2007 Sensory Physiology

Phototransduction

  1. activation of the receptor protein
    • in rods, that is rhodopsin

1 photon à 1 rhodopsin

Step 1
  1. the activated receptor protein stimulates the G-protein transducin
    • GTP is converted to GDP in the process

1 rhodopsin à 100 transducins/s

Step 2
  1. In turn, activated transducin activates the effector protein phosphodiesterase
    • PDE converts cGMP to GMP

1 transducin à 100 PDE/s

Step 3
  1. Falling concentrations of cGMP cause the transduction channels to CLOSE, DECREASING a Na+ current

1 PDE à 1000 GMP/s

Step 4

S&G Figure 10.33

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