Unlike base excision repair, the nucleotide excision repair enzymes do not recognize any particular lesion. Rather, this system works by recognizing distortions to the shape of the double helix, such as those

caused by a thymine dimer or by the presence of a bulky chemical adduct on a base.

TLS Online TPP Program

#Id: 4037

#Unit 7. System Physiology – Animal

Acetylcholine (ACh), released from parasympathetic nerve fibers, activates muscarinic (M2) receptors in the SA node.

TLS Online TPP Program

#Id: 4038

#Unit 7. System Physiology – Animal

activation of the M2 receptors decreases cyclic adenosine 3′,5′-monophosphate (cAMP) in the cells, and this slows the opening of Ca 2+ channels.

TLS Online TPP Program

#Id: 4039

#Unit 7. System Physiology – Animal

βγ subunit of a G protein, open a special set of K + channels. The resulting IKAch slows the depolarizing effect of Ih .

TLS Online TPP Program

#Id: 4040

#Unit 7. System Physiology – Animal

TLS Online TPP Program

#Id: 4041

#Unit 7. System Physiology – Animal

TLS Online TPP Program

#Id: 5255

#Unit 7. System Physiology – Animal

The heart consists of two kinds of muscle cells:

Contractile cells

Conducting cells