Environment and Sensation - MCAT Psychological and Social Foundations
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Which muscle is responsible for changing the shape of the lens during accommodation?
Which muscle is responsible for changing the shape of the lens during accommodation?
The structure responsible for changing the shape of the lens during accommodation is the ciliary muscle. This is a ring of smooth muscle in the middle layer of the eye that is attached to the lens via the suspensory ligament. Contraction and relaxation of the ciliary muscle will cause the suspensory ligament to tighten (in the case of relaxation of the ciliary muscle) or relax (in the case of contraction of the ciliary muscle). This affects the thickness of the lens, allowing for accommodation.
The sphincter pupillae and dilator pupillae are both responsible for changing the shape of the iris, rather than the lens, and the medial rectus muscle is an extrinsic eye muscle that moves the whole eye medially.
The structure responsible for changing the shape of the lens during accommodation is the ciliary muscle. This is a ring of smooth muscle in the middle layer of the eye that is attached to the lens via the suspensory ligament. Contraction and relaxation of the ciliary muscle will cause the suspensory ligament to tighten (in the case of relaxation of the ciliary muscle) or relax (in the case of contraction of the ciliary muscle). This affects the thickness of the lens, allowing for accommodation.
The sphincter pupillae and dilator pupillae are both responsible for changing the shape of the iris, rather than the lens, and the medial rectus muscle is an extrinsic eye muscle that moves the whole eye medially.
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Which division of the nervous system controls the dilator pupillae and is known as the iris dilator muscle?
Which division of the nervous system controls the dilator pupillae and is known as the iris dilator muscle?
Control of the muscles responsible for dilation of the pupil is mediated by the sympathetic division of the autonomic nervous system. During states of fear, sexual arousal, or heightened attention, the pupil will dilate due to the stimulation of the dilator pupillae, or iris dilator muscle.
Control of the muscles responsible for dilation of the pupil is mediated by the sympathetic division of the autonomic nervous system. During states of fear, sexual arousal, or heightened attention, the pupil will dilate due to the stimulation of the dilator pupillae, or iris dilator muscle.
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Deficits in which cranial nerve could cause ptosis (i.e. the drooping of the upper eyelid)?
Deficits in which cranial nerve could cause ptosis (i.e. the drooping of the upper eyelid)?
The levator palpebrae superioris is the muscle responsible for elevating the upper eyelid. It is innervated by CN III, the oculomotor nerve. CN IV (the trochlear nerve) and CN VI (the abducens nerve) are both responsible for innervation of various other muscles of eye movement, while the facial nerve (CN VII) is primarily responsible for control of the muscles of expression, for taste, and for motor innervation to the muscles of the inner ear.
The levator palpebrae superioris is the muscle responsible for elevating the upper eyelid. It is innervated by CN III, the oculomotor nerve. CN IV (the trochlear nerve) and CN VI (the abducens nerve) are both responsible for innervation of various other muscles of eye movement, while the facial nerve (CN VII) is primarily responsible for control of the muscles of expression, for taste, and for motor innervation to the muscles of the inner ear.
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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?
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?
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.”
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.”
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Ciliary and pupillary muscles are innervated by which cranial nerve?
Ciliary and pupillary muscles are innervated by which cranial nerve?
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.
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.
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In which of the following parts of the retina is visual acuity the highest?
In which of the following parts of the retina is visual acuity the highest?
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.
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.
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Which of the following is not a primary function of the extrinsic eye muscles?
Which of the following is not a primary function of the extrinsic eye muscles?
The extrinsic muscles of the eye are primarily responsible for the mechanical movement of the eyeball. The main movements of the eye are convergence during accommodation, saccadic movements, tracking, and maintenance of a horizontal position. Dilation of the pupils is dependent on intrinsic muscles of the eye.
The extrinsic muscles of the eye are primarily responsible for the mechanical movement of the eyeball. The main movements of the eye are convergence during accommodation, saccadic movements, tracking, and maintenance of a horizontal position. Dilation of the pupils is dependent on intrinsic muscles of the eye.
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Which of following is a true statement regarding light and the human eye?
Which of following is a true statement regarding light and the human eye?
The first structure that light will encounter as it enters the eye is the cornea, a transparent protein disc designed to refract light toward the eye interior. The aqueous humor is the liquid medium between the cornea and the lens of the eye. Light will pass through the aqueous humor and the pupil before hitting the lens. The lens then focuses the light onto the back of the eye. The vitreous humor is the liquid medium between the lens and the retina at the back of the eye.
The iris is used to control the shape of the pupil, and does not contain photoreceptors. All photoreceptors are located on the retina, which lines the back wall of the eye. A small region known as the fovea centralis houses a large number of cones (photoreceptors) at the back of the eye, but is part of the greater retinal structure.
The only true statement given is that light will pass through the aqueous humor before passing through the vitreous humor.
The first structure that light will encounter as it enters the eye is the cornea, a transparent protein disc designed to refract light toward the eye interior. The aqueous humor is the liquid medium between the cornea and the lens of the eye. Light will pass through the aqueous humor and the pupil before hitting the lens. The lens then focuses the light onto the back of the eye. The vitreous humor is the liquid medium between the lens and the retina at the back of the eye.
