Overview of Sensory Systems and Eye Anatomy

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Explain the difference between trichromatic coding and opponent-process coding in terms of color perception.

Trichromatic coding suggests that our perception of color is based on the relative activation of three types of cones sensitive to different wavelengths of light (red, green, and blue). Opponent-process coding, on the other hand, proposes that color perception arises from opposing pairs of color channels, such as red-green, blue-yellow, and black-white. These opposing channels work in a way that the activation of one channel inhibits the activation of its counterpart, leading to the perception of specific colors.

What is color constancy and how does the Retinex theory explain it?

Color constancy refers to our ability to perceive the color of an object as relatively constant despite changes in illumination conditions. The Retinex theory proposes that the cortex compares the overall color across the retina, taking into account the surrounding colors, to deduce the true color of an object, maintaining its perceived color even under varying lighting.

How do the responses of the three types of cones contribute to our perception of different colors?

The perception of color arises from the unique combination of activation levels across the three types of cones. Each cone type is maximally sensitive to a different wavelength of light. The relative activation of these cones, based on the wavelengths present in the light, determines the color we ultimately perceive.

What is the role of bipolar cells and ganglion cells in color vision?

Bipolar cells receive input from the photoreceptor cones. They then transmit information to the ganglion cells, which are the output neurons of the retina, sending signals to the brain. Both bipolar and ganglion cells can be involved in opponent-process coding, which allows us to perceive color contrast and edges. Signup and view all the answers

What is color vision deficiency and how does it affect color perception?

Color vision deficiency (also known as color blindness) occurs when one or more of the three types of cones are absent or malfunctioning. This leads to difficulty in distinguishing specific colors, often causing individuals to perceive colors differently than people with normal color vision. The severity varies depending on the type and extent of the deficiency. Signup and view all the answers

What is the name of the structure in the eye that helps focus light on the retina?

Lens Signup and view all the answers

What is the name of the clear, fluid that fills the space between the lens and the retina?

Vitreous Humor Signup and view all the answers

What is the name of the transparent outer layer of the eye that helps to focus light?

Cornea Signup and view all the answers

What is the name of the colored part of the eye that controls the amount of light entering the eye?

Iris Signup and view all the answers

What is the process called that allows the eye to focus on objects at different distances?

Accommodation Signup and view all the answers

What are the three main layers of cells in the retina?

Photoreceptors, Bipolar Cells, Ganglion Cells Signup and view all the answers

What is the name of the location on the retina with the sharpest visual acuity?

Fovea Signup and view all the answers

What is the name of the point on the retina where the optic nerve leaves the eye, creating a blind spot?

Optic Disk Signup and view all the answers

What are the two primary types of photoreceptor cells in the retina?

Rods and cones Signup and view all the answers

What is the name of the light-sensitive pigment found in photoreceptor cells?

Photopigment Signup and view all the answers

What is the name of the molecule that is involved in the photopigment's response to light?

Retinal Signup and view all the answers

What happens to the photoreceptor when light is absorbed by its photopigment?

It hyperpolarizes Signup and view all the answers

What type of neurotransmitter is released by the photoreceptor, and what effect does it have on the bipolar cell?

Inhibitory neurotransmitter, inhibits the bipolar cell Signup and view all the answers

How does light absorption by the photoreceptor ultimately lead to the excitation of the ganglion cell?

Light absorption hyperpolarizes the photoreceptor, which reduces the release of inhibitory neurotransmitter, allowing the bipolar cell to become excited and then excite the ganglion cell. Signup and view all the answers

What type of visual disorder involves the destruction of the fovea and its surrounding area, creating a blind spot on the retina?

Macular degeneration Signup and view all the answers

Study Notes

Sensory Systems Overview

Sensory systems rely on reception, transduction (converting stimulus energy to neuronal signals), and coding (linking stimulus features to neuronal activity).
Visual system is used as an example to describe the processes.

Anatomy of the Eye

Lens: Focuses light.
Vitreous Humor: A transparent jelly-like substance filling the eye.
Cornea: Transparent outer layer of the eye, responsible for refraction.
Iris: Controls the amount of light entering the eye.
Accommodation: Changing lens shape to focus on varying distances.
Retina: Contains photoreceptors and various other cells responsible for detecting light.
Optic Disk: Where optic nerve exits the eye, creating a blind spot.
Optic Nerve: Carries visual information from the retina to the brain.
Fovea: Region of the retina with the highest visual acuity.
Peripheral Vision: Better at detecting dim light.

Cellular Components of the Retina

Photoreceptors (Rods and Cones): Specialized cells sensitive to light.
- Rods: High sensitivity to dim light (120 million).
- Cones: High sensitivity to color and detail (6 million).
Bipolar Cells: Relay information from photoreceptors to ganglion cells.
Ganglion Cells: Generate action potentials, transmitting signals to the brain via the optic nerve.
Amacrine Cells: Modify signals between bipolar and ganglion cells.

Vision Transduction

Photopigment: (retinal + opsin) Chemical that absorbs light.
Photoreceptor Response: Light causes a hyperpolarization in photoreceptors, reducing neurotransmitter release.
Bipolar and Ganglion Cells: Bipolar cells are excited by the reduced inhibition, while Ganglion cells receive the signal and produce action potentials.

Visual Field

The entire area that can be seen by the eye.

Color Vision

Trichromatic Theory: Three types of cones, each maximally sensitive to different wavelengths (red, green, blue).
Opponent-Process Theory: Color perception based on opponent pairs (red-green, blue-yellow).
Color Constancy: Ability to perceive colors consistently despite varying lighting conditions.
Retinex Theory: cortex compares overall color across the retina in order to judge color.

Visual Processing in the Brain

Visual information from the optic nerve travels to specific areas of the brain for further processing.
Areas like V1, V2, V4, and the inferior temporal cortex are involved in visual tasks such as colour, motion, form and shape identification.

Visual Disorders

Macular Degeneration: Damage to the fovea, leading to loss of central vision. Common in older individuals.
Retinitis Pigmentosa: Genetic disorder causing progressive loss of rods, eventually impacting cones.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz provides an overview of sensory systems, focusing on the visual system and the anatomy of the eye. Key components such as the lens, retina, and optic nerve are explored, detailing their functions in visual processing. Test your understanding of how these elements work together to enable vision.