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

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#Unit 2. Cellular Organization

DNA damage response system

halts cell cycle progression and

recruits DNA repair machinery

when DNA is compromised

TLS Online TPP Program

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#Unit 2. Cellular Organization

The protein kinases DNA-PK, ATM, and ATR are activated at sites of damaged DNA

TLS Online TPP Program

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#Unit 2. Cellular Organization

ATR activated by single-stranded DNA breaks.

TLS Online TPP Program

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#Unit 2. Cellular Organization

ATM and DNA-PK are specifically activated by double-strand breaks

TLS Online TPP Program

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#Unit 2. Cellular Organization

ATM and ATR, activate a triad of related protein kinases: Chk1, Chk2, and MK2

TLS Online TPP Program

#Id: 8929

#Unit 2. Cellular Organization

Chk1, Chk2, and MK2

cause cell cycle arrest by inhibiting Cdc25

stabilizing the transcription factor p53, which induces the transcription of CKI p21