5. Cardiac Ion Channels & Action Potentials Flashcards
The slow cardiac APs have a slow _____.
rising phase
Why is electrical activity important in the heart?
- generates repetitive firing in pacemaker cells 2. is a trigger for contraction
What are the 2 types of calcium channels called?
L-type or T-type
Fast cardiac APs arise from _____, _____, and _____.
in the myocardial cells (atrium and ventricle muscles) and in the conductive pathways, perkinge fibers
The slow cardiac APs arise from the ____ and ____.
SA node; AV node
How is the AV node regulated so it fires more slowly than the SA node?
these cells are triggered by the SA node APs, even though they could spontaneously fire
What is responsible for the rapid rising phase of fast APs?
the Na channel
How are the time-dependent cation current K channels evoked?
hyperpolarization
HERG produces ____.
I Kr
What channel is regulated by parasympathetic tone and, when activated, slows down the heart rate?
I kach (GIRK tetramer)
What potassium channel, when mutated, can predispose the pt to a prolonged QT?
I ks (KvLQT1 tetramer + mink), the slow delayed rectifier
What is the difference between the fast and slow APs?
the rising phase
Heart rate is controlled by ____ in the ____.
pacemaker cells; SA node
What is the deactivation process?
closing of the gate
What does the funny current do?
it causes sufficient depolarization to turn on the L-type Ca channels
What generates phase zero of the slow cardiac AP?
activation of the T-type Ca++ channels (I Ca-T) and some L-type Ca++ channels (I Ca-L)
Current flowing into the cell causes ___.
depolarization
What modulates the rate of SA node firing?
the ANS
The direction of propagation is controlled by gap junction position and by _____.
connective tissue insulation
What are ectopic pacemakers?
any cell that is spontaneously starting the heartbeat, other than the SA node
What is the Nernst Potential of Ca?
+124
What are the time-dependent cation current K channels?
If or Ih
Propagation of the AP occurs within the ____ and via ____.
myocardium; specialized conduction pathways
What are the the time-dependent cation current channels permeable to?
K and Na