Lecture 4: Sensorimotor System & Hearing, Balance, Taste, Smell Flashcards
1
Q
all animals have sensory organs containing
A
receptor cells that sense some forms of energy - called stimuli
2
Q
the concept of labeled lines:
A
we can distinguish different types of touch because our skin contains a variety of receptors and uses some lines to signal light touch, others to signal vibration, and yet other lines to signal stretching of the skin
3
Q
sensory transduction
A
Energy transformation from the external to internal world - converting the signal from environmental stimuli into action potentials that our brain can understand
4
Q
free nerve endings
A
pain, itch, and temp
5
Q
merkels disc
A
touch responsive to edges and to isolated points on a surface
6
Q
Meissner corpuscle
A
touch responsive to perceive the forms of objects we touch
7
Q
hair follicle receptor
A
touch
8
Q
Pacinian corpuscle
A
vibration and pressure
9
Q
ruffini corpuscle
A
stretch
10
Q
The structure and function of the Pacinian Corpuscle
A
each corpuscle surronds an afferent nerve ending
vibration applied to the corpuscle stretches part of the neuronal membrane, opening the ion channels and permitting the entry of Na+, which initiates an action potential
as stimulus intensity increases, so does the neurons response until it reaches threshold, triggering an action potential which makes us aware of the stimulus
11
Q
intensity of a stimulus can be represented by:
A
the number and thresholds of activated cells
12
Q
somatosensory system
A
body sensation system
13
Q
receptive field
A
consists of a region of space in which a stimulus will alter that neuron’s firing range
example: which patch of skin must we stimulate to change the activity of one particular touch receptor
14
Q
sensory adaptation
A
progressive decrease in a receptor response to a sustained stimulation
15
Q
phasic receptors
A
display adaptation to stimuli
16
Q
tonic receptors
A
show little or no adaptation and thus can signal the duration of a stimulus
17
Q
sensory systems often shift
A
away from an accurate portrayal of the external world
18
Q
central modulation of sensory information
A
the brain actively controls the information it receives and helps the brain attend to some stimuli more than others
19
Q
somatosensory projections ascend as part of the spinal cords:
A
dorsal column system, a large wedge of white matter in the dorsal spinal cord
20
Q
dermatome
A
the strip of skin that is innervated by a particular spinal nerve
21
Q
describe the pathway of sensory inputs to the CNS
A
touch receptors detect stimulation and send action potentials along axons that enter dorsal roots of the spinal cord. This axon is part of a unipolar neuron, the cell body of which resides in the dorsal root ganglion
once the axon enters the spinal dorsal horn, it joins the dorsal column of white matter and ascends to the brain
in the medulla, the axon from the periphery makes its first synapse, innervating a neuron of the dorsal column nuclei. this medullary neuron in turn sends its axon across the midline and up to the thalamus
at this point, the left thalamus will be receiving information about the right side of the body, this thalamus will in turn send this information to the somatosensory cortex
22
Q
for most senses, information reaches the ________ before being relayed to the cortex
A
thalamus
23
Q
Levels of sensory processing:
A
sensory information enters the CNS through brainstem or spinal cord and travels to the thalamus
the thalamus shares the information with the cerebral cortex, the cortex directs the thalamus to suppress some sensations
primary sensory cortex swaps information with the nonprimary sensory cortex
24
Q
primary sensory cortex
A
generally the initial destination of sensory inputs to the cortex
25
nonprimary sensory cortex
may receive and process the same information, often in collaboration with primary sensory cortex
26
Primary somatosensory cortex (S1)
in postcentral gyrus
receives information from the opposite side of the body
parts if the body especially sensitive to touch have large representations in s1 compared with less sensitive areas
27
sensory homunculus
the size of each body part reflects the proportion of s1 devoted to that part
28
the use of one sensory system influences perception from
another sensory system
humans detect visual signals more accurately if accompanied by a sound
