Term
| What is the main difference between cardiac muscles and other types of muscle? |
|
Definition
| They have intercalated discs |
|
|
Term
| What are intercalated discs composed of? |
|
Definition
Fascia adherens
desmosomes |
|
|
Term
| What proteins are present in sarcomeres? |
|
Definition
1. actin
2. myosin
3. tropomyosin
4. troponins
5. titin |
|
|
Term
| What cells have fast response action potentials? |
|
Definition
| atrial and ventricular cells |
|
|
Term
| What occurs in phase 4 of cardiac cell action potentials? |
|
Definition
a.
resting
potential
b.
sodium
and
calcium
channels
closed
(calcium removed by calcium pump and sodium-calcium exchanger)
c.
potassium
channels
(inward
rectifying)
open
d.
extracellular
concentration
of
Na+
greater
than
intracellular
(removed by Na+/K+ ATPase from cell)
e.
extracellular
concentration
of
K+
less
than
intracellular |
|
|
Term
| What happens in Phase 0 of cardiac action potentials? |
|
Definition
| Fast acting sodium channels open |
|
|
Term
| What are the three possible states of fast-acting sodium channels? |
|
Definition
closed (resting)
open (activated)
closed (inactivated) |
|
|
Term
| What two types of gates are present in fast-acting sodium channels? |
|
Definition
activation channels
inactivation channels |
|
|
Term
| What happens in Phase 1 of cardiac action potential? |
|
Definition
| partial repolarization due to inactivation of sodium channels and efflux of potassium through transient outward channels |
|
|
Term
| What happens in Phase 2 of cardiac action potentials? |
|
Definition
*l-type calcium channels open and remain open
*calcium influx more gradual than sodium
*calcium influx causes release of calcium from SR
*K+ efflux through delayed rectifiers
*plateau caused by equal influx of calcium and efflux of K+ |
|
|
Term
| What happens in Phase 3 of cardiac action potentials? |
|
Definition
*potassium efflux from delayed rectifiers
*K+ efflux outpaces calcium influx
*soon becomes entirely K+ efflux
*repolarizes membrane back to resting potential |
|
|
Term
|
Definition
|
|
