Cardiovascular Physiology 15

Question 1

How does Excitation spread along the sarcolemma from cell to cell?

Answer 1

By gap junctions

Question 2

How does excitation spread to the interior of the myocyte?

Answer 2

By T-tubules

Question 3

What kind of channels do the T-tubules have?

Answer 3

L-type calcium channels

Question 4

When does the permeability of the myocyte to calcium increase?

Answer 4

During the plateau phase of the action potential

Question 5

Why is the permeability of the myocyte to calcium increased during the plateau phase?

Answer 5

Because calcium enters through L-type calcium channels in the sarcolemma and T-tubules and these open during that membrane potential

Question 6

What does the Calcium that enters from the T-tubules and Sarcolemma bind to?

Answer 6

Ryanodine receptors on the Sarcoplasmic reticulum

Question 7

What happens once calcium binds to ryanodine receptors on the sarcoplasmic reticulum?

Answer 7

Calcium exits the sarcoplasmic reticulum through channels and enters the cytoplasm of the cell

Question 8

What does the Calcium released by the SR do?

Answer 8

Binds to Troponin

Question 9

What happens once calcium binds to troponin?

Answer 9

Troponin unblocks actin allowing myosin to bind to it

Question 10

What blocks the cross-bridging of actin and myosin when there is low calcium in the cytoplasm?

Answer 10

Troponin

Question 11

How does excitation spread to the interior of a myocyte?

Answer 11

Through T-tubules

Question 12

What are L-type calcium channels regulated by?

Answer 12

Voltage

Question 13

Are L-type calcium channels modified DHP receptors or no?

Answer 13

Yes

Question 14

What does Troponin bind to?

Answer 14

The thin filaments

Question 15

What is the result of Calcium binding to Troponin?

Answer 15

Troponin undergoes a conformational change and frees the actin binding site allowing actin and myosin to undergo cross bridge cycling

Question 16

What is important to note about the connection between L-type calcium channels and Ryanodine receptors in Cardiac myocytes?

Answer 16

There is no physical coupling or physical connection between the L-type calcium channel ryanodine receptor are not physically connected