10. Why the heart must not undergo tetanus & 11. Contractile cells versus pacemaker cells

The heart must contract and relax as _. If cardiac contractions fused, the chambers could not _, and blood flow would _.

separate events, relax and fill normally, fail

In cardiac muscle, the action potential lasts _. The prolonged depolarization and refractory period prevent a _.

roughly as long as the twitch, second excitation from summing with the current contraction

What is the functional reason for the cardiac plateau potential?

To prevent tetanus

What are the 2 types of excitable cells a heart has? How are they different?

Contratile cells and pacemaker cells, they have different action potentials and jobs

Main job of contractile cardiac myocytes and how it receives excitation:

generate force and pump blood, through gap junctions and produces

a long action potential with a plateau

Main job of pacemaker/autortythmic cells and how it receives excitation:

generates rhythm that initiates cardiac excitation, spontaneously depolarizes and produces repeated action potentials without an external trigger

Pacemaker cells are _; they do not use _ to generate the main pumping force

not contractile, actin and myosin

How are pacemaker cells and contractile cells connected? What is the path they follow?

Through gap junctions, current from pacemaker cells spread to contractile cells and spreads through the contractile-cell network so that myocardium contracts as a unit