Lectures 5 & 6 (test 1) Flashcards
tactile
- displacement of skin
- to identify and manipulate objects
pain
- occurs when there is damage to body tissue
- warning system for harm
itchiness
- haptic sensation
- protects skin from irritants
thermal
- temp changes
- to seek/create a thermally same environment
pleasant
- the response of slow stroking
kinesthesia
- internal sensation
- tell us the location / position of limbs
- to act in our world
what is the sensory organ for touch?
the skin
epidermis
- outer most layer
- protective shield
- sub layers are consistently replenished
dermis
- the bulk of skin tissue
- contains most touch receptors
the touch receptors are found on … (4)
- skin
- mouth
- muscles
- tendons / joints
size of receptor field
the extent of the body area that will elicit a response from that receptor
Pacinian capsule
- mechanoreceptor
- fast adapting
- changes in skin shape
- high-frequency vibration
- fine texture perception
- located in dermis
Ruffini capsule
- mechanoreceptor
- Slow adapting
- skin stretch causing an AP in afferent nerve fiber
- transmit constant pressure
- dermis and deeper tissue
sit parallel to the skin surface
Meisner capsule
- mechanoreceptor
- Fast adapting
- transmit low-frequency vibration
- closest to the skin surface
Merkel cell
- mechanoreceptor
- slow adapting
- Merkel cell neurite complex lie in fingerprint ridges
- superficial
- sustained pressure
as axon diameter decreases, conduction speed _____
decreases
SA I
- texture perception
- pattern / form perception
- sustained pressure
- very low frequency
SA II
- finger position
- sustained pressure
FA I
- low frequency
- stable grasp
- skin slip
FA II
- high frequency
- fine texture perception
How to measure receptive field size include …
- extracellular recording
- activate nerve
- ask what they feel
- is not too painful
central axons of the sensory neurons that transmit temp and pain signals terminate in ______
the dorsal horn
Thermorecptors are in the
epidermal and dermal layers
temp info travels via what 2 fibers
- C fibers
- A delta fibers
(little to no myelination, therefore, travels slowly)
the ratio for cold : warm fibers
30:1
thermoreceptors are activated when there is a _____________
deviation from the physiological zero
at extreme temps, we also activate _______
pain receptors
thermoreceptors sense heat and cold through ____________
TRP channels
transient receptor potential channels
thermoTRPs
what is the only sense we actively avoid?
pain
nociceptors
receptors that detect painful or potentially harmful stimuli, have free nerve endings
2 types of nociceptors
myelinated A-delta fibers: respond to strong heat
unmyelinated c type: respond to intense pressure, intense heat or cold
2 responses when pain is detected
1) stimuli directly affect ion channel in the afferent nerve ending
2) nerve damage releases ATP which activated ion channels
noci-transducers
non-selective cation channels
thermoTRP channels
- different from thermoTRPs
- TRPV1 responds to heat and capsaicin
acid-sensing ion channels
- innervate skeletal and cardiac muscles
- thought to mediate pain through pH change during low O2
ligand-gated ATP receptors
- open in response to extracellular ATP
- allows cations in
a pleasant touch is mediated by ___
unmyelinated C fiber
NOT SAME AS ITCH PAIN C FIBERS
in infant study which stroke rate reduced heart rate
medium (3m/s)
kinesthetic receptors
- sense where and what movements our limbs are making
- are stretch gated channels
muscle spindles
convey the rate at which muscle fibers are changing in length
Golgi tendon organs
provides signals about the tension in the muscles attached to the tendons
joint receptors
activated when joint bent at an extreme angle
tactile mechanoreceptors use what capsule
Pacinian capsule
cell bodies of somatosensory neurons lie in the _______-
dorsal root ganglion
axons of various somatosensory receptors synapse onto ___ out of ___ pairs of spinal nerve
1
31
APs travel from the peripheral end along the axon to central end where they enter the spinal cord at the ______ which is organized into ____
dorsal horn
laminae (layers)
inputs in the spinal cord are organized _______
somatotopically
dermatomes
map of where spinal nerve root maps onto the body
shingles
virsus attacks a spinal nerve which causes it to show up on that nerves corresponding dermatome area of the skin (often in stripes)
primary somatosensory cortex (S1)
- receives info from thalamus via internal capsule
- located in post gyrum (parietal lobe)
- somatotopic organization (into vertical columns)
secondary somatosensory cortex (S2)
receives convergent projections from S1
motor areas of the cortex
- infront of the central sulcus
- increases communication b/w somatosensory and motor neurons
_______ have highest density of mechanorecptors
fingertips
____ areas tend to have smaller receptive fields
S2
cerebral cortex organized into ___ layers
6
info inserted to the cerebral cortex at layer ___
4
proof of neural plasticity
- monkeys increased cortex devotion to digits 2 and three after being trained to use them more
- adults blindfolded for 5 days and noticed an increased area of brain responded to touch than before as par of vision area taken over (used braille) (CROSS MODALITY PLASTICITY)
how does neural plasticity apply to smartphone users
increased thumb sensort representation in the brain
