3.6.1.2 Receptors: Rods and Cones

What type of cells in the retina are primarily responsible for sensitivity to light?

• Cones

• Rods

• Ganglion cells

• Bipolar cells

Answer explanation

Rods are the photoreceptor cells in the retina that are highly sensitive to light, allowing us to see in low-light conditions. In contrast, cones are responsible for color vision and function best in bright light.

Which cells in the retina are responsible for colour vision?

• Rods

• Cones

• Amacrine cells

• Horizontal cells

Answer explanation

Cones are the photoreceptor cells in the retina responsible for color vision. They function best in bright light and allow us to perceive a wide range of colors, unlike rods, which are more sensitive to light but do not detect color.

What is the primary function of rods in the human retina?

• Detecting colour

• Detecting light intensity

• Detecting movement

• Detecting fine detail

Answer explanation

Rods in the human retina are primarily responsible for detecting light intensity, allowing us to see in low-light conditions. They do not detect color, fine detail, or movement as effectively as cones do.

Which type of photoreceptor is more numerous in the human retina?

• Rods

• Cones

• Both are equal

• Neither, they are absent

Answer explanation

Rods are more numerous in the human retina, with about 120 million compared to approximately 6 million cones. Rods are responsible for vision in low light, while cones are for color and detail in brighter light.

Which part of the retina is responsible for the highest visual acuity?

• Optic disc

• Fovea

• Peripheral retina

• Macula

Answer explanation

The fovea is the central part of the retina and contains a high density of cone cells, which are responsible for sharp central vision and high visual acuity, making it the area with the best visual detail.

What is the role of optical pigments in photoreceptors?

• To transmit nerve signals

• To absorb light and initiate a chemical change

• To provide structural support

• To supply nutrients

Answer explanation

Optical pigments in photoreceptors are crucial for absorbing light. This absorption triggers a chemical change that ultimately leads to the transmission of visual signals to the brain, making this choice correct.

How do rods and cones differ in their connection to the optic nerve?

• Rods connect directly, cones do not

• Cones connect directly, rods do not

• Rods share connections, cones have individual connections

• Both have the same type of connections

Answer explanation

Rods share connections to the optic nerve, allowing multiple rods to connect to a single ganglion cell, enhancing sensitivity in low light. In contrast, cones have individual connections, providing high acuity and color vision.

Which type of photoreceptor is more sensitive to dim light?

• Cones

• Rods

• Both are equally sensitive

• Neither, they are not sensitive to dim light

Answer explanation

Rods are more sensitive to dim light than cones. They are responsible for vision in low-light conditions, while cones are more active in bright light and color vision.

What is the primary reason rods are not involved in colour vision?

• They lack optical pigments

• They are not connected to the optic nerve

• They contain only one type of pigment

• They are located in the peripheral retina

Answer explanation

Rods contain only one type of pigment, which makes them sensitive to light but not to color. This limitation is why they are not involved in color vision, unlike cones that have multiple pigments for color detection.

Which cells in the retina are primarily responsible for detecting fine detail?

• Rods

• Cones

• Bipolar cells

• Ganglion cells

Answer explanation

Cones are the photoreceptor cells in the retina responsible for detecting fine detail and color. They function best in bright light, allowing for high-resolution vision, unlike rods, which are more sensitive to light but do not detect detail.