Muscle 12

Question 1

What is different about the TnC in cardiac muscle?

Answer 1

It has a single low affinity calcium binding site rather than two low affinity and two high affinity binding sites like in skeletal muscle

Question 2

What kind of Calcium are Cardiac Myocytes completely dependant on for contraction?

Answer 2

Extracellular calcium

Question 3

What is extracellular calcium the signal for in Myocytes?

Answer 3

It is the signal to cause the release of more calcium from the sarcoplasmic reticulum

Question 4

What happens if the extracellular calcium conc. is 0 in cardiac myocytes?

Answer 4

They will not contract

Question 5

Why is Skeletal muscle not dependant on extracellular calcium?

Answer 5

Foot processes link the L-type calcium channel or the DHP receptor in the T-tubule membrane to the Ryanodine receptor (calcium release channel) in the sarcoplasmic reticulum

Question 6

What does the L-type calcium channel sense in skeletal muscle?

Answer 6

Voltage

Question 7

What physical interaction is found in skeletal muscle contraction?

Answer 7

excitation contraction couple requires the L-type calcium channel or DHP receptor to be physically linked with the Ryanodine receptor in the sarcoplasmic reticulum

Question 8

What does the entrance of calcium through L-type skeletal muscle cause in skeletal muscle?

Answer 8

It did NOT cause the release a calcium from the sarcoplasmic reticulum

Question 9

What is absolutely necessary in L-type channels in Cardiac muscle contraction?

Answer 9

Calcium influx through L-type channels

Question 10

Where are L-type channels found?

Answer 10

In the membrane of the T-tubule

Question 11

What is the difference in calcium concentration between the inside and the outside of the cardiac myocytes at rest?

Answer 11

Calcium concentrations outside the myocyte are much larger than calcium concentrations inside the myocyte

Question 12

What do the L-type calcium channels or DHP receptors open in response to in cardiac muscle?

Answer 12

They open in response to change in membrane potential in the T-tubule

Question 13

What is the Isoform of Ryanodine receptors in cardiac muscle cells?

Answer 13

The Ryanodine receptors are RyR2 isoform

Question 14

What is release of calcium by the SR in cardiac muscle initiated by?

Answer 14

Calcium entry through the L-type voltage gated channels or DHP receptors

Question 15

What is the dyad in cardiac muscle composed of?

Answer 15

The Sarcoplasmic reticulum terminal cisternae and the transverse T tubule

Question 16

How does current spread from cell to cell in cardiac muscle?

Answer 16

Through the gap junctions travelling along the plasma membranes

Question 17

What happens once an action potential is spread through gap junctions in the cardiac muscle cell?

Answer 17

The action potential is propagated through the T-tubules

Question 18

What happens once an action potential is propagated through the t-tubules in cardiac muscle cells?

Answer 18

The L-type calcium channels in the T tubules open and calcium enter the myocyte

Question 19

What is the L-type calcium channels in close proximity to in cardiac muscle cells?

Answer 19

The Cardiac Ryanodine receptors of the sarcoplasmic reticulum

Question 20

What does calcium do once it is released by the L-type calcium channels in Cardiac muscle cell?

Answer 20

Binds to the Ryanodine receptors in the membrane of the sarcoplasmic reticulum causing calcium to be released from the sarcoplasmic reticulum into the cytoplasm

Question 21

What causes the release of calcium from the endoplasmic reticulum in the cardiac myocytes?

Answer 21

The entry of calcium through the L-type calcium channel binding to the Ryanodine receptors on the sarcoplasmic reticulum

Question 22

What is the release of calcium from the sarcoplasmic reticulum in cardiac muscle cells known as?

Answer 22

Calcium induced calcium release

Question 23

What removes calcium from the cytoplasm of cardiac myocytes?

Answer 23

• Sodium calcium exchanger in the plasma membrane NCX (10%)

* SERCA2A (90%)

Question 24

What is SERCA 2A? And what is its role in Cardiac muscle cells?

Answer 24

It is a calcium ATPase or calcium pump that pumps calcium back into the sarcoplasmic reticulum from the cytoplasm

Question 25

What is the primary regulator of SERCA 2A?

Answer 25

Phospholamban (cAMP)