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APHY 101 Exam 5e
Ch. 15 Anatomy and Neuroscience of Eye and Ear
| Question | Answer |
|---|---|
| what percent of all sensory receptors are in the eye? | 70% of all sensory receptors are in the eye |
| what protects the eye? | most of the eye is protected by a cushion of fat, as well as the bony orbit |
| what accessory structures are to the eye? | eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles |
| what are palpebrae and what do they do? | palpebrae are eyelids. they protect the eye anteriorly. the palpebral fissure separates eyelids (Fig. 13.2) |
| what are canthi? | palpebral commissures, also known as the outer or inner corner of the eye, where the upper and lower lids meet |
| what is the difference between the canthi and lacrimal caruncle? | the caruncle is the small, pink, fleshy nodule located in the corner of the eye, whereas the medial canthus is the entire structural angle or corner where the upper and lower eyelids meet |
| what is the physiology of the lacrimal caruncle? | contains glands that secrete a whitish, oil secretion (Sandman's eye sand) |
| internally, how is the eye getting support? | tarsal plates of connective tissue support the eyelids internally |
| what gives the upper eyelid mobility? | levator palpebrae superioris muscle |
| what is the conjunctiva? | transparent membrane that lines the eyelids as the palpebral conjunctiva, covers the whites of the eyes as the ocular conjunctiva, lubricates and protects the eye |
| what does the lacrimal apparatus consist of? | lacrimal glands that secrete tears, and associated ducts |
| what are 4 features of tears? | 1. contain mucus, antibodies, and lysozyme, 2. enter the eye via superolateral excretory ducts, 3. exit the eye medially via the lacrimal punctum, 4. drain into the nasolacrimal duct (Fig. 13.3) |
| how many extrinsic eye muscles are there? | 6 |
| what do the 6 extrinsic eye muscles do? | enable the eye to follow moving objects, and maintain the shape of the eyeball |
| what is the anatomy of the 6 extrinsic eye muscles? | 4 rectus muscles originate from the annular ring in the back of the eye, and 2 oblique muscles move the eye in the vertical plane (Fig. 13.4a, b) |
| what does the lateral rectus do at the eye and what cranial nerve controls it? | la la la laterally moves the eye :) controlled by cranial nerve 6 (abducens) |
| what does the medial rectus do at the eye and what cranial nerve controls it? | medially moves the eye :) and controlled by cranial nerve 3 (oculomotor) |
| what does the superior rectus do at the eye and what cranial nerve controls it? | elevates eye and turns it medially :) controlled by cranial nerve 3 (oculomotor) |
| what does the inferior rectus do at the eye and what cranial nerve controls it? | depresses eye and turns it medially :) controlled by cranial nerve 3 (oculomotor) |
| what does the inferior oblique do at the eye and what cranial nerve controls it? | elevates eye and turns it laterally (!) controlled by cranial nerve 3 (oculomotor) |
| what does the superior oblique do at the eye and what cranial nerve controls it? | depresses eye and turns it laterally (!) controlled by cranial nerve 4 (trochlear) |
| what is the anatomical structure of the eyeball? | it is a slightly irregular hollow sphere with anterior and posterior poles. the wall has 3 tunics. the internal cavity is filled with fluids called humors. the lens separates the internal cavity into anterior and posterior segments (Fig. 13.5a) |
| what are the 3 tunics of the eyeball wall? | fibrous, vascular, and sensory |
| what comprises the fibrous tunic of the eyeball wall? | this outermost coat of the eye is composed of opaque sclera posteriorly and clear cornea anteriorly |
| what does the sclera do for the eye? | protects it and anchors extrinsic muscles |
| what does the cornea do for the eye? | lets light enter it |
| what comprises the vascular tunic for the eye? | aka uvea, the vascular tunic has 3 regions: choroid, ciliary body, and iris |
| what is the choroid region of the vascular tunic of the eye? | a dark brown membrane that forms the posterior portion of the uvea, supplies blood to all eye tunics! |
| what is the ciliary body of the vascular tunic? | a thickened ring of tissue surrounding the lens, composed of smooth muscle bundles (ciliary muscles), and anchors the suspensory ligament that holds the lens in place |
| what is the iris of the vascular tunic? | the iris is the colored part of the eye, and its central opening is the pupil, which regulated the amount of light entering the eye |
| true or false, pupils constrict when the subject matter is interesting or requires problem-solving skills | false, they dilate |
| pupil dilation and constriction | pupil dilation is sympathetic, and constriction is parasympathetic |
| what comprises the sensory tunic of the eyeball? | a delicate two-layered membrane known as the retina, which has a pigmented layer and neural layer |
| what does the pigmented layer of the retina do? | this outer layer of the retina absorbs light and prevent its scattering |
| what does the neural layer of the retina contain? | photoreceptors that transduce light energy, bipolar cells and ganglion cells, amacrine and horizontal cells (Fig. 13.7a) |
