Cardiac Physiology

Question 1

How many cisternae per T-tubule in skeletal fibers?

Answer 1

2 per t tubule

Question 2

T tubules form ___ with ___ within skeletal muscle fibers

Answer 2

triads, SR

Question 3

____ form diads with SR within ____

Answer 3

T tubules cardiac muscle fibers

Question 4

Fast Cardiac A.P

Answer 4

Contracts fast with high amplitude (100mv)

Question 5

Where are Fast Cardiac A.P found?

Answer 5

Atria, Ventricles and Conductive system like punkinje fibers

Question 6

Where are Slow Cardiac A.P found?

Answer 6

SA and AV nodes

Question 7

Slow Cardiac A.P

Answer 7

Contracts slowly with low amplitude (60mV) and automatically depolarizes during resting phase

Question 8

What are the 5 phases of the cardiac A.P cycle?

Answer 8

4--resting potential
0--rapid depolarization
1--incomplete repolarization
2--plateau or slow decline of membrane potential
3--repolarization

Question 9

What are the three elements of a fast cardiac A.P?

Answer 9

Large diameter of cell, fast amplitude and steady fast rise of phase 0

Question 10

How does the cardiac A.P plateau form?

Answer 10

After rapid closure of Na channels s/p threshold, Ca channels open slowly and maintain open state. At the same time, K channels open slowly (unlike in Skeletal). The large concentration of Ca and K causes the plateau.

Question 11

What is the natural pacemaker of the heart?

Answer 11

SA node fibers. Modified cardiac fibers

Question 12

Faster depolarization—>

Answer 12

Faster Heart Rate

Question 13

Ca leaves the SR via SERCA after membrane is inhibited by ____ in Cardiac Fibers and ___ in Skeletal Fibers.

Answer 13

1) Phospholamban

2) Calsequetrin