Physio Ch 10 Flashcards
Under normal conditions, atria contract ___ ahead of ventricles
1/6 of a second
conduct impulses from the sinus node to the atrioventricular (A-V) node
internodal pathways
conducts impulses from the atria into the ventricles
A-V bundle
conduct the cardiac impulses to all parts of the ventricles
right and left bundle branches of Purkinje fibers
where impulses from the atria are delayed
before passing into the ventricles
AV node
a small, flattened, ellipsoid strip of specialized cardiac muscle
SA node
Located superior posterolateral wall of right atrium below and slightly lateral to the opening of the superior vena cava
SA node
a process that can cause automatic rhythmical discharge and contraction
self-excitation
resting membrane potential of the sinus nodal fiber between discharges
-55 to -60 mV
RMP of ventricular muscle fiber
-85 to -90
Why does SA node have lesser RMP or negativity?
Due to cell membrane’s natural leak to sodium and calcium ions (positive ions go inside the fibers)
What are the 3 types of membrane ion channels present in the cardiac muscle?
(1) fast sodium channels
(2) slow sodium-calcium channels
(3) potassium channels
Which channel is responsible for the rapid upstroke spike of the action potential observed in ventricular muscle
fast sodium channels
Which channel is responsible for the plateau of the ventricular action potential
slow sodium-calcium channel
Responsible for returning the cell membrane’s potential to its resting level
potassium channels