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Structure specialized to receive a specific stimulus Sometimes part of a "full sense" organ, which combines nervous tissue and other tissue to enhance the reception

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Receptor

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Organ that combines nervous tissue and other tissue to enhance the reception ofa stimulus Ex: eyes and inner-ear Not somatosensation (touch, pain, pressure)

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Sense organ

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Conversion of energy from one form to another, typically conversion of the stimulus into an electrical signal for the nervous system to interpret

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Transduction

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Small local electrical change, the initial effect of a stimulus as it contacts the receptor When sensory cells are nerve cells, these can build up to trigger an A.P. When sensory cells are NOT nerve cells, there are synaptic vesicles and their release is triggered by ________ _________.

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Receptor potential

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Subjective awareness of stimulus When sensory input reaches the brain

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Sensation

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The type of stimulus received or sensation produced by the receptor

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Modality

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Modality - what? Location - where? Intensity - how much? Duration - how long?

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Information transmitted by receptors

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Some receptors have large _______ _________, this allows you to use fewer receptors to cover an area. Some receptors have small _______ __________, this allows densely packed receptors to provide more detail. The area over which a single receptor can receive sensory stimuli.

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Receptive fields

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Different that habituation. Habituation is top down regulation. ________ __________ is bottom up regulation. The process of slowing the firing of the receptor as a repeated stimulus continues over time.

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Sensory adaptation

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Generate burst of signals when first stimulated, then adapt quickly and send few or no signals during a continued stimulus. Ex: Smell, hair movement, and cutaneous pressure

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Phasic receptors

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Generate signals steadily during a stimulus and adapt slowly Ex: proprioceptors and pain receptors

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Tonic receptors

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Wavelength of human vision

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400-700nm

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Name for eyelids. Cover the eye and prevent foreign matter from damaging the eye.

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Palpebrae

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Covers the inside of the eyelids and part of the anterior side of the eye. Transparent mucous membrane, produces mucus to keep the eye from drying Highly vascularized

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Conjunctiva

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Produces and drains tears: -Lacrimal gland -Lacrimal punctum -Lacrimal canal -Lacrimal sac -Nasolacrimal duct

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Lacrimal apparatus

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Produces tears, located in the frontal bone at the superolateral corner of the eyes

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Lacrimal gland

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Drain for tears

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Lacrimal punctum

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Drains from lacrimal punctum to lacrimal sac

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Lacrimal canal

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empties lacrimal fluid into the nasal cavity

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Nasolacrimal duct

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connect to the eye and allow it to move within the orbit

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Extrinsic eye muscles

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Muscle that moves the eye up

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Superior rectus

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Muscle that moves the eye down

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Inferior rectus

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Muscle that moves the eye laterally

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Lateral rectus

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Muscle that moves the eye medially

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Medial rectus

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Muscle that passes through trochlea (pulley) at superomedial corner of the eye

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Superior oblique

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Muscle that attaches at inferolateral region of the eye

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Inferior oblique

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the sclera (posterior eye wall, opaque) and cornea (anterior eye wall, transparent) made of collagenous CT with blood vessels and nerves

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Fibrous tunic

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Choroid layer, ciliary body and iris

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Vascular tunic

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The retina and the optic nerve AKA the "inner tunic"

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Nervous tunic

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Protects the eye and attaches extrinsic eye muscles

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Sclera

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Allows the passage of light into the eye, very compact, nourished by fluids inside the eye

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Cornea

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Highly vascularized and pigmented, and absorbs excess light Dark layer that absorbs light and contains many blood vessels to nourish the cells of the eye

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Choroid layer

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Forms muscular ring around lens and helps to change the shape of the lens

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Ciliary body

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An adjustable ring around the pupil

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Iris

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An open space in the middle of the iris

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Pupil

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Contains chromatophores (pigmented cells) that give the eye its color

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Anterior border layer

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Blocks stray light

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Posterior pigment epithelium

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Receives light from the environment A sheet of photoreceptors and their nervous associates

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Retina

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Space behind the iris until the lens

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Posterior chamber

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Space between the iris and cornea

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Anterior chamber

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Chamber that contains vitreous humor Largest chamber of the eye

