Chapter 14: The Somatic Nervous System Flashcards
1
Q
Alkaloid
A
substance, usually from a plant source, that is chemically basic with respect to pH and will stimulate bitter
receptors
2
Q
Amacrine cell
A
type of cell in the retina that connects to the bipolar cells near the outer synaptic layer and provides the
basis for early image processing within the retina
3
Q
Ampulla
A
in the ear, the structure at the base of a semicircular canal that contains the hair cells and cupula for
transduction of rotational movement of the head
4
Q
Anosmia
A
loss of the sense of smell; usually the result of physical disruption of the first cranial nerve
5
Q
Anterior corticospinal tract
A
division of the corticospinal pathway that travels through the ventral (anterior) column
of the spinal cord and controls axial musculature through the medial motor neurons in the ventral (anterior) horn
6
Q
Aqueous humor
A
watery fluid that fills the anterior chamber containing the cornea, iris, ciliary body, and lens of the eye
7
Q
Ascending pathway
A
fiber structure that relays sensory information from the periphery through the spinal cord and
brain stem to other structures of the brain
8
Q
Association area
A
region of cortex connected to a primary sensory cortical area that further processes the information
to generate more complex sensory perceptions
9
Q
Audition
A
Sense of hearing
10
Q
Auricle
A
Fleshy external structure of the ear
11
Q
Basilar membrane
A
in the ear, the floor of the cochlear duct on which the organ of Corti sits
12
Q
Betz cells
A
output cells of the primary motor cortex that cause musculature to move through synapses on cranial and
spinal motor neurons
13
Q
Binocular depth cues
A
indications of the distance of visual stimuli on the basis of slight differences in the images
projected onto either retina
14
Q
Bipolar cell
A
cell type in the retina that connects the photoreceptors to the RGCs
15
Q
Broca’s area
A
region of the frontal lobe associated with the motor commands necessary for speech production
16
Q
Capsaicin
A
molecule that activates nociceptors by interacting with a temperature-sensitive ion channel and is the basis
for “hot” sensations in spicy food
17
Q
Cerebral peduncles
A
segments of the descending motor pathway that make up the white matter of the ventral midbrain
18
Q
Cervical enlargement
A
region of the ventral (anterior) horn of the spinal cord that has a larger population of motor
neurons for the greater number of and finer control of muscles of the upper limb
19
Q
Chemoreceptor
A
region of the ventral (anterior) horn of the spinal cord that has a larger population of motor
neurons for the greater number of and finer control of muscles of the upper limb
20
Q
Chief sensory nucleus
A
component of the trigeminal nuclei that is found in the pons
21
Q
Choroid
A
highly vascular tissue in the wall of the eye that supplies the outer retina with blood
22
Q
Ciliary body
A
smooth muscle structure on the interior surface of the iris that controls the shape of the lens through the
zonule fibers
23
Q
Circadian rhythm
A
internal perception of the daily cycle of light and dark based on retinal activity related to sunlight
24
Q
Cochlea
A
auditory portion of the inner ear containing structures to transduce sound stimuli
25
Cochlear duct
space within the auditory portion of the inner ear that contains the organ of Corti and is adjacent to the scala tympani and scala vestibuli on either side
26
Cone photoreceptor
one of the two types of retinal receptor cell that is specialized for color vision through the use of
three photopigments distributed through three separate populations of cells
27
Contralateral
word meaning “on the opposite side,” as in axons that cross the midline in a fiber tract
28
Cornea
fibrous covering of the anterior region of the eye that is transparent so that light can pass through it
29
Corneal reflex
protective response to stimulation of the cornea causing contraction of the orbicularis oculi muscle
resulting in blinking of the eye
30
Corticobulbar tract
connection between the cortex and the brain stem responsible for generating movement
31
Corticospinal tract
connection between the cortex and the spinal cord responsible for generating movement
32
Cupula
specialized structure within the base of a semicircular canal that bends the stereocilia of hair cells when the head
rotates by way of the relative movement of the enclosed fluid
33
Decussate
to cross the midline, as in fibers that project from one side of the body to the other
34
Dorsal column system
ascending tract of the spinal cord associated with fine touch and proprioceptive sensations
35
Dorsal stream
connections between cortical areas from the occipital to parietal lobes that are responsible for the
perception of visual motion and guiding movement of the body in relation to that motion
36
Encapsulated ending
configuration of a sensory receptor neuron with dendrites surrounded by specialized structures
to aid in transduction of a particular type of sensation, such as the lamellated corpuscles in the deep dermis and
subcutaneous tissue
37
Equilibrium
sense of balance that includes sensations of position and movement of the head
38
Executive functions
cognitive processes of the prefrontal cortex that lead to directing goal-directed behavior, which is
a precursor to executing motor commands
