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Physiology Exam 2 > cardiac electrophysiology > Flashcards

Flashcards in cardiac electrophysiology Deck (23):
1

types of myocardial cells

pacemaker or non pacemaker

2

pacemaker cells

slow and automatic depolarizing to threshold- all or nothing. DO NOT stop at resting. Autorythmic at SA or AV node

3

non pacemaker cells

contration and force development. AP when stimulated.

4

pacemakers in the heart

SA node, AV node, His/Purkinje fibers

5

action potential for pacemaker cells

three phases: Phase 4 depolarization, depolarization/action potential, depolarization to rest

6

phase 4 depolarization

membrane potential hits threshold. First, decreased K outflow. Then funny current- slow NA in, then Ca influx- raise membrane potential

7

depolarization/action potential

hit threshold, voltage L type calcium channels open, shoot membrane potential up

8

repolarization to rest

voltage gated K open, repolarizing

9

how is HR modulated?

autonomic innervation of AV/SA nodes

10

parasympathetic

slow down HR. Vagus nerve releases acetylcholine. Slower K closing leads to hyper polarization. decreased funny leads to reduced phase 4 slope, decreased Ica influx leads to late threshold.

11

sympathetic

Increase rate and force of contraction. cardiac plexus releases norepinephrine to AV, SA , and myofibrils. Increased funny current in nodes, increased Ca influx in myocardial cells, more negative threshold. more ATPase activity in myocardium

12

non pacemaker cell AP

5 phages, including a plateau which allows time for filling. Resting potential at -90, requires signal.

13

refractory period in non pacemaker cells

effective/absolute: 0-3 phases, requires relaxation before refuel. no tetanus possible.

14

phases of non pacemaker AP

0- Na influx voltage gated
1- Na inactivation, K open- slight repolarization
2- plateau- increased Ca in with slow K outflow
3- repolarization, Ca closes and K out
4- resting potential

15

sequence of AP through heart

SA node> atrial muscle cell to cell (slow fibers, Atria contract) > AV node > AV junctional fibers (slow)> Fibers exit AV, enter ventricle at His> His divides down septum > bundle branches> perking fibers> myocardium

16

direction of repolarization

backwards

17

SA node

upper right atrium, 60-100

18

AV node

septum, 40-50 beats

19

his perkije fibers

conducting network in ventricles. 20-30 beats per min

20

normal HR for pacemaker potential

72 bpm

21

ionotropic effect

force of contraction- increased funny current in sympathetic.

22

chronotropic effect

heart rate- lower threshold sympathetic

23

what tissue in the heart has the slowest conduction velocity?

atrial junction with the AV node