NSC 201/BCS 240: Exam 3
11/16/2022
University Academic Honesty Policy: “I affirm that I will not give or receive any unauthorized
help on this exam, and that all work will be my own.”
Name __________________________
Answer each of the following questions; each answer is worth two points, unless otherwise
specified. The duration of the exam is 50 minutes. Good luck!
1) In response to photons of light in the center of their receptive field, on-center bipolar cells
become _____ permeable to _____ ions.
A) less, sodium
B) more, sodium
C) less, potassium
D) more, potassium
2) The basilar membrane vibrates most strongly to _____ pure tones at its apex, and it is the
activity of _____ hair cells that increases the motion of the membrane.
A) low frequency; inner
B) low frequency; outer
C) high frequency; inner
D) high frequency; outer
3) Sensory systems often process information in a push-pull fashion: that is, when one
neuron is stimulated by a given stimulus, its corresponding partner is inhibited, and vice
versa when the stimulus is changed to its opposite. Push-pull processing is evident at the
receptor-level for which of the following senses?
A) auditory
B) olfactory
C) vision
D) somatosensory
E) gustatory
4) In the visual system, parvocellular is to magnocellular as
A) moving is to stationary targets
B) low-contrast is to high-contrast sensitivity
C) bottom is to top layers of thalamus
D) blobs is to interblobs
E) none of the above
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5) Motor correction commands are conveyed down the spinal cord to _____ dermatome and
activate motor units with _____ innervation ratios.
A) one – high
B) one – low
C) many – high
D) many – low
6) Sensory receptors may or may not have axons that project towards the CNS. Of the
following senses (balance, sight, smell, sound, taste, touch), how many have receptors
with axons?
A) one
B) two
C) three
D) four
E) five
F) six
7) One basic function of the gustatory system is to identify tastes as nutritious or antinutritious. Sensitivity is greatest to which of the following type of tastants?
A) sweet
B) sour
C) bitter
D) salt
E) umami
8) A patient is experiencing a complete loss of vision for stimuli in the periphery of the right
visual hemi-field; otherwise, their vision is normal. Where are two possible sites of
damage along the visual pathway?
A) right nasal retina and right optic tract
B) right nasal retina and left optic tract
C) right temporal retina and right optic tract
D) right temporal retina and left optic tract
9) Anosmia is a well-described symptom of Corona Virus Disease 2019, and has been linked
to altered transduction. Which of the following proteins are effected?
A) G-proteins
B) receptor proteins
C) binding proteins
D) channel proteins
10) The somatosensory system is characterized by systems having both fast and slow
receptors, which are sensitive to initial and on-going stimulation, respectively. Which of
the following systems is an exception to this rule?
A) balance
B) touch
C) joints
D) muscles
E) pain
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Questions 11-13: short answer. Be concise and write legibly in the space provided.
11) Sensory systems code stimuli in a “generalist” or “specialist” manner. Define these terms,
and for one sense explain how/where the code changes back and forth up the pathway.
Generalists respond to many stimuli; specialists respond to one/few stimuli.
Gustatory: receptors are generalists (multiple receptor types on each cell), afferents are
specialists (because each innervates many receptors that share one taste in common),
and cortex is generalist (population code; inputs are widespread).
Olfaction: receptors are generalists (each protein responds to many odorants), the
glomeruli (and the associated mitral/tufted cells) are specialists due to lateral inhibition,
and cortex is generalist (population code; inputs are widespread).
12) Primary sensory cortices initiate one or two output pathways. Name them, define their
function, list which cortices contribute to each, and name the ultimate targets of both.
Dorsal stream: “where” processing; sources: visual (V1), auditory (A1) and
somatosensory (S1) cortices; target: posterior parietal association cortex
Ventral stream: “what” processing; sources: visual (V1), auditory (A1), somatosensory
(S1), gustatory (G1) and olfactory (O1) cortices; target: ventrolateral prefrontal
association cortex
13) Describe the three principles of the organization/function of the somatic motor system (i.e.,
defining characteristics of the whole system as compared/contrasted to sensory systems).
