Lab 10 Special Senses: Vision and Audition

Sensory receptors

Structures that respond to stimuli in the external and internal environment and body & are classified according to that stimulus.

General receptors

Widely distributed receptors responding to touch, pressure, pain, and temperature.

Somatic receptors

Sensory receptors found in the skin and musculoskeletal organs.

Visceral receptors

Sensory receptors found inside visceral organs.

Specialized receptors

Highly specialized receptor cells housed in specialized organs for special senses (Gustation (taste), olfaction (smell), vision, hearing & equilibrium, and audition (hearing)).

Transducer function

Sensory receptors convert stimuli into afferent nerve impulses.

Mechanoreceptors (Stimulus TYPE classification)

Receptors responding to touch or pressure stimuli.

Chemoreceptors (Stimulus TYPE classification)

Receptors responding to chemical stimuli.

Photoreceptors (Stimulus TYPE classification)

Receptors responding to light stimuli.

Nociceptors (Stimulus TYPE classification)

Receptors responding to intense thermal, chemical, or mechanical stimuli resulting in pain.

Thermoreceptors (Stimulus TYPE classification)

Receptors responding to temperature changes.

Exteroceptors (Stimulus SOURCE classification)

Receptors located on the body surface responding to external stimuli.

Interoceptors (Stimulus SOURCE classification)

Receptors located deep inside the body responding to internal stimuli.

Proprioceptors (Stimulus SOURCE classification)

Internal receptors located ONLY in musculoskeletal organs.

Palpebrae conjunctiva (eyelid)

Superior & inferior eyelids cover the eye anteriorly. Meet medially at the medial commissure & lateral commissure.

Lacrimal caruncle

Modified sweat gland at the medial commissure providing lubrication.

Conjunctiva

Thin mucous membrane lining the internal surface of the eyelids. Lubricates surface of eyeball.

Lacrimal glands

Secrete watery, alkaline tears w/ antibacterial enzyme called lysozymeto clean, lubricate, protect eye. Travel across eye & drain thru lacrimal puncta into lacrimal canaliculi into lacrimal sac.

Nasolacrimal duct

Receives tears & transports them to nasal cavity

Inferior oblique muscle action

Elevates eye and rotates it laterally.

Inferior rectus muscle action

Depresses the eye.

Medial rectus muscle action

Moves the eye medially.

Lateral rectus muscle action

Moves the eye laterally.

Superior oblique muscle action

Depresses the eye and rotates it laterally.

Superior rectus muscle action

Elevates the eye.

Fibrous layer of the eye

Outer layer composed of the cornea and sclera.

Cornea function

Bends light as it enters the eye.

Cornea oxygen source

Gets oxygen via diffusion rather than blood vessels.

Cornea transplant

Only human tissue that can be transplanted without rejection fear.

Sclera

White of the eye that protects it and serves for muscle attachment.

Vascular layer of the eye

Middle layer containing choroid, ciliary body, and iris.

Choroid function

Supplies oxygen/nutrients and contains melanocytes absorbing excess light.

Ciliary body

Thickened choroid part regulating lens shape and secreting aqueous humor.

Iris function

Contains pigmented cells giving eye color; contains smooth muscle that regulates pupil size & amount of light entering eye.

Retina

The inner neural layer containing photoreceptors triggers stimulation of optic nerves & impulse transmission to occipital lobe.

Outer pigmented epithelium

Absorbs light and prevents scattering in the retina.

Rods

Photoreceptors enabling low-light and peripheral vision; concentrated in periphery.

Cones

Photoreceptors enabling visual acuity(sharpness) and color vision. Concentration highest @ center of eye.

3 types of cones

blue, green, red = other colors are due to stimulation intensity of 2+ cones.

Bipolar cells

Receive electrical impulses directly from rods and cones.

Retinal ganglion cells

Synapse with bipolar cells and their axons form optic nerves.

Optic disc

Blind spot where the optic nerve exits with no photoreceptors.

Macula lutea

Lateral to optic disc; responsible for high color vision; contains Fovea Centralis.

Fovea centralis

Retinal area with the most rods and cones and sharpest vision.

Lens

Biconcave structure that bends light via refraction using crystallin protein.

Suspensory ligaments

Structures holding the lens in place.

Anterior cavity

Subdivided by Iris into the Anterior & Posterior chambers.

Aqueous humor (Anterior cavity)

Secreted by ciliary body into both chambers.

Vitreous humor

Gel-like fluid fills the posterior cavity to provide internal support for the posterior part of the eye. Keeps retina firmly against vascular choroid.

Tapetum lucidum

Reflective choroid part in animals that increases available light (part of vascular layer of light). Reflects light back through the retina and increases the light available to the photoreceptors making their eyes glow at night.

Visual acuity

Measurement of spatial resolving capacity applied to central vision.

20/20 vision

Ability to read the 20-foot line on a Snellen chart from 20 feet.

