PSY 210 cutaneous senses Flashcards
what are the skin layers
epidermis and dermis
what are the 4 mechanoreceptors + type
merkel, meissner, ruffini, pacinian
receptors, corpuscle, cylinder, corpuscle
what are mechanoreceptors used for
responding to frequency on skin
MERKEL Hz + respond to
0.3 - 3 Hz
pressure
MEISSNER Hz + respond to
3 - 40 Hz
flutter / FEATHER
RUFFINI Hz + respond to
15 - 400 Hz
stretching skin
PACINIAN Hz + respond to
10 - 500 HZ
vibration
slow & fast adaptation organization of receptors
SA1: Merkel
SA2: Ruffini
RA1: Meissner
RA2: Pacinian
what do slow adapting (SA) receptors do
action potential keeps firing
- adapts slowly to a stimulus
what do rapid-adapting (RA) receptors do
fires at first, stops, bursts at end
- adapts quickly to a stimulus
what is receptive field
area of skin that’s being stimulated
SMALL receptive field are __
& perception of ___
- SA1: Merkel AND RA1: Meissner
- pressure, flutter
LARGE receptive field are __
& perception of ___
- SA2: Ruffini AND RA2: Pacinian
- stretch, vibration
passive touch
- NOT MANIPULATING
- touching chair, leaning on something, clothes, hands on something
active touch use what mechanoreceptors __ in grabbing a cup
- SA1 (Merkel) = small details
- SA2 (Ruffini) = grasp
- RA1 (Messner) = texture
Thermoreceptors differentiated, temps
WARM FIBERS:
- increase firing rate w/ higher temp, 44C
COLD FIBERS:
- increase firing rate w/ temp, 30C
what do thermoreceptors do
- HAVE OVERLAP
- neurons tuned to temperature to fire
- continuously firing
- no response to pressure
what do nociceptors do?
detect pain or stimuli that can potentially cause damage to the skin
nociceptors can react with
thermoreceptors, not really mechano
overlap in thermoreceptors helps us sense __
wide range of temperature
Nociceptors are __, ___, and ___
- mechanosensitive: reactive to mechanical reaction to skin
- mechanothermal: respond to temperature
- polydomal: react to many forms of stimuli
NEURONAL PATHWAY(s)
- PERIPHERAL NERVES (bundle of skin fibers)
- MEDIAL LEMNISCAL (proprioception: position of limbs and touch)
- straight to SOMATOSENSORY CORTEX (S1)
- SECONDARY SOMATOSENSORY CORTEX (S2)
- PERIPHERAL NERVES (bundle of skin fibers)
- SPINOTHALAMIC (temperature and pain)
- VENTRAL POSTERIOR NUCLEUS (thalamus)
- SOMATOSENSORY CORTEX (S1)
- SECONDARY SOMATOSENSORY CORTEX (S2)
detailed organization of the somatosensory cortex
1- HOMUNCULUS
• little man
• 10 body maps (form, texture, pain)
2- CORTICAL MAGNIFICATION
• due to receptive field size
• bigger body part = more sensitive touch
3- COLUMNAR ORGANIZATION
• tactile feature detectors (thalamus and cortex)
• center-surround organization; similar to cells in visual system
• movement, orientation
how to test tactile acuity
2-point discrimination
What is 2-point discrimination?
- point at which you feel 2 stimuli
- varies across body
- due to larger and small receptive field
FINGERTIP versus CALF 2-point discrimination
FINGER:
- smaller/lower 2-point threshold
- small receptive field
- more receptors: CLOSER
- larger representation in cortex
CALF:
- larger/higher 2-point threshold
- large receptive field
- less receptors: FURTHER APART
- smaller representation in cortex
plasticity of somatosensory cortex
- changes in representations in musicians
- referred sensation (phantom limbs)
- – changed representation in brain
- – can lose plasticity (if don’t practice/use often)
plasticity study
monkey: 1- suture 2 inner digits together (couldn't distinguish the 2 in cortex) 2- amputate a digit (map for adjacent digits expanded from missing digit)
