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12 Cards in this Set

  • Front
  • Back
vascular smooth muscle is controlled by?
1. local tissue
2. nervous system
What are the resting membrane potential of ventricular cardiac muscle and of SA + AV nodes?
ventricular muscle --> -90mV
SA + AV nodes --> -55mV
inward flow of + charge means depolarization, is that increased or decreased excitation?
increased excitation
What does permeability and conductance mean?
permeability (P) = ease of movement of an ion down a concentration gradient.
conductance (g) = ease of movement of an ion down a electrical gradient
The Nernst equation helps us determine what?
it helps us estimate the electrical potential that would just balance the K+ concentration gradient.
What are 3 Ca channel blockers during ventricular muscle AP?
What effect would they have on the heart?

less depolarization. less contractile force.
What are the events that are responsible for the plateau potential during ventricular muscle AP?
1. inward Ca current via L type Ca channel. (which is also voltage dependent and catecholamine sensitive)
2. increase in Na permeability via a slow channel
3. decrease in K+ permeability
Phase 0 of ventricular muscle AP is due to?
rapid depolarization.
voltage dependent, tetrodotoxin sensitivve Na channels open.
Phase 1 of ventricular muscle AP is due to?
1. outward movement of K
2. inactivation of the fast Na channel.
What is supranormal period?
When stimulation at a lower level than normal can produce a propagated but often lower than normal response.
Phase 4 of SA + AV node is due to?
1. decreased K permeability
2. increase Na and Ca permeability. (Na channel is non-fast type)
What is the purpose of the long absolute refractory period for the cardiac muscles?
1. it takes time for the cell contractile events to occur
2. prevents premature stimulation + sustained unctrolled contractions