Exercise 18. Special Senses: The Ear and the Eye

elevates eye and turns it laterally, oculomotor (III)

Name the muscle action and cranial nerve innervation (and #) of the inferior oblique

depresses eye and turns it medially, oculomotor (III)

Name the muscle action and cranial nerve innervation (and #) of the inferior rectus

moves eye laterally, abducens (VI)

Name the muscle action and cranial nerve innervation (and #) of the lateral rectus.

moves eye medially, oculomotor (III)

Name the muscle action and cranial nerve innervation (and #) of the medial rectus

depresses eye and turns it laterally, trochlear (IV)

Name the muscle action and cranial nerve innervation (and #) of the superior oblique

elevates eye and turns it medially, oculomotor (III)

Name the muscle action and cranial nerve innervation (and #) of the superior rectus

spiral ganglion, cochlear nerve

Nerve fibers synapse with the hair cells in the spiral organ of Corti at their base. The somas of these nerve cells form the ______________ and their axons form the ___________, the auditory portion of the 8th cranial nerve.

endolymph, spiral organ of Corti

The scala media contains a potassium-rich fluid called ______________ and houses the _______________, the site where mechanical sound energy is converted to nerve signals.

sensorineural

_______________ hearing loss involves the inner ear (destruction of hair cells), cochlear branch of Cranial Nerve VIII, or the auditory areas of the brain. It can be caused by loud noises, viral infections, medications, and certain diseases.

conductive

________________ hearing loss involves the outer or middle ear. It may be due to blockage, infection, or damage to the ear canal, ear drum (tympanic membrane), or ossicles.

tapetum lucidum

brightly colored iridescent reflecting layer of the choroid (found in nocturnal animals)

orbicularis oculi

In addition to the six muscles located within the orbit, the more superficial ____________ completely surrounds the eye anteriorly. It allows us to close the eye, squint, blink, and wink.

photoreceptors, rods, cones, bipolar neurons, ganglion neurons

In the innermost layer of the retina (the neural layer), the _______________ (the __________ (for dim light) and the ___________ (for color)) are responsible for the initial reception and transduction; they form the deepest portion of the neural layer. _______________ and ____________ form two superficial layers of the neural retina.

lysozyme

Tears contain salt and an antibacterial enzyme called _______________.

vestibule, semicircular canals

The ___________ and the three ________________ of the inner ear are responsible for our sense of equilibrium.

oval window, round window

The ____________ serves as the entrance to the scala vestibuli and the _____________ as the exit for the scala tympani.

pigmented epithelium, neural

The retina is divided into: 1) the outermost ______________, which decreases image blur by absorbing light and preventing light reflection within the eye. It also supplies essential nutrients to the innermost layer. 2) the innermost ____________ layer, which allows for conversion (transduction) of light energy into nerve impulses.

cataract

A _______________ is a clouding of the lens due to a clumping of its proteins.

presbyopia

After around 40 years of age, lens stiffness increases the near point of vision, the closest that an object can be and still be in focus. This age-related change, called ___________, makes it increasingly difficult to read at close range.

retinal tunic

Collectively, the lens, the cornea, and the vitreous humor refract or bend light waves, focusing them on the inner most layer of the eye, or the ______________.

orbit

Each eye sits in a deep bony socket of the face called an ___________.

tympanic membrane, ossicles, malleus, incus, stapes, oval window

Initially, sound waves move down the auditory canal and strike the eardrum (__________________) at the end of the canal. As vibrations pound the eardrum, it moves, and pushes the chain of _____________ (bones) in the middle ear. These bones, the hammer (______________), anvil (______________), and stirrup (_____________) move as a unit, and push on the _____________ of the cochlea in the inner ear. **The skeletal muscles of the middle ear provide some protection from loud sounds by serving as brakes that restrict tympanic membrane and ossicular movement.**

conjunctivitis

Irritants or pathogens can cause inflammation of a thin mucous membrane called the conjunctiva that lines the inside of the eyelid and, excluding the cornea, covers the anterior surface of the eye. This condition is referred to as ______________ or pinkeye.

Otitis media, tympanostomy, myringotomy

Middle ear infections (_____________) are more common in children than in adults. To correct this, an otolaryngologist (ENT) inserts a small tube in the tympanic membrane in a procedure called _____________ or ____________.

tensor tympani, stapedius, auditory (eustachian) tube

Other notable structures of the middle ear include two tiny skeletal muscles, the ______________ and the ____________, and the ________________. **The skeletal muscles of the middle ear provide some protection from loud sounds by serving as brakes that restrict tympanic membrane and ossicular movement.**

lacrimal puncta, lacrimal canaliculi, lacrimal sack, nasolacrimal duct

Released from the superior lateral corner of the eye, the tears move medially toward the nose where they drain into a tiny hole called the ______________, then through the _____________ into the _____________. Finally, the tears flow into the ____________ that empties int the nasal cavity.

suspensory ligaments, accommodation, aqueous humor, Canal of Schlemm, closed angle glaucoma

