Lecture 9 Vision 1

Sensation

How cells detect stimuli in the environment (such as light, sound, heat, etc) and how they transduce (=convert) these signals into a change in membrane potential and neurotransmitter release.

Perception

The conscious experience and interpretation of sensory information.

Photoreceptor cells

Cells in our eyes that transduce light into a change in membrane potential.

Light

Electromagnetic energy that travels in waves/packets (photons).

Visible light

A tiny slice of the electromagnetic spectrum that humans can see (~380-750nm).

Wavelengths

Different wavelengths correspond to different colors (short = violet/blue, long = orange/red).

Electromagnetic spectrum

The range of all types of electromagnetic radiation, from low energy (radio waves) to high energy (gamma rays).

Temperature

How much kinetic energy (movement energy) the atoms and molecules in something have.

Atomic Collisions

The interactions between atoms that occur as they move faster and collide harder with each other, indicating heat.

Vitamin A (retinal)

A molecule that twists in response to a photon of visible light, starting a chain reaction in photoreceptor cells.

Opsin

A protein in photoreceptor cells that, when activated by retinal, triggers a biochemical cascade changing the cell's membrane potential.

Cones

Photoreceptor cells responsible for color vision, with three types: Blue (S), Green (M), and Red (L).

Rods

Photoreceptor cells that are ~100x more light-sensitive than cones, great in dim light, and perceive lightness and darkness.

Grayscale vision

Vision that perceives shades of gray instead of color, typically seen in low-light conditions.

Trichromatic coding

The process by which the brain compares relative activity across the three cone types to perceive colors.

Additive light mixing

The mixing of red and green light to create yellow, as seen in screens.

Brightness

How much total light is present.

Hue

The wavelength that dominates, corresponding to the color name.

Saturation

How pure a color is versus how gray or washed-out it appears.

Saccades

Quick jumps made by the eyes to scan scenes.

Smooth pursuit

The smooth tracking of a moving target by the eyes.

Fovea

The central part of the retina that supports high-resolution color vision.

Peripheral vision

Vision that is sensitive to dim light but provides low-resolution grayscale images.

Cone Cells

Photoreceptor cells in the fovea responsible for color vision and sharp detail.

Bipolar Cell

A type of neuron that connects cone cells to ganglion cells in the retina.

Ganglion Cell

A type of neuron that receives signals from bipolar cells and transmits them to the brain.

Periphery

Outer part of the retina that contains rod cells, which are sensitive to dim light and motion but cannot see color.

Rod Cells

Photoreceptor cells in the periphery that are sensitive to dim light and motion but only see in grayscale.

Protanopia

Color vision deficiency caused by missing red cone opsin, leading to trouble distinguishing reds and greens.

Deuteranopia

Color vision deficiency caused by missing green cone opsin, resulting in similar red and green issues.

Tritanopia

Rarer color vision deficiency caused by missing blue cone opsin, leading to blue-yellow problems.

Visual Acuity

Sharpness of vision, which depends on the number of cones and their connection to the brain.

Cornea

Fixed front lens of the eye that does most of the focusing and can be reshaped in laser eye surgery.

Iris

Colored ring that controls the size of the pupil, regulating how much light enters the eye.

Lens

Fine-focus structure in the eye that changes shape to focus on near or far objects.

Retina

Back layer of the eye that contains photoreceptors and is responsible for capturing light.

Optic Disk

Area where optic nerves exit the eye, containing no photoreceptors, resulting in a blind spot.

Spin Energy

Energy associated with the nucleus of an atom spinning.

Rotational Energy

Energy related to the whole molecule spinning or tumbling.

Vibrational Energy

Energy from atoms shaking back and forth within a molecule.

Electronic Energy

Energy from electrons jumping between orbitals around the nucleus.

Emission

Process by which energy turns into light when a molecule relaxes back to a lower-energy state.

Absorption

Process where an electron is captured in a high energy orbital state when visible light is absorbed.

Reflection

Process where an electron temporarily oscillates but remains in its orbital state, allowing color to be seen.

Transmission

Process where an electron cannot readily absorb the energy of light, resulting in transparency.

Surface Color

Determined by the wavelengths a surface reflects rather than absorbs.