| in the retina, there are ganglion cells and the optic disc. where are the ganglion cell axons? | they run along the inner surface of the retina and leave the eye as the optic nerve |
| what is the optic disc? | the site where the optic nerve leaves the eye; it lacks photoreceptors (the blind spot) |
| what are the types of photoreceptors in the retina? | rods and cones |
| what is the function of rods? | respond to dim light, for gray-tone vision (B&W), and are used for peripheral vision |
| what is the function of cones? | respond to bright light, have high-acuity color vision, have 3 varieties (red, blue, green whose wavelength they absorb), are found in the macula lutea, and are concentrated in the fovea centralis |
| what segments does the lens separate the internal eye into? | anterior and posterior segments; anterior also has two chambers anterior and posterior |
| what is the clear gel of the posterior segment of the eye called? | vitreous humor |
| what 4 things does the vitreous humor do? | transmits light, supports the posterior surface of the lens, holds the neural retina firmly against the pigmented layer, contributes to intraocular pressure |
| what is the plasmalike fluid of the anterior segment? | aqueous humor, that drains via the canal of Schlemm (aqueous humor supports, nourishes, and removes wastes) |
| what 2 parts is the anterior segment of the eye divided into (Fig. 13.9)? | anterior and posterior CHAMBERS - anterior between the cornea and the iris; posterior between the iris and the lens |
| what is the lens of the eye? | a biconvex (*convex on both sides), transparent, flexible, avascular structure that allows precise focusing of light onto the retina, is composed of epithelium and lens fibers |
| what is the effect of aging on the lens? | it becomes more compact and dense and loses its elasticity |
| light is a form of electromagnetic radiation. what energy waves does electromagnetic radiation include? | all energy waves from short gamma rays to long radio waves |
| our eyes respond to a small portion of the electromagnetic radiation spectrum. what is this called? | visible spectrum |
| true or false, cones in the retina all respond to the same wavelengths of the visible spectrum | false, different cones in the retina respond to different wavelengths of the visible spectrum (Fig. 13.10b) |
| what happens when light passes through the convex lens of the eye? | its speed changes and it bends so that the rays converge to a focal point, and forms an upside down image and reversed (Fig. 13.11) |
| what is the pathway of light entering the eye? | cornea, aqueous humor, lens, vitreous humor, and the neural layer of the retina to the photoreceptors |
| how many times and where is light refracted at the eye? | 1. at the cornea 2. entering the lens 3. leaving the lens |
| true or false, it is the lens curvature and shape that allow for fine focusing of an image | true |
| true or false, light from a distance takes more adjustment for proper focusing of the eye | false, the far point of vision is 20 ft. - the distance beyond which the lens does not need to change shape to focus |
| what 3 things does close vision require? | accommodation, constriction, and convergence |
| what is accommodation? | thickening of the lens by ciliary muscles to increase refractory (light-bending) power |
| what is constriction? | the pupillary reflex constricting the pupils to prevent divergent light rays from entering the eye |
| what is convergence? | medial rotation of the eyeballs toward the object being viewed |
| the PNS enables close-up vision through the accommodation reflex, which involves what? | contracting the ciliary muscle to increase lens curvature, constricting the pupil to improve depth of field, and converging the eyes |
| true or false, an emmetropic eye is a normal eye with light focusing properly | true |
| problems of refraction - nearsightedness | myopia where the focal point is in front of the retina - corrected with a concave lens |
| problems of refraction - farsightedness | hyperopia where the focal point is behind the retina - corrected with a convex lens |
| Fig. 13.16 illustrates the visual pathways | axons of retinal ganglion form the optive nerve, whose medial fibers decussate @ optic chiasm; most fibers of the optic tracts continue to the lateral geniculate body of the thalamus |
| where do the other optic tract fibers go? | they end in superior colliculi (initiating visual reflexes) and pretectal nuclei (involved with pupillary reflexes) |
| where do optic radiations travel? | from the thalamus to the visual cortex in the occipital (!) lobe of the brain |
| what is the mechanism of hearing? | sound vibrations beat against the eardrum, which push against the ossicles (malleus, incus, and stapes). the stapes transmits these vibrations to the fluid in the inner ear via the oval window |
| what happens past the oval window of the ear? | shearing forces pull on hair cells, and moving hair cells stimulates the cochlear nerve that sends impulses to the brain |
| what is sound? | a pressure disturbance originating from a vibrating object (alternating areas of high and low pressure), composed of areas of rarefaction and compression |
