Using the clock analogy again, the DNA associated with H2A.H2B is located from 5 o’clock to 9 o’clock on either face of the nucleosome disc.

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#Id: 5449

#Unit 7. System Physiology – Animal

Refractory period is divided into:

Absolute refractory period

Relative refractory period

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#Id: 5450

#Unit 7. System Physiology – Animal

The absolute refractory period overlaps with almost the entire duration of the action potential. During this period, no matter how great the stimulus, another action potential cannot be elicited.

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#Id: 5451

#Unit 7. System Physiology – Animal

The basis for the absolute refractory period is closure of the inactivation gates of the Na+ channel in response to depolarization. These inactivation gates are in the closed position until the cell is repolarized back to the resting membrane potential.

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#Id: 5452

#Unit 7. System Physiology – Animal

The relative refractory period begins at the end of the absolute refractory period and overlaps primarily with the period of the hyperpolarizing afterpotential.

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#Id: 5453

#Unit 7. System Physiology – Animal

During the relative refractory period, stronger than normal stimuli can cause excitation

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#Id: 5454

#Unit 7. System Physiology – Animal

The basis for the relative refractory period is the higher K+ conductance than is present at rest.