ANATOMY – CH. 16 Study Guide: Special Senses – Flashcards
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What are the three divisions of the Ear?
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Outer, middle and inner ear.
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What are the functions of the Outer and Middle Ear?
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to participate in hearing only.
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What is the function of the Inner Ear?
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for both hearing and balance/equilibrium
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What is the function of the Auricle?
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to act as a funnel to bring sound waves into the external acoustic meatus.
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What structures are found in the middle ear?
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-Tympanic Membrane -Auditory Ossicles [malleus, incus, stapes] -Oval Window -Round Window
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What is the function of the Tympanic Membrane?
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Separates the outer ear from the middle ear and transmits air vibrations to auditory ossicles.
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What is the function of the Auditory Ossiciles?
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transmit sound from external ear to internal ear. Increase force but not the amplitude of vibrations transmitted by tympanic membrane.
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What is the function of the Oval Window?
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sound vibrations of the stapes vibrate against and are transmitted
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What is the function of the Round Window?
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dissipates left-over energy in cochlea.
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What is the function of the Auditory Tube?
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Equalize air pressure between the inner ear and the outside.
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What are the reflexive muscles that protect us from loud sounds?
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Tympanic reflex and consists muscles of the stapes and malleus that reflex to limit the vibration of the ossicles to prevent damage.
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What structures are found in the inner ear?
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-Vestibule -Semicircular Canals -Cochlea
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What is the function of the Vestibule?
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Utricle and saccule- balance and position of head; movement
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What is the function of Semicircular Canals?
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concerned with movement and equilibrium; ampullae are swellings near utricle
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What is the function of the Cochlea?
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contains receptors for hearing and converts mechanical sound to nerve impulses
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Where are the receptors for hearing located?
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in the cochlea
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Where are the receptors for head movement [linear acceleration and static equilibrium] located?
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macula of utricle & saccule in vestibule
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Were are the receptors for angular acceleration located?
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semicircular ducts within the semicircular circles
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How are the Receptors of the Macula of Uticle in the Ear Different?
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HORIZONTAL ORIENTATION within ear, HEAD TILTED heavy OTHOLITHIC MEMBRANE pulls DOWNWARD, bending the receptor hairs and signaling the vestibular nerve to tell the brain that the head is tilted.
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How are the Receptors of the Macula of Saccule in the Ear Different?
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VERTICLE ORIENTATION within the ear so heavy OTOLITHS (calcium carbonate crystals: ear stones) PULL DOWNWARD on the hairs whenever the HEAD IS UPRIGHT signaling the brain that the head is in untilted position.
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How are the Receptors of the Macula [Uticle and Saccule] in the Ear Similar?
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Both monitor movements of ACCELERATION, body jolts forward, upward, or sideways in a straight line, the heavy otolithic membrane lags behind, bending the hairs and signaling the brain.
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The receptors for hearing as well as balance and equilibrium
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- cell itself is known as the "Hair" cell. It sends information through vestibular nerve fibers or in the case of hearing cochelar nerve fibers.
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What is the fluid that is found in the Ampullae?
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Cupula contains a jelly-like-cap. Endolymph surrounds it and pushes on the Cupula, which also move the stereocillia thus bending (activating) the hair cells.
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What is the fluid that is found in the Uticle and Saccule?
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Endolymph
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What is the fluid that is found in the Cochlea?
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Cochlear Duct: Endolymph fluid Scala Vestibuli/Scala Tympani: Perilymph Fluid - both structures merge onto the round window.
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Describe the Hearing Pathway:
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1)Sound waves are concentrated in the Auricle bring the sound waves into the External Acoustic Meatus. 2)Sound waves then vibrate the tympanic membrane, which converts the sound waves into mechanical vibrations. 3)These vibrations causes the bones of the middle ear called ossicles (malleus, incus and stapes) to vibrate. 4)The stapes pounds on the oval window (inner ear), vibrations off of the oval window travel through the the perilymph fluid of the Vestibuli and Tympani. 5)Stereocilia cells embedded in the membrane of receptors for hearing in the cochlea cause the Hair cells to move, ultimately sending information through the cochlear nerve to the cerebellum where the information is then processed.
