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54 Cards in this Set
- Front
- Back
Somatosensory systems
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get info into CNS
largely from outside world but also from our bodies info from muscles that tells about body position |
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4 Attributes to a stimulus
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1. modality
2. intensity/strength 3. Timing/duration 4. Location |
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Modaility defines
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a general class of stimulation
vision, hearing, touch, smell, taste receptors respond to a specific type of energy from the physical world |
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Sumodalities of vision, taste
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vision- color, form, depth
taste- salty, sweet, sour, bitter, umami |
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Labled Line Code
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has to do w/ Modality
certain nerves carry specific types of sensory information Muller-1826 |
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Intensity/Strength is signaled by
Population Code |
the freqency code (rate law)or number of APs
-more APs=higher intensity more receptors stimulated w/ a higher intensity of a stimulus |
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Timing or Duration
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defined as when the receptor starts and stops to respond
all receptors adapt. only differece is how quickly |
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slowly adapting rec
rapidly adapting rec |
continues to fire APs
stops firing APs even w/ stim still there |
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Location (5)
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receptor fields in dfft areas
especially important for vision and touch less impt for taste/smell |
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Receptor Fields form
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Topographic maps
-touch-somatotopic, vision-visuotopic orderly 1-to-1 representation of rec in skin and location of RF in brain |
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fine tactile descrimination have
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a higher density of receptors
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how are receptors classified?
fxn? |
by the type of stimulus to which they are most sensitive
transduction of phys stimulus into a neural stimulus 1. gen APs or 2. gen receptor potentials |
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5 Types of Receptors
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1. photoreceptors
2. chemoreceptors 3. mechanoreceptors 4. thermoreceptors 5. Nociceptors-pain |
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2 kinds of projections
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1. serial/heirarchal processing
2. parallel processing |
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Serial or heirarchial processing produces what?
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complexity
neurons synapse in order, in series |
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Parallel Processing
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2 pathways in series
used OFTEN in CNS b/c its FASTER much more efficient than series can be crossed or uncrossed |
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convergence w/ receptor fields
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individually small RFs converge/synapse on a neuron that has a larger RF
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4 Perceptual Modalities
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1. Tactile
2. Proprioception 3. Thermal 4. Pain |
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Tactile
Proprioception |
cutaneous, fine discrimination touch, fine detai
in muscles and joints. used to plan and make mvmts |
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Mechanoreceptors
key distinction b/w rapidly and slowly adapting rec |
respond to mechanical deformation of skin
"where its located" |
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4 Types of Cutaneous rec
capsulated unencap |
Pacinian, Meis, Ruff, Merkel
pacinian, meisner, Ruffini merkel-free nerve ending |
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higher 2pt descrim accomplished by
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having a high density of rec in a small area
small RFs large RF have a harder time w/ 2pt descrim |
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most sensitive areas of your body have
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the greatest density of rec, smallest RFs
hands/face |
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what breaks the 1-rec/1-type of touch rule?
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free nerve endings
Cornea only has free endings but can detect several dfft stimuli |
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Superficial mechanorec
Deep mechanorec |
Meissner, Merkel
Pacinian, Ruffini |
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Rapidly Adapting rec
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respond to just the onset
1. Superficial Meisner 2. deep Pacinian |
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Slowly Adapting rec
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respond to sustained input
1. superficial Merkel 2. Deeper Rufini |
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2Ms=superficial
P/R=deep 2corpuscles=rapidly adapting 2endings=slowly adapting |
meisner, merkel
pacinian, ruffini meisner, pacinian merkel, ruffini |
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which receptors have small RF
fine tactile stimulation |
merkel, meisner
pacinian do NOT detected by superficial receptors |
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Proprioception
2 kinds of receptors |
detects stationary body position, mvmt of jts/musc, and can evaluate shape of objects
1. Muscle Spindles 2. Golgi Tendon Organs |
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Muscle Spindles
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proprioception
long,thin, stretch rec in voluntary muscle Parallel to muscle synapse on excit MN in ventral horn |
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what is a safety feature for overextension of muscle?
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muscle spindles synapse on excit MN in ventral horn
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Golgi Tendon Organ
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in series w/ muscle
in tendon, at end of extrafusal muscle fiber sensitive to contraction |
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Henry Head's theory
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dfft axons carry dfft aspects of touch
regrow at dfft times |
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Erlanger and Gasser
light/descriminatory touch pain/temp carried by |
first oscilloscopes
thicker axons-faster A->C, I->IV thinner axons-slower |
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Parallel Processing in CNS
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fine touch and prop carried along same pathway
pain and temp carried along dfft pathway |
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Dermatomes
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length-wise down the extremities and horizontally around the trunk
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DC/ML
2nd order neurons in.. |
fine touch, prop
ascnd ipsilaterally FC-lat, FG-med nuc cuneatus, and nuc gracillus |
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3rd order neurons in DCML pathway
ascend to.... |
from VPM/VPL of thalmus
input from body-lateral input from head-medial via IC to Parietal Lobe |
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Medial Lemniscus
Lateral Lemniscus |
deals w/ SS
Auditory information |
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Facial input to DC/ML
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goes into principal nuc in the pons
from pons on, it travels w/ the ML |
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Pain and Temperature Pathway
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Spinothalamic Tract STT
ascending in AL portion of lateral column 3rd order neuron projections go to many different places |
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part of the AL pathway that goes to the thalmus
and.. |
Spinothalamic Tract
spinoreticular formation -impt in arousal spinomesencephalic- midbrain -may block relay of pain |
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why is it difficult to interfere w/ pain pathways in the brain?
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more diffuse
3rd order neurons from thalmus go to not only SS cortex, but the parietal lobe, ant cingulate gyrus, and insular cortex |
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damage to 1 side of the SC
damage to 1 side of the Medulla |
pain-contralat, touch/prop-ipsi
pain and touch/prop contralat |
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Ventroposterior complex of thalmus
receives input from |
relay nucleus for touch
VPM-VPL really just one ML and STT |
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STT synapse on, CNV
ML synapses on |
VPM
VPL |
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Criteria for defining areas of the Cortex
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1. staining-cytoarchitecture
2. representation of periphery 3. unique nerual properties 4. unique pattern of connections 5. unique deficits w/ damage |
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Brodman's Areas in Parietal cortex for SS
from meial-->lateral |
3a, 3b, 1, and 2
4cytoarchitectural areas feet-->head |
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original consensus on SS cortex
Current View |
there were just 2 areas
SI and SII 8-10 SS cortex on each side each brodman area has its own map *1-to-1 result in cytoarchitecture to mapping |
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why do we have multiple areas in the SS cortex?
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probably b/c of specialization
8-10dfft areas |
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cutaneous input goes to areas?
Propioceptive input goes to areas? |
areas 3b and 1
areas 2 and 3a |
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cortical areas consist of columns
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vertical collections of neurons that do the same thing
all correspond to same RF and probably same submodality |
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Plasticity
immediate changes suggest delayed changes suggest |
some parts of the brain maintain plasticity
unmasking of latent inputs, disinhibition sprouting of connections |