Reflex Action & Sense Organs — NEET Biology MCQs with Solutions
Free NEET Biology Reflex Action & Sense Organs MCQs with step-by-step solutions (16 questions). Part of Neural Control and Coordination. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Reflex Action & Sense Organs · easy · theory
A rapid, automatic, involuntary response to a stimulus (e.g. knee-jerk) is called a:
A. Tropism
B. Conditioned thought
C. Voluntary action
D. Reflex action ✓ Correct
Solution: A reflex action is an involuntary, automatic response mediated by the spinal cord (reflex arc).
Q2 — Reflex Action & Sense Organs · easy · theory
The light-sensitive layer of the eye that contains the photoreceptor cells is the:
A. Iris
B. Sclera
C. Cornea
D. Retina ✓ Correct
Solution: The retina holds the rods and cones (photoreceptors) that detect light.
Q3 — Reflex Action & Sense Organs · medium · theory
The photoreceptor cells responsible for colour vision and functioning in bright light are the:
A. Rods and cones equally
B. Bipolar cells
C. Cones ✓ Correct
D. Rods
Solution: Cones (with photopsins) enable colour and bright-light (photopic) vision; rods handle dim light.
Q4 — Reflex Action & Sense Organs · medium · theory
The part of the ear that converts sound vibrations into nerve impulses is the:
A. Eardrum
B. Pinna
C. Ear ossicles
D. Cochlea (organ of Corti) ✓ Correct
Solution: The cochlea houses the organ of Corti, whose hair cells transduce sound vibrations into nerve impulses.
Q5 — Reflex Action & Sense Organs · hard · theory
The correct sequence of the reflex arc is:
A. Spinal cord → receptor → effector
B. Effector → motor neuron → receptor
C. Receptor → sensory neuron → spinal cord (interneuron) → motor neuron → effector ✓ Correct
D. Receptor → motor neuron → sensory neuron → effector
Solution: A reflex arc: receptor → afferent (sensory) neuron → CNS interneuron → efferent (motor) neuron → effector (muscle/gland).
Q6 — Reflex Action & Sense Organs · hard · theory
The three ear ossicles (malleus, incus, stapes) in the middle ear function to:
A. Detect body balance
B. Convert light to impulses
C. Produce ear wax
D. Amplify and transmit sound vibrations to the inner ear ✓ Correct
Solution: The ossicles amplify and relay vibrations from the eardrum to the oval window of the cochlea.
Q7 — Reflex Action & Sense Organs · easy · numerical
The photosensitive pigment present in the rod cells of the retina, responsible for vision in dim light, is:
A. Melanin
B. Rhodopsin ✓ Correct
C. Haemoglobin
D. Iodopsin
Solution: Rods contain the purple pigment rhodopsin (visual purple), which is highly sensitive to low light and mediates dim-light (scotopic) vision. Cone pigments (photopsins/iodopsin) mediate colour vision.
Q8 — Reflex Action & Sense Organs · easy · numerical
The region of the retina where the optic nerve leaves the eye and which lacks photoreceptors is the:
A. Fovea centralis
B. Optic chiasma
C. Yellow spot
D. Blind spot ✓ Correct
Solution: At the blind spot the optic nerve exits the eyeball; it contains no rods or cones, so no image is formed there. The fovea (in the yellow spot) has the densest cones and sharpest vision.
Q9 — Reflex Action & Sense Organs · easy · numerical
The three ear ossicles that transmit and amplify sound vibrations across the middle ear, in the correct order from the tympanic membrane to the oval window, are:
A. Incus → malleus → stapes
B. Malleus → stapes → incus
C. Malleus → incus → stapes ✓ Correct
D. Stapes → incus → malleus
Solution: Vibrations pass from the tympanic membrane through the malleus (hammer) to the incus (anvil) and then the stapes (stirrup), which transmits them to the oval window of the cochlea.
