Rush Advanced Pharmacology NSG 531 Exam 3 With Correct Answers Latest.
what is the difference between cardiac myocyte action potential and that of the
... [Show More] CNS or
ANS? - ANSWER 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? - ANSWER 0 -
depolarization
1 - partial repolarization
2 - plateau
3 - repolarization
4 - resting membrane potential
what happens during phase 0 of the non-pacemaker action potential - 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 - ANSWER partial
repolarization
Rush Advanced Pharmacology NSG 531
Exam 3 With Correct Answers Latest
what happens during phase 2 of the non-pacemaker action potential - 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 - ANSWER
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 - ANSWER resting
membrane potential where we are in between action potentials there is no net change in
ovltage inside the cell
When does contraction take place? - ANSWER begins towards the end of repolarization
and ends at some point during repolarization
refractory period - ANSWER 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 - ANSWER limits frequency of cardiac
contractions
allows for adequate filling time
prevents sustained contractions
how are pacemaker cells different from non-pacemaker cell - 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 - ANSWER 0 - rapid depolarization
3 - repolarization
4 - slow depolarization
what happens during phase 0 of the pacemaker action potential - 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 - ANSWER repolarization
potassium channels now open up, potassium rushes out, repolarizes
what happens during phase 4 of the pacemaker action potential - 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 pacemkaer APs - 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 wont 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 - 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 nonpacemaker - calcium comes flooding
into myocytes, so we now have calcium in the cell and a sarcoplasmic recticulum (a
resovior for calcium)
receptors called RYR (ligand gated calcium channels)
calcium then comes out - coming int the cell from the calcium channels and the
sarcoplasmic recticulum. [Show Less]