Photoreceptor cell

Photoreceptor cells are specialized sensory neurons located in the retina of the eye. Their primary function is to convert light into electrical signals that can be processed by the nervous system—a process known as visual signal transduction[3][5]. There are three main types in mammals: 1. **Rod photoreceptors** – Highly sensitive to low light levels and responsible for night vision; contain rhodopsin as their visual pigment and do not mediate color vision. 2. **Cone photoreceptors** – Function best under bright light conditions and enable color vision; contain different opsins sensitive to specific wavelengths. 3. **Intrinsically photosensitive retinal ganglion cells** – Contain melanopsin and contribute mainly to non-image-forming responses such as circadian rhythm regulation. Structurally, these cells have distinct compartments including an outer segment packed with membrane discs containing opsins for photon capture, an inner segment rich in mitochondria for energy production, a nucleus-containing cell body, and a synaptic terminal that communicates with downstream neurons via neurotransmitter release[1][2][3]. Photoreceptor dysfunction or degeneration is implicated in several blinding diseases such as retinitis pigmentosa and age-related macular degeneration[1][2]. While they are essential cellular components of the visual system, "photoreceptor cell" refers to a class of cells rather than a single molecular target or receptor protein.

Other names

Rod photoreceptor cellCone photoreceptor cellRetinal photoreceptorPhotoreceptive neuron