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What are the three layers of the eye?
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-Fibrous: most superficial -Vascular: deep to the fibrous -Sensory Layers: deepest layer
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What is the function of the Lacrimal Gland?
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It sits superiorly and lateral and functions to produce tears.
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What is the function of tears?
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protects the eye by: -keeping the eye moist -contains antibodies to fight off infections
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Describe the path of tears
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travels inferiorly and medially entering the lacrimal sac and emptying into the nasolacrimal duct.
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What is the function of the Nasolacrimal Duct?
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to accept fluid from the lacrimal sac emptying into the nasal cavity.
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What are the two cavities of the eye (segments) and what type of fluid is found in each?
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-Anterior Segment: from the lens forward and contains aqueous humor fluid -Posterior Segment: from the lens toward the posterior end and contains vitreous humor.
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What keeps the eyeball round?
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fluid
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Describe the Sclera Fibrous Layer (tunic) and the function
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white of the eye that provides an anchoring for the eye muscle.
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Describe the Cornea Fibrous Layer (tunic) and the function
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continuous with the sclera, it bends light and allows light to enter the eye.
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What bends light the most: Lens or Cornea
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Cornea
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Describe the vascular layer of the Choroid and its function
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Vascular Layer: continuous with the ciliary body, it is the posterior 5/6 and becomes the iris on the outermost layer Function: Prevents light scatter by absorbing the light
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Describe the vascular layer of the Ciliary Body and its function
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Vascular Layer: consists of smooth muscle, thickened ring of tissue encircling the lens Function: Focuses the lens
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Ciliary processes generate Suspensory Ligaments that do what?
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ligaments that suspend from the Ciliary Body that hold the lens in place and make aqueous humor
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What is Accommodation:
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the changing of the ciliary body when the Suspensory Ligaments contract or expand changing the shape of the lens.
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Describe the vascular layer of the Pupil and its function
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Vascular Layer: opening of the iris Function: opening for light
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Describe the vascular layer of the Iris and its function
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Vascular Layer: visible, colored part of the eye and has smooth muscle fibers Function: allows light to enter
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Describe the vascular layer of the Lens and its function
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Vascular Layer: a thick transparent, biconvex disc held in place posterior to the iris by the suspensory ligaments of the ciliary body Function: changes shape to allow focusing of the light on the retina.
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The retina is the only structure located in the
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Sensory Layer
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Describe the Outer Pigmented Layer of the Retina and its function
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lies against the choroid and absorbs light preventing it from scattering within the eye.
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Describe the Inner Neural Layer of the Retina and its function
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thicker inner sheet of nervous tissue that contains the light-sensitive photoreceptor cells [cones and rods]
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The Neural Layer contains three main types of Neurons:
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-Photoreceptor Cells [cones and rods] -Bipolar Cells -Ganglion Cells
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What are Cones for?
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seeing in color
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What are Rods for?
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seeing in black and white vision
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In dim light conditions, what color do we see in?
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black and white as it doesn't require a lot of light for Rods to be activated. Conversely, Cones require a lot of light to be activated.
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How many different kinds of Cones are there?
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3 for each of the primary colors. The colors that we see are a result of mixing the 3 kinds of cones.
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How do the Bipolar and Ganglion Cells work together?
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When stimulated by light, the photoreceptors neurons signal the bipolar cells, which then signal the ganglion cells to generate nerve impulse potentials. The ganglion cells run the internal surface of the retina converging to form the optic nerve.
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What is located in the Macula Lutea?
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Fovea Centralis and it creates the sharpest image.
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Why is the optic disc considered the blind spot?
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we can not see light that hits that part of the eye because there are no photoreceptors located there.
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What is the Optic Nerve?
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where cells and axons come together in the posterior end of the eye
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Which parts of the eye decusate and which parts do not?
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light that hits the lateral side of the eye does not decusate. Light that hits the medial side of the eye does.
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What is Binocular Vision?
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our eyes are focused slightly medially so you have overlapping. This gives us a better sense of depth perception.
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What part of the brain does most visual information travel to?
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cerebral cortex
