Rush - Advanced Pharmacology - NSG 531 - Exam 3
Q&A’s Latest Solution (100% HELPFUL)
What is the difference between cardiac myocyte action potential and that of the CNS or ANS?
- ANS ✔✔ - nerve cell action potential is very short
Cardiac action potential is much longer
They are longer to have adequate filling time in order to get a good contraction for a
reasonable bolus of blood
The only way this can happen is if the action potential is longer
This will also mean that the refractory period will be longer
What are the 5 phases of the non-pacemaker action potential? - ANS ✔✔ - 0 - depolarization
1 - Partial repolarization
2 - Plateau
3 - Repolarization
4 - Resting membrane potential
What happens during phase 0 of the non-pacemaker action potential - ANS ✔✔ -
depolarization
Voltage gated sodium channels are opening up until we get past threshold
What happens during phase 1 of the non-pacemaker action potential - ANS ✔✔ - partial
repolarization
What happens during phase 2 of the non-pacemaker action potential - ANS ✔✔ - plateau
Calcium channels open (L-type because they are long)
Potassium is still open
Potassium out and calcium in - they are opposing each other in voltage giving the plateau
This is when the ventricles are filling
,Rush - Advanced Pharmacology - NSG 531 - Exam 3
Q&A’s Latest Solution (100% HELPFUL)
What happens during phase 3 of the non-pacemaker action potential - ANS ✔✔ -
repolarization
Calcium channels are closed
Potassium channels are the only thing open taking their positive charge with them making
the interior more negative
What happens during phase 4 of the non-pacemaker action potential - ANS ✔✔ - resting
membrane potential where we are in between action potentials there is no net change in
voltage inside the cell
When does contraction take place? - ANS ✔✔ - begins towards the end of repolarization and
ends at some point during repolarization
Refractory period - ANS ✔✔ - during phase 0, 1, 2, and part of phase 3 the cell is refractory
to the initiation of new action potentials
Many antiarrhythmic drugs increase the Refractory period which reduces myocyte
excitability
What are the benefits of the refractory period - ANS ✔✔ - limits frequency of cardiac
contractions
Allows for adequate filling time
Prevents sustained contractions
How pacemaker cells are different from non-pacemaker cell - ANS ✔✔ - no resting
membrane potential - no point where it is flat
There are very few sodium channels in pacemaker - sodium channels are not driving
depolarization - calcium is
, Rush - Advanced Pharmacology - NSG 531 - Exam 3
Q&A’s Latest Solution (100% HELPFUL)
Only 3 phases
Comprised of cells within the SA node
Generate regular, spontaneous action potentials
What are the phases of pacemaker action potential - ANS ✔✔ - 0 - rapid depolarization
3 - Repolarization
4 - Slow depolarization
What happens during phase 0 of the pacemaker action potential - ANS ✔✔ - Rapid
depolarization
Something is coming to open voltage gated calcium channels (L-type) calcium comes rushing
in
What happens during phase 3 of the pacemaker action potential - ANS ✔✔ - repolarization
Potassium channels now open up, potassium rushes out, repolarizes
What happens during phase 4 of the pacemaker action potential - ANS ✔✔ - slow
depolarization
With potassium rushing out we are all the way down at -60
Funny sodium channels open up until voltage reaches -50
T-type (transient) calcium channels open up until voltage reaches -40
L-type calcium channels then open back up
Describe how non-pacemaker APs can mimic pacemaker APs - ANS ✔✔ - Hypoxia and
ischemia
When the resting membrane potential is not getting enough oxygen it is going to become
more positive because you need oxygen to produce ATP. If we are deficient in ATP then the
NA K ATPase pump won’t be functioning
Q&A’s Latest Solution (100% HELPFUL)
What is the difference between cardiac myocyte action potential and that of the CNS or ANS?
- ANS ✔✔ - nerve cell action potential is very short
Cardiac action potential is much longer
They are longer to have adequate filling time in order to get a good contraction for a
reasonable bolus of blood
The only way this can happen is if the action potential is longer
This will also mean that the refractory period will be longer
What are the 5 phases of the non-pacemaker action potential? - ANS ✔✔ - 0 - depolarization
1 - Partial repolarization
2 - Plateau
3 - Repolarization
4 - Resting membrane potential
What happens during phase 0 of the non-pacemaker action potential - ANS ✔✔ -
depolarization
Voltage gated sodium channels are opening up until we get past threshold
What happens during phase 1 of the non-pacemaker action potential - ANS ✔✔ - partial
repolarization
What happens during phase 2 of the non-pacemaker action potential - ANS ✔✔ - plateau
Calcium channels open (L-type because they are long)
Potassium is still open
Potassium out and calcium in - they are opposing each other in voltage giving the plateau
This is when the ventricles are filling
,Rush - Advanced Pharmacology - NSG 531 - Exam 3
Q&A’s Latest Solution (100% HELPFUL)
What happens during phase 3 of the non-pacemaker action potential - ANS ✔✔ -
repolarization
Calcium channels are closed
Potassium channels are the only thing open taking their positive charge with them making
the interior more negative
What happens during phase 4 of the non-pacemaker action potential - ANS ✔✔ - resting
membrane potential where we are in between action potentials there is no net change in
voltage inside the cell
When does contraction take place? - ANS ✔✔ - begins towards the end of repolarization and
ends at some point during repolarization
Refractory period - ANS ✔✔ - during phase 0, 1, 2, and part of phase 3 the cell is refractory
to the initiation of new action potentials
Many antiarrhythmic drugs increase the Refractory period which reduces myocyte
excitability
What are the benefits of the refractory period - ANS ✔✔ - limits frequency of cardiac
contractions
Allows for adequate filling time
Prevents sustained contractions
How pacemaker cells are different from non-pacemaker cell - ANS ✔✔ - no resting
membrane potential - no point where it is flat
There are very few sodium channels in pacemaker - sodium channels are not driving
depolarization - calcium is
, Rush - Advanced Pharmacology - NSG 531 - Exam 3
Q&A’s Latest Solution (100% HELPFUL)
Only 3 phases
Comprised of cells within the SA node
Generate regular, spontaneous action potentials
What are the phases of pacemaker action potential - ANS ✔✔ - 0 - rapid depolarization
3 - Repolarization
4 - Slow depolarization
What happens during phase 0 of the pacemaker action potential - ANS ✔✔ - Rapid
depolarization
Something is coming to open voltage gated calcium channels (L-type) calcium comes rushing
in
What happens during phase 3 of the pacemaker action potential - ANS ✔✔ - repolarization
Potassium channels now open up, potassium rushes out, repolarizes
What happens during phase 4 of the pacemaker action potential - ANS ✔✔ - slow
depolarization
With potassium rushing out we are all the way down at -60
Funny sodium channels open up until voltage reaches -50
T-type (transient) calcium channels open up until voltage reaches -40
L-type calcium channels then open back up
Describe how non-pacemaker APs can mimic pacemaker APs - ANS ✔✔ - Hypoxia and
ischemia
When the resting membrane potential is not getting enough oxygen it is going to become
more positive because you need oxygen to produce ATP. If we are deficient in ATP then the
NA K ATPase pump won’t be functioning
