1
Q
sensory receptors
A
- connect to the cortex through a sequence of intervening relaying neurons that allow each sensory system to mediate different responses and to interact with other sensory systems
- transduce or convert energy to neural activity, light, photons
2
Q
vision sensory receptors
A
light energy is converted to chemical energy into further receptors of the retina, which actually is part of the brain, and this chemical energy is in turn converted to action potentials
3
Q
auditory system conversion
A
air pressure waves are converted first to mechanical energy, which eventually activates the auditory receptors that produce action potentials
4
Q
somatosensory sensory system
A
mechanical energy activates receptor cells that are sensitive to touch or pressure → receptors generate action potentials
5
Q
pain
A
tissue damage releases chemicals that act like neurotransmitter to activate pain fibers and produce action potentials
6
Q
taste and olfaction
A
chemical molecules carried on the air or contained in food, fit themselves into receptors of various shapes to activate action potentials
*
7
Q
auditory receptors
A
- respond to sound wave frequencies between 20 and 20,000 Hertz
- elephants can actually hear and produce sounds below 20 Hertz
- bats can hear and produce sounds as high as 120,000 Hertz
8
Q
color deficient
A
lack one or more types of photoreceptors for color vision, the red, blue, and green cones
can see many colors, but not the same colors as people with all three cones can
9
Q
action potentials
A
- dendrite of a somatosensory neuron is wrapped around the base of the hair
- when the hair is displaced in a certain direction, the dendrite is stretched by the displacement
- sodium channels in the dendrites’ membrane are stretch sensitive, so they open in response to scratching
- if the influx of sodium ions in the stretch-sensitive channels is sufficient, the resulting voltage change will depolarize the dendrite to its threshold, or an action potential, and the voltage-gated, sensitive, K plus, and sodium channels, will open, resulting in a nerve impulse heading to the brain
10
Q
receptive fields
and ex
A
- area from which a stimulus can activate a sensory receptor
- not only sample sensory information, but also help locate sensory events in space and facilitate different actions in space
- localize sensations
- ex: Our lower visual receptive field facilitates the use of our hands in making skilled actions. Whereas, our upper visual field facilitates our movements through our more distant surroundings.
11
Q
rapidly adapting receptors
+ ex x2
A
- receptor that responds at the onset of stimulus on the body
- easy to activate, but stop responding after very short time
- ex: if you touch your arm very lightly, you will immediately detect a touch, but if you keep your finger still, the sensation will fade as receptors adapt → detect the movement of objects
- ex: rods - respond to visible light of any wavelength and have lower response threshold than do the slowly adapting cone shaped receptors which are instead sensitive to color and position
12
Q
slowly adapting receptors
ex
A
- receptor that responds for the duration of a stimulus on the body
- react to stimulation slowly
- ex: if you push a little harder when you first touch your arm, you will feel the touch longer
13
Q
exteroceptive receptors
ex
A
receptor that responds to external stimuli
ex: optic and auditory flow -> useful in telling us how fast we are going, whether we are going in a straight line, or up or down, and whether we are moving, or an object in the world is moving
14
Q
optic flow
A
(exteroceptive receptors)
stimulus configuration - when you run, visual stimuli appear to stream past
15
Q
auditory flow
A
(exteroceptive receptors)
when you move past the sound source, you hear changes in sound intensity that take place because of your changing location
16
Q
interoceptive receptor
ex
A
- receptor that responds to internal stimuli
- position and movement of our bodies
- interpret meaning from external stimuli
- ex: learn from interoceptive receptors in our muscles and joints, and in the vestibular organs of the inner ear
17
Q
receptor density
A
- receptor density determines a sensory system’s sensitivity
- ex: tactile receptors on the fingers are numerous compared with those on the arm
18
Q
two point sensitivity
A
You can prove this by moving the tips of two pencils apart to different degrees, as you touch different parts of your body. The ability to recognize the presence of two pencil points close together, is highest on the parts of the body having the most touch receptors
19
Q
interneurons
(sensory system)
A
- all receptors connect to cortex through sequence of 3 or 4 interneurons
20
Q
first relay for pain receptors
A
- first relay for pain receptors in the spinal cord is related to reflexes that produce withdrawal from a painful stimulus
- Even after damage to the spinal cord that cuts it off from the brain, a limb will still withdraw from a painful stimulus, why? Because rapidly drawing your fingers from a hot stove is a reflex produced at the spinal level.
