CV - Quiz 2 resting membrane potentials, electrical activity of heart, excitation-contrtaction coupling

Question 1

Relative to the outside of a cell is the inside positive or negative in charge?

Answer 1

-Negative

Question 2

Is potassium higher in concentration inside or outside of a cardiac muscle cell?

Answer 2

-Potassium is higher inside the cell

Question 3

Is sodium higher in concentration inside or outside of a cell?

Answer 3

-Sodium concentration is higher outside the cell.

Question 4

What prevents potassium from leaking out of a cell until the concentration is the same on the outside and inside of the cell?

Answer 4

-As the K+ leaves cell, negativity increases on the inside of the cell membrane and electrostatically attracts K+. This electrostatic force prevents K+ from leaving cell.

Question 5

What does the Nernst Equation calculate?

Answer 5

-When chemical driving force (-) electrostatic driving force, NO net movement of K+ = equilibrium.

Question 6

What ion makes the major contribution to the resting membrane of the cardiac muscle cell?

Answer 6

-Potassium is the major determinant of the Resting Membrane Potential.

Question 7

What ion makes a small contribution to the resting membrane potential?

Answer 7

-Sodium

Question 8

What ion pump returns ion concentrations back to baseline?

Answer 8

-The Na+-K+-ATPase Pump

Question 9

How does the Na+-K+ - ATPase pump contribute to the resting membrane potential?

Answer 9

-For every 3 Na+ going OUT of the cell 2 K+ would be going INTO the cell.

Question 10

What ion moves rapidly into a cell during depolarization?

Answer 10

• Na+

Question 11

What ion exits the cell to restore the baseline electrical charge in a cell during repolarization?

Answer 11

• +K

Question 12

What restores ion concentrations back to their baseline levels?

Answer 12

• Na+-K+- ATPase Pump

Question 13

In what part of the heart are Fast-Response Action Potentials (non-pacemaker action potentials) found?

Answer 13

• Atrial myocardial fibers, Ventricular myocardial fibers, Purkinje fibers

Question 14

In what part of the heart are Slow-Response Action Potentials (pacemaker action potentials) typically found?

Answer 14

• Sinoatrial node and atioventricular node

Question 15

What are some of the differences between Non-pacemaker and Pacemaker action potentials?

Answer 15

• (Fast response = non-pacemaker) and (Slow-response = pacemaker)
• RMP = Slow > Fast; Slope of upstroke = Fast > Slow; Amplitude of action potential = Fast >Slow; Overshoot of action potential = Fast > Slow

Question 16

What are the 5 phases of the Non-pacemaker (Fast-Response) action potential?

Answer 16

• Phase 0 = Depolarization
• Phase 1 = Partial Repolarization
• Phase 2 = Plateau
• Phase 3 = Repolarizaiton
• Phase 4 = Resting Membrane Potential

Question 17

Which ions contribute to the various phases?

Answer 17

• Phase 0 = Na+
  -Phase 1 = Inactivation of Na+ channels ends transient outward K+ current
  -Phase 2 = Slow inward Ca++ currents ( L-type calcium channels) Outward K+ currents.
  -Phase 3 = Outward K+ (repolarization) Na+ channel recovery begins during relative refractory period.
  -Phase 4 = Na+, K+-ATPase Na+-Ca++ exchanger
  ATP-driven Ca++ Pump

Question 18

What is another name for Phase 2 in a Non-pacemaker cell?

Answer 18

• Plateau

Question 19

Release of a large amount of calcium from the Sarcoplasmic Reticulum is triggered by entry of which ion?

Answer 19

small amounts of Calcium

Question 20

What is the function of the Sarcoplasmic Reticulum within a cardiac muscle cell?

Answer 20

regulate intracellular calcium concentration

Question 21

Which ion is the major determinant of the Resting Membrane Potential in Cardiac cells?

Answer 21

Potassium

Question 22

What are the various phases found in Pacemaker (Slow Response) Action Potentials?

Answer 22

0,(no phase 1), 2 (very brief),3,4

Question 23

Which ions contribute to the various phases in the Pacemaker Action Potential?

Answer 23

Zero - calcium influx
Three - Potassium influx (repolarized), low Ca
Four - Na, lower K+ and elevated Ca

Question 24

What are the different refractory periods associated with the cardiac action potentials?

Answer 24

• Effective or Absolute (ERP) - no action potential can happen
• Relative (RRP)

Question 25

What is automaticity?

Answer 25

Ability of focal area of heart to generate pacemaking stimuli

Question 26

What is diastolic depolarization?

Answer 26

slow iinward leakage of Na+ through funny channels, Ca++ influx, K+ efflux

Question 27

What effects on aspects of diastolic depolarization will cause changes in heart rate?

Answer 27

``` -Increasing sympathetic stimulation Muscarinic receptor antagonist B-Adrenoceptor agonists Circulating catecholamines Hypokalemia Hyperthyrodism Hyperthermia -Decreasing Parasympathetic stimulation Muscarinic receptor agonists B-blockers Ischemia/hypoxia Hyperkalemia Sodium and calcium channel blocker Hypothermia ```

Question 28

Which pacemaker region of the heart is typically dominant?

Answer 28

SA node

Question 29

What is Overdrive Suppression?

Answer 29

2ndary pacemeakers are hyperpolarized when driven beyond their set rate

Question 30

What is a sarcomere?

Answer 30

the basic contractile unit of myocite, between two Z-lines

Question 31

Cardiac cells are arranged in a branching network that is known as what?

Answer 31

functional syncytium

Question 32

What are T-tubules in a cardiac muscle cell?

Answer 32

openings from sarcolemma that run deep. Let ions (Na+, Ca++) exchange between extra and intracellular compartments

Question 33

What is the Sarcoplasmic Reticulum?

Answer 33

extensive branching tubular netwrok to regulate intracellular calcium, storage and realease of calcium

Question 34

What is Excitation-Contraction coupling? pg 43 in book

Answer 34

coupling between myocyte action potentials and contraction

Question 35

What is the trigger for release of large amounts of calcium from the Sarcoplasmic Reticulum?

Answer 35

small amounts of calcium influx causes release of large amount of calcium from sarcoplasmic reticulum

Question 36

What is this process called whereby large amounts of calcium are released from the Sarcoplasmic Reticulum into the cell?

Answer 36

Calcium-Induced Calcium Release

Question 37

The presence of what ion allows binding between actin and myosin?

Answer 37

Calcium

Question 38

What is the function of Troponin in the binding between actin and myosin?

Answer 38

To inhibit actin and myosin from binding

Question 39

What is the Sliding Filament Model ?

Answer 39

ratcheting of myosin heads along the actin filaments

Question 40

Is ATP required for cardiac muscle relaxation?

Answer 40

Yes