Which part of the eye is the opening through which light initially passes?
answer
The pupil is the small opening in the center of the iris through which light initially passes.
question
Which of the following statements does not describe a vertebrate eye?
answer
It contains many light-sensing columns called ommatidia.
question
True or false? The "blind spot" in vertebrate eyes is a region of the retina that contains no photoreceptors.
answer
true
question
Which part of the eye contains the densest concentration of cone cells?
answer
Fovea
question
Which part of the eye bends light to focus it on the retina?
answer
Lens
question
Which of the following statements about photoreception is true?
answer
The retinal molecule changes shape when it absorbs light.
question
True or false? Cone cells are color photoreceptors that use different retinal molecules to absorb different wavelengths of light.
answer
False
question
Identify the correct statement(s) about the resting membrane potential of a cell.
answer
Concentration gradients of potassium (K+) and sodium (Na+) across the plasma membrane represent potential energy.
Potassium (K+) and sodium (Na+) gradients are maintained by active transport in a resting mammalian neuron.
question
If the membrane potential of a neuron decreases, the membrane potential _____.
answer
becomes less negative
question
Why is an action potential an all-or-none response to stimuli?
answer
Because voltage-gated ion channels open when membrane potential passes a particular level
question
The plasma membrane of a neuron has voltage-gated sodium and potassium channels. What is the effect of membrane depolarization on these channels?
answer
Membrane depolarization first opens sodium channels and then opens potassium channels.
question
What causes the falling phase of the action potential? Select the best answer.
answer
Inactivation of voltage-gated sodium channels and the opening of voltage-gated potassium channels
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