The _________________ connect the lens and the ciliary body in the uvea (middle layer of the eye). As the ciliary body contracts, the lens thickens, allowing the eye to focus on nearby objects (_________________). In addition to adjusting lens shape, the ciliary body produces a clear, watery substance called the ____________, which nourishes the lens and the cornea and influences intraocular pressure. Secreted by the ciliary processes of the ciliary body, it is drained from the eye via the ______________. Blockage of this causes a build-up of aqueous humor and increased intraocular pressure. This results in _______________, a condition that may cause vision loss and, if untreated, blindness.

ciliary body, lens, iris, pupil, oculomotor (III)

The anterior portion of the uvea consists of: 1) __________, which is a ring of muscles surrounding the transparent disk called the ___________. (in the posterior) 2) __________, a pigmented ring of muscles surrounding a central hole, the ___________, which is innervated by the _____________ nerve. (in the anterior)

elastic, throat

The auditory tube, made of __________ cartilage, connects the middle ear to the __________. Helpful when there are changes in altitude, the tube opens with a yawn or swallow to equalize air pressure and improve our sense of hearing.

optic nerve, optic disk, blind spot

The axons of the ganglion neurons form the ____________ that passes out of the posterior eye and transports impulses toward the occipital cortex. The ____________ is the point of exit for the optic nerve. Because this region contains no photoreceptors, it is referred to as the ___________.

scala, scala vestibuli, scala tympani, perilymph

The cochlea is arranged in three layers of fluid-filled chambers (___________ or ducts) divided by a series of membranes. The upper chamber (_____________) and lower chamber (______________) are connected to one another by a hole at the narrow end of the cochlea, the apex. These chambers are filled with a fluid called ___________.

mechanical energy, electrical impulses

The cochlea, a snail-shaped bony tube, converts __________ into _____________.

palpebrae

The eyelids (______________) with attached eyelashes act like doors around the eye that close to protect it from debris and harsh environmental conditions.

vestibular membrane, basilar membrane, scala media, cochlear duct

The floor of the scala vestibuli, the ___________, and the roof of the scala tympani, the ______________, form the walls of the middle chamber called the ____________ or the ____________.

cochlea

The inner ear contains the organ of hearing called the ______________.

vitreous humor

The lens separates the eye into the anterior and posterior segments. Aqueous humor fills the anterior segment. The clear, jelly-like _____________ fills the posterior segment and maintains the shape of the eye.

temporal, sound waves, mechanical energy

The middle ear, housed in the _____________ bone, converts ______________ into ________________.

auricle, pinna, auditory (ear) canal

The outer ear is composed of the ____________ or ___________, the fleshy structure on each side of the head, and the _____________.

sclera, cornea

The outer fibrous layer of the eye is composed primarily of the avascular __________, referred to as "the white of the eye", and the ___________, the most anterior portion of the eye. Made of connective and epithelial tissue, the transparent cornea acts as a window allowing light to enter the eye.

macula lutea, fovea centralis

The region of the retina with the greatest number of photoreceptors is called the __________ or "yellow spot". Primarily composed of cones, this area has a central region called the _______________. This region is responsible for our greatest visual acuity.

anterior, posterior, lateral, endolymph, ampullaris, cupula

The semicircular canals detect and signal changes in rotational movement. The three canals, identified as ___________, _______________, and __________, form right angles with one another. Like the scala media of the cochlea, the semicircular canals contain _____________. Similar to the macula of the vestibular chambers, each canal contains a specialized sensory region (the ___________) with hair cells and kinocilia. Capped by the gel-like ___________, the hair cells synapse with neurons at their base.

vestibular ganglion, vestibular nerve

The somas of the nerve cells synapsing with the semicircular and the vestibular hair cells form the ________________; their axons form the _____________ (the vestibular portion of the 8th cranial nerve).

hair cells, microvilli, stereovilli

The spiral organ of Corti consists of a base with four rows of specialized cells, called _____________, which sit on the basilar membrane. At their apical surface, they have long, stiff ____________ called ______________.

tectorial membrane

The stereovilli of hair cells in the spiral organ of Corti are covered by a rigid membrane called the ____________ that forms the roof of the organ of Corti.

fibrous tunic, uveal tunic, retinal tunic

The three layers of the eye from outermost to innermost include the ___________, the ___________, and the ___________.

choroid

The uvea, the middle later of the eye is vascular and more complex than the fibrous tunic. The dark, pigmented posterior portion of the uvea is called the ____________. It contains blood vessels to nourish the retina and melanin to absorb light and protect the internal features of the eye from UV radiation.

utricle, saccule, macula, kinocilium, otolithic membrane

The vestibule is divided into two chambers, the anterior ___________ responsible for the perception of horizontal movement and the posterior ___________ responsible for the perception of vertical movement. Within each vestibular chamber, a specialized region called the ___________, contains hair cells each with a very long cilia called a _____________. Similar to the organ of Corti, the long hair cells are covered by a membrane, the ______________.

lacrimal gland

To wash and wet the eye, the _____________ secretes tears.