Biol 14 Week 3 Sensory System Pt. 2

Iris

The colored part of the eye that controls the size of the pupil and regulates the amount of light entering the eye.

Sclera

The white, outer layer of the eye that provides structure and protection.

Choroid

The middle layer of the eye, rich in blood vessels, that provides nutrients to the retina and absorbs excess light.

Cornea

The transparent, dome-shaped part of the eye that focuses light onto the retina. It is the major refractive element of the eye.

Lens

The adjustable refractive element of the eye that fine-tunes focus depending on the distance of the object being viewed. It changes shape for near and far vision.

Pupil

The circular opening in the center of the iris that controls the amount of light entering the eye.

Photoreceptor Cells (Rods and Cones)

Cells in the retina that detect light and convert it into electrical signals. Rods are responsible for vision in low light, while cones are responsible for color vision and sharp central vision.

Phototransduction

The process by which light signals are converted into electrical signals by photoreceptor cells in the retina.

Rods

Photoreceptor cells responsible for vision in low light conditions. They are most concentrated in the peripheral retina.

Cones

Photoreceptor cells responsible for color vision and high-acuity vision. They are concentrated in the fovea, the center of the retina.

Fovea

The central part of the retina that provides the sharpest vision and contains a high density of cone cells.

Rhodopsin

The photopigment found in rod cells, responsible for the initial step of phototransduction in low light conditions.

Transducin

A G-protein activated in phototransduction by the absorption of light by rhodopsin, leading to the activation of phosphodiesterase (PDE).

Phosphodiesterase (PDE)

An enzyme activated by transducin that breaks down cGMP, causing a reduction in its concentration and leading to the closure of cGMP-gated ion channels in photoreceptor cells.

Dark Current

The flow of ions (mainly Na+ and Ca2+) into the photoreceptor cells in the dark, which maintains a slight depolarization of the cell. In the light, the dark current decreases, leading to hyperpolarization.

Retinal Ganglion Cells

Neurons in the retina that receive input from bipolar cells and transmit visual signals to the brain via their axons in the optic nerve.

Lateral Inhibition

A mechanism that enhances the contrast between neighboring photoreceptors, helping to sharpen the perception of edges and objects.

Fovea Centralis

The central part of the retina with the highest concentration of cones and the highest acuity for vision.

Accommodation Reflex

The change in the shape of the lens to focus on objects at different distances. The lens flattens for far vision and rounds up for near vision.

Auditory Transduction

The process of converting sound vibrations into electrical signals in the cochlea of the inner ear.

Cochlea

A spiral-shaped organ in the inner ear that detects sound vibrations and converts them into electrical signals for auditory processing.

Basilar Membrane

A membrane inside the cochlea that vibrates in response to sound and plays a key role in converting sound into neural signals by stimulating hair cells.

Hair Cells (Auditory)

Sensory cells in the cochlea responsible for transducing sound vibrations into electrical signals. They are located on the basilar membrane and are critical for hearing.

Vestibulocochlear Nerve (Cranial Nerve VIII)

The cranial nerve that transmits sound and balance information from the ear to the brain.

Tonotopic Organization

The spatial arrangement of sound frequency processing in the auditory cortex, where cells that respond to similar frequencies are grouped together.

Sound Localization

The ability to identify the location of a sound based on the differences in time and intensity between the two ears.

Pinna

The outer part of the ear that captures and funnels sound waves into the ear canal.