The iris is used to control the shape of the pupil, and does not contain photoreceptors. All photoreceptors are located on the retina, which lines the back wall of the eye. A small region known as the fovea centralis houses a large number of cones (photoreceptors) at the back of the eye, but is part of the greater retinal structure.
The only true statement given is that light will pass through the aqueous humor before passing through the vitreous humor.
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Diana takes the subway to and from school every day. Her family’s apartment, situated in a low-income neighborhood of New York City, is a thirty-minute walk from the subway station. During her trips to the subway, Diana loves to watch people work, play, and socialize. She feels very safe in her community because she trusts the people around her.
Diana’s mother is having trouble seeing clearly. The lens of her eye appears white and cloudy. Which of the following most likely describes this situation?
Diana takes the subway to and from school every day. Her family’s apartment, situated in a low-income neighborhood of New York City, is a thirty-minute walk from the subway station. During her trips to the subway, Diana loves to watch people work, play, and socialize. She feels very safe in her community because she trusts the people around her.
Diana’s mother is having trouble seeing clearly. The lens of her eye appears white and cloudy. Which of the following most likely describes this situation?
The symptoms describe a “cataract.” Cataracts form when a protein coat builds up and cause a white barrier to form that limits vision. It is normally surgically removed. “Astigmatism” is a misshapen cornea that can also cause vision problems. “Conjunctivitis” is a disorder that is made evident by the inflammation of the sclera, or white part of the eye. Last, “glaucoma” describes damage caused to the optic nerve, usually by a buildup of excess fluid in the eye.
The symptoms describe a “cataract.” Cataracts form when a protein coat builds up and cause a white barrier to form that limits vision. It is normally surgically removed. “Astigmatism” is a misshapen cornea that can also cause vision problems. “Conjunctivitis” is a disorder that is made evident by the inflammation of the sclera, or white part of the eye. Last, “glaucoma” describes damage caused to the optic nerve, usually by a buildup of excess fluid in the eye.
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Which of the following is the term for the process by which the eye's lens changes shape to bring close or distant objects into focus on the retina?
Which of the following is the term for the process by which the eye's lens changes shape to bring close or distant objects into focus on the retina?
The lens of the eye must be able to change its shape in order to re-focus the vision on near or far objects as the eye moves. This process is called “accommodation.” On the other hand, “convergence” is the ability of the eyes to move toward one another in order to focus on objects that are very close up. “Mydriasis” is the term for dilation of the pupil, and "contrast" is a visible quality of difference in color or brightness of objects, and not a function of the eye itself.
The lens of the eye must be able to change its shape in order to re-focus the vision on near or far objects as the eye moves. This process is called “accommodation.” On the other hand, “convergence” is the ability of the eyes to move toward one another in order to focus on objects that are very close up. “Mydriasis” is the term for dilation of the pupil, and "contrast" is a visible quality of difference in color or brightness of objects, and not a function of the eye itself.
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In myopia, which of the following abilities is impaired?
In myopia, which of the following abilities is impaired?
Myopia, often called nearsightedness, is an inability to being distant objects into clear focus. This may be due either to excess curvature of the cornea or to length of the eyeball itself causing the focal point of light rays to fall in front of the retina, rather than against it.
Myopia, often called nearsightedness, is an inability to being distant objects into clear focus. This may be due either to excess curvature of the cornea or to length of the eyeball itself causing the focal point of light rays to fall in front of the retina, rather than against it.
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Which of the following terms describes the inability to focus vision on close-up objects?
Which of the following terms describes the inability to focus vision on close-up objects?
“Presbyopia” is the term for the inability to focus the vision on close-up objects. It is most commonly caused by loss of elasticity of the lens of the eye as individuals age.
On the other hand, the other choices are incorrect. “Amblyopia” is a general term used to denote cases in which one eye is communicating less visual information to the brain, resulting in a loss of vision in that eye In other words, the brain learns to ignore visual stimulation from the non-dominant eye. A common cause of amblyopia is “strabismus”—commonly known as “lazy eye.” It is defined as a lack of coordination between extraocular muscles that prevents the eyes from orienting in the same direction. In this case, there will almost always be a dominant eye, and if the condition is not corrected in childhood, the non-dominant eye generally suffers permanent vision loss. “Nystagmus” is a condition of involuntary eye movement (i.e. the eye seems to shudder, generally in a horizontal plane) that may or may not be associated with visual impairment. It can have numerous etiologies, including nervous system disorders, alcohol or drug reaction, congenital defect, or inner-ear disorder.
“Presbyopia” is the term for the inability to focus the vision on close-up objects. It is most commonly caused by loss of elasticity of the lens of the eye as individuals age.
