Cardiovascular-Renal I: Exam 1 Pt 8

Direction of action potential (AP) propagation through the excitatory system

SA node

inter-nodal pathways

AV node

Bundle of His

Tawara (bundle) branches

Purkinje fibers

What is the function of the SA node?

pacemaker

generates AP at the fastest rate

What is the function of the AV node?

slows down the AP propagation

makes sure the entire atrial muscle is excited and contracted before the AP goes on the ventricles

What makes pacemaker potential unique?

pre-potential due to leaky nonspecific cation channels (funny channels)

What is the role of voltage-gated Na+ channels in ventricular AP?

fast depolarization

What is the role of voltage-gated Ca²+ channels in ventricular AP?

plateau phase-> refractory period

prevent heart from tetanizing

What is a tetanized muscle?

tetanized muscle is one in a state of continuous contraction

What is the role of voltage-gated K+ channels in ventricular AP?

repolarization

What is the role of voltage-gated Na+/K+ ATPase in ventricular AP?

reset normal distribution of ions

Explain Phase 4 (pacemaker potential) of SA node AP.

slow depolarization due to Na+ and Ca2+ leak until threshold (funny channels)

Explain Phase 0 of SA Node AP.

at threshold, Ca2+ channels open

Explain Phase 3 of a pacemaker potential.

K+ channels open during repolarization.

T/F: Pacemaker potential has a plateau like ventricular AP

False

How long is the refractory period of cardiac muscle fibers

last almost as long as entire muscle twitch

What prevent cardiomyocytes from tetanizing?

Na+ channels are inactive until membrane is repolarized