3C. Seeing the World: Retina to Cortex

• What type of wave is the sensory signal for visual processing?

  A transverse wave
• What part of the electromagnetic spectrum does the visible spectrum represent?

  A very small part
• What is the relationship between wavelength and frequency in the equation \(c = f\lambda\)?

  Wavelength and frequency are inversely related
• What is the wavelength of violet light?

  ~380 nm
• What is the wavelength of red light?

  ~700 nm
• What is the role of the dioptric apparatus in the eye?

  • It consists of the cornea and lens.
  • It is essential for the transduction process in the retina.
• What is the function of the cornea?

  It allows light through without being diffracted
• What percentage of the eye's refractive power does the cornea provide?

  About 2/3
• What is the function of the lens in the eye?

  It provides the other 1/3 of the eye's refractive power
• How does the lens adjust its refractive power?

  By changing its shape
• Where should light focused by the cornea and lens reach?

  A focal point on the retina
• What condition occurs when transparency is lost in the eye?

  Cataracts
• What are refractive errors?

  Common issues caused by incorrectly focused light signals
• What can cause refractive errors in the eye?

  Incorrect power of the dioptric apparatus or abnormal eyeball length
• What happens if light is too bent or the eyeball is too long?

  The focal point will fall short of the retina
• What happens if light is not bent enough or the eyeball is too short?

  The focal point will fall too long for the retina
• What is a common correction for long-sightedness?

  Glasses that increase refraction
• What is a common correction for short-sightedness?

  Glasses that counter refraction
• What is the role of photoreceptors in the retina?

  They transduce light into electrical signals
• Where are photoreceptors located in the retina?

  At the very back of the retina
• What happens to light before it reaches the photoreceptors?

  It passes through several transparent retinal layers
• What do cones and rods connect to after transduction?

  Bipolar cells
• How do cones differ from rods in terms of mapping?

  Cones have 1-2-1 mapping
• What is the trade-off of rod convergence?

  Sensitivity is gained but spatial acuity is lost
• What do bipolar cells do in the retina?

  They carry the signal to retinal ganglion cells
• What do the axons of retinal ganglion cells form?

  The optic nerve
• How many rods are there compared to cones in the retina?

  20:1
• Where are cones most prevalent in the retina?

  In the fovea
• What is the significance of the fovea?

  It provides great acuity
• What photopigment is found in the outer segment of rods?

  Rhodopsin
• What shape do the stacks of rhodopsin form?

  A comb shape
• What is contained in the inner segment of the rod?

  Typical animal cell organelles
• What photopigment is found in the outer segment of cones?

  Opsin
• How does the structure of opsin differ from rhodopsin?

  Opsin has more caps and forms a cone shape
• What causes different wavelength sensitivities in photoreceptors?

  Different photosensitive pigments
• What color is rhodopsin sensitive to?

  Greyish-green
• What types of opsin are sensitive to different colors?

  Blue, red, and green
• How do most colors activate photoreceptors?

  They activate more than one type of cell
• What is color blindness?

  The decreased ability to see colors
• How is most color blindness inherited?

  It affects males more than females