Q10 — Reflex Action & Sense Organs · easy · numerical
The sensory receptor structure that rests on the basilar membrane inside the cochlea and converts sound vibrations into nerve impulses is the:
A. Crista ampullaris
B. Macula
C. Organ of Ruffini
D. Organ of Corti ✓ Correct
Solution: The organ of Corti sits on the basilar membrane within the cochlea and bears hair cells that transduce sound-induced vibrations into nerve impulses carried by the auditory nerve.
Q11 — Reflex Action & Sense Organs · medium · numerical
In a monosynaptic reflex such as the knee-jerk, the reflex arc involves only:
A. A chain of many interneurons between sensory and motor neurons
B. One sensory and one motor neuron with a single synapse in the spinal cord ✓ Correct
C. The cerebrum for conscious processing before the response
D. Two motor neurons and no sensory neuron
Solution: The knee-jerk is a monosynaptic reflex: the afferent (sensory) neuron synapses directly with the efferent (motor) neuron in the spinal cord, with no interneuron. Polysynaptic reflexes include one or more interneurons.
Q12 — Reflex Action & Sense Organs · medium · numerical
Arrange the components of a typical reflex arc in the correct order of impulse flow: (1) effector, (2) receptor, (3) motor neuron, (4) sensory neuron, (5) spinal cord (interneuron).
A. 2 → 3 → 5 → 4 → 1
B. 4 → 2 → 5 → 3 → 1
C. 2 → 4 → 3 → 5 → 1
D. 2 → 4 → 5 → 3 → 1 ✓ Correct
Solution: A stimulus excites the receptor; the sensory neuron carries the impulse to the spinal cord (interneuron), which passes it to the motor neuron, which acts on the effector. Order: receptor → sensory neuron → spinal cord → motor neuron → effector.
Q13 — Reflex Action & Sense Organs · medium · numerical
Assertion (A): The withdrawal of the hand from a hot object occurs before the brain perceives the pain. Reason (R): The spinal reflex arc allows the motor response to be initiated at the spinal cord without waiting for processing by the brain.
A. Both A and R are true but R is not the correct explanation of A
B. Both A and R are true and R is the correct explanation of A ✓ Correct
C. A is false but R is true
D. A is true but R is false
Solution: In a spinal reflex the response is generated at the spinal cord, so the hand withdraws before the impulse reaching the brain produces conscious pain. R correctly explains the speed of the withdrawal.
Q14 — Reflex Action & Sense Organs · medium · numerical
Adjustment of the focal length of the eye lens to focus on near or far objects, achieved by the ciliary muscles altering the curvature of the lens, is called:
A. Accumulation
B. Accommodation ✓ Correct
C. Adaptation
D. Refraction
Solution: Accommodation is the ability of the eye to focus objects at different distances by changing the curvature (and hence focal length) of the lens through contraction and relaxation of the ciliary muscles.
Q15 — Reflex Action & Sense Organs · medium · numerical
The part of the inner ear responsible for maintenance of balance and detection of the position and movement of the head is the:
A. Cochlea with its organ of Corti
B. Tympanic membrane with the ossicles
C. Vestibular apparatus with its semicircular canals ✓ Correct
D. Eustachian tube with the middle ear
Solution: The vestibular apparatus, including the three semicircular canals and the otolith organs, detects head movement and position and is responsible for maintaining balance and equilibrium. The cochlea deals with hearing, not balance.
Q16 — Reflex Action & Sense Organs · medium · numerical
Which of the following statements about rods and cones of the retina is correct?
A. Cones are more numerous at the periphery of the retina than at the fovea
B. Rods work best in bright light and are packed most densely in the fovea
C. Cones function in bright light and mediate colour vision, whereas rods function in dim light ✓ Correct
D. Rods contain iodopsin and are responsible for high-acuity colour vision
Solution: Cones operate in bright light and are responsible for colour vision and sharp central acuity (dense at the fovea), while rods contain rhodopsin and function in dim light. Only the first statement is correct.