21
Q
pain pathway
A
- spinal cord - reflex
- relays in the brainstem, esp in midbrain PAG
- neocortex
- ex: pain you feel
22
Q
periaqueductal gray matter
A
- surround cerebral aqueduct
- prompt many complex responses to pain stimuli
- behavioral activation and emotional responses
- enduring pain that you feel long after touching a hot stove may be related to neural activity in the periaqueductal gray matter nuclei
23
Q
neocortex
A
- not only localize pain in a body part, but also identify the felt pain, its external cause, and possible remedies
- cortex can also adapt to our experience with hot stoves so that we know in advance not to touch one
24
Q
gating
with ex
A
- inhibition of sensory information produced by descending signals from the cortex
- the messages sensory systems carry can be modified at neural relays
- descending impulses from the cortex can block or amplify pain signals at the level of the brainstem and at the level of the spinal cord
- ex: when excited or playing a sport
- can also amplify sensory signal
- ex: when we think about the injury, it might feel much more painful because a descending signal from the brain now amplifies the pain signal from the spinal cord
- ex: attention: form of gating that takes place in the cortex, one that allows us to move efficiently from one action to another
- hierarchical code sent from sensory receptors, through neural relays, is interpreted in the brain, especially in the neocortex, and eventually translated into perception, memory, and action
25
sensory coding
* firing rate/activity
* amount of increase or decrease can encode the stimulus intensity
* ex: qualitative visual changes (ie red to green) an be encoded by activity in different neurons or even by different levels of discharge in the same neurons
* more activity by a neuron might signify a redder, and less activity greener
* also related to what other neurons are doing
* ex: ability to perceive colors as constant under a wide range of sensory conditions is a computation made by the brain
* color constancy
26
color constancy
enables us to see green as green under a wide range of illumination → brain is not simply recording sensory stimuli, but rather is manipulating sensory input so that it is behaviorally useful
27
how do we percieve touch, smell, and sound as different from one another?
1. different sensations are processed in distinct regions of the cortex
2. we learn through experience to distinguish them
3. each sensory system has a preferential link with certain behaviors constituting a distinct neural wiring that helps keep each system distinct at all organizational levels
28
sensory systems have subsystems that are surprisingly independent in the behaviors with which they are associated
name them
1. suprachiasmic nucleus
2. pretectum
3. pineal gland
4. superior colliculus
5. accessory optic nucleus
6. visual cortex
7. frontal eye fields
29
suprachiasmatic nucleus
circadian rhythm in response to light and feeding
30
pretectum
pupils constrict in bright light and dilate in dim light
31
pineal gland
* long term circadian rhythm
* release of the chemical melatonin in the pineal gland
32
superior colliculus
head orientation
33
accessory optic nucleus
eye movement in response to head movement
34
visual cortex
* pattern and depth perceptions, color vision, visual tracking
* ex: pathways for pattern perception, color vision, depth perception, and visual tracking
35
frontal eye fields
voluntary eye movement
36
topographic organization
neural-spatial representation of the body or areas of the sensory world a sensory organ detects
37
38
light hitting eye process
When rays of light enter the eye through the cornea, which bends them slightly, they pass through the lens which bends them to a much greater degree to focus the visual image upside down and backward on the receptors at the back of the eye.
39
lights having to pass through the layer of retinal cells, poses little obstacle to our visual acuity for reasons:
1. the cells are transparent and the photoreceptors are extremely sensitive
* can be excited by a single photon
2. fibers forming the optic nerve bend away from the retina central part or fovea, so as not to interfere with the passage of light through the retina
40
photoreceptive cells in retina
rods and cones
* induce action potentials in retinal ganglion cells
* other retinal cell including horizontal and amacrine cells contribute to the readiness processing of visual information
* each photoreceptor points in a slightly different direction, and so, has a unique receptive fields
41
rods
* sensitive to dim light
* night vision
* distribution: absent entirely from the fovea and more sparsely distributed over the rest of the retina
* in bright light, acuity is best when looking directly at things and dim light acuity is best when looking slightly away
42
cones
* transduce bright light
* daytime vision
* distribution: packed together densely in the fovea region
* three types: each type maximally responsive to a different set of wavelengths, red or blue or green mediate color vision
43
optic chiasm and on
* just before entering the brain, the two optic nerves, one from each eye meet and form the optic chasm
* At this point, about half the fibers from each eye cross, so the right half of each eye's visual field is represented in the left hemisphere. And the left half of each eye's visual field is represented in the right hemisphere.
* Having entered in the brain proper, the optic tract still consisting of retinal ganglion cells, axons diverges to form two main pathways.
