156
SECTION II
Physiology of Nerve & Muscle Cells
stimulus is applied. As the stimulus is increased, the magnitude
of the receptor potential increases. When it reaches a critical
threshold, an action potential is generated in the sensory nerve.
■
Converting a receptor stimulus to a recognizable sensation is
termed sensory coding. All sensory systems code for four ele-
mentary attributes of a stimulus: modality, location, intensity,
and duration.MULTIPLE-CHOICE QUESTIONS
For all questions, select the single best answer unless otherwise directed.
- Pacinian corpuscles are
A) a type of thermoreceptor.
B) usually innervated by A
δ
nerve fibers.
C) rapidly adapting touch receptors.
D) slowly adapting touch receptors.
E) nociceptors. - Adaptation to a sensory stimulus produces
A) a diminished sensation when other types of sensory stimuli
are withdrawn.
B) a more intense sensation when a given stimulus is applied
repeatedly.
C) a sensation localized to the hand when the nerves of the bra-
chial plexus are stimulated.
D) a diminished sensation when a given stimulus is applied
repeatedly over time.
E) a decreased firing rate in the sensory nerve from the recep-
tor when one’s attention is directed to another matter. - Sensory systems code for the following attributes of a stimulus:
A) modality, location, intensity, and duration
B) threshold, receptive field, adaptation, and discrimination
C) touch, taste, hearing, and smell
D) threshold, laterality, sensation, and duration
E) sensitization, discrimination, energy, and projection - In which of the following is the frequency of stimulation not lin-
early related to the strength of the sensation felt?
A) sensory area of the cerebral cortex
B) specific projection nuclei of the thalamus
C) lateral spinothalamic tract
D) dorsal horn
E) cutaneous receptors - Which of the following receptors and sense organs are
incorrectly
paired?
A) rods and cones : eye
B) receptors sensitive to sodium : taste buds
C) hair cells : olfactory epithelium
D) receptors sensitive to stretch : carotid sinus
E) glomus cells : carotid body
6. Which best describes the law of specific nerve energies?
A) No matter where a particular sensory pathway is stimulated
along its course to the cortex, the conscious sensation pro-
duced is referred to the location of the receptor.
B) A nerve can only be stimulated by electrical energy.
C) Receptors can respond to forms of energy other than their
adequate stimuli, but the threshold for these nonspecific
responses is much higher.
D) For any given sensory modality, the specific relationship
between sensation and stimulus intensity is determined by
the properties of the peripheral receptors.
E) The sensation evoked by impulses generated in a receptor
depends in part on the specific part of the brain they ulti-
mately activate.
7. Which of the following does
not
contain cation channels that are
activated by mechanical distortion, producing depolarization?
A) olfactory receptors
B) Pacinian corpuscles
C) hair cells in cochlea
D) hair cells in semicircular canals
E) hair cells in utricle
CHAPTER RESOURCES
Barlow HB, Mollon JD (editors):
The Senses.
Cambridge University
Press, 1982.
Bell J, Bolanowski S, Holmes MH: The structure and function of
Pacinian corpuscles: A review. Prog Neurobiol 1994;42:79.
Haines DE (editor):
Fundamental Neuroscience for Basic and Clinical
Applications,
3rd ed. Elsevier, 2006.
Iggo A (editor):
Handbook of Sensory Physiology.
Vol 2,
Somatosensory System.
Springer-Verlag, 1973.
Kandel ER, Schwartz JH, Jessell TM (editors):
Principles of Neural
Science,
4th ed. McGraw-Hill, 2000.
Mountcastle VB:
Perceptual Neuroscience.
Harvard University Press,
1999.
Squire LR, et al (editors):
Fundamental Neuroscience,
3rd ed.
Academic Press, 2008.