On the other hand, the other choices are incorrect. “Amblyopia” is a general term used to denote cases in which one eye is communicating less visual information to the brain, resulting in a loss of vision in that eye In other words, the brain learns to ignore visual stimulation from the non-dominant eye. A common cause of amblyopia is “strabismus”—commonly known as “lazy eye.” It is defined as a lack of coordination between extraocular muscles that prevents the eyes from orienting in the same direction. In this case, there will almost always be a dominant eye, and if the condition is not corrected in childhood, the non-dominant eye generally suffers permanent vision loss. “Nystagmus” is a condition of involuntary eye movement (i.e. the eye seems to shudder, generally in a horizontal plane) that may or may not be associated with visual impairment. It can have numerous etiologies, including nervous system disorders, alcohol or drug reaction, congenital defect, or inner-ear disorder.
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Which of the following structures of the eye is not responsible for the refraction and focusing of light?
Which of the following structures of the eye is not responsible for the refraction and focusing of light?
Light is refracted and focused by the cornea, the anterior chamber, and the lens. The retina is a thin layer of nervous system tissue, which receives focused light patterns and transmits those patterns to the brain via photoreceptor cells.
Light is refracted and focused by the cornea, the anterior chamber, and the lens. The retina is a thin layer of nervous system tissue, which receives focused light patterns and transmits those patterns to the brain via photoreceptor cells.
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Which of the following is not a bone of the middle ear?
Which of the following is not a bone of the middle ear?
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.
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.
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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?
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?
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.
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.
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Which of the following structures is the main sensory organ associated with hearing?
Which of the following structures is the main sensory organ associated with hearing?
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.
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.
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Which of the following is not a function of the eustachian tube?
Which of the following is not a function of the eustachian tube?
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.
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.
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Which of the following is not a cause of a conductive hearing loss?
Which of the following is not a cause of a conductive hearing loss?
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.
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.
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What is the definition of a "just-noticeable difference"?
What is the definition of a "just-noticeable difference"?
Just-noticeable difference (JND) is the amount that a stimulus needs to change for someone to be able to notice it at least half the time. For example, the JND needed to perceive that a light is brighter is a two percent change in the brightness of the light’s illumination. This means that when the brightness goes up by two percent, we would be able to notice a difference half of the time or more.
Just-noticeable difference (JND) is the amount that a stimulus needs to change for someone to be able to notice it at least half the time. For example, the JND needed to perceive that a light is brighter is a two percent change in the brightness of the light’s illumination. This means that when the brightness goes up by two percent, we would be able to notice a difference half of the time or more.
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Signal detection studies measure an individual’s ability to detect certain stimuli. They involve exposure to stimuli at varying magnitudes and ask subjects to detect any changes in their perceptual experience of the stimuli (i.e. the just-noticeable difference). Perceiving magnitude differences in stimuli depends on the type of sensory experience (e.g. touch or sound) and is based on proportional rather than absolute amounts.
Imagine a hypothetical study that asked participants to perceive changes in amplitude of a sound stimulus. In this experiment, the researchers wanted to know how much the amplitude needed to change in order for an individual to detect a difference. They decided to test the just-noticeable difference at three different amplitudes: low, medium, and high. Participants in each category listened to the initial sound, and then the amplitude was increased or decreased slightly until participants detected a difference.
Imagine that this study used a forced choice design in which participants had to select "the same" or "different" after hearing a pair of sounds at different amplitudes. As the amplitude of the comparison sound increased, which type of signal detection response would be most likely, regardless of the initial sound?
Signal detection studies measure an individual’s ability to detect certain stimuli. They involve exposure to stimuli at varying magnitudes and ask subjects to detect any changes in their perceptual experience of the stimuli (i.e. the just-noticeable difference). Perceiving magnitude differences in stimuli depends on the type of sensory experience (e.g. touch or sound) and is based on proportional rather than absolute amounts.
Imagine a hypothetical study that asked participants to perceive changes in amplitude of a sound stimulus. In this experiment, the researchers wanted to know how much the amplitude needed to change in order for an individual to detect a difference. They decided to test the just-noticeable difference at three different amplitudes: low, medium, and high. Participants in each category listened to the initial sound, and then the amplitude was increased or decreased slightly until participants detected a difference.
Imagine that this study used a forced choice design in which participants had to select "the same" or "different" after hearing a pair of sounds at different amplitudes. As the amplitude of the comparison sound increased, which type of signal detection response would be most likely, regardless of the initial sound?
In forced-choice signal detection method, responses can be classified into four categories: miss (failing to identify a changed stimulus), false alarm (identifying an unchanged stimulus as changed), correct rejection (identifying an unchanged comparison as the same as the initial stimulus), or hit (correctly identifying a comparison stimulus that differs from the initial stimulus). As the amplitude is increased, it is also more likely that the subject would be able to correctly identify a changed stimulus. The greater the discrepancy in magnitude for the two sounds, the more likely the participant will get a hit.
In forced-choice signal detection method, responses can be classified into four categories: miss (failing to identify a changed stimulus), false alarm (identifying an unchanged stimulus as changed), correct rejection (identifying an unchanged comparison as the same as the initial stimulus), or hit (correctly identifying a comparison stimulus that differs from the initial stimulus). As the amplitude is increased, it is also more likely that the subject would be able to correctly identify a changed stimulus. The greater the discrepancy in magnitude for the two sounds, the more likely the participant will get a hit.
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