Electrical Activity of the Heart - Quiz 2

Question 1

The oustide of the cell is _______ charged relative to the inside of the cell which is _______ charged.

Answer 1

Positively, Negatively

Question 2

Is concentration of Potassium higher inside or outside the cell

Answer 2

Inside

Question 3

Is sodium concentration higher inside or outside the cell?

Answer 3

Outside

Question 4

What stops potassium from leaking out of cell when concentration K⁺ is the same inside and outside?

Answer 4

Electrostatic force - the negativity inside the cell

Question 5

What does the Nernst Equation calculate?

Answer 5

Equilibrium Potential

Chemical Force = Electrostatic Force
(Of Potassium)

Question 6

Goldman Equation

Answer 6

Membrane Potential when Na, K, and Cl are involved

Question 7

What ion contributes the most to the resting membrane potential of the cardiac cell?

Answer 7

Potassium

Question 8

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

Answer 8

Sodium

Question 9

The ion pump that returns ion concentrations back to baseline in resting membrane potential?

Answer 9

Na+, K+ ATPase

Question 10

Sodium/Potassium-ATP Pump

Answer 10

• Steady inward leak of Na+ would depolarize cell
• Metabolic pump, pumps out Na from cell and pumps in K+
• Pumps OUT 3 Na+ and Pumps IN 2 K+
• Electrogenic Pump
• Partially inhibited by digitalis

Question 11

What ion moves rapidly into a cell during depolarization?

Answer 11

Sodium

Question 12

How is the baseline electrical charge restored during cell repolarization?

Answer 12

Potassium channels open and rapid diffusion of potassium to exterior reestablishes normal resting membrane potential

Question 13

Where are the Fast-Response Action Potentials located?

Answer 13

Atrial Myocardial Fibers

Ventricular Myocardial Fibers

Purkinje Fibers

Question 14

Where are the Slow-Response Action Potentials?

Answer 14

SA & AV Node

Question 15

Differences between Fast and Slow Cardiac Action Potentials

Answer 15

• Resting Membrane Potential: Slow > Fast
• Slope of Upstroke: Fast > Slow
• Amplitude of Action Potential: Fast > Slow
• Overshoot of Action Potential: Fast > Slow

Question 16

Phases of Fast Response Action Potential

Answer 16

Phase 0: Depolarization

Phase 1: Partial Repolarization

Phase 2: Plateau

Phase 3: Repolarization

Phase 4 Resting Membrane Potential

Question 17

Phase 0 (Fast Response)

Answer 17

Depolarization - fast sodium channels open - rapid influx of sodium (+20 mv)

Question 18

Phase 1 (Fast Response)

Answer 18

Initial Repolarization - fast sodium channels close - potassium leaves cell through open potassium channels

Question 19

Phase 2 (Fast Response)

Answer 19

Plateau - L-type calcium channels open. Ca+ entering is equal to K+ leaving

Question 20

This entry of this small amount of ion into the cell triggers release of a large amount of calcium into the sarco plasmic reticulum.

Answer 20

Calcium through the L-type calcium channels

Question 21

What happens when a large amount of calcium leave the sarcoplasic reticulum

Answer 21

Calcium binds with Troponin-C

Myosin binds to actin and contraction of the myocyte

Question 22

Which ion is the major determinant of the Resting Membrane Potential?

Answer 22

Potassium

Question 23

Phase 3 (Fast Response)

Answer 23

Rapid Repolarization - calcium channels close and potassium channels open.

Potassium exits cell, ending plateau phase and returns cell membrane to resting level.

Question 24

Phase 4 (Fast Response)

Answer 24

Restoration of Ionic Concentrations

• Na⁺, K⁺-ATPase
• Na⁺-Ca⁺⁺ Exchanger
• ATP-driven Ca⁺⁺ Pump

Question 25

Phases of Slow Response (Pacemaker) Action Potential

Answer 25

Phase 4: Cations from adjacent cell Phase 0: Calcium Influx Phase 2: very brief plateau phase Phase 3: Repolarization: Ca+ channels close and Lots of K+ leaves

Question 26

Effective Refractory Period

Answer 26

Absolute Refractory Period - impossible for another action potential to triggered

Question 27

Relative Refractory Period

Answer 27

Period where an action potential can be triggered if the stimulus is large/strong enough

Question 28

Automaticity

Answer 28

Ablity of a focal area of the heart to generate pacemaking stimuli

Question 29

What is the heart's dominate pacemaker

Answer 29

SA Node

Question 30

Where does the depolarization wave flow from the SA node?

Answer 30

In all directions

Question 31

Diastolic Depolarization

Answer 31

* Inward Na⁺ - via funny sodium channels * Ca⁺⁺ Influx * K⁺ Efflux

Question 32

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

Answer 32

Neurotransmitters Norepi, acetylcholine, succinylcholine, T1-T4 cardiac accelerators

Question 33

Overdrive Supression

Answer 33

Sinus node controls beat of heart because its discharge is faster than any other part of the heart. Automaticity of pacemaker cells become depressed after a high frequency of excitation * Due to Na⁺, K⁺-ATPase * More Na⁺ is forced out than K⁺ entering at higher heart rates - hyperpolarize * Slow diastolic depolarization needs more time to reach threshold

Question 34

What is a sarcomere?

Answer 34

Structural unit of striated muscle tissue between two Z-lines

Question 35

The name of the branching network that cardiac cells are arranged in

Answer 35

Intercalated Discs

Question 36

T-Tubules

Answer 36

Extensions of cell membrane that penetrate into the center of skeletal and cardiac muscle cells * Open to exterior of muscle fiber - can communicate with fluid surrounding muscle fiber

Question 37

Sarcoplasmic Reticulum

Answer 37

Membrane bound structure in muscle cells that store and regulate calcium movement

Question 38

What is the process called when large amounts of calcium are released form the Sarcoplasmic Reticulum into the cell?

Answer 38

Calcium-Induced Calcium Release (CICR)

Question 39

What ion allows binding between actin and myosin?

Answer 39

Calcium

Question 40

Function of Troponin

Answer 40

Inhibit Actin and Myosin From Binding 1. Calcium binds to Troponin C - conformational change 2. Myosin heads bind to actin leading to cross-bridge movement and shortens sarcomere 3. Calcium goes back to SR 4. Calcium is removed from Troponin-C and myosin unbinds from actin

Question 41

Function of ATP in the heart

Answer 41

ATP needed for crossbridge movement, muscle shortening (contraction), and muscle relaxation

Question 42

Excitation Contraction Coupling

Answer 42

Coupling between myocyte actional potentials and contraction

Question 43

Sliding Filament Model

Answer 43

Mechanism of muscle contraction Myosin (thick) filaments slide past actin (thin) filaments during muscle contraction