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What effect would an anti-arrhythmic drug have on the resting membrane potential of cardiac myocytes and on the upstroke of the cardiac action potential and conduction velocity of myocardial cells?

* Anti-arrhythmic drugs inactivate many fast Na+ channels in the heart.

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Lelia Lubowitz
Lelia LubowitzLv2
28 Sep 2019

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Related questions

The cardiac cells also generate Action Potentials, and are also impacted by TTX (tetrodoxin), although their channels are a little different, and respond individually to TTX. Describe the normal mechanism and role of F-type V-G Na+ channels in creating myocardial Pacemaker Potential

 in slow fibers (SAN, AVN) and

 in fast fibers (Purkinje).

This is the peak depolarization in an action potential. At this point in an action potential two events start to happen.

1. Na+ channels begin to inactivate, which is equivalent to closing.

2. A majority of the K+ channels are beginning to open.

Determine what happens to the membrane potential when voltage-gated K+ channels are open simultaneously with voltage-gated Na+ channels (and the leak K+ channels which are still open). Increase the membrane permeability to K+ by increasing it to 115.

i. What happens to the membrane potential Em? __________________________

j. Why does the membrane potential change in this direction? __________________________ Now inactivate the voltage-gated Na+ channels by reducing the membrane permeability for Na+ back to 1. k. What is the new membrane potential? _____________

l. Is the new membrane potential less negative or more negative than the resting membrane potential listed in line ‘b’ of this section? _____________

m. Why? (hint: what 2 types of K+ channels are open now?) n. Under the current ionic concentrations given, what is the most negative value that the membrane potential could reach? _____________ (Increase the permeability of the membrane to K+ to confirm your answer.)

o. What equilibrium potential has the same value? _____________

p. At this point in the action potential, when the membrane potential is more negative than the resting potential, the membrane potential is said to be hyperpolarized. What happens to voltage-gated K+ channels (membrane permeability to K+) to bring the membrane potential back to its resting potential near -70mV?_____________

When the membrane potential became more negative than the Threshold potential, the inactivated voltage-gated Na+ channels became reactivated. After the voltage-gated K+ channels closed to enable the membrane potential to return to resting membrane potential they became ready to open again. Both channels are ready to open again in order to fire another action potentia

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When an action potential reaches a synapse, what happens to the Ca2+ channels, Ca2+ ions, neurotransmitters, transmitter-gated ion channels, and the post synaptic neuron?

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