phys exam 3: ch 18 part 2

Coordinated heartbeats are a function of

• desmosomes

• gap junctions

• intrinsic cardiac conduction system

Noncontractile cells are

• autorhythmic cells

• not this

rapid, irregular contractions that cannot pump blood and eventually leads to brain death

• arrhythmias

• fibrillation

intrinsic cardiac conduction system initiates and distributes impulses

• True

• False

Have unstable resting membrane potentials due to opening of slow Na channels

• Myocardiocytes

• pacemaker cells (autorhythmic cells)

myocardiocytes have fast gated Na channels

• True

• False

At threshold in pacemaker cells, ___ channels open

• Na

• K

• Ca

What causes the rising phase of the action potential in pacemaker cells?

• K efflux

• Ca influx

• Na influx

Repolarization results from

• Ca channels closing

• Na channels opening

• K channels opening

• Na channels closing

slow Na channels open

• pacemaker potential

• depolarization

• repolarization