The unit of s is seconds Most values of s are between 10-13 and 10-11 second. To
eliminate the exponents, the value of s is usually reported in svedbergs (S). 1 svedberg 10-13 second.

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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.

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#Unit 7. System Physiology – Animal

SA node has Prepotential or pacemaker potential which is the gradual potential rise from the resting membrane potential to threshold  ( -40 mV) & this occur spontaneously

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#Id: 4014

#Unit 7. System Physiology – Animal

Membrane ion channels that play important roles in generation of the action potential:

T (transient) channels 

L (long-lasting) channels Voltage gated potassium ion channel