Question

Sensory neurons of the retina are
(a) Maculae and cristae
(b) Pacivian and Ruffini’s corpuscles
(c) Rods and cones
(d) All of the above

Answer 1

Hint: A sensory receptor is a specialized neuron that detects a specific physical stimulus. The photoreceptors process light energy. Most sensory receptors do not have axons as their cell bodies synapse on dendrites or cell bodies of neurons.

Complete step by step answer:
The retina is a layer of tissue on the back portion of the eye that contains cells responsive to light or photoreceptors. Rods are sensitive enough to respond to a single photon, but functioning together they are optimized for the ability to see in poor light. Cones are optimized for responding to fine detail and colour, they need a lot more light and work best in broad daylight. When light hits the retina it is first processed in the photoreceptors located in the back of the retina.
Rods
- Rods are distributed over most of the retina except near the fovea.
- No rods at all in the central part of the fovea.
- Rods are connected in groups, there are far fewer optic nerves going to the brains than rods.
- Rod vision detects edges and motion very well.
- Rod pigments are bleached by light and are less effective in bright light, rods take about 20 to 30 minutes of dark adaptation before they are most efficient.
Cones
- There is a concentration in the fovea, a region about 1.5 mm in diameter. Most acute visions are limited to foveola, covering nearly 0.4 mm.
- Color vision is provided by three types of cones with different coloured light absorption red, green and blue cones.
So, the correct answer is, ‘Rods and cones.’

Note:
$\text{Photoreceptor}\to \text{Bipolar cells}\to \text{Ganglion cells}$
- The light passes through the cornea, pupil and lens on its way to the retina to photoreceptors which absorb and then convert into electrical potentials that carry information to the brain.
- The retina performs dual function involving the two different receptors that are rods and cones.
- Inside the eye, there are eighteen times more rods than cones. These are arranged in such a way as to produce the best combination of night and day vision.