44
geniculostriate pathway
main
* runs from the retina to the lateral geniculate nucleus LGN, a nucleus of the thalamus to the primary visual cortex in the occipital lobe
* takes part in pattern, color, and motion recognition and includes conscious visual functions
45
46
lateral geniculate nucleus (LGN)
layers
* layers 2, 3, 5
* receive fibers from the ipsilateral eye on the same eye, on the same side
* layers 1, 4, 6
* receive fibers from the contralateral eye
47
lateral geniculate nucleus (LGN)
visual field
* topography of visual field is reproduced in each LGN layer
* central parts → central part of visual field
* peripheral parts → peripheral field
* LGN cells → layer 4 of primary visual cortex (aka V1)
* V1/striate cortex - very large in primates and appears striped
* visual field is upside down, inverted, and reversed in V1
48
damage to tectopulvinar pathway
visual ataxia: inability to recognize where objects are located
49
damage to geniculostriate system
* impairments in pattern, color and motion perception as well as visual-form agnosia
* agnosia: inability to recognize objects
50
sound localization
identifying source of air pressure waves
51
echolocalization
identifying and locating objects by bouncing sound waves off them as well as the ability to detect the complexity of pressure waves
52
why auditory system is complex:
1. many transformations of pressure waves take place within the ear before action potentials are generated in the auditory nerve
2. the auditory nerve projects to many targets in the brain stem and cortex
53
frequency
* speed of pressure changes = changes in pitch
* frequency of a sound is transduced by the longitudinal and structure of the basilar membrane
* Higher sound frequencies cause maximum peaks near the cochlear base that is near the oval window
* Lower sound frequencies cause maximum peaks near the apex, farthest from the oval window
54
amplitude
intensity of pressure changes = loudness
55
timbre
complexity of pressure changes = perceived uniqueness of tonal quality of a sound
56
pinna
outer ear
external structure, which catches waves of air pressures and directs them into the external ear canal, which amplifies them somewhat and directs them to the eardrum at its inner end
57
58
middle ear
* inner side of eardrum
* air-filled chamber that contains the three smallest bone in the human body connected in a series
* includes ossicles and ear drum
59
60
eardrum
Sound waves striking the eardrum, vibrate it at frequency varying with the wave's frequency
61
ossicles
* hammer, anvil and stirrup
* attach the ear drum to the oval window of the inner ear
* amplify and convey vibrations to the oval window
62
cochlea
* contains the auditory sensory receptors called hair cells
* rolled up into the shape of a snail shell
* filled with fluid and floating in the middle of this fluid is the basilar membrane
* hair cells are embedded in a part of the basilar membrane called the organ of Corti
* hair cells maximally disturbed at the point at which the wave peaks producing their maximal neural discharge at that place
63
64
basilar membrane
narrow and thick at its base near the round window and thinner and wider at its apex within the cochlea
65
perception of sound
1. sounds are caught in the outer ear and amplified by the middle ear
* pressure waves in the air are amplified and transformed a number of times in the ear, by deflection in the pinna, by oscillation of the travel through the external ear canal and by the movement of the bones of the middle ear to the cochlea
2. In the inner ear, they are converted to action potentials on the auditory pathway going to the brain and we interpret the action potentials as our perception of sound.
3. When sound waves strike the ear drum also termed the tympanic membrane, this membrane vibrates.
66
tonotopic organization
* different points on the basilar membrane represent different sound frequencies also applies to the auditory cortex
* projections from hair cells of the organ of Corti form a representation of the basilar membrane in the neocortex
* receptive field of a hair cell is not a point in space, but rather a particular sound frequency
* composes the auditory systems
67
pathway connecting cochlea to primary auditory area in the superior temporal gyrus
1. The axons of hair cells leave the cochlear to form the major part of the **auditory nerve**, the eighth cranial nerve. This nerve, first projects to the **medulla** in the hindbrain.
2. Synapse in either in the **dorsal or ventral cochlear nuclei, or in the superior olivary nucleu**s. The axons of neurons in these areas form the **lateral lemniscus**, which terminates in discrete zones of the **inferior colliculus** in the midbrain
3. _Two_ distinct pathways emerge from the colliculus, crossing to the **ventral and the dorsal medial geniculate nuclei** in the thalamus.
* The ventral region: -\> **core auditory cortex, A1** or Brodmann's area 41
* _identifies_ the sound
* The dorsal region: -\> **secondary auditory regions**
* ****indicates its _spatial_ source
68
vestibular system
information from the vestibular system allows us not only to balance, but also to record and replay actively in the mind's eye, the movements we have made
69
inner ear
contains the organs that allow you to perceive your own motion, and to stand upright without loosing your balance
70
hair cells in vestibular system
bend when the body moves forward, or when the head changes position relative to the body
71
72
semicircular canals
* oriented in the three planes that correspond to the three dimensions in which we move
* collectively, they can represent any head movement
73
otholith organs
sensitive to the head's static position in space - balance
74
fibers from balance receptors
* project over the eighth cranial nerve to a number of nuclei in the brain stem
* nuclei interact in the hind brain to help keep us balanced while we move
* also aid in controlling eye movements at the mid-brain
75
exteroceptive function
enables us to feel the world around us
76
interoceptive function
monitoring internal bodily events and informing the brain about the position of body segments relative to one another and about the body in space
77
submodalities of somatosensory system
* 1,2,3: mediate our perceptions of sensations, such as pain, touch, and body awareness
* 4: mediate balance
* composed of a set of interoceptive receptors within the inner ear
78
somatosensory receptors
types
nociception, hapsis, proprioception
79
nociception
* noxious perception → perception of pain, temp, and itch
* most consist of free nerve endings
* CNS (esp in cortex) - where pain is perceived
* phantom limb pain
* Many internal organs, including the heart and kidney and blood vessels, have pain receptors but the ganglion neurons carrying information from these receptors lack pathways to the brain
* instead they synapse with spinal cord neurons that receive no susceptive information from the body's surface
80
neurons in spinal cord that relay pain, temp, and itch messages to the brain recieve two sets of signals:
1. from the body's surface
2. other from the internal organs
* cannot distinguish between the two sets of signals → pain in body organs is often felt as referred pain coming from the body surface
81
hapsis
* our tactile perception of objects
* hapsis receptors enable fine touch and pressure, allowing us to identify objects we touch and grasp
* occupy both superficial and deep skin layers and are attached to body hairs as well
* When touch is lost, not only do we lose the information that it normally provides about the objects we handles or the movements we make, but movement is affected as well.
82
proprioception
* the perception of body location and movement
* proprioceptors encapsulated nerve endings sensitive to the stretch of muscles and tendons and to joint movements
83
major somatosensory pathways:
1. posterior spinothalamic tract
2. anterior spinothalamic tract
84
posterior spinothalamic tract
major spinothalamic tract
* for hapsis, pressure, and proprioception, body awareness
* fibers of somatosensory neurons that make up the hapsis and proprioception system are relatively large, heavily myelinated, and for the most part, rapidly adapting
* cell bodies are located in the posterior root ganglion
* dendrites project to sensory receptors in the body and their axons project into the spinal cord
85
posterior
86
anterior spinothalamic tract
major somatosensory pathway
* for nociception
* fibers are somewhat smaller, less myelinated, and more slowly adapting than those of the haptic and proprioception pathway
* follow the same course to enter the spinal cord but once there project to relay neurons in the more central regions of the spinal cord, the **substantia gelatinosa**
* second relay cells then send their axons across to the other side of the cord where they form the anterior spinothalamic tract
* anterior fibers eventually join the posterior hapsis and proprioception fibers in the **medial lemniscus**
87
anterior
88
brown-sequard syndrome
* unilateral spinal cord injury that cuts the somatosensory pathways in that half of the spinal cord
* results in the bilateral symptoms
* loss of hapsis and proprioception occurs unilaterally on the side of the body where damage occurred
* loss of nociception occurs contralaterally on the side of the body opposite to the injury
* unilateral damage to the points where the pathways come together, that is to the posterior roots, brainstem, and thalamus, affects hapsis, proprioception, and nociception equally because these parts of the pathways are in proximity
89
homonculus
(penfield 1930s)
Wilder Penfield first stimulated the sensory cortex in the conscious epilepsy patients and asked them to report the sensation they felt he created a topographic map that represents the body surface on the primary somatosensory cortex, S1
The results show that the primary somatosensory cortex contains a number of homunculi, one for each of its subregion, 3a, 3b, 1, and 2.
90
taste receptors
taste buds
* bumps on the tongue called papillae are probably there to help the tongue grasp food → taste buds lie buried around them
* chemicals in food dissolve in the saliva that coats the tongue, and disperse through the saliva to reach the taste receptors
* If the tongue is dry, the taste buds receive few chemical signals and food is difficult to taste
* taste receptors also found in gut and other places
* may play a role in food absorption, metabolism and appetite
91
types of taste receptors
* 5 main types:
* each responds to different chemical component in food
* Sweet, Sour, Salty, Bitter and Umami
92
super tasters
perceived certain tastes as strong and offensive, whereas others are indifferent to them
93
underlying basis for species, and individual difference in taste
stems from differences in the genes, for taste receptors
94
smell receptors
* axons projecting from the **olfactory receptors** -\> **glomeruli mitral cells** in olfactory bulb -\> form the **olfactory tract** (Cranial nerve one) -\> **pyriform cortex** -\> hypothalamus, the amygdala, the entorhinal cortex of the temporal lobe and the orbital frontal cortex, the area of the prefrontal cortex (located behind the eye sockets)
95
types of smell receptors
Receptor hair cells, supporting hair cells, and an underlying layer of basal cells
96
outer epithelial surface
* covered by a layer of mucus, in which the receptor cells cilia are embedded
* others must pass through the mucus to reach the receptors → changes in its properties, such as occur when we have a cold, may influence how easily we can detect an odor
97
three cranial nerves carry information from the tongue:
* glossopharyngeal nerve, the vagus nerve, and the chorda tympani branch of the facial nerve
* all three enter solitary tract
98
gustatory
99
solitary tract
main gustatory pathway
divides into two routes:
* red
* goes to the **VPM** of the thalamus → which in turn sends out two pathways:
* **s1**
* sensitive to tactile stimuli
* probably responsible for **localizing tastes** on the tongue
* region just rostral to s2, in the **insular cortex**
* probably dedicated entirely to **taste**, because it is not responsive to tactile stimulation
* blue
* leads to the **p****ontine taste area**→ projects to the**lateral hypothalamus**and**amygdala**
100
olfactory pathway
101
olfactory pathways
* major output of olfactory bulb: lateral olfactory tract, which passes ipsilateral to the pyriform cortex, the amygdala and the entorhinal cortex
* pyriform cortex primary projection goes to the central part, of the dorsal medial nucleus in the thalamus → projects to the orbital frontal cortex. Which can be considered the primary olfactory neocortex
* two classes of neurons
* responsive to specific orders
* broadly tuned
102
sensation
registration by the sensory systems of physical or chemical energy from the environment and its transduction into nervous system activity
103
perception
* subjective interpretation of sensation by the brain
* our sensory impressions are affected by the context in which they can place, our emotional states and our experiences.
104
illusions
demonstrate complex perceptual phenomena → mediated by the neocortex and illustrate that we do not simply respond to sensory information
105
synesthesia
* the ability to perceive a stimulus of one sense, as the sensation of a different sense
* most common: colored hearing
* synesthetes grouped into two classes:
* projectors
* associators
* can be distinguished by self reports and they perform differently on perceptual tests
* ex: stroop test
106
projectors
* experience sensory mixing as reality
* ex: when looking at numbers printed in black text for example, seven appears yellow to a projector whereas two looks blue
107
associators
* experience sensory mixing in their minds' eye
* ex: associating one number with one color, and one another number with one another color, but not actually seeing those colors
108
stroop test
participants read color words say red, printed in a different color say blue, projectors take longer than associate to respond → because the color mixes can produce interference
109
Zamm 2013
synesthesia
* used diffusion tensor imaging to measure the extent of fiber connections between the auditory and visual cortices in participants who saw colors when they heard sounds and in participants who did not
* Those who displayed synesthesia had **more connections** between the auditory and visual cortices
110
Rouw and Scholte 2010
synesthesia
* examined brain differences in projectors and associators using functional magnetic resonance imaging, fMRI
* projectors: activation associated with **sensory mixing in the sensory cortex**
* associators: activation in **association cortices** and brain regions associated with **memory**
111
sensory synergies
* sensory systems exist at all levels of the nervous system and their interactions are mediated by these sensory connections
112
the property that sets sensory receptors apart from other cells is their ability to
convert energy into nerve impulses
113
the ability to discriminate individual stimuli is highest from surfaces with
* small closely spaced receptive fields
* large widely spaced receptive fields
* large closely spaced receptive fields
* small widely spaced receptive fields
small, closely spaced receptive fields
114
the common output of sensory transduction in all sensory systems is?
an action potential
115
receptors that respond to external stimuli are called \_\_\_; receptors that respond to our own activity are called \_\_\_
exteroceptive; interoceptive
116
voluntary eye movements are largely regulated by neural circuits centered in the
frontal eye fields
117
the axons of the ___ from the optic nerve
retinal ganglion cells
118
the ___ is to hearing as the retina is to seeing
organ of Corti
119
the peak of the traveling wave in the basilar membrane varies with the ___ of the sound
frequency
120
according to tonotopic theory
different points on the basilar membrane represent different sound frequencies
121
pitch is MOST closely related to
frequency
122
otholith organs ar associated with the sense of
balance
123
aa patient who can not locate the position of her limbs in space unless she is looking at them is suffering from a loss of
proprioception
124
olfaction aand gustation are known as the
chemical senses
125
the subjective experience that results from sensory processing is referred to as
perception
126
* connect to the cortex through a sequence of intervening relaying neurons that allow each sensory system to mediate different responses and to interact with other sensory systems
* transduce or convert energy to neural activity, light, photons
sensory receptors
127
light energy is converted to chemical energy into further receptors of the retina, which actually is part of the brain, and this chemical energy is in turn converted to action potentials
vision sensory receptors
128
air pressure waves are converted first to mechanical energy, which eventually activates the auditory receptors that produce action potentials
auditory system sensory receptors
129
mechanical energy activates receptor cells that are sensitive to touch or pressure → receptors generate action potentials
somatosensory sensory system
130
tissue damage releases chemicals that act like neurotransmitter to activate pain fibers and produce action potentials
pain
131
chemical molecules carried on the air or contained in food, fit themselves into receptors of various shapes to activate action potentials
*
taste and olfaction
132
lack one or more types of photoreceptors for color vision, the red, blue, and green cones
color deficient
133
* area from which a stimulus can activate a sensory receptor
* not only sample sensory information, but also help locate sensory events in space and facilitate different actions in space
* localize sensations
* ex: Our lower visual receptive field facilitates the use of our hands in making skilled actions. Whereas, our upper visual field facilitates our movements through our more distant surroundings.
