L1. Calcium signalling in the heart

Question 1

Where does intracellular calcium primarily come from in cardiac myocytes?

Answer 1

From the sarcoplasmic reticulum

Question 2

What triggers calcium release from the sarcoplasmic reticulum?

Answer 2

Calcium influx through L-type calcium channels

Question 3

What is a calcium transient?

Answer 3

A rapid increase in intracellular calcium concentration following depolarization

Question 4

What is Fura-2?

Answer 4

A calcium indicator dye used for measuring intracellular calcium

Question 5

Why is confocal microscopy preferred for calcium imaging?

Answer 5

It provides superior spatial resolution by eliminating out-of-focus light

Question 6

What is the primary advantage of ratiometric dyes like Fura-2?

Answer 6

They reduce movement artifacts by measuring a ratio of emissions at two wavelengths

Question 7

What is a calcium spark?

Answer 7

A localized calcium release event from ryanodine receptors

Question 8

What differentiates a calcium spark from a calcium wave?

Answer 8

Sparks are localized, while waves propagate across the cell

Question 9

What causes a calcium wave?

Answer 9

High calcium load in the sarcoplasmic reticulum, increasing ryanodine receptor sensitivity

Question 10

How are calcium sparks synchronized during excitation-contraction coupling?

Answer 10

Almost all junctional coupling regions contribute, resulting in synchronized sparks

Question 11

What is the function of the Na+/Ca2+ exchanger?

Answer 11

To extrude calcium from the cell while importing sodium

Question 12

What is the function of SERCA in calcium signaling?

Answer 12

It pumps calcium back into the sarcoplasmic reticulum

Question 13

Why is calcium signaling slower in atrial myocytes compared to ventricular myocytes?

Answer 13

Because L-type calcium channels and ryanodine receptors are not closely coupled

Question 14

What structural difference affects calcium signaling in atrial myocytes?

Answer 14

Atrial myocytes lack T-tubules, having Z-tubules instead

Question 15

What happens to calcium transients during β1-adrenergic stimulation?

Answer 15

They increase in amplitude and speed

Question 16

What is the role of the calcium clock in sinoatrial node cells?

Answer 16

It contributes to rhythmic calcium release, driving the heartbeat

Question 17

What is the role of the membrane clock in sinoatrial node cells?

Answer 17

It involves ion channel activity driving action potential generation

Question 18

What effect does IP3 have on SAN cells?

Answer 18

It increases calcium spark frequency and action potential amplitude

Question 19

What is line scan confocal microscopy?

Answer 19

A method that captures calcium release events with high temporal resolution by scanning a single line

Question 20

Why is caffeine used in calcium signaling experiments?

Answer 20

To activate ryanodine receptors and release stored calcium from the sarcoplasmic reticulum

Question 21

What happens to calcium sparks when ryanodine receptors are blocked?

Answer 21

They are suppressed, indicating dependency on these receptors

Question 22

What are elementary calcium events?

Answer 22

Localized calcium release events such as calcium sparks

Question 23

How do IP3 receptors contribute to calcium signaling?

Answer 23

They facilitate calcium release near the nucleus and other subcellular locations

Question 24

Where are IP3 receptors localized in ventricular myocytes?

Answer 24

Primarily near the nucleus and intercalated discs

Question 25

What happens to calcium waves under normal conditions?

Answer 25

They are suppressed due to spatial separation of junctions

Question 26

What role does mitochondrial calcium play?

Answer 26

It regulates calcium homeostasis and will be discussed in subsequent lectures

Question 27

How does β-adrenergic stimulation affect calcium signaling?

Answer 27

It enhances calcium transients and increases force of contraction

Question 28

What is the significance of dyads in cardiac cells?

Answer 28

They are sites of close interaction between T-tubules and sarcoplasmic reticulum for efficient calcium signaling

Question 29

How does calcium signaling change in failing hearts?

Answer 29

IP3 receptor activity is increased, leading to prolonged action potentials

Question 30

What is the 'cluster bomb' effect in calcium signaling?

Answer 30

One L-type calcium channel can activate multiple ryanodine receptors

Question 31

What causes calcium release propagation as waves?

Answer 31

High sarcoplasmic reticulum calcium loads

Question 32

What is the role of HCN channels in SAN cells?

Answer 32

They contribute to pacemaker activity by generating depolarizing currents

Question 33

What is the function of the plasma membrane calcium ATPase (PMCA)?

Answer 33

To extrude calcium from the cell and maintain calcium homeostasis

Question 34

Why are single wavelength dyes used in calcium imaging?

Answer 34

To achieve higher temporal resolution for fast events like calcium sparks

Question 35

What experimental technique is used to study calcium dynamics in whole hearts?

Answer 35

Langendorff-perfused heart preparations

Question 36

How do atrial calcium transients differ at the edge versus the center of the cell?

Answer 36

Transients are faster and have higher amplitude at the edge

Question 37

What experimental evidence supports the presence of IP3 receptors in cardiac myocytes?

Answer 37

Calcium responses to IP3 in permeabilized myocytes

Question 38

What is a major difference in calcium signaling between ventricular and atrial myocytes?

Answer 38

Ventricular myocytes have tightly coupled T-tubules and sarcoplasmic reticulum

Question 39

How does IP3 affect calcium waves?

Answer 39

It increases frequency and amplitude of calcium waves

Question 40

What is the primary calcium channel involved in excitation-contraction coupling?

Answer 40

L-type calcium channel (LTCC)