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54 Cards in this Set

  • Front
  • Back
Somatosensory systems
get info into CNS
largely from outside world
but also from our bodies
info from muscles that tells about body position
4 Attributes to a stimulus
1. modality
2. intensity/strength
3. Timing/duration
4. Location
Modaility defines
a general class of stimulation
vision, hearing, touch, smell, taste
receptors respond to a specific type of energy from the physical world
Sumodalities of vision, taste
vision- color, form, depth
taste- salty, sweet, sour, bitter, umami
Labled Line Code
has to do w/ Modality
certain nerves carry specific types of sensory information

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
Timing or Duration
defined as when the receptor starts and stops to respond

all receptors adapt. only differece is how quickly
slowly adapting rec

rapidly adapting rec
continues to fire APs

stops firing APs even w/ stim still there
Location (5)
receptor fields in dfft areas

especially important for vision and touch
less impt for taste/smell
Receptor Fields form
Topographic maps
-touch-somatotopic, vision-visuotopic
orderly 1-to-1 representation of rec in skin and location of RF in brain
fine tactile descrimination have
a higher density of receptors
how are receptors classified?

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
5 Types of Receptors
1. photoreceptors
2. chemoreceptors
3. mechanoreceptors
4. thermoreceptors
5. Nociceptors-pain
2 kinds of projections
1. serial/heirarchal processing
2. parallel processing
Serial or heirarchial processing produces what?
neurons synapse in order, in series
Parallel Processing
2 pathways in series
used OFTEN in CNS b/c its FASTER
much more efficient than series

can be crossed or uncrossed
convergence w/ receptor fields
individually small RFs converge/synapse on a neuron that has a larger RF
4 Perceptual Modalities
1. Tactile
2. Proprioception
3. Thermal
4. Pain

cutaneous, fine discrimination touch, fine detai
in muscles and joints. used to plan and make mvmts

key distinction b/w rapidly and slowly adapting rec
respond to mechanical deformation of skin

"where its located"
4 Types of Cutaneous rec

Pacinian, Meis, Ruff, Merkel
pacinian, meisner, Ruffini

merkel-free nerve ending
higher 2pt descrim accomplished by
having a high density of rec in a small area
small RFs

large RF have a harder time w/ 2pt descrim
most sensitive areas of your body have
the greatest density of rec, smallest RFs

what breaks the 1-rec/1-type of touch rule?
free nerve endings

Cornea only has free endings but can detect several dfft stimuli
Superficial mechanorec

Deep mechanorec
Meissner, Merkel

Pacinian, Ruffini
Rapidly Adapting rec
respond to just the onset

1. Superficial Meisner
2. deep Pacinian
Slowly Adapting rec
respond to sustained input

1. superficial Merkel
2. Deeper Rufini

2corpuscles=rapidly adapting
2endings=slowly adapting
meisner, merkel
pacinian, ruffini

meisner, pacinian
merkel, ruffini
which receptors have small RF

fine tactile stimulation
merkel, meisner

pacinian do NOT

detected by superficial receptors

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
Muscle Spindles
long,thin, stretch rec in voluntary muscle
Parallel to muscle
synapse on excit MN in ventral horn
what is a safety feature for overextension of muscle?
muscle spindles synapse on excit MN in ventral horn
Golgi Tendon Organ
in series w/ muscle
in tendon, at end of extrafusal muscle fiber
sensitive to contraction
Henry Head's theory
dfft axons carry dfft aspects of touch

regrow at dfft times
Erlanger and Gasser

light/descriminatory touch

pain/temp carried by
first oscilloscopes

thicker axons-faster
A->C, I->IV
thinner axons-slower
Parallel Processing in CNS
fine touch and prop carried along same pathway
pain and temp carried along dfft pathway
length-wise down the extremities and horizontally around the trunk

2nd order neurons in..
fine touch, prop
ascnd ipsilaterally
FC-lat, FG-med
nuc cuneatus, and nuc gracillus
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
Medial Lemniscus

Lateral Lemniscus
deals w/ SS

Auditory information
Facial input to DC/ML
goes into principal nuc in the pons
from pons on, it travels w/ the ML
Pain and Temperature Pathway
Spinothalamic Tract STT

ascending in AL portion of lateral column
3rd order neuron projections go to many different places
part of the AL pathway that goes to the thalmus

Spinothalamic Tract

spinoreticular formation
-impt in arousal
spinomesencephalic- midbrain
-may block relay of pain
why is it difficult to interfere w/ pain pathways in the brain?
more diffuse
3rd order neurons from thalmus go to not only SS cortex, but the parietal lobe, ant cingulate gyrus, and insular cortex
damage to 1 side of the SC

damage to 1 side of the Medulla
pain-contralat, touch/prop-ipsi

pain and touch/prop contralat
Ventroposterior complex of thalmus

receives input from
relay nucleus for touch
VPM-VPL really just one

ML and STT
STT synapse on, CNV

ML synapses on

Criteria for defining areas of the Cortex
1. staining-cytoarchitecture
2. representation of periphery
3. unique nerual properties
4. unique pattern of connections
5. unique deficits w/ damage
Brodman's Areas in Parietal cortex for SS

from meial-->lateral
3a, 3b, 1, and 2

4cytoarchitectural areas

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
why do we have multiple areas in the SS cortex?
probably b/c of specialization
8-10dfft areas
cutaneous input goes to areas?

Propioceptive input goes to areas?
areas 3b and 1

areas 2 and 3a
cortical areas consist of columns
vertical collections of neurons that do the same thing

all correspond to same RF and probably same submodality

immediate changes suggest
delayed changes suggest
some parts of the brain maintain plasticity

unmasking of latent inputs, disinhibition
sprouting of connections