The Eye: Retina Function and Structure
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Questions and Answers

Which cone type is stimulated to a value of about 42?

  • Blue cone
  • Yellow cone (correct)
  • Green cone
  • Red cone

    • Color blindness occurs equally in males and females.

    False

    What genetic condition is discussed in relation to color perception?

    Red-green color blindness

    Color blindness almost never occurs in ______ because they have two X chromosomes.

    <p>females</p> Signup and view all the answers

    Match the color cones with their respective performance percentage of maximum light absorption:

    <p>Blue = 50 Green = 83 Red = 99 Yellow = 42</p> Signup and view all the answers

    What is the reason males are more likely to be colorblind?

    <p>They have only one X chromosome.</p> Signup and view all the answers

    The blue cone has a performance percentage of 36 percent.

    <p>True</p> Signup and view all the answers

    Which type of genetic inheritance pattern affects red-green color blindness?

    <p>X-linked recessive</p> Signup and view all the answers

    What is the process called when rhodopsin decomposes?

    <p>Hyperpolarization</p> Signup and view all the answers

    The first stage in the formation of rhodopsin requires no metabolic energy.

    <p>False</p> Signup and view all the answers

    What are the completely split products of rhodopsin decomposition?

    <p>Scotopsin and all-trans retinal</p> Signup and view all the answers

    The enzyme ________ catalyzes the conversion of all-trans retinal into 11-cis retinal.

    <p>retinal isomerase</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Metarhodopsin I = Intermediate form of rhodopsin after initial decomposition Metarhodopsin II = Activated rhodopsin that excites electrical changes Scotopsin = Protein that re-combines with retinal Sodium-potassium pump = Maintains negative potential inside the rod cell</p> Signup and view all the answers

    How do the rods transmit the visual image to the central nervous system?

    <p>In the form of optic nerve action potentials</p> Signup and view all the answers

    Potassium ions are pumped from the outside to the inside of the rod cell.

    <p>False</p> Signup and view all the answers

    What is the role of the outer segment of the rod?

    <p>It contains photoreceptor discs.</p> Signup and view all the answers

    What role do horizontal cells play in the visual pathway?

    <p>They enhance visual contrast through lateral inhibition.</p> Signup and view all the answers

    All bipolar cells respond in the same way to glutamate released by rods and cones.

    <p>False</p> Signup and view all the answers

    What is electrotonic conduction important for in the visual pathway?

    <p>Graded conduction of signal strength.</p> Signup and view all the answers

    A hyperpolarizing bipolar cell responds to glutamate by _______.

    <p>hyperpolarizing</p> Signup and view all the answers

    Which of the following best describes the signal transmission in bipolar cells?

    <p>Half transmit positive signals and half transmit negative signals.</p> Signup and view all the answers

    The outputs of horizontal cells are always excitatory.

    <p>False</p> Signup and view all the answers

    What phenomenon is essential for helping to ensure the transmission of visual patterns?

    <p>Lateral inhibition.</p> Signup and view all the answers

    Match the types of bipolar cells with their responses:

    <p>Depolarizing bipolar cell = Excited by glutamate Hyperpolarizing bipolar cell = Inhibited by glutamate Lateral inhibition = Enhances visual contrast Horizontal cell = Provides inhibitory output</p> Signup and view all the answers

    What happens to sodium ions when light strikes the rod?

    <p>More sodium ions leave the rod</p> Signup and view all the answers

    The membrane potential approaches -70 to -80 millivolts when the rod is in complete darkness.

    <p>False</p> Signup and view all the answers

    What is the role of the sodium-potassium pump in photoreceptors?

    <p>To maintain steady levels of sodium and potassium inside the cell.</p> Signup and view all the answers

    In the dark, levels of ______ are high which keeps sodium channels open.

    <p>cGMP</p> Signup and view all the answers

    How does light intensity affect the degree of hyperpolarization of the rod?

    <p>Higher light intensity increases hyperpolarization</p> Signup and view all the answers

    What is the function of phosphodiesterase in the visual process?

    <p>To remove cGMP</p> Signup and view all the answers

    In cones, the change in receptor potential occurs four times slower than in rods.

    <p>False</p> Signup and view all the answers

    When sodium channels close in response to light, the photoreceptors ______.

