There are 18 different antigenic subtypes for HA and 11 for NA.

TLS Online TPP Program

#Id: 5436

#Unit 7. System Physiology – Animal

The membrane potential moves toward the equilibrium potential for Na+ (+60 - +65mV) but does not reach it during the action potential, because the increase in Na+ conductance is short-lived.

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#Id: 5437

#Unit 7. System Physiology – Animal

The Na+ channels rapidly enter a closed state called inactivated state and remain in this state for a few milliseconds

TLS Online TPP Program

#Id: 5438

#Unit 7. System Physiology – Animal

Voltage-gated sodium channel has two gates:

activation gate near the outside of the channel 

Inactivation gate near 

the inside of the channel 

TLS Online TPP Program

#Id: 5439

#Unit 7. System Physiology – Animal

During overshoot  

the direction of the electrical gradient for Na+ is reversed because the membrane potential is reversed & this limits Na + influx 

TLS Online TPP Program

#Id: 5440

#Unit 7. System Physiology – Animal

During overshoot 

the voltage-gated K+  channels open & contribute to repolarization

TLS Online TPP Program

#Id: 5441

#Unit 7. System Physiology – Animal

The opening of voltage-gated K+ channels is slower and more prolonged than the opening of the Na + channels, and much of the increase in K + conductance comes after the increase in Na+ conductance