39
External ear
structures on the lateral surface of the head, including the auricle and the ear canal back to the tympanic
membrane
40
Exteroceptor
sensory receptor that is positioned to interpret stimuli from the external environment, such as
photoreceptors in the eye or somatosensory receptors in the skin
41
Extraocular muscle
one of six muscles originating out of the bones of the orbit and inserting into the surface of the
eye which are responsible for moving the eye
42
Extrapyramidal system
pathways between the brain and spinal cord that are separate from the corticospinal tract and
are responsible for modulating the movements generated through that primary pathway
43
Fasciculus cuneatus
lateral division of the dorsal column system composed of fibers from sensory neurons in the
upper body
44
Fasciculus gracilis
medial division of the dorsal column system composed of fibers from sensory neurons in the lower
body
45
Fibrous tunic
outer layer of the eye primarily composed of connective tissue known as the sclera and cornea
46
Fovea
exact center of the retina at which visual stimuli are focused for maximal acuity, where the retina is thinnest, at
which there is nothing but photoreceptors
47
Free nerve ending
configuration of a sensory receptor neuron with dendrites in the connective tissue of the organ, such
as in the dermis of the skin, that are most often sensitive to chemical, thermal, and mechanical stimuli
48
Frontal eye fields
area of the prefrontal cortex responsible for moving the eyes to attend to visual stimuli
49
General sense
any sensory system that is distributed throughout the body and incorporated into organs of multiple
other systems, such as the walls of the digestive organs or the skin
50
Gustation
Sense of taste
51
Gustatory receptor cells
sensory cells in the taste bud that transduce the chemical stimuli of gustation
52
Hair cells
mechanoreceptor cells found in the inner ear that transduce stimuli for the senses of hearing and balance
53
Incus
(also, anvil) ossicle of the middle ear that connects the malleus to the stapes
54
Inferior colliculus
last structure in the auditory brainstem pathway that projects to the thalamus and superior colliculus
55
Inferior oblique
extraocular muscle responsible for lateral rotation of the eye
56
Inferior rectus
extraocular muscle responsible for looking down
57
Inner ear
structure within the temporal bone that contains the sensory apparati of hearing and balance
58
Inner segment
in the eye, the section of a photoreceptor that contains the nucleus and other major organelles for
normal cellular functions
59
Inner synaptic layer
layer in the retina where bipolar cells connect to RGCs
60
Interaural intensity difference
cue used to aid sound localization in the horizontal plane that compares the relative
loudness of sounds at the two ears, because the ear closer to the sound source will hear a slightly more intense
sound
61
Interaural time difference
cue used to help with sound localization in the horizontal plane that compares the relative
time of arrival of sounds at the two ears, because the ear closer to the sound source will receive the stimulus
microseconds before the other ear
62
Internal capsule
segment of the descending motor pathway that passes between the caudate nucleus and the putamen
63
Interoceptor
sensory receptor that is positioned to interpret stimuli from internal organs, such as stretch receptors in the
wall of blood vessels
64
Ipsilateral
word meaning on the same side, as in axons that do not cross the midline in a fiber tract
65
Iris
colored portion of the anterior eye that surrounds the pupil
66
Kinesthesia
colored portion of the anterior eye that surrounds the pupil
67
Lacrimal duct
duct in the medial corner of the orbit that drains tears into the nasal cavity
68
Lacrimal gland
gland lateral to the orbit that produces tears to wash across the surface of the eye
69
Lateral corticospinal tract
division of the corticospinal pathway that travels through the lateral column of the spinal
cord and controls appendicular musculature through the lateral motor neurons in the ventral (anterior) horn
70
Lateral geniculate nucleus
thalamic target of the RGCs that projects to the visual cortex
71
Lateral rectus
extraocular muscle responsible for abduction of the eye
72
Lens
component of the eye that focuses light on the retina
73
Levator palpebrae superioris
muscle that causes elevation of the upper eyelid, controlled by fibers in the oculomotor nerve
74
Lumbar enlargement
region of the ventral (anterior) horn of the spinal cord that has a larger population of motor
neurons for the greater number of muscles of the lower limb
75
Macula
enlargement at the base of a semicircular canal at which transduction of equilibrium stimuli takes place within the ampulla
76
Malleus
(also, hammer) ossicle that is directly attached to the tympanic membrane
77
Mechanoreceptor
receptor cell that transduces mechanical stimuli into an electrochemical signal
78
Medial geniculate nucleus
receptor cell that transduces mechanical stimuli into an electrochemical signal
79
Medial lemniscus
fiber tract of the dorsal column system that extends from the nuclei gracilis and cuneatus to the
thalamus, and decussates
80
Medial rectus
extraocular muscle responsible for adduction of the eye