receptive fields
and ex
134
* receptor that responds at the onset of stimulus on the body
* easy to activate, but stop responding after very short time
* ex: if you touch your arm very lightly, you will immediately detect a touch, but if you keep your finger still, the sensation will fade as receptors adapt → detect the movement of objects
* ex: rods - respond to visible light of any wavelength and have lower response threshold than do the slowly adapting cone shaped receptors which are instead sensitive to color and position
rapidly adapting receptors
ex x2
135
* receptor that responds for the duration of a stimulus on the body
* react to stimulation slowly
* ex: if you push a little harder when you first touch your arm, you will feel the touch longer
slowly adapting receptors
ex
136
receptor that responds to external stimuli
ex: optic and auditory flow -\> useful in telling us how fast we are going, whether we are going in a straight line, or up or down, and whether we are moving, or an object in the world is moving
exteroceptive receptors
ex
137
(exteroceptive receptors)
stimulus configuration - when you run, visual stimuli appear to stream past
optic flow
138
(exteroceptive receptors)
when you move past the sound source, you hear changes in sound intensity that take place because of your changing location
auditory flow
139
* receptor that responds to internal stimuli
* position and movement of our bodies
* interpret meaning from external stimuli
* ex: learn from interoceptive receptors in our muscles and joints, and in the vestibular organs of the inner ear
interoceptive receptor
ex
140
* receptor density determines a sensory system's sensitivity
* ex: tactile receptors on the fingers are numerous compared with those on the arm
receptor density
141
You can prove this by moving the tips of two pencils apart to different degrees, as you touch different parts of your body. The ability to recognize the presence of two pencil points close together, is highest on the parts of the body having the most touch receptors
two point sensitivity
142
* all receptors connect to cortex through sequence of 3 or 4 interneurons
interneurons
143
* relays in the brainstem, esp in midbrain PAG
* behavioral activation
* emotional responses
* ex: pain you feel
pain pathway
144
prompt many complex responses to pain stimuli and includes behavioral activation and emotional responses
periaqueductal gray matter
145
* not only localize pain in a body part, but also identify the felt pain, its external cause, and possible remedies
* cortex can also adapt to our experience with hot stoves so that we know in advance not to touch one
neocortex
146
* inhibition of sensory information produced by descending signals from the cortex
* the messages sensory systems carry can be modified at neural relays
* ex: descending impulses from the cortex can block or amplify pain signals at the level of the brainstem and at the level of the spinal cord
* ex: when excited or playing a sport
* can also amplify sensory signal
* ex: when we think about the injury, it might feel much more painful because a descending signal from the brain now amplifies the pain signal from the spinal cord
* ex: attention: form of gating that takes place in the cortex, one that allows us to move efficiently from one action to another
* hierarchical code sent from sensory receptors, through neural relays, is interpreted in the brain, especially in the neocortex, and eventually translated into perception, memory, and action
gating
with ex
147
* firing rate/activity
* amount of increase or decrease can encode the stimulus intensity
* ex: qualitative visual changes (ie red to green) an be encoded by activity in different neurons or even by different levels of discharge in the same neurons
* more activity by a neuron might signify a redder, and less activity greener
* also related to what other neurons are doing
* ex: ability to perceive colors as constant under a wide range of sensory conditions is a computation made by the brain
* color constancy
sensory coding
148
enables us to see green as green under a wide range of illumination → brain is not simply recording sensory stimuli, but rather is manipulating sensory input so that it is behaviorally useful
color constancy
149
circadian rhythm in response to light and feeding
suprachiasmatic nucleus
150
pupils constrict in bright light and dilate in dim light
pretectum
151
* long term circadian rhythm
* release of the chemical melatonin in the pineal gland
pineal gland
152
head orientation
superior colliculus
153
eye movement in response to head movement
accessory optic nucleus
154
* pattern and depth perceptions, color vision, visual tracking
* ex: pathways for pattern perception, color vision, depth perception, and visual tracking
visual cortex
155
voluntary eye movement
frontal eye fields
156
neural-spatial representation of the body or areas of the sensory world a sensory organ detects
topographic organization
157
* sensitive to dim light
* night vision
rods
158
* transduce bright light
* daytime vision
cones
159
main
* runs from the retina to the lateral geniculate nucleus LGN, a nucleus of the thalamus to the primary visual cortex in the occipital lobe
* takes part in pattern, color, and motion recognition and includes conscious visual functions
geniculostriate pathway
160
visual ataxia
damage to tectopulvinar pathway
161
* impairments in pattern, color and motion perception as well as visual-form agnosia
* agnosia
damage to geniculostriate system
162
identifying source of air pressure waves
sound localization
163
identifying and locating objects by bouncing sound waves off them as well as the ability to detect the complexity of pressure waves
echolocalization
164
* speed of pressure changes = changes in pitch
frequency
165
intensity of pressure changes = loudness
amplitude
166
complexity of pressure changes = perceived uniqueness of tonal quality of a sound
timbre
167
outer ear
external structure, which catches waves of air pressures and directs them into the external ear canal, which amplifies them somewhat and directs them to the eardrum at its inner end
pinna
168
* inner side of eardrum
* air-filled chamber that contains the three smallest bone in the human body connected in a series
* includes ossicles and ear drum
middle ear
169
* hammer, anvil and stirrup
* amplify and convey vibrations to the oval window
ossicles
170
* contains the auditory sensory receptors called hair cells
* rolled up into the shape of a snail shell
* filled with fluid and floating in the middle of this fluid is the basilar membrane
* hair cells are embedded in a part of the basilar membrane called the organ of Corti
* hair cells maximally disturbed at the point at which the wave peaks producing their maximal neural discharge at that place
cochlea
171
narrow and thick at its base near the round window and thinner and wider at its apex within the cochlea
basilar membrane
172
* different points on the basilar membrane represent different sound frequencies also applies to the auditory cortex
tonotopic organization
173
balance
record and replay actively in the mind's eye, the movements we have made
vestibular system
174
contains the organs that allow you to perceive your own motion, and to stand upright without loosing your balance
inner ear
175
bend when the body moves forward, or when the head changes position relative to the body
hair cells in vestibular system
176
* oriented in the three planes that correspond to the three dimensions in which we move
* collectively, they can represent any head movement
