Lecture 4 - Contraction

Question 1

What does arrival of an electrical signal to a cell cause?

Answer 1

Depolarisation

Question 2

What is the first channel to open during cardiac muscle cell depolarisation?

Answer 2

L type calcium channels (LTCC) - allowing calcium to enter

Question 3

What happens after calcium enters the cell from LTCCs during depolarisation?

Answer 3

Calcium binds to RyR which is attached to SR (calcium store). This initial binding of calcium activates the RyR, initiating further release of calcium

Question 4

What does calcium induced calcium release (CICR) refer to?

Answer 4

Although a small amount of calcium enters the cell, it can produce a large response as the calcium then goes onto to release more calcium - calcium induced calcium release.

Question 5

How much does Ca2+ concentration rise due to CICR?

Answer 5

Ca2+ concentration rises 10+ fold
Extracellular: 2 mM,
Cytosol: 0.1–1 μM
SR: 1 mM

LTCC: 25% of Ca2+
RyR2 - SR: 75% of Ca2+

Question 6

In cardiac muscle depolarisation causes:
A. Direct opening of Ca2+-release channels (RyR2) on SR
B. Ca2+-induced Ca2+ release
C. Increase in intracellular Ca2+ from 1 mM to 10 mM
D. Opens the funny Na+ channels

Answer 6

B. Ca2+-induced Ca2+ release