BRAINCAKECones
Cones are photoreceptors that work in bright light and give detailed, colour vision. There are about 6 million in each human retina, mostly concentrated in the fovea.
Cones contain a light-sensitive pigment called iodopsin. Like rhodopsin, it consists of retinal joined to an opsin protein, but the opsin is different. Iodopsin is less sensitive than rhodopsin: it needs a higher light intensity to break down. This is why cones do not work in dim light, and why colours seem to disappear at night.
Cones respond to light in the same way as rods. Light breaks down the pigment, Na+ channels close, the cone hyperpolarises and stops releasing inhibitory neurotransmitter, so the bipolar neurone it synapses with is stimulated.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
Key terms in this lesson
- visual acuity
- The ability to distinguish fine detail; the sharpness of vision.
- retinal convergence
- The connection of many rod cells to a single bipolar neurone, allowing their small responses to add together.
More in Mammalian Nervous System
- Sensory Receptors
- The Human Eye
- The Retina
- Rods
- Colour Vision
- Formation of the Brain
- Major Areas of the Brain
- Other Areas of the Brain
All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics