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Score — click each question to reveal the answer
Q1
During accommodation for near vision, the ciliary muscle and lens:
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A. ciliary muscle contracts, lens becomes more convex
B. ciliary muscle relaxes, lens flattens
C. ciliary muscle contracts, lens flattens
D. ciliary muscle relaxes, lens becomes more convex
✅ Answer: A. ciliary muscle contracts, lens becomes more convex
For near vision the ciliary muscle contracts → zonules slacken → the elastic lens rounds up → more refractive power.
Q2
The 'near reflex' triad for viewing a close object consists of:
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A. accommodation, divergence and pupil dilation
B. accommodation, convergence and pupil constriction
C. relaxation, divergence and dilation
D. blinking, convergence and dilation
✅ Answer: B. accommodation, convergence and pupil constriction
Looking at a near object triggers lens accommodation, ocular convergence and pupillary constriction (miosis) together.
Q3
Most refraction of light entering the eye occurs at the:
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A. lens
B. vitreous
C. cornea
D. retina
✅ Answer: C. cornea
The cornea provides most (fixed) refractive power; the lens provides the fine, variable adjustment (accommodation).
Q4
In myopia (short-sightedness), the image focuses ___ the retina and is corrected with a ___ lens.
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A. behind; concave
B. in front of; convex
C. behind; convex (converging)
D. in front of; concave (diverging)
✅ Answer: D. in front of; concave (diverging)
Myopia: eyeball too long / too much power → image in front of the retina → corrected by a concave (diverging) lens. Hyperopia = convex lens.
Q5
Presbyopia (age-related difficulty with near vision) is due to:
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A. loss of lens elasticity (reduced accommodation)
B. corneal clouding
C. retinal detachment
D. raised intraocular pressure
✅ Answer: A. loss of lens elasticity (reduced accommodation)
With age the lens stiffens and loses elasticity, so accommodation declines — corrected with a convex reading lens.
Q6
Which photoreceptors function in dim light and detect no colour?
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A. cones
B. rods
C. ganglion cells
D. bipolar cells
✅ Answer: B. rods
Rods (rhodopsin) give high-sensitivity, low-acuity, colourless vision in dim light (scotopic). Cones give colour, high-acuity photopic vision.
Q7
The visual pigment of rods is:
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A. iodopsin
B. melanin
C. rhodopsin
D. haemoglobin
✅ Answer: C. rhodopsin
Rhodopsin = opsin + 11-cis retinal. Light isomerises retinal to all-trans, starting the phototransduction cascade.
Q8
When light strikes a photoreceptor, the cell:
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A. depolarizes and releases more glutamate
B. fires action potentials
C. releases acetylcholine
D. hyperpolarizes and releases less glutamate
✅ Answer: D. hyperpolarizes and releases less glutamate
Light → ↓cGMP → Na⁺ channels close → the cell HYPERPOLARIZES and releases LESS glutamate (the reverse of most receptors).
Q9
In darkness, the photoreceptor's 'dark current' is maintained by:
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A. high cGMP keeping Na⁺ channels open
B. low cGMP closing channels
C. Ca²⁺ influx only
D. rhodopsin activation
✅ Answer: A. high cGMP keeping Na⁺ channels open
In the dark, high cGMP holds Na⁺ channels open → steady depolarization (dark current) and continuous glutamate release.
Q10
Highest visual acuity occurs at the:
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A. optic disc
B. fovea centralis
C. peripheral retina
D. ora serrata
✅ Answer: B. fovea centralis
The fovea is packed with cones (and has minimal overlying layers), giving the sharpest, most detailed vision.
Q11
In the visual pathway, fibres from the nasal half of each retina cross at the:
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A. lateral geniculate nucleus
B. optic radiation
C. optic chiasm
D. superior colliculus
✅ Answer: C. optic chiasm
Nasal retinal fibres decussate at the optic chiasm; the pathway then runs optic tract → LGN → optic radiation → V1 (occipital cortex).
Q12
Night blindness (nyctalopia) is classically caused by deficiency of:
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A. vitamin C
B. vitamin D
C. vitamin K
D. vitamin A
✅ Answer: D. vitamin A
Vitamin A (retinal) is needed to regenerate rhodopsin; its deficiency impairs rod (dim-light) vision → night blindness.
Q13
The middle-ear ossicles transmit vibration from the tympanic membrane to the oval window in the order:
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A. malleus → incus → stapes
B. incus → malleus → stapes
C. stapes → incus → malleus
D. malleus → stapes → incus
✅ Answer: A. malleus → incus → stapes
Sound: tympanic membrane → malleus → incus → stapes → oval window.
Q14
The main function of the middle-ear ossicles is:
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A. producing endolymph
B. amplifying sound by impedance matching
C. detecting head rotation
D. secreting wax
✅ Answer: B. amplifying sound by impedance matching
The large tympanic membrane focusing onto the small oval window (area ratio ~17:1) plus the ossicular lever matches the impedance of air to cochlear fluid.
Q15
The receptor cells for hearing in the cochlea are the:
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A. rods
B. Purkinje cells
C. hair cells of the organ of Corti
D. otolith cells
✅ Answer: C. hair cells of the organ of Corti
Hair cells on the basilar membrane (organ of Corti) transduce sound: stereocilia bending opens K⁺ channels → depolarization → CN VIII signal.
Q16
High-frequency sounds are detected at the ___ of the cochlea (tonotopic / place coding).
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A. apex
B. middle
C. oval window
D. base
✅ Answer: D. base
The basilar membrane is narrow and stiff at the base (high frequencies) and wide and floppy at the apex (low frequencies).
Q17
A patient with otosclerosis (fixation of the ossicles) has which type of hearing loss?
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A. conductive
B. sensorineural
C. central
D. mixed cortical
✅ Answer: A. conductive
Conductive deafness = a problem in the outer/middle ear (wax, otitis media, otosclerosis). Sensorineural = cochlea or CN VIII damage.
Q18
Rotational (angular) acceleration of the head is detected by the:
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A. utricle
B. semicircular canals
C. saccule
D. cochlea
✅ Answer: B. semicircular canals
The three semicircular canals sense angular acceleration (endolymph bends the cupula). The otolith organs sense linear acceleration/gravity.
Q19
Linear acceleration and head tilt (gravity) are detected by the:
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A. semicircular canals
B. organ of Corti
C. utricle and saccule (otolith organs)
D. tympanic membrane
✅ Answer: C. utricle and saccule (otolith organs)
The utricle and saccule contain otolith-weighted hair cells that respond to linear acceleration and head tilt.
Q20
Red–green colour blindness is most commonly:
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A. a rod disorder
B. caused by vitamin A deficiency
C. acquired from loud noise
D. an X-linked cone-opsin defect (commoner in males)
✅ Answer: D. an X-linked cone-opsin defect (commoner in males)
Red–green colour blindness is an X-linked recessive defect of cone opsins, so it is far commoner in males.
1Accommodation+
The adjustment of the lens for near vision: the ciliary muscle contracts, the zonules slacken, and the elastic lens becomes more convex, increasing its refractive power so a near object is focused on the retina.
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2Rhodopsin+
The visual pigment of rods, made of the protein opsin plus 11-cis retinal (a vitamin-A derivative). Light isomerises the retinal to all-trans, activating transducin and beginning the phototransduction cascade.
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3Myopia+
Short-sightedness: parallel light from a distant object is focused IN FRONT of the retina because the eyeball is too long or the refractive power too great. Corrected with a concave (diverging) lens.
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4Tonotopic (place) coding+
The mapping of sound frequency to position along the basilar membrane: high frequencies stimulate the narrow, stiff base and low frequencies the wide, floppy apex, so pitch is encoded by which hair cells are activated.
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5Conductive deafness+
Hearing loss from impaired transmission of sound through the outer or middle ear (e.g. wax, otitis media, otosclerosis), as opposed to sensorineural deafness, which is from damage to the cochlea or auditory nerve.
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6Vestibular apparatus+
The inner-ear organ of balance: the three semicircular canals detect angular (rotational) acceleration, and the otolith organs (utricle and saccule) detect linear acceleration and head tilt/gravity, signalling via cranial nerve VIII.
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Essay 1
Describe accommodation and the common refractive errors of the eye with their correction.
10 marks
Accommodation
Light is refracted mainly by the cornea (fixed) and finely focused by the lens (variable). For a NEAR object: parasympathetic stimulation → the ciliary muscle contracts → the suspensory zonules slacken → the elastic lens becomes more convex (↑refractive power). The near reflex triad = accommodation + convergence + miosis.
Refractive errors
- Myopia (near-sighted): image in FRONT of the retina (eyeball too long); corrected with a concave (diverging) lens.
- Hyperopia (far-sighted): image BEHIND the retina (eyeball too short); corrected with a convex (converging) lens.
- Astigmatism: unequal corneal curvature → corrected with a cylindrical lens.
- Presbyopia: age-related loss of lens elasticity → ↓accommodation → corrected with a convex reading lens.
Marking guide (10 marks): accommodation mechanism (ciliary muscle, lens convex) 3 · near triad 1 · myopia + concave lens 1.5 · hyperopia + convex lens 1.5 · astigmatism 1.5 · presbyopia 1.5
Essay 2
Describe phototransduction and contrast rods with cones.
10 marks
In darkness
High cGMP keeps Na⁺ channels open (the 'dark current') → the photoreceptor is depolarized and steadily releases glutamate.
In light
A photon activates rhodopsin (opsin + 11-cis retinal → all-trans) → activates transducin → phosphodiesterase → ↓cGMP → Na⁺ channels CLOSE → the cell hyperpolarizes → releases LESS glutamate → signal passes to bipolar and ganglion cells.
Rods vs cones
- Rods: rhodopsin; dim-light (scotopic) vision; high sensitivity, low acuity; no colour; peripheral retina.
- Cones: three opsins; bright-light (photopic) vision; colour; high acuity; concentrated at the fovea.
Marking guide (10 marks): dark current (high cGMP, glutamate release) 2 · light cascade (rhodopsin → transducin → ↓cGMP → hyperpolarize → ↓glutamate) 4 · rods features 2 · cones features 2
Essay 3
Describe how sound is conducted from the outer ear to the inner ear, and the role of impedance matching.
10 marks
Conduction
The pinna and ear canal funnel sound to the tympanic membrane, which vibrates. The middle-ear ossicles — malleus → incus → stapes — transmit the vibration to the oval window, setting the cochlear fluid in motion.
Impedance matching
Airborne sound would mostly reflect off the fluid-filled cochlea. The middle ear overcomes this by amplifying the pressure: the large tympanic membrane concentrates its force onto the much smaller oval window (area ratio ~17:1), and the ossicles act as a lever. This impedance matching lets sound energy pass efficiently into the cochlear fluid.
Marking guide (10 marks): outer ear → tympanic membrane 2 · ossicle chain malleus→incus→stapes→oval window 3 · impedance-matching problem (air vs fluid) 2 · area ratio + lever amplification 3
Essay 4
Describe cochlear transduction and how the cochlea codes sound frequency.
10 marks
Transduction
Oval-window vibration creates a travelling wave along the basilar membrane, which carries the organ of Corti with its hair cells. Movement bends the hair-cell stereocilia → mechanically-gated K⁺ channels open → the hair cell depolarizes → releases transmitter onto cochlear (CN VIII) afferents.
Frequency (place) coding
The basilar membrane varies in width and stiffness along its length: the base (narrow, stiff) resonates to high frequencies and the apex (wide, floppy) to low frequencies. Thus the position of maximal vibration encodes pitch (von Békésy's place theory).
Intensity
Loudness is coded by the amplitude of vibration and the firing rate / number of hair cells activated.
Marking guide (10 marks): travelling wave + organ of Corti/hair cells 3 · stereocilia bending → depolarization → CN VIII 3 · tonotopy base=high, apex=low 3 · intensity coding 1
Essay 5
Describe how the vestibular apparatus detects motion and head position.
10 marks
Semicircular canals
Three canals in mutually perpendicular planes detect angular (rotational) acceleration. Head rotation moves the endolymph, which bends the cupula and the embedded hair cells, signalling rotation.
Otolith organs (utricle and saccule)
Detect linear acceleration and head tilt/gravity. Calcium-carbonate otoliths sit on a gelatinous membrane over the hair cells; gravity and linear movement displace them, bending the stereocilia.
Output
Hair-cell signals travel in cranial nerve VIII to the vestibular nuclei, driving the vestibulo-ocular reflex (stabilises gaze during head movement) and postural reflexes (balance).
Marking guide (10 marks): semicircular canals — angular acceleration, cupula 3 · otolith organs — linear acceleration/gravity, otoliths 3 · hair-cell transduction 2 · CN VIII → VOR + postural reflexes 2