81
Mesencephalic nucleus
component of the trigeminal nuclei that is found in the midbrain
82
Middle ear
space within the temporal bone between the ear canal and bony labyrinth where the ossicles amplify sound
waves from the tympanic membrane to the oval window
83
Multimodal integration area
region of the cerebral cortex in which information from more than one sensory
modality is processed to arrive at higher level cortical functions such as memory, learning, or cognition
84
Neural tunic
layer of the eye that contains nervous tissue, namely the retina
85
Nociceptor
Receptor cell that senses pain stimuli
86
Nucleus cuneatus
medullary nucleus at which first-order neurons of the dorsal column system synapse specifically
from the upper body and arms
87
Nucleus gracilis
medullary nucleus at which first-order neurons of the dorsal column system synapse specifically from
the lower body and legs
88
Odorant molecules
Volatile chemicals that bind to receptor proteins in olfactory neurons to stimulate the sense of
smell
89
Olfaction
Sense of smell
90
Olfactory bulb
central target of the first cranial nerve; located on the ventral surface of the frontal lobe in the cerebrum
91
Olfactory epithelium
region of the nasal epithelium where olfactory neurons are located
92
Olfactory sensory neuron
receptor cell of the olfactory system, sensitive to the chemical stimuli of smell, the axons
of which compose the first cranial nerve
93
Opsin
receptor cell of the olfactory system, sensitive to the chemical stimuli of smell, the axons
of which compose the first cranial nerve
94
Optic chiasm
decussation point in the visual system at which medial retina fibers cross to the other side of the brain
95
Optic disc
decussation point in the visual system at which medial retina fibers cross to the other side of the brain
96
Optic nerve
second cranial nerve, which is responsible visual sensation
97
Optic tract
name for the fiber structure containing axons from the retina posterior to the optic chiasm representing their
CNS location
98
Organ of Corti
structure in the cochlea in which hair cells transduce movements from sound waves into
electrochemical signals
99
Osomoreceptor
Receptor cell that senses differences in the concentrations of bodily fluids on the basis of osmotic
pressure
100
Ossicles
Three small bones in the middle ear
101
Otolith
eceptor cell that senses differences in the concentrations of bodily fluids on the basis of osmotic
pressure
102
Otolithic membrane
gelatinous substance in the utricle and saccule of the inner ear that contains calcium carbonate
crystals and into which the stereocilia of hair cells are embedded
103
Outer segment
in the eye, the section of a photoreceptor that contains opsin molecules that transduce light stimuli
104
Outer synaptic layer
layer in the retina at which photoreceptors connect to bipolar cells
105
Oval window
membrane at the base of the cochlea where the stapes attaches, marking the beginning of the scala
vestibuli
106
Palpebral conjunctiva
membrane attached to the inner surface of the eyelids that covers the anterior surface of the
cornea
107
Papilla
membrane attached to the inner surface of the eyelids that covers the anterior surface of the
cornea
108
Photoisomerization
chemical change in the retinal molecule that alters the bonding so that it switches from the
11-cis-retinal isomer to the all-trans-retinal isomer
109
Photon
individual “packet” of light
110
Photoreceptor
receptor cell specialized to respond to light stimuli
111
Premotor cortex
cortical area anterior to the primary motor cortex that is responsible for planning movements
112
Primary sensory cortex
region of the cerebral cortex that initially receives sensory input from an ascending pathway
from the thalamus and begins the processing that will result in conscious perception of that modality
113
Proprioception
sense of position and movement of the body
114
Proprioceptor
receptor cell that senses changes in the position and kinesthetic aspects of the body
115
Pupil
open hole at the center of the iris that light passes through into the eye
116
Pyramidal decussation
location at which corticospinal tract fibers cross the midline and segregate into the anterior
and lateral divisions of the pathway
117
Pyramids
segment of the descending motor pathway that travels in the anterior position of the medulla
118
Receptor cell
cell that transduces environmental stimuli into neural signals
119
Red nucleus
midbrain nucleus that sends corrective commands to the spinal cord along the rubrospinal tract, based on
disparity between an original command and the sensory feedback from movement
120
Reticulospinal tract
extrapyramidal connections between the brain stem and spinal cord that modulate movement,
contribute to posture, and regulate muscle tone
121
Retina
nervous tissue of the eye at which phototransduction takes place
122
Retinal
cofactor in an opsin molecule that undergoes a biochemical change when struck by a photon (pronounced with a
stress on the last syllable)
123
Retinal ganglion cell (RGC)
neuron of the retina that projects along the second cranial nerve
124
Rhodopsin
photopigment molecule found in the rod photoreceptors
125
Rod photoreceptor
one of the two types of retinal receptor cell that is specialized for low-light vision
126
Round window
