MCAT Social and Behavioral Sciences : Environment and Sensation

Study concepts, example questions & explanations for MCAT Social and Behavioral Sciences

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Example Questions

Example Question #11 : Environment And Sensation

In order to successfully accommodate for changes in depth of field, lens of the eye must perform which of the following functions when re-focusing on a closer object?

Possible Answers:

Thicken

Rotate

Tilt

Flatten

Correct answer:

Thicken

Explanation:

When looking at objects that are close, the lens of the eye must “thicken” to accommodate changes in depth of field. This is accomplished by contraction of the ciliary muscle, which allows the suspensory ligament to stretch. The lack of tension then allows the lens to draw up into its thicker resting state. If the vision is shifted to a far object, then ciliary muscles will relax, which increases tension on the lens via the suspensory ligament and causes it to "flatten." The lens does not “tilt” or “rotate.”

Example Question #11 : Vision

Ciliary and pupillary muscles are innervated by which cranial nerve?

Possible Answers:

The ocular nerve (CN II)

The trigeminal nerve (CN V)

The abducens nerve (CN IV)

The oculomotor nerve (CN III)

Correct answer:

The oculomotor nerve (CN III)

Explanation:

Ciliary and pupillary muscles are innervated by CN III, the oculomotor nerve. This nerve is also responsible for elevation of the upper eyelid, and innervation of the superior rectus, medial rectus, inferior rectus, and inferior oblique muscles of the eye. The abducens nerve (CN VI) innervates a single extraocular muscle: the lateral rectus. The optic nerve is primarily involved in transmission of visual signals from the retina to the brain, and the trigeminal nerve is not directly involved in ocular movement or function.

Example Question #12 : Vision

In which of the following parts of the retina is visual acuity the highest?

Possible Answers:

Optic disc

Cornea

Fovea

Lens

Correct answer:

Fovea

Explanation:

The fovea centralis is a zone of densely packed cone cells in the center of the macula lutea of the retina. Because of this it is the region capable of the highest degree of visual acuity. The optic disc is the point of exit for ganglion cell axons of the optic nerve. This is an area absent of rods or cones, and so is considered a "blind spot" of the eye. Last, the cornea and lens are not part of the retina.

Example Question #11 : Environment And Sensation

Which of the following is not a cause of a conductive hearing loss?

Possible Answers:

Foreign body in the external ear canal

Impacted cerumen

Loud noises

Acute otitis media

Perforated eardrum

Correct answer:

Loud noises

Explanation:

Conductive hearing loss occurs when sound is not conducted through the external auditory canal to the tympanic membrane and the ossicles. Causes include acute otitis media, performated eardrum, impacted cerumen (earwax), or a foreign body in the external canal. A sensorineural hearing loss occurs when there is damage to the fine hairs in the cochlea caused by loud noise.

Example Question #1 : Physiology Of The Ear

Which of the following is not a bone of the middle ear?

Possible Answers:

Pinna

Incus 

Stapes

Malleus

Correct answer:

Pinna

Explanation:

The "malleus," "incus," and "stapes" are the three bones that make up the ossicles of the middle ear. Together they work to transform sound waves into mechanical vibrations. The "pinna" is not a bone at all, but rather the anatomical term for the fleshy, cartilaginous outer ear.

Example Question #12 : Environment And Sensation

Sound waves enter the outer ear and vibrate the tympanic membrane, which causes the transmission of sound waves through the ossicles to the inner ear. In what order do the ossicles vibrate? 

Possible Answers:

Incus, stapes, and malleus

Stapes, malleus, and incus

Malleus, incus, and stapes

Incus, malleus, and stapes

Correct answer:

Malleus, incus, and stapes

Explanation:

The ossicle that attaches directly to the tympanic membrane is the malleus, or "hammer." This bone articulates with the incus, or "anvil," which then articulates with the stapes, or "stirrup" (so called because of it's resemblance to the stirrup of a saddle). The stapes in turn attaches to the oval window of the fluid-filled inner ear. 

Example Question #13 : Environment And Sensation

Which of the following structures is the main sensory organ associated with hearing?

Possible Answers:

The scala tympani

Tympanic membrane

Bony labyrinth

Eustachian tube

Organ of Corti

Correct answer:

Organ of Corti

Explanation:

The main sensory organ of hearing is a small structure within the cochlea called the “organ of Corti.” It contains hair cells, which are sensory receptor cells capable of responding to changes in pressure of the fluid of the inner ear. The organ of Corti is sandwiched between the three fluid-filled chambers, or scalae: the scala vestibuli, the scala tympani, and the scala media.

The “bony labyrinth” is a separate part of the inner ear that plays a role in balance and equilibrium. The “eustachian tube” is not a part of the inner ear, but rather a channel between the middle ear and the pharynx.

Example Question #4 : Physiology Of The Ear

Which of the following is not a function of the eustachian tube?

Possible Answers:

Production of perilymph

Equalization of pressure in the middle ear

Removal of cellular and bacterial waste

Drainage of fluid from the middle ear

Correct answer:

Production of perilymph

Explanation:

The eustachian tube primarily functions to equalize pressure between the middle ear and the atmosphere, remove cellular and bacterial waste from the middle ear, and to drain fluid from the middle ear into the pharynx. Cells within the inner ear produce perilymph. 

Example Question #1 : Visual Receptors

Which photoreceptor cell is primarily responsible for detecting nuances in color?

Possible Answers:

Rods

Cones and rods

Cones

Photosensitive retinal ganglion cells

Correct answer:

Cones

Explanation:

Cones are the primary photoreceptor cells responsible for transmitting information about color. They are the only photoreceptor cell type that is capable of differentiating between colors. Rod cells are not capable of color vision and primarily transmit information in regards to contrast. They are most active in very low light, while cone cells are most active in levels of high light. This is why it is difficult to perceive color at very low light levels. Photosensitive retinal ganglion cells do not transmit visual information to the brain - rather, they are involved in physiological processes such as pupillary reflex and circadian rhythms. 

Example Question #2 : Visual Receptors

Which of the following is the term for the light-sensitive cells of the retina?

Possible Answers:

Photogenic receptor cells

Photoreceptor cells

Aural cells of the retina

Photophilic cells

Correct answer:

Photoreceptor cells

Explanation:

The light sensitive cells of the retina are called "photoreceptor cells." This is a group of cells with various functions regarding the transmission of information about brightness, color, and contrast. None of the other structures listed are cell types of the eye.

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