CV Quiz 2

Question 1

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

Answer 1

• Increases HR:
  
  • SNS stimulation
  • Muscarinic receptor antagonist
  • B-adrenoreceptor agonist
  • Circulating catecholamines
  • Hypokalemia
  • Hyperthyroidism
  • Hyperthermia
• Decreases HR:
  
  • PNS stimulation
  • Muscarinic receptor agonists
  • B-blockers
  • Ischemia/hypoxia
  • Hyperkalemia
  • Na/Ca channel blockers
  • Hypothermia

Question 2

What does the Nernst Equation calculate?

Answer 2

Equilibrium potential- electrical potential needed to keep an ion from diffusing down its chemical gradient thereby changing its concentration across membrane

Question 3

What are T-tubules in a cardiac muscle cell?

Answer 3

Deep invaginations of the external sarcolemma that permits intra/extra-cellular ion exchange deep within myocyte during de/re-polarization

Question 4

What are the various phases found in Pacemaker (Slow Response) Action Potentials? Which ions contribute to the various phases?

Answer 4

• Phase 0 (Upstroke of AP)
  
  • Ca influx
• Phase 3 (Repolarization)
  
  • K efflux
• Phase 4 (Spontaneous depolarization)
  
  • Na and Ca influx
  • K efflux

Question 5

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

Answer 5

SA and AV node

Question 6

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

Answer 6

Pumps 3 Na out and 2 potassium into cell, maintaining their concentration gradients across the membrane

Question 7

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

Answer 7

Functional syncytium

Question 8

What is a sarcomere?

Answer 8

Contractile unit of the myocyte

Question 9

Which pacemaker region of the heart is typically dominant?

Answer 9

SA node

Question 10

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

Answer 10

Regulate intracellular Ca

Question 11

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

Answer 11

K

Question 12

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

Answer 12

Potassium

Question 13

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

Answer 13

Small amount of calcium

Question 14

What is the Sarcoplasmic Reticulum?

Answer 14

Branching, tubular network that surrounds myofilaments that regulates intracellular Ca concentration

Question 15

What ion pump returns ion concentrations back to baseline?

Answer 15

Na, K-ATPase Pump

Question 16

Is ATP required for cardiac muscle relaxation?

Answer 16

Yes

Question 17

What is automaticity?

Answer 17

The ability of a focal area of the heart to generate pacemaking stimuli

Question 18

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

Answer 18

Plateau

Question 19

Is the inside of a cell postive or negative?

Answer 19

Negative

Question 20

What are the 5 phases of the Non-pacemaker (Fast-Response) action potential? Which ions contribute to the various phases?

Answer 20

• Phase 0 = Depolarization
  
  • Na Influx
• Phase 1 = Partial repolarization
  
  • Na Stops, K efflux
• Phase 2 = Plateau
  
  • Ca influx (L-type Ca channels), K efflux
• Phase 3 - Repolarization
  
  • K efflux
• Phase 4 = Resting membrane potential
  
  • Ratio of intra- to extra-cellular K

Question 21

What is the Sliding Filament Model?

Answer 21

1. Ca binds TN-C
2. Cross-bridge formation between actin and myosin
3. ATP hydrolysis
4. Thin filaments slide over myosin during cross-bridge cycling
5. Sarcomere shortens
6. Muscle contraction occurs

Question 22

What is diastolic depolarization? What ions are associated with it?

Answer 22

Ionic mechanisms for initiating spontaneous depolarization in a pace-making cell

• Na/Ca influx
• K efflux

Question 23

What is Overdrive Suppression?

Answer 23

Automaticity of pacemaker cells becomes depressed after a period of excitation at a high frequency

Question 24

What restores ion concentrations back to their baseline levels?

Answer 24

Na, K-ATPase pump

Na/Ca Exchanger

ATP-driven Ca pump

Question 25

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

Answer 25

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 26

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

Answer 26

Ca binds to troponin to initiate a cross-bridge formation between Myosin and Actin

Question 27

What ion makes a small contribution to RMP?

Answer 27

Na

Question 28

What ion moves rapidly into a cell during depolarization?

Answer 28

Na

Question 29

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

Answer 29

Outside

Question 30

What is Excitation-Contraction coupling?

Answer 30

When AP causes depolarization of a myocyte

Question 31

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

Answer 31

* Atrial and ventricular myocardial fibers * Purkinje fibers

Question 32

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

Answer 32

Potassium

Question 33

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

Answer 33

Inside

Question 34

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

Answer 34

Ca

Question 35

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

Answer 35

Calcium-induced Calcium Release (CICR)

Question 36

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

Answer 36

1. Absolute (effective) refractory period * No new AP can be generated 2. Relative refractory period * Very strong stimulus needed to cause AP

Question 37

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

Answer 37

* Resting membrane potential- Slow \> fast * Slope of upstroke- Fast \> slow * Amplitude of action potential- Fast \> slow * Overshoot of action potential- Fast \> slow

Question 38

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

Answer 38

Ca