a P wave indicate?
Atrial fibrillation
What does an elevated ST segment in an EKG represent?
STEMI