Lecture 5

Question 1

Resting Heart Rate (Healthy Adult)?

Answer 1

70 bpm

Question 2

Resting Heart Rate (Athlete)?

Answer 2

50 bpm

Question 3

Resting Heart Rate (Newborn)?

Answer 3

135 bpm

Question 4

Heart Rate Range?

Answer 4

20-250 bpm

Question 5

ECG?

Answer 5

Measure when it contracts and relaxes and it has 12 leads

Question 6

Factors affecting current flow?

Answer 6

1) Number of Cell-Cell Gap Junctions
2) Cell Diameter
3) Cell Alignment

Question 7

Gap Junctions are made out of?

Answer 7

Connexons

Question 8

Phase 0?

Answer 8

“Depolarization Phase”
-Activation of “fast” voltage-gated Na and Ca channels
(Inward Na flux and Ca flux)

Question 9

Phase 1?

Answer 9

“Early Depolarization Phase”
-Activation of a “transient outward” voltage-gated K channels
(outward K flux) Inaction of Na channels

Question 10

Phase 2?

Answer 10

“Plateau Phase” (because not repolarizing or depolarizing)
-Activation of voltage-gated Ca channels, Activation of “delayed rectifier” K channels (Inward Ca flux and outward K flux counteract each other)

Question 11

Phase 3?

Answer 11

“Final Depolarization Phase”
-Inactivation of voltage-gated Ca current, Activation of delayed rectifier K channels, And inward rectifier K channels
(outward K flux)

Question 12

Phase 4?

Answer 12

“Diastolic “Resting” Potential”
-Activated inward rectifier K channels
(outward K flux)

Question 13

Different ion channels?

Answer 13

Na+, Ca2+, and K+

Question 14

Depolarizing?

Answer 14

Inward Na+ and Ca2+ currents

Question 15

Depolarizing/Hyper?

Answer 15

Outward K+ currents

Question 16

Effective Refractory Period?

Answer 16

(ERP) Cell cannot fire another action potential

Question 17

Relative Refractory Period?

Answer 17

(RRP) Cell can fire another action potential, but amplitude is reduced

Question 18

ERP and RRP are caused by?

Answer 18

Inactivation state of voltage-gated Na and/or Ca channels

Question 19

Automaticity?

Answer 19

Initiates Heart Beat

Question 20

Rhythmicity?

Answer 20

Regular Pacemaking Activity

Question 21

Dominant Pacemaker?

Answer 21

SA Node (with SA Node dysfunction, AV Node can become dominant pacemaker)

Question 22

Resting Heart Rate is Reduced by?

Answer 22

Basal Parasympathetic Tone

Question 23

Exercise reduces?

Answer 23

Parasympathetic tone increase Sympathetic tone

Question 24

Duration of the Cardiac AP is significantly longer than the?

Answer 24

Neuronal AP

Question 25

Cardiac AP being longer results in?

Answer 25

An extended refractory period that provides sufficient time for Heart chambers to fill with blood before depolarizing AP wave comes along

Question 26

Pacemaker cells?

Answer 26

-Slower rising phase in Phase 0
-No early repolarization Phase 1
-No plateau phase Phase 2
-Presence of a slowly depolarizing “pacemaker” potential during Phase 4
-Phase 4 (“resting potential”) is more depolarized in pacemaker cells

Question 26

Pacemaker cells?

Answer 26

-Slower rising phase in Phase 0
-No early repolarization Phase 1
-No plateau phase Phase 2
-Presence of a slowly depolarizing “pacemaker” potential during Phase 4
-Phase 4 (“resting potential”) is more depolarized in pacemaker cells

Question 27

“Funny” Channel is responsible for?

Answer 27

Automaticity (all pacemaker cells express the “funny” channel)

Question 28

(“Slow” Pacemaker AP)
Phase 0?

Answer 28

-No Na+ inward
-Calcium current
-Voltage-dependent Ca channel (slower because Ca2+ slower than Na+)

Question 29

(“Slow” Pacemaker AP)
Phase 3?

Answer 29

-Potassium current
-Voltage-dependent K channel
-Ca+ closed

Question 30

(“Slow” Pacemaker AP)
Phase 4?

Answer 30

-Involves Na+ channel
-“Funny” pacemaker current
-Cyclic-nucleotide gated Na channel
-Necessary for automaticity (because activated by hyperpolarization, increased Na+ slow depolarization of Phase 4)

Question 31

SA Node Cell?

Answer 31

Membrane potential for triggering all-or-nothing AP

Question 32

Altering automaticity and firing frequency (HR)?

Answer 32

1) Change slope of Phase 4 (increased time of depolarization)
2) Hyperpolarization during Phase 4 (increased time to depolarize)
3) A change in threshold for firing

Question 33

Parasympathetic?

Answer 33

Rest and Digest

Question 34

Sympathetic?

Answer 34

Fight or Flight

Question 35

Heart is innervated by?

Answer 35

-Both parasympathetic and sympathetic nerves (mainly myocardial regions)

Question 36

Innervation of nodal regions are?

Answer 36

Predominantly, but not exclusively, parasympathetic