The Nervous System: Sensory Systems - Vision

Flashcards covering key vocabulary terms related to the anatomy, physiology, and clinical aspects of the nervous system's sensory vision system.

Sclera

The outermost layer of the eye, protective and white.

Cornea

The transparent, fixed curve part of the outermost eye layer, refracts light entering the eye.

Choroid

The middle layer of the eye, providing blood supply.

Ciliary body

Part of the middle layer of the eye containing zonular fibers and ciliary muscle, involved in accommodation.

Iris

Part of the middle layer that regulates the amount of light entering the eye through the pupil, consisting of inner circular and outer radial smooth muscles.

Pupil

The opening in the center of the iris through which light enters the eye.

Retina

The inner neural tissue layer of the eye containing photoreceptors, bipolar cells, amacrine cells, horizontal cells, and ganglion cells.

Photoreceptors

Receptor cells in the retina (rods and cones) that convert light energy to nerve signals.

Fovea

A central pit in the retina, primarily containing cones, responsible for sharp central vision.

Optic disk

The blind spot in the retina where the optic nerve and blood vessels exit the eye, lacking photoreceptors.

Aqueous humor

Fluid filling the anterior and posterior chambers of the anterior segment of the eye.

Vitreous humor

Gel-like substance filling the posterior segment (vitreous chamber) of the eye.

Refraction

The bending of light waves as they pass from one medium density to another, crucial for focusing light in the eye.

Accommodation

The process of increasing lens curvature to enable the eye to focus on near objects, involving parasympathetic control of the ciliary muscle.

Emmetropia

Normal vision, where distant and near objects are focused on the retina with appropriate accommodation.

Myopia

Near-sightedness, where the lens is too strong for the eyeball's length, causing distant objects to be focused in front of the retina.

Hyperopia

Far-sightedness, where the lens is too weak for the eyeball's length, causing near objects to be focused behind the retina.

Presbyopia

Hardening of the lens, typically with age, making it difficult to focus on near objects.

Cataract

Opacity of the lens, leading to cloudy vision.

Glaucoma

Increased volume of aqueous humor and degeneration of the optic nerve.

Astigmatism

Irregularities of the lens or cornea, leading to blurred or distorted vision.

Rods

Outer photoreceptor cells in the retina primarily responsible for black-and-white vision and vision in low light, containing rhodopsin.

Cones

Outer photoreceptor cells in the retina primarily responsible for color vision and high acuity vision in bright light, containing L, M, and S opsins.

Ganglion cells

Inner layer cells in the retina whose axons form the optic nerve and transmit action potentials to the brain.

Macula lutea

A yellowish central area of the retina that includes the fovea.

Macular degeneration

A clinical defect involving the degeneration of the macula lutea, leading to central vision loss.

Phototransduction

The conversion of light energy into electrical nerve signals by photoreceptors.

Photopigments

Light-sensitive molecules in photoreceptors, each composed of retinal and an opsin (e.g., rhodopsin in rods, L/M/S opsins in cones).

Melanopsin

A special photopigment found in certain photoreceptors that links light input to circadian rhythms.

Optic nerve

Cranial nerve II, formed by the axons of ganglion cells, transmitting visual information from the eye to the brain.

Optic chiasm

The point where axons from the nasal retina cross to the contralateral side, while temporal retina axons remain ipsilateral.

Lateral geniculate body

A region in the thalamus where optic tract neurons synapse before projecting to the visual cortex.

Parallel processing

Different types of visual information (color, shape, movement) are transferred by specific neurons along parallel pathways to the primary visual cortex and higher cortical areas.

Depth perception

The brain's ability to construct a three-dimensional image from the two slightly different perspectives provided by the monocular visual fields to create a binocular visual field.