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Vitreous chamber

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A watery fluid that nourishes the lens, iris, and cornea Produced by the ciliary body Flows from posterior chamber to anterior chamber, through the pupil and then out of the eye through venous sinus

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Aqueous humor

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Most of the eye is filled with ________ ________. Gelatinous substance that keeps the eye in shape Not recycled much, problems hard to manage

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Vitreous humor

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Transparent mass composed of flattened transparent cells (lens fibers) Attached to ciliary body by suspensory ligaments and sits posterior to the pupil Acts as a prism to focus light on the retina

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Lens

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Patch of cells lateral to the optic disc A yellowish central area of the retina that is rich in cones and that mediates clear detailed vision

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Macula lutea

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Pit at the center of macula Receives finest detail in images

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Fovea centralis

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Process in which the brain uses surrounding signals to predict what should be in the blind spot

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Visual filling

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The visual axis of both eyes orients to the same object

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Convergence of eyes

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Pupil constricts to keep light from passing through the edges of the lens, where refraction is not as great

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Constriction of pupils

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Ciliary body contracts and lens relaxes, making lens more round and refracting light more, focusing light from closer object onto retina

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Accommodation

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Receptors which capture photons of light and transduce the signal for interpretation by the brain

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Photoreceptor cells

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Non-neuron receptor cell with a cylindrical outer segment containing RHODOPSIN, senses contrast but not color

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Rod

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Non-neuron receptor cell with a conical outer segment containing PHOTOPSIN, senses color but not contrast

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Cone

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420 nm wavelength Blue-ish

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S cone

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531 nm wavelength Green-ish

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M cone

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558 nm wavelength Red-ish

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L cone

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Contains photopigments while inner segments contain mitochondria and organelles Cell body contains nucleus and processes taht synapse with neurons

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Outer segment

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Contain mitochondria and organelles. Situated between photopigments and cell body

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Inner segment

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Visual purple The pigment of rods a visual pigment consisting of RETINAL and OPSIN.

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Rhodopsin

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A class of protein that, together with retinal, constitutes the photopigments

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Opsin

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A chemical synthesized from vitamin A; joins with an opsin to form a photopigment

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Retinal

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Only in cones. Responsible for color. Based on different wavelengths. -Red -Blue -Green

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Photopsin

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Day vision Daytime lighting, cones do the bulk of the work

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Photopic

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Night vision Cannot resolve finely detailed images; extensive neuronal convergence. Rods do the work.

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Scotopic

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default bend shape of retinal rods (In Dark)

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cis-retinal

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Light converts cis-retinal to ___-_________ position

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trans-retinal

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Adjustment in vision when you move from dark to light.

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Light adaptation

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Adjustment in vision when you move from light to dark.

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Dark adaptation

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One receptor cannot have both high sensitivity and high resolution.

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Duplicity theory

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Inability to see some or all color

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Colorblindness

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The most common form of color blindness. Sex linked to X chromosome. More common in men.

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Red-green colorblindness

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Perception of space and depth caused chiefly by the fact that the eyes receive different images

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Stereoscopic vision

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fibers coming from the medial regions of the eyes decussate, and will go to the contralateral visual cortex of the brain, while fibers coming from the lateral regions do not decussate and will go to the ipsilateral visual cortex

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Hemidecussation

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Nearsightedness caused by an elongated eyeball

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Myopia

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Farsightedness caused by eyeball being shortened

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Hyperopia

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Eyes cannot focus light rays entering from different planes at the same time resulting from a misshapen lens

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Astigmatism

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impaired vision as a result of aging poor near vision due to reduced accommodation of the lens from reduced flexibility•Corrected with bifocals

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Presbyopia

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Increased pressure in the eye puts pressure on and causes damage to the optic nerve

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Glaucoma

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lens becomes opaque, so light cannot pass through, resulting in blurred vision

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Cataracts

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retina separates from the back of the eye due to trauma, diabetes, or decreased vitreous fluid volume, causing blurred vision, "floaters," and shadows in the visual field

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Detached retina

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incomplete maturation of visual system due to infection or vitamin A deficiency causes monocular vision loss

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Amblyopia

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damage to the occipital lobe renders individual unable to perceive visual input, though the eyes are undamaged

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Cortical blindness

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