semicircular canals
177
sensitive to the head's static position in space - balance
otholith organs
178
* project over the eighth cranial nerve to a number of nuclei in the brain stem
* nuclei interact in the hind brain to help keep us balanced while we move
* also aid in controlling eye movements at the mid-brain
fibers from balance receptors
179
enables us to feel the world around us
exteroceptive function
180
monitoring internal bodily events and informing the brain about the position of body segments relative to one another and about the body in space
interoceptive function
181
* perception of pain, temp, and itch
* most consist of free nerve endings
* damaged/irritated → endings secrete chemicals, usually peptides, that stimulate the nerve, producing action potentials that then convey messages about pain, temperature, or itch to the CNS
* CNS (esp in cortex) - where pain is perceived
* phantom limb pain
* Many internal organs, including the heart and kidney and blood vessels, have pain receptors but the ganglion neurons carrying information from these receptors lack pathways to the brain
* instead they synapse with spinal cord neurons that receive no susceptive information from the body's surface
nociception
182
1. from the body's surface
2. other from the internal organs
* cannot distinguish between the two sets of signals → pain in body organs is often felt as referred pain coming from the body surface
neurons in spinal cord that relay pain, temp, and itch messages to the brain recieve two sets of signals:
183
* our tactile perception of objects
* enable fine touch and pressure, allowing us to identify objects we touch and grasp
* occupy both superficial and deep skin layers and are attached to body hairs as well
hapsis
184
* the perception of body location and movement
* nerve endings sensitive to the stretch of muscles and tendons and to joint movements
proprioception
185
1. posterior spinothalamic tract
2. anterior spinothalamic tract
major somatosensory pathways:
186
* for hapsis, pressure, and proprioception, body awareness
* fibers of somatosensory neurons that make up the hapsis and proprioception system are relatively large, heavily myelinated, and for the most part, rapidly adapting
* cell bodies are located in the posterior root ganglion
* dendrites project to sensory receptors in the body and their axons project into the spinal cord
posterior spinothalamic tract
187
* for nociception
* fibers are somewhat smaller, less myelinated, and more slowly adapting than those of the haptic and proprioception pathway
* follow the same course to enter the spinal cord but once there project to relay neurons in the more central regions of the spinal cord, the substantia gelatinosa
* second relay cells then send their axons across to the other side of the cord where they form the anterior spinothalamic tract
* anterior fibers eventually join the posterior hapsis and proprioception fibers in the medial lemniscus
anterior spinothalamic tract
188
* unilateral spinal cord injury that cuts the somatosensory pathways in that half of the spinal cord
* results in the bilateral symptoms
* loss of hapsis and proprioception occurs unilaterally on the side of the body where damage occurred
* loss of nociception occurs contralaterally on the side of the body opposite to the injury
* unilateral damage to the points where the pathways come together, that is to the posterior roots, brainstem, and thalamus, affects hapsis, proprioception, and nociception equally because these parts of the pathways are in proximity
brown-sequard syndrome
189
(penfield 1930s)
Wilder Penfield first stimulated the sensory cortex in the conscious epilepsy patients and asked them to report the sensation they felt he created a topographic map that represents the body surface on the primary somatosensory cortex, S1
The results show that the primary somatosensory cortex contains a number of homunculi, one for each of its subregion, 3a, 3b, 1, and 2.
homonculus
190
perceived certain tastes as strong and offensive, whereas others are indifferent to them
super tasters
191
stems from differences in the genes, for taste receptors
underlying basis for species, and individual difference in taste
192
Receptor hair cells, supporting hair cells, and an underlying layer of basal cells
types of smell receptors
193
* covered by a layer of mucus, in which the receptor cells cilia are embedded
* others must pass through the mucus to reach the receptors → changes in its properties, such as occur when we have a cold, may influence how easily we can detect an odor
outer epithelial surface
194
* glossopharyngeal nerve, the vagus nerve, and the chorda tympani branch of the facial nerve
* all three enter solitary tract
gustatory pathways
three cranial nerves carry information from the tongue:
195
main gustatory pathway
divides into two routes:
* red
* goes to the ventral posterior medial nucleus, the VPM of the thalamus → which in turn sends out two pathways:
* s1
* sensitive to tactile stimuli, probably responsible for localizing tastes on the tongue
* region just rostral to s2, in the insular cortex
* probably dedicated entirely to taste, because it is not responsive to tactile stimulation
* blue
* leads to the pontine taste area → which in turn projects to the lateral hypothalamus and amygdala
solitary tract
196
registration by the sensory systems of physical or chemical energy from the environment and its transduction into nervous system activity
sensation
197
* subjective interpretation of sensation by the brain
* our sensory impressions are affected by the context in which they can place, our emotional states and our experiences.
perception
198
demonstrate complex perceptual phenomena → mediated by the neocortex and illustrate that we do not simply respond to sensory information
illusions
199
* the ability to perceive a stimulus of one sense, as the sensation of a different sense
* most common: colored hearing
* synesthetes grouped into two classes:
* projectors
* associators
* can be distinguished by self reports and they perform differently on perceptual tests
* ex: stroop test
synesthesia
200
* experience sensory mixing as reality
* ex: when looking at numbers printed in black text for example, seven appears yellow to a projector whereas two looks blue
projectors
201
* experience sensory mixing in their minds' eye
* ex: associating one number with one color, and one another number with one another color, but not actually seeing those colors
associators
202
participants read color words say red, printed in a different color say blue, projectors take longer than associate to respond → because the color mixes can produce interference
stroop test
203
* sensory systems exist at all levels of the nervous system and their interactions are mediated by these sensory connections
sensory synergies
204
205
submodality of taste
* taste receptors in the front 2/3 of the tongue:
* send info to brain through the **facial nerve number 7**
* ****posterior 1/3:
* send info to the brain through the **glossopharyngeal nerve (**cranial nerve 9)
206
submodality of oflaction
* olfactory system has as many as 400 receptor types, each dedicated to detecting a particular odor. In principle, if each smell were linked to a particular behavior, it would have a multitude of olfactory sub-modalities
* ex: other animals have better olfactory systems
* The mouse, for example, has as many as 1000 kinds of olfactory receptors. In most mammals, the neocortex represents the sensory field of each modality, vision, hearing, touch, smell, taste, not once, but many times.