one of the two types of retinal receptor cell that is specialized for low-light vision
127
Rubrospinal tract
descending motor control pathway, originating in the red nucleus, that mediates control of the limbs
on the basis of cerebellar processing
128
Saccule
structure of the inner ear responsible for transducing linear acceleration in the vertical plane
129
Scala tympani
portion of the cochlea that extends from the apex to the round window
130
Scala vestibuli
portion of the cochlea that extends from the apex to the round window
131
Sclera
White of the eye
132
Semicircular canals
structures within the inner ear responsible for transducing rotational movement information
133
Sensory homunculus
topographic representation of the body within the somatosensory cortex demonstrating the
correspondence between neurons processing stimuli and sensitivity
134
Sensory modality
a particular system for interpreting and perceiving environmental stimuli by the nervous system
135
Solitary nucleus
medullar nucleus that receives taste information from the facial and glossopharyngeal nerves
136
Somatosensation
general sense associated with modalities lumped together as touch
137
Special sense
any sensory system associated with a specific organ structure, namely smell, taste, sight, hearing, and
balance
138
Spinal trigeminal nucleus
component of the trigeminal nuclei that is found in the medulla
139
Spinothalamic tract
ascending tract of the spinal cord associated with pain and temperature sensations
140
Spiral ganglion
location of neuronal cell bodies that transmit auditory information along the eighth cranial nerve
141
Stapes
(also, stirrup) ossicle of the middle ear that is attached to the inner ear
142
Stereocilia
array of apical membrane extensions in a hair cell that transduce movements when they are bent
143
Stretch reflex
response to activation of the muscle spindle stretch receptor that causes contraction of the muscle to
maintain a constant length
144
Submodality
specific sense within a broader major sense such as sweet as a part of the sense of taste, or color as a part
of vision
145
Superior colliculus
structure in the midbrain that combines visual, auditory, and somatosensory input to coordinate
spatial and topographic representations of the three sensory systems
146
Superior oblique
extraocular muscle responsible for medial rotation of the eye
147
Superior rectus
extraocular muscle responsible for looking up
148
Supplemental motor area
cortical area anterior to the primary motor cortex that is responsible for planning
movements
149
Suprachiasmatic nucleus
hypothalamic target of the retina that helps to establish the circadian rhythm of the body
on the basis of the presence or absence of daylight
150
Taste buds
structures within a papilla on the tongue that contain gustatory receptor cells
151
Tectorial membrane
Component of the organ of Corti that lays over the hair cells, into which the stereocilia are
embedded
152
Tectospinal tract
extrapyramidal connections between the superior colliculus and spinal cord
153
Thermoreceptor
sensory receptor specialized for temperature stimuli
154
Topographical
relating to positional information
155
Transduction
process of changing an environmental stimulus into the electrochemical signals of the nervous system
156
Trochlea
cartilaginous structure that acts like a pulley for the superior oblique muscle
157
Tympanic membrane
Ear drum
158
Umami
taste submodality for sensitivity to the concentration of amino acids; also called the savory sense
159
Utricle
structure of the inner ear responsible for transducing linear acceleration in the horizontal plane
160
Vascular tunic
middle layer of the eye primarily composed of connective tissue with a rich blood supply
161
Ventral posterior nucleus
nucleus in the thalamus that is the target of gustatory sensations and projects to the
cerebral cortex
162
Ventral stream
connections between cortical areas from the occipital lobe to the temporal lobe that are responsible for
identification of visual stimuli
163
Vestibular ganglion
location of neuronal cell bodies that transmit equilibrium information along the eighth cranial
nerve
164
Vestibular nuclei
location of neuronal cell bodies that transmit equilibrium information along the eighth cranial
nerve
165
Vestibule
in the ear, the portion of the inner ear responsible for the sense of equilibrium
166
Vestibulo-ocular reflex (VOR)
reflex based on connections between the vestibular system and the cranial nerves of
eye movements that ensures images are stabilized on the retina as the head and body move
167
Vestibulospinal tract
extrapyramidal connections between the vestibular nuclei in the brain stem and spinal cord that
modulate movement and contribute to balance on the basis of the sense of equilibrium
168
Visceral sense
sense associated with the internal organs
169
Vision
Special sense of sight based on transduction of light stimuli
170
Visual acuity
property of vision related to the sharpness of focus, which varies in relation to retinal position
171
Vitreous humor
viscous fluid that fills the posterior chamber of the eye
172
Working memory
```
function of the prefrontal cortex to maintain a representation of information that is not in the
immediate environment
```
173
Zonule fibers
fibrous connections between the ciliary body and the lens