29
association areas
process a mixture of inputs from different modalities
30
synesthesia
when seeing a number evokes a colour, or music becomes a taste
31
three components of pain experience
the sensory-discriminative dimension (throbbing, gnawing, shooting)
the motivational-affective (emotional) dimension (tiring, sickening, fearful)
an overall cognitive-evaluative dimension (no pain, mild. excruciating)
32
nociceptors
on free nerve endings specialized to detect damage
33
substances in injured tissue:
serotonin, histamine, and various enzymes and peptides can stimulate nociceptors
34
Peripheral Mediation of Pain
damaged cells release substances that excite free nerve endings that function as nociceptors
action potential generated in the periphery can reflexively excite blood vessels and mast cells to produce inflammation
stimulated mast cells release histamine and a chloroquine-like molecule
information enters through dorsal root and synapses on neurons in dorsal horn
pain fibers release glutamate as a transmitter and substance P as a neuromodulator in the spinal cord. the dorsal horn cells then send information across the midline and up to the thalamus
35
SCN9A gene
encodes a sodium channel expressed in free nerve endings that serve as nociceptors
36
study of capsaicin TRPV1
the chemical that makes chili peppers spicy hot
TRPV1 receptor, or vanilloid receptor 1, detects the spicy heat
belongs to a larger family of proteins called transient receptor potential (TRP) ion channels
37
TRPM3
detects even higher temperatures than TRPV1, but does not respond to capsaicin
found on A-delta fibers, which are large diameter myelinated axons, so the action potentials reach spinal cord quickly
38
Nerve fibers that possess TRPV1 consist of:
thin, unmyelinated fibers called C-fibers
initial sharp pain from burning yourself is conducted by fat A delta fibers activated by TRPM3 receptors, and the long-lasting dull ache after arises from slower C fibers and their TRPV1 receptors
39
Substance P
a peptide that selectively boosts pain signals and remodels pain pathway neurons
40
pain information is integrated in the:
cingulate cortex
41
neuropathic pain
neurons continue to directly signal pain and amplifies the pain signal, in the absence of any tissue damage
e.g. phantom limb pain
42
gate control theory
hypothesizes that "spinal gates"-- modulation sites at which pain can be facilitated or blocked-- control the signal that gets through the brain
43
analegesia
absence of pain
44
endorphins
bing to specific receptors in the brain to reduce pain
this action is pronounced in brainstem region called the periaqueductal gray
45
transcutaneous electrical nerve stimulation
mild electrical stimulation is applied to nerves around injury sites to relieve pain
we know that TENS acts at least in part by releasing endogenous opioids
46
placebo effect
placebos work by activating the brains endogenous opioid system
47
acupuncture
resembles a placebo
48
stress activates:
both an opioid-dependent form of analgesia, which can be blocked by naloxone
endogenous analgesic systems allow a wounded individual to fight or escape rather than be overwhelmed with pain
49
placebo
may activate endorphin-mediated pain control
50
hypnosis
alters brains perception of pain
51
stress
uses both opioid and non-opioid mechanisms
52
cognitive
may activate endorphin-mediated pain control system
53
opiates
bind to opioid receptors in periaqueductal gray and spinal cord
54
spinal block
blocks pain signals in the spinal cord
55
anti-inflammatory drugs
block chemical inflammatory signals at the site of injury
56
cannabinoids
act in nociceptor endings, spinal cord, and brain
57
TENS/mechanical
on large fibers, blocks or alters pain signal to brain
58
central gray
electrically activates endorphin-mediated pain control systems, blocking pain signal in the spinal cord
59
motor plan
a complex set of commands to muscles that is established before an act occurs
60
Electromyography
track simple movements that make up and act by recording the electrical activity of muscles as they contract
61
antagonist muscle group
When one muscle group contracts, it stretches the other group— they are antagonists. E.g.bicep and tricep.
62
synergists
Muscles that act together to move a limb are synergists
63
At the neuromuscular junction,
the neurotransmitter acetylcholine (ACh) is released.
