Embryos from homozygous skn-1-deficient mothers lack both pharyngeal mesoderm & endoderm derivatives of EMS.

TLS Online TPP Program

#Id: 5268

#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.

TLS Online TPP Program

#Id: 5269

#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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#Id: 5270

#Unit 7. System Physiology – Animal

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

TLS Online TPP Program

#Id: 5271

#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.

TLS Online TPP Program

#Id: 5272

#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

TLS Online TPP Program

#Id: 5273

#Unit 7. System Physiology – Animal

Between heartbeats, influx of positively charged sodium ions causes a slow rise in the resting membrane potential in the positive direction.