Excitation-Contraction

Question 1

a left BBB causes a ____ widening

Answer 1

a QRS widening. Decreases efficiency of contraction.

Question 2

___ is in high concentration inside the cell and ___ predominates outside the cell.

Answer 2

K+ is in high concentration inside the cell and Na+ predominates outside the cell.

Question 3

an impulse is created when Na+ rushes into the cell along with Ca2+ into the ___ tubules. This Ca2+ binds onto ___ receptors inside the ___ ___ and causes Calcium induced calcium release into the cell. This excess calcium binds to ___ which moves ____ off the myosin head and allows for cardiac contraction.

Answer 3

an impulse is created when Na+ rushes into the cell along with Ca2+ into the TRANSVERSE tubules. This Ca2+ binds onto RYANODINE receptors inside the SARCOPLASMIC RETICULUM and causes Calcium induced calcium release into the cell. This excess calcium binds to TROPONIN which moves TROPOMYOSIN off the myosin head and allows for cardiac contraction.

Question 4

a sudden increase in ___ concentraion inside the cell causes myocardial contraction. What pumps it all out?

Answer 4

increase in Ca2+. must pump it back out for relaxation. two ways:

1. intracellular channel pump
2. serca pump back into sarcoplasmic reticulum.

Question 5

Why is it that In energy depleted states (Ischemia) the
myocardium is stiffened?

Answer 5

O2 isrequired to generate ATP via ETC. SERCA and Myosin head binds new ATP. tehrefore, if tehre’s not enough ATP, SERCA will not pump Ca2+ back into the SR and myosin heads will not release. Therefore, the muscle gets stiff.

Question 6

How does Beta adrenergic receptors affect SERCA

Answer 6

when NE binds to BR, it causes a second messenger system (PKA) to phosphorylate Lambin. P-Lambin inhibits SERCA and prevents Ca2+ from getting taken back into SR. therefore Ca2+ stays in the cytoplasm. Causes more contraction.