    <p>hyperpolarize</p> Signup and view all the answers

    The cones are more sensitive to light than the rods.

    <p>False</p> Signup and view all the answers

    What happens to the photochemicals in rods and cones after prolonged exposure to bright light?

    <p>They are reduced to retinal and opsins.</p> Signup and view all the answers

    The peak absorbent wavelength for rods is ______ nanometers.

    <p>505</p> Signup and view all the answers

    What is the approximate range of sodium ions flow that can be blocked through channel closure in rods?

    <p>More than 1 million ions</p> Signup and view all the answers

    Match the following types of pigments with their peak absorbent wavelengths:

    <p>Rhodopsin = 505 nanometers Green-sensitive pigment = 535 nanometers Red-sensitive pigment = 570 nanometers Blue-sensitive pigment = 445 nanometers</p> Signup and view all the answers

    In terms of color vision, how do rods contribute under dark conditions?

    <p>Rods are highly sensitive and can detect low light levels, amplifying the effect of a single photon.</p> Signup and view all the answers

    The sensitivity of cones allows color vision in extremely dim light.

    <p>False</p> Signup and view all the answers

    What is the primary role of X cells in the retina?

    <p>Representing discrete retinal locations for fine details</p> Signup and view all the answers

    Y cells in the retina are responsible for color vision.

    <p>False</p> Signup and view all the answers

    How many rods and cones are there on average per ganglion cell?

    <p>60 rods and 2 cones</p> Signup and view all the answers

    The Y cells transmit signals to the brain at speeds of ______ m/sec or faster.

    <p>50</p> Signup and view all the answers

    Match the type of cell with its primary function:

    <p>X cells = Responsible for color vision Y cells = Transmit rapid changes in visual images Amacrine cells = Analyze visual signals before they leave the retina Ganglion cells = Send signals to the brain</p> Signup and view all the answers

    Which type of amacrine cell is sensitive to movement across the retina in a specific direction?

    <p>Directionally sensitive amacrine cells</p> Signup and view all the answers

    The number of ganglion cells in the retina is greater than that of cones.

    <p>False</p> Signup and view all the answers

    What type of information do Y cells communicate to the central nervous system?

    <p>Rapid changes in visual images</p> Signup and view all the answers

    Study Notes

    The Eye: II. Receptor and Neural Function of the Retina

    • The retina is the light-sensitive portion of the eye, containing cones (color vision) and rods (dim light, black and white).
    • Signals travel through retinal neurons to the optic nerve and cerebral cortex.
    • The retina has ten layers: pigment layer, photoreceptor layer, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion layer, optic nerve fiber layer, and inner limiting membrane.
    • Light passes through layers to reach rods and cones at the outer edge of the retina.
    • The fovea, a central area, is densely packed with cones for acute vision.
    • Rods and cones are photoreceptors with outer and inner segments, a nucleus, and a synaptic body.
    • The outer segment contains rhodopsin (rods) or color pigments (cones) for light sensitivity.
    • Rhodopsin consists of scotopsin and retinal.
    • Light activates rhodopsin, triggering a cascade of events leading to hyperpolarization of the rod, which excites the nerve signals.
    • Vitamin A is a crucial component in rhodopsin formation and adaptation.
    • Dark adaptation increases retinal sensitivity, while light adaptation reduces it.
    • Cones have three types of color pigments (blue, green, red) enabling color vision.
    • Cones and rods send signals along retinal pathways and neurons (horizontal/amacrine/bipolar/ganglion cells).
    • Ganglion cells transmit signals via the optic nerve.
    • Lateral inhibition sharpens visual contrast.
    • Bipolar cells, horizontal and amacrine cells transmit signals, some are depolarizing, others hyperpolarizing
    • Electrical signals (not action potentials) conduct most signals within the retina, except for the ganglion cells.
    • The retina's sensitivity to light changes as light levels adjust (adaptation).
    • Color blindness occurs when a type of cone is missing, typically red-green color blindness.

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    Description

    Explore the intricate workings of the retina, the light-sensitive area of the eye. This quiz delves into the roles of rods and cones, the layers of the retina, and the neural pathways that connect to the brain. Test your understanding of how the retina processes visual information.

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