64
The motor neuron, together with all muscle fibers it innervates, is known as a
motor unit. Some motor units are bigger than others, e.g.thigh muscle vs face muscles)
The fibers respond to the release of ACh triggering the molecular events that cause contraction.
65
Proprioception
the collection of information about body movements and position.
66
muscle spindle
is a capsule, buried in other muscle fibers, that contains intrafusal fibers—it responds to stretch.
67
Golgi tendon organs
are sensitive to muscle tension. Golgi tendon organs detect overloads that threaten to tear muscles and tendons and may cause sudden relaxation (dropping something you cannot carry).
68
The Stretch Reflex Circuit
a weight dropped into the hand stretches the biceps muscle
the stretch excites the muscle spindle, which sends action potentials to the dorsal spinal cord
the action potentials synapse onto motor neurons in the spinal cord that cause the biceps to contract, restoring the arm to its original position
the muscle spindle also excites interneurons, causing the triceps to relax when the bicep contracts
69
the pyramidal system
consists of neuronal cell bodies within the frontal cortex and their axons, which pass through the brainstem, forming the pyramidal tract to the spinal cord
70
extrapyramidal system
tracts outside the pyramids of the medulla, they and their connections are lumped together as the extrapyramidal system
lesions interfere with systems that regulate and fine-tune motor behaviour
projections pass to the spinal cord via specialized motor regions (retiuclar formation and red nucleus) of the midbrain and brainstem. the basal ganglia are an important point of origin for extrapyramidal projections
71
M1
the primary motor cortex occupies a single large cortical gyrus: the precentral gyrus
M1 will cause movement in the corresponding region of the right side of the body
72
The Supplementary motor Cortex and Premotor cortex together make up the:
nonprimary motor corte
73
Supplementary Motor cortex:
seems important for the initiation of movement sequences
74
Premotor cortex
seems to be activated when motor sequences are guided by external events
75
In M1recordings from monkeys making arm movements, commands can be observed:
M1 cells change firing rate according to the direction of the movement.
*Each cell has one direction that elicits the highest discharge rates. *An average of neuronal activity allows scientists to predict the direction of arm movements.
76
77
Motor cortex damage can cause
plegia(paralysis) or paresis (weakness) of voluntary movements.
78
A subregion of premotor cortex (F5) contains cells called
mirror neurons.
these neurons fire before making a movement as when observing another individual make the same movement
79
The basal ganglia
are a group of interconnected forebrain nuclei that modulate movement
*Caudate nucleus, putamen, and globus pallidus
*With inputs from the substantia nigra and subthalamic nucleus
help control the amplitude and direction of movement and are important in
- initiation of movement
- movements performed by memory rather than by sensory control
80
The cerebellum receives inputs from
sensory sources and other brain motor systems.
*Guides movement through inhibition
*Helps fine-tune skilled movements
81
Damage to extrapyramidal systems impairs
movement
Common symptoms of cerebellar damage include abnormal gait and posture, especially ataxia(loss of coordination) of the legs.
82
Decomposition of movement
describes gestures that are broken into segments instead of being executed smoothly.
83
Parkinson’s disease
caused by progressive loss of dopaminergic cells in the substantia nigra, which results in slowed movement, tremors in the hands and face, rigid posture, and reduced facial expression.
84
Huntington’s disease
caused by progressive damage to the basal ganglia, especially the caudate and putamen, which results in increasingly excessivemovement, beginning with clumsiness and twitches of the fingers and face.
85
Amplitude, or intensity, measured in
decibels(dB) and perceived as loudness
86
Frequency, measured in
number of cycles per second, or hertz(Hz), and perceived as pitch
87
sound from a musical instrument contains
A fundamental—the basic frequency
Harmonics—multiples of that frequency
Timbre—characteristic sound quality of an instrument, determined by the intensities of its harmonics
88
External ear
Pinna—collect sound waves
Ear canal (or auditory canals)
The shape of the external ear modifies the character of sound frequencies that reach the middle ear
89
Three ossicles
—the malleus, incus, and stapes—connect the tympanic membrane(eardrum) to the oval window.
