Advanced Pharmacology - NSG 531 - Exam 3
Questions & Answers 2025
What is the difference between cardiac myocytes action potential and that of the
CNS or ANS? –
CORRECT ANSWER- Nerve cell action potential is very short.
Cardiac action potential is much 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
when the action potential is longer which also means that the refractory period will
be longer.
What are the 5 phases of the non-pacemaker action potential? - CORRECT
ANSWER- 0 - depolarization
1 - Partial repolarization
2 - Plateau
3 - Repolarization
4 - Resting membrane potential
What happens during phase O of the non-pacemaker action potential - CORRECT
ANSWER- depolarization.
Voltage gated sodium channels are opening up until we get past threshold
What happens during phase 1 of the non-pacemaker action potential - CORRECT
ANSWER- Partial Repolarization?
What happens during phase 2 of the non-pacemaker action potential - CORRECT
ANSWER- 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
What happens during phase 3 of the non-pacemaker action potential - CORRECT
ANSWER- repolarization?
Calcium channels are closed
Potassium channels are the only thing open taking their positive charge with them
making the interior more negative
1
,What happens during phase 4 of the non-pacemaker action potential - CORRECT
ANSWER- 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? - CORRECT ANSWER- begins towards the
end of repolarization and ends at some point during repolarization
Refractory period - CORRECT ANSWER- during phase 0, 1, 2, and part of phase
3 the cell is refractory to the initiation of new action potentials
Many ant arrhythmic drugs increase the Refractory period which reduces myocytes
excitability
What are the benefits of the refractory period - CORRECT ANSWER- limits
frequency of cardiac contractions
Allows for adequate filling time
Prevents sustained contractions
How pacemaker cells are different from non-pacemaker cell - CORRECT
ANSWER- 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
Only 3 phases
Comprised of cells within the SA node
Generate regular, spontaneous action potentials
What are the phases of pacemaker action potential - CORRECT ANSWER- 0 -
rapid depolarization
3 - repolarization
4 - slow depolarization
What happens during phase 0 of the pacemaker action potential - CORRECT
ANSWER- 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 - CORRECT
ANSWER- repolarization
Potassium channels now open up, potassium rushes out, repolarizes
2
, What happens during phase 4 of the pacemaker action potential - CORRECT
ANSWER- 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 - CORRECT
ANSWER- 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
If someone is hypoxic in a focal area - say they have a resting membrane potential
at -45 - the fast sodium channels won't open - they start using calcium to open - so
they would convert into action potentials that use calcium (hence how they mimic
pacemaker aps)
Excitation-contraction coupling - CORRECT ANSWER- sequence of events from
motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's
sarcomeres
Conversion of depolarizing currents into contractile force
L-type calcium channels open up in phase 2 in non pacemaker - calcium comes
flooding into myocytes, so we now have calcium in the cell and a sarcoplasmic
reticulum (a reservoir for calcium)
Receptors called RYR (lagans gated calcium channels)
Calcium then comes out - coming in the cell from the calcium channels and the
sarcoplasmic reticulum
Describe how calcium binds to cause contraction - CORRECT ANSWER- when
there is an influx of calcium in the cell there is a myosin head separated by
troponin. Little binding sites for the myosin exist on the aktin but it can't get to it
because of the troponin. Calcium therefore binds to the tropinin causing a
conformational change in troponin so it will move and take the tropomyosin with
it. The myosin can then bind to the aktin molecules when it binds it activates ATP
The ATP will be used to generate the sliding of the aktin and the myosin filaments
against each other shortening the muscle cell causing contraction
3
Questions & Answers 2025
What is the difference between cardiac myocytes action potential and that of the
CNS or ANS? –
CORRECT ANSWER- Nerve cell action potential is very short.
Cardiac action potential is much 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
when the action potential is longer which also means that the refractory period will
be longer.
What are the 5 phases of the non-pacemaker action potential? - CORRECT
ANSWER- 0 - depolarization
1 - Partial repolarization
2 - Plateau
3 - Repolarization
4 - Resting membrane potential
What happens during phase O of the non-pacemaker action potential - CORRECT
ANSWER- depolarization.
Voltage gated sodium channels are opening up until we get past threshold
What happens during phase 1 of the non-pacemaker action potential - CORRECT
ANSWER- Partial Repolarization?
What happens during phase 2 of the non-pacemaker action potential - CORRECT
ANSWER- 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
What happens during phase 3 of the non-pacemaker action potential - CORRECT
ANSWER- repolarization?
Calcium channels are closed
Potassium channels are the only thing open taking their positive charge with them
making the interior more negative
1
,What happens during phase 4 of the non-pacemaker action potential - CORRECT
ANSWER- 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? - CORRECT ANSWER- begins towards the
end of repolarization and ends at some point during repolarization
Refractory period - CORRECT ANSWER- during phase 0, 1, 2, and part of phase
3 the cell is refractory to the initiation of new action potentials
Many ant arrhythmic drugs increase the Refractory period which reduces myocytes
excitability
What are the benefits of the refractory period - CORRECT ANSWER- limits
frequency of cardiac contractions
Allows for adequate filling time
Prevents sustained contractions
How pacemaker cells are different from non-pacemaker cell - CORRECT
ANSWER- 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
Only 3 phases
Comprised of cells within the SA node
Generate regular, spontaneous action potentials
What are the phases of pacemaker action potential - CORRECT ANSWER- 0 -
rapid depolarization
3 - repolarization
4 - slow depolarization
What happens during phase 0 of the pacemaker action potential - CORRECT
ANSWER- 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 - CORRECT
ANSWER- repolarization
Potassium channels now open up, potassium rushes out, repolarizes
2
, What happens during phase 4 of the pacemaker action potential - CORRECT
ANSWER- 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 - CORRECT
ANSWER- 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
If someone is hypoxic in a focal area - say they have a resting membrane potential
at -45 - the fast sodium channels won't open - they start using calcium to open - so
they would convert into action potentials that use calcium (hence how they mimic
pacemaker aps)
Excitation-contraction coupling - CORRECT ANSWER- sequence of events from
motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's
sarcomeres
Conversion of depolarizing currents into contractile force
L-type calcium channels open up in phase 2 in non pacemaker - calcium comes
flooding into myocytes, so we now have calcium in the cell and a sarcoplasmic
reticulum (a reservoir for calcium)
Receptors called RYR (lagans gated calcium channels)
Calcium then comes out - coming in the cell from the calcium channels and the
sarcoplasmic reticulum
Describe how calcium binds to cause contraction - CORRECT ANSWER- when
there is an influx of calcium in the cell there is a myosin head separated by
troponin. Little binding sites for the myosin exist on the aktin but it can't get to it
because of the troponin. Calcium therefore binds to the tropinin causing a
conformational change in troponin so it will move and take the tropomyosin with
it. The myosin can then bind to the aktin molecules when it binds it activates ATP
The ATP will be used to generate the sliding of the aktin and the myosin filaments
against each other shortening the muscle cell causing contraction
3