20/200 vision

If you can only read the 200 ft line, then you have 20/200 vision (legally blind).

Astigmatism

Lens has uneven curvature on one of its surfaces. Causes things to be blurred in one axis but sharp in other axes.

Color blindness inheritance

Sex-linked hereditary condition affecting 8 percent of males, 0.5 percent females.

Protanopia (If red cones lack)

See blue green & purple tinted reds as grey.

Deuteranopia (If green cones lack)

See red, green, yellow, orange, brown hues as shades of yellow & blue.

Depth perception

Ability to distinguish relative position or distance depending on the images position presented to both retinas.

Binocular vision

Required for depth perception; the ability of both eyes & brain working together to create a single, clear, 3D image of the world.

Myopia (nearsightedness)

Difficulty of seeing objects at a distance. Eyeball is slightly longer than usual from front to back; causes light rays to focus at a point in front of retina instead of directly on its surface.

Myopia correction

Corrected using concave lenses.

Hyperopia (farsightedness)

Difficulty seeing objects close up. Eyeball is slightly shorter than usual from front to back; causes light rays to focus at a point behind the retina.

Hyperopia correction

Corrected using convex lenses.

Auricle / Pinna

Directs sound waves to auditory canal.

External Auditory Canal

Receives sound waves

Ceruminous glands

Lined in external auditory canal and produces cerumen or earwax.

Tympanic membrane (eardrum)

Barrier between outer and middle ear that vibrates from sound.

Middle ear

Air filled cavity within temporal bone that extends to oval window of the inner ear

Auditory ossicles

Three small bones: malleus, incus, and stapes.

Auditory ossicles function

Transmit and amplify sound waves in the middle ear.

Pharyngotympanic tube (Eustachian tube)

Connects middle ear to nasopharynx to equalize pressure.

Inner ear

Houses sensory organs for hearing & equilibrium in labyrinth (Semicircular Canals, Cochlea, Vestibule)

Perilymph

Fluid filling the outer bony labyrinth of the inner ear.

Endolymph

Fluid filling the inner membranous labyrinth of the inner ear.

Spiral organ

Located in the cochlea; sits on basilar membrane & contains specialized hair cells with stereocilia projecting into endolymph.

When basilar membrane vibrates

Stereocilia bend & open Potassium (K+) channels on hair cells.

Hair cell depolarization

Occurs when K+ flows into hair cells.

What hair cell depolarization causes

Release of neurotransmitters that send messages thru the cochlear nerve to the vestibulocochlear nerve to the brain.

Utricle and saccule subdivisions

The vestibule of the inner ear is subdivided into the utricle and saccule. Contains receptor organs called Maculae.

Maculae cell types

Maculae contain hair cells and supporting cells that provide sensory information for static equilibrium.

Static equilibrium function

Provides sensory information concerning head position and linear acceleration.

Dynamic equilibrium organs

Semicircular canals and crista ampullaris for angular acceleration.

Vestibulocochlear nerve formation

Action potentials travel along the vestibular nerve and join with the cochlear nerve.

Static equilibrium neural pathway

Impulses travel from the vestibule to the vestibular nerve, to the vestibulocochlear nerve, and finally to the brain.

Semicircular canals base expansion

They expand at their base to form structures called the ampulla.

Crista ampullaris

Receptor structure located inside each ampulla containing hair cells and supporting cells.

Stereocilia and cupula

Stereocilia of hair cells project into the gelatinous membrane known as the cupula.

Vestibular nerve function in equilibrium

Transmits signals related to angular acceleration and deceleration (dynamic equilibrium) from the inner ear to the brain.

Conduction deafness

Hearing loss caused by damage to the eardrum and/or ossicles.

Sensorineural deafness

Hearing loss caused by damage to the cochlea, cochlear nerve, vestibule, vestibular nerve, or vestibulocochlear nerve.

Auditory Processing Disorder

Condition in which there is normal hearing sensitivity, but the brain struggles to properly process, recognize, or interpret speech & sounds; especially in nosy environments.

Sound and speech

Are tied together, especially with language processing in the brain.

Wernicke's area

Manages language comprehension, word meaning, and lexical selection; Damage = nonsensical speech.

Broca's Area

Manages speech production, motor planning for the tongue, and grammatical structure; Damage = slow, broken, difficult speech

Weber's Test

Diagnostic test for assessing hearing loss & differentiating between conductive vs sensorineural hearing loss.

Weber's Test procedure

Tuning fork is placed on top of the head.

Rinne's Test

Diagnostic test for assessing hearing loss & differentiating between conductive vs sensorineural hearing loss, comparing air vs bone conduction.

Rinne's Test procedure

Tuning fork is placed on the lateral aspect of the head at the ear.

Romberg's Test

Neurological exam used to assess balance & coordination.

Audiometry

Instrument used to determine hearing losses in the audible range of normal speech (125 - 8,000 Hz).