photoreceptor

Examples of photoreceptor in the following topics:

• Plant Responses to Light

  • The response of plants to light is mediated by different photoreceptors: a protein covalently-bonded to a light-absorbing pigment called a chromophore; together, called a chromoprotein.
  • The chromophore of the photoreceptor absorbs light of specific wavelengths, causing structural changes in the photoreceptor protein.
  • Sensory photoreceptors absorb light in these particular regions of the visible light spectrum because of the quality of light available in the daylight spectrum.

• Classification of Receptors by Stimulus

  • Sensory receptors are primarily classified as chemoreceptors, thermoreceptors, mechanoreceptors, or photoreceptors.
  • During vision, rod and cone photoreceptors respond to light intensity and color.

• Optic (II) Nerve

  • The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
  • The eye's blind spot is a result of the absence of photoreceptors in the area of the retina where the optic nerve leaves the eye.

• Transduction of Light

  • When light hits a photoreceptor, it causes a shape change in the retinal, altering its structure from a bent (cis) form of the molecule to its linear (trans) isomer.
  • Photoreceptors in the retina continuously undergo tonic activity.
  • Sometimes horizontal cells carry signals from one rod or cone to other photoreceptors and to several bipolar cells.
  • When a rod or cone stimulates a horizontal cell, the horizontal cell inhibits more-distant photoreceptors and bipolar cells, creating lateral inhibition.
  • (a) Rhodopsin, the photoreceptor in vertebrates, has two parts: the trans-membrane protein opsin and retinal.

• Overview of Sensation

  • Sight or vision (ophthalmoception) is the ability of the eye(s) to focus and detect images of visible light on photoreceptors in the retina that generate electrical nerve impulses for varying colors, hues, and brightness.
  • There are two types of photoreceptors: rods and cones.
  • Our nervous system has sensory systems and organs that mediate each sense and these systems rely on chemoreceptors, photoreceptors, mechanoreceptors, or thermoreceptors to detect the state of the internal or external environment.

• Vision: The Visual System, the Eye, and Color Vision

  • Visual reception occurs at the retina where photoreceptor cells called cones and rods give an image color and shadow.
  • Photoreceptor cells found in this region have the specialized capability of phototransduction, or the ability to convert light into electrical signals.
  • There are two types of these photoreceptor cells: rods, which are responsible for scotopic vision (night vision),  and cones, which are responsible for photopic vision (daytime vision).

• Sensory Modalities

  • The transduction of light into neural activity occurs via the photoreceptors in the retina.
  • When a particle of light hits the photoreceptors of the eye, the photopigment of the photoreceptor undergoes a chemical change leading to a chain of chemical reactions occur.

• Classification of Receptors by Location

  • For example, sensory receptors in the retina are almost entirely photoreceptors.

• Blue Light Response

  • Like all plant photoreceptors, phototropins consist of a protein portion and a light-absorbing portion, called the chromophore, which senses blue wavelengths of light.
  • Cryptochromes are another class of blue-light absorbing photoreceptors.

• Anatomy of the Eye

  • There are two types of photoreceptors in the retina: rods and cones.
  • Rods and cones are photoreceptors in the retina.