Question

What is the light-sensitive molecule found in intrinsically photosensitive retinal ganglion cells of mammalian retina? a. Melanopsin b. Transducin c. Rhodopsin d. Cryptochrome e. Peropsin

Short answer

Answer: Melanopsin

Step-by-step solution

Identification

Identify the light-sensitive molecule present in intrinsically photosensitive retinal ganglion cells of the mammalian retina.

Review options

Review the given options and select the correct answer. a. Melanopsin b. Transducin c. Rhodopsin d. Cryptochrome e. Peropsin

Choose the correct option

Melanopsin is the correct answer. It is the light-sensitive molecule found in intrinsically photosensitive retinal ganglion cells of the mammalian retina. The correct answer is (a) Melanopsin.

Key concepts

Intrinsically Photosensitive Retinal Ganglion Cells

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are a special type of neuron found in the mammalian retina. Unlike most cells in the eye that rely on rods and cones to detect light, these cells are unique because they can sense light independently. They do this with the help of a light-sensitive molecule called melanopsin.
ipRGCs play a significant role beyond regular vision. They are crucial for regulating non-image-forming visual functions. This includes controlling our circadian rhythms, which are the body's biological clock that responds to light and darkness throughout the day. ipRGCs also help in adjusting the pupil size and other reflexive functions.
Here are some key points about ipRGCs:

• They contain melanopsin, which makes them sensitive to light.
• They help process signals for non-visual responses to ambient light.
• They are a small subset of the total ganglion cells in the retina.

Mammalian Retina

The mammalian retina is a complex, multi-layered structure at the back of the eye. It is primarily responsible for capturing light and converting it into neural signals, which are then sent to the brain for processing.
The retina consists of several types of cells that are crucial for vision:

• Photoreceptors: These include rods, which are sensitive to low light levels, and cones that detect color.
• Bipolar Cells: They relay signals from photoreceptors to ganglion cells.
• Ganglion Cells: These cells transmit the visual information from the retina to the brain via the optic nerve.
• Horizontal and Amacrine Cells: These modulate and refine the signals as they pass through the retina.

The mammalian retina is remarkable for its ability to adapt to varying light conditions. This adaptability ensures that animals can see across a wide range of lighting situations.

Light-sensitive Molecules

Light-sensitive molecules are specialized proteins that enable cells to respond to light stimuli. They are crucial for the process of converting light into a biological response, a fundamental part of vision.
The most important light-sensitive molecules in the retina are found in photoreceptor cells. Here are some key molecules involved:

• Melanopsin: Found in ipRGCs, it is crucial for regulating circadian rhythms and reflex responses to light.
• Rhodopsin: Located in rods, it allows vision under low-light conditions.
• Photopsin: Varieties of photopsin are present in cones, supporting color vision.

These molecules undergo structural changes upon absorbing light. This change triggers a cascade of events, ultimately leading to the conversion of a light stimulus into an electrical signal. This signal is then processed by the brain to form visual perceptions. Each of these molecules plays a distinct role in different aspects of visual and non-visual functions, showcasing the diversity and complexity of the mammalian visual system.