A&P Test 4 Flashcards
When you have depolarization going from left to right, what kind of deflection would you expect?
Positive
If you have repolarization going from left to right (the same way as depolarization) what kind of deflection would you expect?
negative deflection
When we have repolarization going from right to left, (opposite of depolarization), what kind of deflection would you expect?
a positive deflection
(double negative)
what is another name for phase 4 in the slow action potential?
diastolic depolarization
the faster the rate of diastolic depolarization the faster the __________ will be
heart rate
What is phase 0 due to in the slow action potential?
Slow L type ca++ channels
slow to open and stay open longer than fast Na+ channels
The slope of Phase 0 is really important in determining what in the heart?
How fast an ap is going to propagate around the heart
what is the slope of phase 3 due to in the slow AP?
L-type Ca++ closing and VG K+ channels opening
Is there a phase 2 in slow action potentials?
Possibly. This depends on the textbook/article. Most leave it out
Is there a phase 1 in slow action potential?
no!
In the AV node, what is the VRM?
more negative than the SA node
Are there HCN channels in the nodal tissue?
yes, highest density in the SA node but there are some in the AV node as well
AP in the ventricular endocardium start _______ AP’s in the epicardium, and the ventricular endocardium tissue is repolarized ________ AP’s in the epicardium.
before
after
repolarization happens in the ventricular epicardial tissue before the repolarization is _____ in the ventricular endocardial tissue
complete
Why is it important to have the more superficial tissues in the heart contracting at the same time as the slower subendocardial tissues?
What does this idea explain?
Because we want a coordinated contraction and efficient ejection
it explains why the ventricular endocardial AP is longer than the ventricular epicardial AP. So the inside and outside of the heart is contracting at the same time.
The atria action potential looks different from nodal tissue and ventricular APs in what way?
the 0 slope is very steep (pretty much straight up an down) the plateau phase is shorter, and the AP in the atrial epicardial tissue and atrial endocardial tissue look the same (bc the atria doesn’t have to pump against a lot of force)
Kind of looks like a mix between a slow action potential and a fast action potential
How long (in seconds) does it take for the SA node to self depolarize and generate an action potential?
.83 seconds
60 seconds in a minute
=72bpm
without any input from the sympathetic chains or vagus stimulation, how fast would the SA node AP be?
110 beats per minute
If you have a normal amount of sympathetic nervous system in a heart rate without vagus stimulation, how fast would the heart rate be?
120
If you have a normal amount of vagal stimulation and you remove the sympathetic stimulation from the heart, how fast would the heart rate be?
60-62 BPM
Which has the most effect on the heart rate ? sympathetic or vagal
vagal
What is the secondary pacemaker?
AV node
If the AV node was the pacemaker of the heart, how fast would your heart rate be?
40-60BPM
If the Purkinje fibers became the pacemaker of the heart, how fast would your heart rate be?
15-30 BPM