| how is sound represented visually? | represented by a sine wave in wavelength, frequency, and amplitude |
| what are the 4 properties of sound? (recognize for multiple choice) | frequency, pitch, amplitude, and loudness (Fig. 13.22) |
| what is frequency? | the number of waves that pass a given point in a given time |
| what is pitch? | perception of different frequencies (we hear from 20-20,000 Hz) |
| what is amplitude? | intensity of a sound measured in decibels (dB) |
| what is loudness? | subjective interpretation of sound intensity |
| what is the route of sound to the inner ear? | outer ear, middle ear, inner ear; then, stimulation of the organ of Corti, generation of impulses in the cochlear nerve, and fluid wave energy is dissipated by bulging of round window |
| what are the 4 parts of the outer ear? | pinna, auditory canal, eardrum |
| what are the 3 parts of the middle ear and where do they go? | malleus, incus, stapes, go to the oval window |
| what are the 2 parts of the inner ear and where to they go? | scalas vestibuli and tympani go to the cochlear duct |
| what 3 things do audible sound waves do in resonating the basilar membrane? (Fig. 13.23) | penetrate through the cochlear duct, vibrate the basilar membrane, excite specific hair cells according to the frequency of the sound |
| what is the organ of Corti? | a structure in the cochlea of the inner ear which produces nerve impulses in response to sound vibrations |
| what is the anatomy of the organ of Corti? | composed of supporting cells and outer and inner hair cells; afferent fibers of the cochlear nerve attach to the base of hair cells (stereocilia) |
| what anatomical points are noteworthy about the stereocilia hairs? | they protrude into the endolymph and touch the tectorial membrane |
| what is the neuroscience of exciting hair cells in the organ of Corti? (Fig. 13.21c) | bending cilia opens mechanically gated ion channels and causes a graded potential and release of a neurotransmitter (probably glutamate); the NT causes cochlear fibers to transmit impulses to the brain, where sound is perceived |
| what are 4 steps of the auditory pathway to the brain for sound? | 1. cochlear impulses pass via spiral ganglion to cochlear nuclei 2. impulses are sent to the superior olivary nucleus and inferior colliculus 3. impulses pass to the auditory cortex 4. auditory pathways decussate (cortices receive input from both ears) |
| why is the auditory pathway unusual? | it has 4 neurons rather than the typical 3 for a sensory pathway |
| what are 4 types of deafness or maladies to the ear? | conduction deafness, sensorineural deafness, tinnitus, Meniere's syndrome |
| what is conduction deafness? | something hampers sound conduction to the fluids of the inner ear (earwax, perforated eardrum, osteosclerosis of ossicles) |
| what is sensorineural deafness? | deafness resulting from damage to neural structures at any point from the cochlear hair cells to the auditory cortical cells |
| what is tinnitus? | ringing or clicking sound in the ears while auditory stimuli are absent |
| what is Meniere's syndrome? | labyrinth disorder that affects the cochlea and the semicircular canals, causing vertigo, nausea and vomiting |
| what keeps us oriented/ at equilibrium? | vestibular apparatus that has equilibrium receptors in the semicircular canals (monitor dynamic equilibrium) and vestibule (monitor static equilibrium), maintaining our orientation and balance in space |
| what are maculae & their anatomy? (Fig. 13.24) | sensory receptors for static equilibrium in the vestibule. they contain supporting cells and hair cells |
| what is the anatomy of a hair cell in the vestibule? | each hair cell has stereocilia and kinocilium embedded in the otolithic membrane (a jellylike mass studded with tiny CaCO3 stones called otoliths) |
| what do utricular hairs respond to? | horizontal movement, affected by gravity such that otolithic movement bends kinocilia which increase/decrease rate of AP production in vestibular nerve (cranial nerve 8) |
| what do saccular hairs respond to? | vertical movement |
| what is the receptor for dynamic equilibrium? | the crista ampullaris (Fig. 13.25), responds to angular movements |
| what is the anatomy of the crista ampullaris? | each crista, located in the ampulla of each semicircular canal, has support cells and hair cells that extend into a gel-like mass called the cupula; dendrites of vestibular nerve fibers encircle the base of the hair cells |
| how are crista ampullaris receptors activated? | cristae respond to changes in velocity of rotatory movements of the head, and the directional bending of hair cells in the cristae informs brain of rotational movements of the head |
| what are the 3 modes of input for balance and orientation? | vestibular receptors, visual receptors, and somatic receptors (joint capsule receptors in the cervical spine) |
| what do balance/orientation receptors allow our body to do? | respond reflexively to maintain balance, although when these 3 types of receptors send conflicting information to the brain, the result is vertigo and nausea |
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