Touch Flashcards
somatosensation
blanket term for touch
the collective sensory signals from skin, muscle, tendons, joints, and other internal receptors
2 receptors included in somatosensation
proprioception
- our sense of where our body moves
kinesthesia
- our sense of how our body moves through space
difference between proprioception and kinesthesia
pro - sense of body
kin - more about body movement through space
do you know where your nose is?
this is considered __________
now touch your nose
this is considered ________
proprioception; kinesthesia
outer layer of the skin
epidermis
secondary layer of the skin
dermis
3 criteria of tactile receptors
type of stimulation to which they respond
size of their receptive fields
rate of adaptation (fast vs. slow)
fast vs slow rate of adaptation in touch
fast - quick touch
slow - ex. forget what the clothes on your body feel like since they have been in contact for a while
4 tactile mechanoreceptors
meissner corpuscles
merkel discs
pacinian corpuscles
ruffini endings
meissner corpuscles
low frequency vibrations and grasp stability
- fast adapting (FA I Fibers)
- small receptive fields
- close to the surface of skin
merkel discs (neurite complexes)
coarse texture and pattern
- slow adapting (SA I Fibers)
- small receptive fields
- close to the surface of the skin
pacinian corpuscles
high frequency vibrations and fine texture
- fast adapting (FA II Fibers)
- large receptive fields
- deep in the skin
ruffini endings
finger position
- slow adapting (SA II Fibers)
- large receptive fields
- deep in the skin
tactile receptors closer to the surface have … (2 things)
smaller receptive fields
higher acuity
tactile receptors not close to the surface have … (2 things)
large receptive fields
low acuity
what does myelination do to neurons
coating allows for signals to get across faster
a-alpha fiber/associated receptor
fastest with the most myelination; proprioceptor
a-beta fiber/associated receptor
2nd fastest, good amount of myelination; mechanoreceptor
a-delta fiber/associated receptor
3rd fastest, a little myelination; pain and temperature
c fiber/associated receptor
slowest fiber, no myelination; pain, temperature, itch
our muscles, tendons, and joints also have mechanoreceptors for ______ & ________
kinesthesia; proprioception
muscle spindle
inside our muscle wrapped around it to sense as muscle contracts to allow brain to regulate tension
people who have a loss of proprioception are unable to …
coordinate properly
thermoreceptors
separate warm and cold fibers that cover different ranges of temperatures (non-painful temps)
thermoreceptors have ion channels that respond to ________ changes as well as some that respond to ________
temperature; chemical
what are thermoreceptors generally measured in comparison to your actual …
skin temperature
cold fibers have a _____ range while warmth fibers have a _____ range
wider; sharper
nociception
pain, can detect damage, excessive heat/cold, chemical/noxious stimuli
2 types of nociception/pain fibers
a-delta
- medium sized, myelinated to quickly transmit pain and temperature information
- quick sharp pain (ex. when someone stabs you)
c-fiber
- narrow, unmyelinated that transmit a slower signal of pain and temperature information
- slower, throbbing sensation to make you aware that you are still hurt
TRPs
thermo and chemical receptors
type of receptor dictates type of sensation
nociception is at the ____ of the temperature scale
ends
if you lack a-delta fibers, you will …
know you are in pain but won’t be able to identify where exactly it hurts
if you lack c fibers, you can …
tell someone you have been hurt but won’t feel it long term
tactile information passes to the _____ ____ of the spinal cord before extending up to the brain
dorsal horn
spinothalamic pathway
spine –> thalamus
carries the slower signals, generally about skin temperature and longer pain
dorsal column-medial lemniscal (DCML) pathway
carries the faster signals from skin, muscles, etc.
supports proprioception
need to constantly be sensing your body position, so needs to be fast
which pathway is faster: spinothalamic or DCML
DCML
what type of organization does the somatosensory cortex maintain?
somatotopic
another word for somatotopic
homunculus: a body map in the brain
is the homunculus 1-to-1? subject to remapping?
no; yes
what does the homunculus do to areas that need to be particularly sensitive, similar to the fovea
cortical magnification
2 major networks for touch/pain in the brain
sensory-discriminative
- S1, etc. your basic sense of touch
emotional-aversive: anterior cingulate, PFC
- more tied to pain responses
- also cognitive/emotional aspects
- helps down regulate pain if need to power through
pain can be heavily modulated by ________ and ________ factors
emotional; cognitive
gate control theory
pain can incorporrate modulating signals from the brain, and can even be blocked by other local signals at the dorsal horn of the spine, such as from rubbing or scratching
ex. if you were bit by a mosquito, you can block the pain temporarily by itching it
analgesia
pain relief, come in many forms
hyperalgesia
heightened response to pain
consequence of an injury
can get ongoing pain from issues in the nervous system: neuropathic pain
neuropathic pain
pain system malfunction
touch is relatively ______
fast
touch is faster than ______ but slower than ______
vision; hearing
haptic perception
knowledge of the world derived from info about touch and proprioception
know how to position hand to grab something and know what most things feel like before touching it
different materials produce different ____
timbres
course materials, like sandpaper, are perceived by _____ fibers
SA I
finer materials, like fabric, are perceived by _____ fibers
FA II
the FA II afferents fire in _____ with the vibrations from the fabric as it moves across the skin
synchrony
haptic guide action
our experience of touch and proprioception allow us to pre-plan actions and maintain actions
haptic object knowledge
aka “What” system
can recognize objects by their 3D properties but can’t recognize a 2D outline of an object
what features pop out during haptic search? what don’t?
do: rough vs smooth, hard vs soft, cool vs warm
don’t: shifts in the same texture (horizontal to vertical lines)
why is braille raised dots and not letters? why do we trace them with our fingertips?
we are bad at identifying 2D objects; maximum acuity at the fingertips
tactile agnosia
inability to recognize objects via touch, usually in one hand (contralateral to the damage)
is visual object recognition fine with tactile agnosia?
yes
the “where” system of touch
you have some knowledge about here things are via touch, can often find your alarm in the morning without seeing it
evidence that, like vision, this system is tied to the parietal cortex
hemineglect extends to …
touch and proprioception
example of sensory integration
rubber-hand illusion