90
Sound waves in the air strike the
tympanic membrane and cause it to vibrate with the same frequency as the sound.
This vibration also causes ossicles to move, which amplifies vibrations. These vibrations are crucial for converting vibrations in the air to movements of fluid in the inner ear.
91
cochlea of the inner ear
converts vibrations into neural activity
92
The cochlea has three parallel canals:
Scala vestibuli(vestibular canal)
*Scala media (middle canal)
*Scala tympani (tympanic canal)
93
round window
a membrane that separates the tympanic canal from the middle ear
94
Organ of Corti
a receptor system in the scala media
has three main structures:
*Sensory cells, or hair cells
*supporting cells
*Terminations of the auditory nerve fibers
The basilar membrane is the base of the organ of Corti.
95
Sound vibrations cause the basilar membrane to
ripple
96
different parts of the basilar membrane respond to different frequencies:
high frequency: have greatest effect at the base, where is it narrow and relatively stiff
low frequency: produce larger response near apex, where it is wider and more flexible
97
sterocillia
tiny hairs protrude from each hair cell
Stereocilia are connected to each other by tip links—tiny fibers that open ion channels when the stereocilia bend.
*A depolarization of the hair cell occurs and neurotransmitter is released.
98
inner hair cells
a single row near the central axis
99
outer hair cells
three rows
100
vestibulocochlear nerve
cranial nerve VIII contacts the bases of the hair cells
101
IHC afferents
convey action potentials that provide sound perception to the brain.
102
IHC efferents
lead from the brain to the IHCs, allowing the brain to control responsiveness of IHCs.
103
OHC afferents
convey information to the brain about the mechanical state of the basilar membrane, not sounds themselves.
104
OHC efferents
lead from the brain to OHCs, allowing the brain to modify the stiffness of the basilar membrane, thus sharpening and amplifying sounds.
105
Auditory signal pathway from cochlea to cortex
Auditory nerve fibers from IHCs terminate in the cochlear nuclei.
The cochlear nuclei then send information to the superior olivary nuclei.
Superior olivary nuclei pass this information, from both ears, to the inferior colliculi—the primary auditory centers of the midbrain.
Outputs of the inferior colliculi go to the medial geniculate nuclei of the thalamus.
Pathways from here extend to auditory cortex.
IHC-cocholear nuclei-superior olivary nuclei-inferior colliculi-medial geniculate nuclei of the thalamus- auditory cortex
106
auditory pathways have tonotopic organization
They are arranged in a map of low to high frequency. At higher levels, auditory neurons are excited by certain frequencies and inhibited by neighboring ones, resulting in the ability to discriminate tiny differences.
107
sound mainly activates the
primary auditory cortex (A1)
108
differences in frequency are important for our sense of pitch
frequency - a physical property of sound
pitch - our subjective perception of sound
109
place coding
pitch is determined by the location of activated hair cells
the base of cochlea responds to high frequencies and signals treble, and activation of receptors near apex which responds to low frequencies, signals base
110
temporal coding
encodes the frequency of auditory stimuli in the firing rate of auditory neurons
111
infrasound
less than 20 Hz
112
ultrasound
More than 20,000 Hz
113
interaural intensity difference
result from the intensity of a sound
depending on the species, intensity differences occur because one ear is pointed more directly towards the sound source or because the head casts a shadow, preventing sounds originating on one side (off-axis sounds)
the head shadow effect is most pronounced for higher frequencies
114
interaural temporal differences
differences between the two ears in the time of arrival of sounds
one ear is always a little closer to an off-axis sound than the other ear is
onset disparity: the difference between the two ears in hearing the beginning of a sound
ongoing phase disparity: the continuing mismatch between the two ears in the time of arrival of all the peaks and troughs that make up the sound wave
115
spectral filtering
The structure of the external ear can reinforce some frequencies, anddiminish others
116
Heschl's gyrus
