Question

1. Which of the following best describes the electrical response of photoreceptors in the light?
A)Depolarization

B)Hyperpolarization

2. Which event occurs in photoreceptors during photo-transduction in response to dark?
      
A) Phosphodiesterase activity increases
      
B) cGMP concentration increases
      
C) Glutamate release decreases
      
D)Transducin activity increases

3. After odor molecules bind to odor receptors, a sequence of intracellular events occurs causing hyperpolarization of the olfactory receptor cell membrane.
      
A) True

B) False
  

4. Which of the following is not a characteristic of rods?
      
A) Night vision
      
B) Black and white vision
      
C) Little convergence
      
D) Low sharpness

Answer 1

1. A) Hyperpolarization

• The absorption of rods and cones is mediated by decreased release of glutamate.
• In the dark atmosphere, the depolarization occurs.

2. B) cGMP concentration increases

• In the dark, the level of secondary messenger cGMP levels is high
• This allows cGMP-gated sodium channels for a steady inward current
• These dark currents retain the cell in depolarized state (-40 mV).

3.False

• Once the olfactory receptor cells bind odor molecules, a sequence of intracellular activities occurs
• which terminates at the entrance of sodium ions
• Sodium ions depolarize the olfactory receptor cell.

4. D) Low sharpness

• Rods are responsible for highest visual acuity.
• Rod cells respond to single photon light