207
bipolar cells and retinal ganglion cells
photoreceptive cells in eye synapse on **bipolar cells** which induce graded potentials --\> induce action potentials in retinal ganglion cells --\> connect in bundle at optic disc (blind spot) --\> optic nerve
208
209
210
ventral part of visual field represented:
* ventral part of visual field represented at back of visual cortex
* peripheral towards the front
* upper part represented below the fissure at middle of occipital lobe
* lower part represented above calcarine fissue
211
tectopulvinar pathway
* takes part in detecting and orienting to visual stimulation
* eye -\> superior colliculus -\> visual areas
* reaches the visual areas in the temporal and parietal lobes through relays in the lateral posterior-pulvinar complex of the thalamus
* mammals - additional projection from the colliculus to the cortex via this thalamic pulvinar nucleus provides information to the cortex about the absolute special location of objects
212
* takes part in detecting and orienting to visual stimulation
* eye -\> superior colliculus -\> visual areas
* reaches the visual areas in the temporal and parietal lobes through relays in the lateral posterior-pulvinar complex of the thalamus
* mammals - additional projection from the colliculus to the cortex via this thalamic pulvinar nucleus provides information to the cortex about the absolute special location of objects
tectopulvinar pathway
213
214
contrast auditory and visual systems
In contrast with the visual system pathways, the projections of the auditory system provide both ipsilateral and contralateral inputs to the cortex. So, there is a bilateral representation of each cochlear nucleus in both hemispheres. As described for the visual system, A1 projects to many other regions of the neocortex forming multiple tonotopic maps.
215
216
pain gate
* we often rub the area around an injury or shake a limb to reduce the pain sensation → increase the activity in fine touch and pressure pathways and can block information transmission in spinal cord relays
* interneuron in spinal cord recieves excitatory input from fine touch and pressure pathway and inhibitory input from the pain and temp pathway
* the activity of the interneuron determines whether pain and temp info is sent to the brain
217
* we often rub the area around an injury or shake a limb to reduce the pain sensation → increase the activity in fine touch and pressure pathways and can block information transmission in spinal cord relays
* interneuron in spinal cord recieves excitatory input from fine touch and pressure pathway and inhibitory input from the pain and temp pathway
* the activity of the interneuron determines whether pain and temp info is sent to the brain
* how inhibitory interneuron in the spinal cord can block transmission in the pain pathway
* activating this inhibitory neuron via collaterals from the fine touch and pressure pathway provides the physical substrate through which rubbing an injury or each can gate sensation
pain gate
218
your eyes and ears sense activity in your environment. what happens next?
the physical stimuli you perceived are turned into electrical signals called action potentials
219
a neuron has inputs connected to the auditory region of the brain. we can assume that this neruon plays a role in:
auditory perception
220
the main sensory organ located in the back of the nasal cavity is the:
olfactory epithelium
* inside nasal cavity
* layer of cells at the bottom
* olfactory bulb is on top of it
221
what is the neuromuscular junction?
the location where motor neurons make contact with muscle fibers
222
the ventral premotor cortex contains most of the \_\_, which fire when a monkey or human witnesses the performing of actions similar to their own actions
mirror neurons
223
complex cognition and planning is directed mostly by which part of the frontal lobes?
* premotor cortex
* lateral prefrontal cortex
* frontopolar cortex
* primary motor cortex
lateral prefrontal cortex
224
225
it is hypothesized that the cerebellum may control nonmotor as well as motor functions. evidence for this is the fact that:
the cerebellum has outputs going to frontal lobe
226
the spinal cord is made up of:
white and gray matter
227
upper motor neurons are located in the:
spinal cord
228
the ventral horn in the spinal cord contains these neurons:
lower motor neurons
229
upper motor neurons
* found in cerebral cortex and brainstem and carry info down to activate interneurons which then signal muscles
* cell body in upper motor cortex
230
the pinna, auditory canal, and tympanic membrane all make up the:
outer ear
231
information travels from the LGN to the primary visual cortex via the:
optic radiations
232
the photoreceptors that are most sensitive to light are:
rods
233
the abnormal movements seen in adults with huntington's disease are thought to be caused by the hyperactivity of neurons secreting \_\_\_.
dopamine - hyperactivity
234
nociception receptors damaged/irritated
damaged/irritated → endings secrete chemicals, usually peptides, that stimulate the nerve, producing action potentials that then convey messages about pain, temperature, or itch to the CNS
