Properties of Sensory Receptors

Q-1. Warmth sensation is sensed by
a) Pacinian capsule
b) Meissner’s capsule
c) Raffine end organ
d) Krause’s end bulb
e) None of the above.

Answer: None of the above.
Explanation:
Principal sensory modalities and sensory modalities Receptor:
Vision: Rods and cones
Hearing: Hair cells (Organ of Corti)
Smell: Olfactory neurons
Taste: Taste receptor cells
Rotational acceleration: Hair cells (semi-circular canals)
Linear acceleration: Hair cells (utricle and saccule)
Touch-Pressure: Nerve endings
Warmth, cold and pain: Nerve endings
Muscle spindle: Nerve endings

Q-2. What are some of the modalities of sensation that are detected by free nerve endings?
a) Crude touch
b) Pain
c) Tickle sensations
d) Muscle stretch
e) All

Answer: All
Explanation:
See above explanation.

Q-3. The receptors of pain is
a) Ruffini organs
b) Meckel’s bodies
c) Golgi bodies
d) Free nerve endings

Answer: Free nerve endings
Explanation:
See above explanation.

Q-4. Pacinian corpuscles are
a) Rapidly adapting touch receptors
b) Slowly adapting touch receptors
c) Temperature receptor
d) Pressure receptors.

Answer: Rapidly adapting touch receptors
Explanation:
The Pacinian corpuscles are touch receptors. When a maintained stimulus of constant strength is applied to a receptor; the frequency of the action potentials in its sensory nerve declines over time. This phenomenon is known as adaptation or desensitization.
The degree to which adaptation occurs varies from one sense to another. Light touch appears to have rapidly adapting receptors, for example, whereas spindle and nociceptor input is slowly adapting.
This appears to have some value to the individual. Thus, light touch would be distracting if it were persistent; and, conversely, slow adaptation of spindle input is needed to maintain posture.
Similarly, input from nociceptors provides a warning that would lose its value if it adapted and disappeared.

Q-5. Pacinian corpuscles are major receptors for
a) Pressure
b) Pain
c) Touch
d) Temperature

Answer: Touch
Explanation:
See above explanation.

Q-6. Pacinian corpuscles transmit which sensation:
a) Touch
b) Vibration
c) Cold
d) Heat

Answer: Touch
Explanation:
See above explanation.

Q-7. Phantom limb phenomenon is explained by
(PGMCET 07, AIIMS 05)
a) Law of projection
b) Weber Fechner law
c) Fechner’s law of degeneration
d) Pascal’s law

Answer: Law of projection
Explanation:
No matter where a particular sensory pathway is stimulated along its course to the cortex, the conscious sensation produced is referred to the location of the receptor. This principle is called the law of projection. Cortical stimulation experiments during neurosurgical procedures on conscious patients illustrate this phenomenon. For example, when the cortical receiving area for impulses from the left hand is stimulated, the patient reports sensation in the left hand, not in the head. Another dramatic example is seen in amputees. Some of these patients may complain, often bitterly, of pains and proprioceptive sensation in the absent limb (phantom limb). The ends of the nerves cut at the time of amputation often form nerve tangles called neuromas. These may discharge spontaneously or when pressure is put on them. The impulses generated in them are in nerve fibers that previously came from sense organs in the amputated limb, and the sensations evoked are projected to where the receptors used to be. However, there is evidence that plasticity in sensory systems within the CNS is also involved in the phantom limb phenomenon.

Q-8. A man loses his right hand in a farm accident, four year later; he has episodes of severe pain in the missing hand (Phantom limb pain). A detailed PET scan study of his cerebral cortex might be expected to show
a) Expansion of the right hand area in his right somatic sensory area 1 (SI)
b) Expansion of the right hand area in his left SI
c) Projection of fibre from neighboring sensory areas into the right hand area of his right SI.
d) Projection of fibers from neighboring sensory areas into the right hand area of his left SI.

Answer: Projection of fibers from neighboring sensory areas into the right hand area of his left SI.
Explanation:
See above explanation.

Q-9. Weber – Fechner law is
a) Magnitude of sensation is proportional to number or receptor stimulated.
b) Magnitude of sensation is proportional to amplitude of action potential or receptor.
c) Magnitude of sensation is proportional of logarithm of intensity of stimulus
d) Intensity of frequency of stimulus

Answer: Magnitude of sensation is proportional of logarithm of intensity of stimulus
Explanation:
Magnitude of the sensation felt is proportionate to the log of the intensity of the stimulus (Weber – Fechner Law). It now appears, however, that a power function more accurately describes this relation. In other words, R= KSA
Where R is the sensation felt, S is the intensity of the stimulus and for any specific sensory modality, K and A are constants. The frequency of the action potentials generated in sensory nerve fiber is also related to the intensity of initiated stimulus by a power function.

Q-10. Weber Fechner law deals with
a) Frequency discrimination
b) Receptive field organization
c) Intensity discrimination
d) Two point discrimination

Answer: Intensity discrimination
Explanation:
See above explanation.

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Q-11. Weber Fechner law is related with (AI 1997)
a) Amplitude
b) Surface area
c) Number of sensory fibre involvement
d) Stimulus discrimination

Answer: Stimulus discrimination
Explanation:
See above explanation.

Q-12. Intensity of sensory stimulation is directly related to
a) Duration of action potential
b) Frequency of action potential
c) Amplitude of action potential
d) All of the above

Answer: Frequency of action potential
Explanation:
See above explanation.

Q-13. The intensity of sensory stimuli is determined by:
a) Duration of latent period
b) Amplitude of action potential
c) Frequency of action potential
d) Amplitude of generation potential

Answer: Frequency of action potential
Explanation:
See above explanation.

Q-14. Intensity and amplitude are proportional to
a) Weber – Fechner law
b) Starling’s law
c) Slaw
d) Hardy slaw

Answer: Weber – Fechner law
Explanation:
See above explanation.

Q-15. Weber Fechner law is (AIIMS Nov 08)
a) Magnitude of stimulus strength perceived is approximately proportionate to the log of the intensity of stimulus strength
b) Magnitude of stimulus strength perceived is directly proportional to the intensity of stimulus strength
c) Threshold of receptor is directly proportional to stimulus strength
d) Threshold of receptor is inversely proportional to stimulus strength

Answer: Magnitude of stimulus strength perceived is approximately proportionate to the log of the intensity of stimulus strength
Explanation:
See above explanation.