Like sensory systems, the somatic motor system has hierarchical organization, (with
association cortex at the highest level and muscles at the lowest level). Unlike sensory
systems, motor output is guided by sensory input (e.g., primary motor cortex receives
proprioceptive feedback from primary somatosensory cortex) and learning changes the
nature and locus of sensorimotor control (e.g., higher to lower centers).
For the sets below, match each item on the left with the single best choice from the items
(answers) on the right. Write your answer on the line in front of the number. Some answers
may be used multiple times, others not at all.
With regard to transduction in sensory systems: second messenger used and dominant ion
flowing to make current go in (responses graded independently: 1 pt each)
2nd M
Ion
(A-E)
(J-N)
_B__ _N__
14) looking at a sunset
_D__ _M__
15) tasting a cookie
_E__
16) feeling pain
_J__
_A__ _L__
17) smelling a flower
_E__
18) balancing on a bicycle
_K__
Second messenger
Ion
A) cAMP
B) cGMP
C) DAG
J) calcium
K) potassium
L) chloride
D) IP3
E) none
M) sodium
N) none
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With regard to sensory and motor pathways through thalamic nuclei: structures in the
ascending pathway and cortical target lobe (1 pt each)
Path
Lobe
(A-F)
(J-M)
_B__ _K__ 19) ventral lateral
_D__ _K__ 20) dorsomedial
_F__
_J__
21) medial geniculate
_A__
_M_
_E__
_K__ 23) ventral anterior
22) ventral posterior
In Path
Target lobe
A) semicircular canals
B) inferior olive
C) retina
J) temporal
D) olfactory bulb
E) globus pallidus
F) superior olive
K) frontal
L) occipital
M) parietal
With regard to the information carried in different spinal cord pathways:
__C___ 24) makes you look
__D___ 25) bends down at the waist
__A___ 26) reduces free nerve activity
__B___ 27) knows that your arm is raised
__A___ 28) wriggles (moves) toes in warm sand
With regard to structure/function relationships in sensory and motor systems:
_J___ 29) regional optic flow
_L___ 30) non-distorted, topographic cortex
_A___ 31) mirror neurons
_D___ 32) forms intent to move
_B___ 33) exteroception
_G___ 34) speech production center
_Q___ 35) olfaction
_N___ 36) votes on specific set of instructions
_H___ 37) dyslexia
_P___ 38) extra-striate (beyond V1) color vision
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With regard to structure/dysfunction relationships in sensory and motor systems:
_H___ 39) failure to forewarn of pain (no alert
that the body has been injured)
_D___ 40) common site of epilepsy
_C___ 41) blindness
_J___ 42) inability to taste/vomit
_F___ 43) uncoordinated movement
(damaged relay center)
_H___ 44) poor sound localization ability
Questions 45-50: multiple-choice. Circle only one answer per question.
45) A fast motor unit consists of a motor neuron and all of the _____ fibers it innervates
_____ blood vessels.
A) extrafusal, near to
B) extrafusal, far from
C) intrafusal, near to
D) intrafusal, far from
46) The receptive fields of layer IV simple cells are roughly ______ in shape, and driven by
inputs from ______ eye(s).
A) circular, one
B) circular, two
C) rectangular, one
D) rectangular, two
47) The ascending pathways for each of the three major extra-personal sensory systems
decussate in the brain. Which, if any, completes its decussation at the lowest division of
the brain (i.e., neurons in this structure of the ascending pathway are sensitive to stimuli
only in the opposite hemi-field)?
A) sight
B) sound
C) touch
D) equal
48) In the pain withdrawal reflex, flexors are excited and extensors are inhibited. Which
neurotransmitters affect the respective motor neuron pools?
A) acetylcholine and GABA
B) acetylcholine and glycine
C) glutamate and GABA
D) glutamate and glycine
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49) Activation with natural strength stimulation of one spot on the homunculus in the
precentral gyrus produces
A) a feeling of something touching one spot on the skin
B) a feeling of pressure over a wide area of the body
C) movement of individual muscles
D) motion of many body parts centered around a particular area
50) Rate adaptation -- wherein a neuron usually fires fewer and fewer action potentials over
the course of a long-duration stimulus -- is observed in many sensory systems. All of the
following systems show rate adaptation except:
A) vision
B) temperature
C) smell
D) taste
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