the primary auditory cortex where music is first processed
117
amusia
lifelong inability to discern tunes or sing
associated with abnormal function in right frontal lobe and impoverished connectivity between frontal and temporal cortex
118
Conduction deafness
disorders of the outer or middle ear prevent sounds from reaching the cochlea
119
sensorineural deafness
hair cells fail to respond to movement of the basilar membrane; no action potentials fired
*Caused by genetic mutations, infections, ototoxic effects of drugs, loud sounds
*Damage to hair cells can result in tinnitus, a persistent ringing in the ears
120
central deafness
damage to auditory brain areas such as by stroke, tumors or traumatic brain injury
121
word deafness
selective difficulty recognizing normal speech sounds; normal speech and hearing of nonverbal sounds
122
cortical deafness
difficulty recognizing all complex sounds, verbal or nonverbal; rare
123
Parts of the vestibular system:
*Semicircular canals—three fluid-filled tubes, connected to the utricle and saccule
Canals (tubes) are oriented in three planes of head movement:
1. Nodding(pitch, y-axis)
2. Shaking(yaw, z-axis)
3, Tilting(roll, x-axis)
*Ampulla—enlarged chamber at the base of the canals; contains hair cells
124
receptors in the utricle and saccule provide
acceleration and deceleration signals
125
head movements initiate flow of fluid in:
semicircular canal of the same plane, which deflects stereocilia in the ampulla, signaling movement in the brain
126
Many vestibulocochlear nerve fibers terminate in the
vestibular nuclei in the brainstem; some project directly to the cerebellum.
127
motion sickness
too much vestibular excitation
128
sensory conflict theory
sickness occurs when we receive contradictory sensory such as between vestibular and visual input
one hypothesis is that nausea evolved to rid the body of ingested toxins that presumably triggered dizziness
129
five basic tastes
salty, sour, sweet, bitter, umami
130
three kinds of taste papillae
circumvallate, foliate, fungiform
131
taste buds
embedded in the papillae, extend microvilli into a pore where they can contact tastants
132
salty
Sodium (Na+) ions enter taste cells via sodium channels, causing depolarization.
*A second salt sensor is TRPV1 (transient receptor potential vanilloidtype 1), which increases sensitivity to Na+and alsodetects cations of other salts in food.
133
sour
Acids release hydrogen ions (H+) and taste sour.
*Sour taste cells all seem to contain the same type of ion channel that allows an influx of protons, which depolarizes the cell.
*The same receptor detects carbonation in drinks
134
sweet, bitter and umami
all activate second messangers within the cell
135
sweet
detected by a heterodimer of T1R2 and T1R3
136
bitter
detected by T2R receptors
*Each bitter-sensing cell produces most or all of the different bitter receptors.
*High sensitivity to bitter evolved to detect poison.
137
umami
meaty-savory flavor—is detected by two types of receptors:
*Metabotropic glutamate receptor that responds to glutamate: Stimulated by monosodium glutamate (MSG), a flavor enhancer
*Receptor that is a combination of T1R1 and T1R3: Responds to most dietary amino acids
138
gustatory system
extends from the tongue to brainstem nuclei, to the thalamus, and ultimately to the somatosensory cortex
The brain may simply monitor which specific axons are active to determine which tastes are present.
*May be a labeled line system *
Other four tastes remain intact when receptors for one taste are inactivated
139
olfaction
sense of smell
140
anosmia
inability to smell
141
olfactory epithelium
types of cells in epithelium: supporting cells, basal cells, receptor neurons
142
odorants
inhaled molecules that interact with olfactory receptor proteins on the dendrites
143
olfactory neurons differ from neurons of the brain:
incredible diversity of receptor subtypes
die and are replaced in adulthood
144
olfactory bulb
each olfactory axon extends onto this bulb of the brain
the axon terminates on a specific glomerulus, which receives information from one specific class of odorant recpetors
145
glomeruli
organized like a map, adjacent glomeruli receive input from the receptors that are closely related
146
olfactory information is conveyed to the brain via
mitral cells which extend from glomeruli in the olfactory bulbs to various regions of the forebrain
