A&P CH. 15

Color vision has much greater resolution than night vision (vision that is mostly in shades of gray). Which of the following is the best explanation for why this is so?

A single cone photoreceptor often connects to a single bipolar cell and a single ganglion cell while as many as 100 rods will converge to a single ganglion cell.

The ability to clearly see objects at a distance but not close up is properly called ________.

hyperopia

What are the names of the bones at A, in order from left to right?

malleus, incus, stapes This is the correct order of these bones.

How many ossicles are found in the ear?

three The tympanic cavity is spanned by the three smallest bones in the body: the auditory ossicles. These bones, named for their shape, are the malleus (hammer), the incus (anvil), and the stapes (stirrup). The proximal end of the malleus is secured to the tympanic membrane, and the base of the stapes fits into the oval window.

Name the structure represented by (1).

tympanic membrane The tympanic membrane is located at the terminus of the external acoustic canal.

Which of the following taste sensations is incorrectly matched to the chemicals that produce it?

umami-triglycerides and fatty acids

The only special sense NOT fully functional at birth is the sense of ________.

vision

What is the main function of the rods in the eye?

vision in dim light

Identify the neuron that is last in the transmission pathway of light information, given the cells shown in this image.

A. Ganglion cells are last in the transmission pathway seen here. Their role is to transmit the visual signals to the thalamus.

Which part of the inner ear houses receptors most responsive to rotational (angular) movements of the head?

A. The semicircular canals house the receptors for sensing rotational (angular) motion of the head.

Identify the muscle responsible for depressing the eye and turning it laterally.

A. This muscle's action is to depress the eye (because of its upward pulling action) and to turn the eye laterally.

Which of the following is the best explanation of why it is difficult to discriminate the color of an object at night?

At night, the amount of light entering the eye is insufficient to stimulate the cone cells but is sufficient to stimulate the rod cells.

A middle ear infection (otitis media) would be located in which region?

B. Letter B includes the air-filled chamber containing the malleus, incus, and stapes. An infection here would be called "otitis media."

Identify the choroid.

B. The choroid is the part of the vascular layer that lies posterior to the cornea's edge and under the sclera.

Identify the type of neuronal cell that detects bright light and provides high-resolution color vision.

C. The cone cells are photoreceptor cells that require brighter light. By differentiating input from three different types of cones, the brain can differentiate color and high resolution.

Identify the layer that contains both a single-celled pigmented layer and a neural layer.

C. The inner layer (retina) contains both the pigmented layer and the neural layer.

Which letter indicates structures involved in detection of BOTH hearing and equilibrium?

C. The internal ear possesses the structures for both hearing and equilibrium sensing.

Humans can see several thousand shades of color but have cone photoreceptors that are sensitive to only three (perhaps four) wavelengths of light. Wha is the best explanation for why we see so many colors?

Color perception is achieved by activation of various combinations between the three cone types.

Which of the following is the best explanation for our perception of color?

Cones come in three types, each sensitive to different wavelengths of light.

What part of the inner ear houses the receptor organ of hearing, the spiral organ (organ of Corti)?

D. The cochlea houses the spiral organ (of Corti), which senses hearing.

Contraction of the ciliary muscle causes the lens to bend the light less.

False

Sound is generally perceived in the occipital lobe of the cerebral cortex.

False

The anterior chamber of the eye is filled with vitreous humor.

False

The neural layer of the retina prevents excessive scattering of light within the eye.

False

As light hits the retina, the first structure the light encounters is a rod or a cone.

False Contrary to what might make sense, light has to pass through the ganglion cells, through the bipolar cells, and finally strikes the rods and the cones.

Paralysis of which eye muscle would prevent the right eye from looking to the left?

Medial rectus

How are the olfactory receptors activated?

Odorants dissolve in the mucus and bind to receptors. Dissolved odorants stimulate olfactory sensory neurons by binding to receptor proteins in the olfactory cilium membranes. This triggers the opening of cation channels, which results in generation of a receptor potential. Ultimately (assuming threshold stimulation), an action potential is conducted to the first relay station in the olfactory bulb.

Why are the waves represented by the number 3 being sensed closer to the oval window than those represented by 4?

The waves at 3 have a higher frequency than 4 The spiral organ (organ of Corti) sorts waves by frequency. Higher frequencies are detected nearer to the oval window, while lower frequencies are detected further down the basilar membrane.

Identify the function of the structures labeled (2) in this image.

They conduct sound waves and amplify the vibrations within the middle ear. The auditory ossicles are set in motion by the tympanic membrane and conduct sound waves to the oval window.

In order for sound to reach the spiral organ (of Corti), the auditory ossicles must vibrate the oval window and set the endolymph in motion.

True

Light passes through the entire thickness of the neural layer of the retina to excite the photoreceptors.

True

Sour taste receptors are stimulated by hydrogen ions of acidic food substances.

True

The function of the lens of the eye is to allow precise focusing of light on the retina.

True

The mucous membrane that lines the eyelids and is reflected over the anterior surface of the eyeball is the conjunctiva.

True

The optic disc forms a blind spot where the optic nerve leaves the eyeball.

True

Without a functioning crista ampullaris, the semicircular canals would not function.

True

As the ciliary muscle relaxes, the suspensory ligaments tighten and stretch the lens, allowing for distance vision.

