Lecture 1D-electrophys

Question 1

Trace the electrical current from SA node–>Purkinje Fibers

Answer 1

SA node–>Internodal Tracks/Interatrial tracts–>AV node–>bundle of HIS (AV bindle)–>R/L His/Bundle branches–>Purkinje fibers

Question 2

What does the APPEARANCE of the cardiac action potential depend on?

Answer 2

WHERE it is measured

Question 3

What are the two types of cardiac action potentials?

Answer 3

1.Non-Pacemaker/Fast 2.Pacemaker/Slow

Question 4

Where do the non-pacemaker/fast A.P.s begin?

Answer 4

Atria & Purkinje fibers

Question 5

Where do the pacemaker/slow APs begin?

Answer 5

SA node and AV node

Question 6

What is happening in Phase 0 of fast response cardiac AP?

Answer 6

Na+ cannels open (normal AP)…Depolarization

Question 7

What is happening in Phase 1 of fast response cardiac AP?

Answer 7

Initial Repolarization, K+ channels open/Na+ channels close (normal)

Question 8

What is happening in phase 2 of fast response cardiac AP?

Answer 8

BOOM Plateau phase..ECM Ca2+ comes rushing in! (K+ still effluxing too)

Question 9

What is the REAL purpose of the ECM Ca2+ rush in?

Answer 9

CICR!!! Calcium-Induced Calcium Release

Question 10

What are the receptors that control the Ca2+ release from the sarcoplasmic reticulum?

Answer 10

Ryan-o-dine Receptors (binds the NTs/hormones/Ca2+)

Question 11

What is happening in phase 3 fast response cardiac ap?

Answer 11

Normal Repolarization: K+ efflux (Ca2+ channels eventually close)

Question 12

What is happening in phase 4 of fast response cardiac ap?

Answer 12

K+ remain open, Ca2+ extrusion mechanisms remain open

Question 13

What are the three ways we can move Ca2+ out of the muscle fibers? (to relax)

Answer 13

1. SarcoplasmicReticulum Ca2+ pumps (back into SER) 2.Sarcolemmal Pumps (out of cell) 3.NCX (sodium calcium exchangers)

Question 14

What is the main job of the refractory period?

Answer 14

To prevent tetanus of the heart!

Question 15

What are the two refractory periods for fast response AP?

Answer 15

1. Effective/Absolute=NO CHANCE IN HELL for another AP 2.Relative= eh, maybe another AP if its strong enough..

Question 16

What is happening in Phase 0 of slow response cardiac ap? BIG POINT HERE

Answer 16

Ca2+ conductance (NOT Na+ LIKE EVERY OTHER CELL!!!)

Question 17

What is happening in phase 3 of slow response cardiac action pot?

Answer 17

Normal Repolarization…(K+ efflux)

Question 18

What is happening in phase 4 of slow response cardiac ap?

Answer 18

*the magic step…Na+ slowly coming in, called the “funny” inward current :)

Question 19

What is the heart rate determined by?

Answer 19

of times SA node discharges

Question 20

What reflects the time required for excitation to spread throughout cardiac tissue?

Answer 20

Conduction Velocity

Question 21

When is CV the fastest? Slowest?

Answer 21

Fastest: Purkinje System…Slowest:AV node

Question 22

What is a negative Chronotropic Effect?

Answer 22

SA Node firing rate DOWN…Slower then normal HR, bradycardia

Question 23

What is a positive Chronotropic effect?

Answer 23

SA Node firing rate UP…Faster then normal HR, tachicardia

Question 24

What are changes in CV in the AV node?

Answer 24

DromoTropic effects

Question 25

What are changes in CV in the SA node?

Answer 25

Chronotropic effects

Question 26

What structures have Parasympathetic innervation? What do not?

Answer 26

Atria, SA and AV nodes...NO VENTRICALS

Question 27

What is the NT for Parasym? What are the receptors?

Answer 27

Ach...Muscarinic Receptors

Question 28

What structures have sympathetic innervation?

Answer 28

SA node, AV node, atria, AND VENTRICALS

Question 29

What is the NT for Sympatheic? Receptors?

Answer 29

NorEpinephrine and Beta1-receptors

Question 30

Which slow response cardiac ap does parasym control?

Answer 30

Phase 4- depolarization (Ifunny) (Na+ influx)

Question 31

Which slow response cardiac ap does symp control?

Answer 31

Phase 4- depolarization (Ifunny) (Na+ influx)