During S phase

DNA-bound G1 cohesins Convert into cohesive complexes by cohesin acetyl transferases (CoATs)

which acetylate Smc3 subunit & prevents unloading of cohesins by Pds5-Wapl, thereby stabilizing the cohesins on chromosomes.

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#Unit 7. System Physiology – Animal

Phase 4 (resting membrane potential) averages about −90 millivolts.

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#Unit 7. System Physiology – Animal

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#Unit 7. System Physiology – Animal

The SA node exhibits automaticity; it can spontaneously generate action potentials without neural input.

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#Unit 7. System Physiology – Animal

SA node has an unstable resting membrane potential. The “resting membrane potential” of the sinus nodal fiber between discharges has a negativity of about −55 to −60 millivolts.

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#Unit 7. System Physiology – Animal

The cause of less negative RMP of SA node is that the cell membranes of the sinus fibers are naturally leaky to sodium and calcium ions.

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#Unit 7. System Physiology – Animal

The inherent leakiness of the sinus nodal fibers to sodium and calcium ions causes their self-excitation.