True Sympathetic innervation relaxes the ciliary body. As the muscle relaxes, it pulls on the suspensory ligaments, which put tension on the lens. This allows images that are farther away to focus on the retina.

Select the statement below that is NOT true with regards to the process of light adaptation.

a. Rhodopsin is uncoupled from light transduction. b. The activity of rods is reduced by rapid bleaching of rhodopsin. c. Visual acuity is diminished. d. Retinal sensitivity decreases. c. Visual acuity is diminished.

In a person who is color-blind, which of the following would you most expect to see?

absence of green or red cones in their foveae

Name the structure located in the enlarged swellings in the tubes at A.

ampulla Ampullae are structures found at the end of semicircular canals that respond as fluid shifts because of rotation movement.

The blind spot of the eye is caused by ________.

an absence of photoreceptors where the optic nerve leaves the eye

Transduction of lower frequency sound waves occurs at the __________ of the cochlea.

apex The apex is wider and more flexible, which makes it more receptive to lower frequencies.

Receptors for hearing are located in the ________.

cochlea

During close vision, what actions must the eye take to bring an object into focus?

contract the ciliary body Contracting the ciliary body would allow the lens to recoil and bulge, which would enhance focus on close objects.

As light travels through the eye, it passes through several structures or chambers before reaching the retina. Which list below gives those structures in the correct order?

cornea, anterior chamber, pupil, lens, posterior segment

Nerve fibers from the medial aspect of each eye ________.

cross over to the opposite side at the chiasma

Tom is a 45-year-old male that has lost his ability to hear high frequency sounds. The most likely explanation for this would be ________.

damage to the hair cells near the oval window in the cochlear duct

Which layer of the eye is indicated by letter A?

fibrous The fibrous layer includes the tough sclera (the "white" of the eye) as well as the transparent cornea.

The cells of the retina in which action potentials are generated are the ________.

ganglion cells

There are three layers of neurons in the retina. The axons of which of these neuron layers form the optic nerves?

ganglion cells

Where are equilibrium receptors located?

in the semicircular canals and in the vestibule of the ear The equilibrium receptors in the semicircular canals and vestibule are collectively called the vestibular apparatus. The receptors in the vestibule monitor linear acceleration and the position of the head with respect to gravity. Because gravity is constant, this is sometimes called our sense of static equilibrium. The semicircular canals monitor changes in head rotation, sometimes called our sense of dynamic equilibrium.

The eye muscle that rotates the eye upward and turns the eye laterally is the ________.

inferior oblique

Name the muscle at D.

inferior rectus The inferior rectus originates from the common tendinous ring at the back of the orbit and inserts into the inferior surface of the eye.

Dark adaptation ________.

involves accumulation of rhodopsin

What structure regulates the amount of light passing to the visual receptors of the eye?

iris

The first "way station" in the visual pathway from the eye, after there has been partial crossover of the fibers in the optic chiasma, is the ________.

lateral geniculate body of the thalamus

The elasticity of the lens decreases with age. This leads to which of the following?

less accommodation of the lenses and difficulty focusing on nearby objects

What structure in the eye creates a visual blind spot?

optic disc The optic disc, where the optic nerve exits the eye, is a weak spot in the posterior wall of the eye because it is not reinforced by the sclera. The optic disc is also called the blind spot because it lacks photoreceptors, so light focused on it cannot be seen. Nonetheless, we do not usually notice these gaps in our vision because the brain uses a sophisticated process called filling in to deal with absence of input.

Which of the following structures is NOT part of the external ear?

pharyngotympanic tube

In the visual pathways to the brain, the optic radiations project to the ________.

primary visual cortex

What is the portion of the eye that allows light to pass into the posterior chamber?

pupil The pupil is a central opening in the iris that allows light to enter the eye.

During dark adaptation, ________.

rhodopsin accumulates in the rods

You want to look up and to your right. Which extrinsic eye muscles would be the most active in each eye?

right eye: inferior oblique left eye: superior rectus The right eye requires both elevation and lateral movement. The inferior oblique would accomplish both of these. The left eye requires both elevation and medial movement. The superior rectus, because it approaches the eye from the medial side, turns the eye medially as it elevates.

Which photoreceptor cells respond to very dim light?

rods Rods are our dim-light and peripheral vision receptors. They are more numerous and far more sensitive to light than cones are, but they do not provide sharp images or color vision. This is why colors disappear and the edges of objects appear fuzzy in dim light and at the edges of our visual field.

Which of the following structures contain receptors that monitor changes in head rotation?

semicircular canals The receptor for rotational acceleration, called the crista ampullaris or simply crista, is a minute elevation in the ampulla of each semicircular canal. The semicircular canals monitor changes in head rotation, called our sense of dynamic equilibrium.

Which middle ear ossicle is attached to, and transmits vibratory motion to, the oval window?

stapes The stapes is attached to the oval window, a thin membrane that separates the middle ear and the internal ear. The function of the ossicles is to transmit the vibratory motion of the eardrum to the oval window. In sequence, the tympanic membrane vibrations are transferred to the malleus, then the incus, and finally the stapes. As the stapes vibrates, it moves the oval window, which in turn sets the fluids of the internal ear into motion, eventually exciting the hearing receptors.

Which portion of the ear is responsible for sound transduction?

the cochlea There are hair cells in the cochlea that are sensitive to different wavelengths of sound. These hair cells transduce the sound waves into neural signals.