As cells enter into the S phase of the cell cycle, two kinases, CDK and DDK, are activated.  DDK phosphorylates loaded Mcm2-7 helicase, and CDK phosphorylates Sld2 and Sld3.Phosphorylated Sld2 and Sld3 bind to Dpb11, and together these proteins facilitate binding of the helicase-activating proteins, Cdc45 and GINS, to the helicase.  

TLS Online TPP Program

#Id: 3978

#Unit 7. System Physiology – Animal

Myocardial fibers have a resting membrane potential of approximately –90 mV.

TLS Online TPP Program

#Id: 3979

#Unit 7. System Physiology – Animal

The individual fibers are separated by membranes, but depolarization spreads radially (syncytium) because of the presence of gap junctions.

TLS Online TPP Program

#Id: 3984

#Unit 7. System Physiology – Animal

In cardiac muscle, the action potential is caused by opening of three types of channels

Voltage activated fast sodium channels 

L-type calcium channels (slow calcium channels or calcium-sodium channels)

Voltage activated potassium ion channels

TLS Online TPP Program

#Id: 3987

#Unit 7. System Physiology – Animal

Phase 0 (depolarization), fast sodium channels open. 

TLS Online TPP Program

#Id: 3989

#Unit 7. System Physiology – Animal

Phase 1 (initial repolarization), fast sodium channels close

TLS Online TPP Program

#Id: 3991

#Unit 7. System Physiology – Animal

Phase 2 (plateau), calcium channels open and fast potassium channels close.