6.4 Cardiac action potentials Flashcards Preview

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Flashcards in 6.4 Cardiac action potentials Deck (14)
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1
Q

What regulates cardiac action potentials?

A

action potentials in the Intrinsic Conduction System (NOT the nervous system)

2
Q

What are funny channels, what do they do?

A

Unique to pacemaker cells. Na+ channels
-60mV to -50mV
open at -60mV

3
Q

How to cardiac pacemaker cells depolarize?

A
  • 50mV to -40 mV: T-type Ca2+ channels open, Ca2+ in

- 40 mV to 0: L-typle Ca2+ channels open, cell quickly depolarizes to 0

4
Q

How do cardiac pacemaker cells repolarize?

A

Ca2+ channels close, K+ channels open, back to -60mV, cycle restarts

5
Q

What is the resting potential for cardiomyocytes?

A

-90mV

6
Q

Describe cardiomyocyte depolarization

A

-90mV to +20mV INSTANTLY

Na+ channels open, Na+ IN

7
Q

What is the plateau phase?

A

+20mV to 0mV
Na+ inactivate
Ca2+ open, Ca2+ in
Creates a long refractory period to allow muscle time to respond to the AP, contract fully before next signal

8
Q

Describe cardiomyocite repolarization

A

0 to -90 mV
Ca2+ channels close
K+ open, K+ IN

9
Q

How do action potentials spread through heart muscle?

A

Action potentials will spread through cardiac muscle gap junctions and lead to contraction of cardiac muscle

10
Q

Within the heart muscle cell, what happens when an action potential is received?

A

myocardium,T-tubules depolarize
Ca2+ enters via extracellular Ca2+
Sarcoplasmic Reticulum releases Ca2+ into the sarcoplasm **”Calcium induced calcium release”
Ca2+ binds troponin, releases tropomyosin
CROSSBRIDGES form requiring ATP

11
Q

Why is a long refractory period important?

A

Protects against dysrhythmias

12
Q

In a supra ventricular dysthymia, what pacemaker cells are involved? What part of the heart?

A

SA, AV nodes

atria

13
Q

In a ventricular dysthymia, what pacemaker cells are involved? What part of the heart?

A

Bundle to His
Purkinje fibers
Ventricle

14
Q

What is a heart block?

A

conduction between the atria and ventricles is not functioning properly (atria and ventricles beat independently)