Lecture 9- Touch Flashcards
interoception
awareness of your own body
exteroception
awareness of your immediate surroundings
cutaneous
related to the skin
proprioception
related to body position
kinesthesis
related to body movements
nocioception
related to pain and discomfort
thermoreceptors
respond to heat or cold
- active between temps below 35C
-cool: responding when temp is below 5C “numb”
-warm: responding when temp rises to 35C, most active at 49C, then pain receptors start responding
mechanoreceptors
respond to mechanical stimuli (stroking, stretching, or vibration of the skin)
chemoreceptors
respond to chemical substances on the skin
free nerve endings
send info related to skin temp… also send info related to pain
free nerve endings are implicated as receptor cells for which 3 systems:
- cold perception
-heat perception
-pain perception
polymodal
receptors that can code for a bunch of different things
nociceptors
type of receptor that responds to stimuli that can damage skin tissue
3 layers of skin
- epidermis
-dermis
-hypodermis
epidermis
-provides a barrier for infection
-helps with thermoregulation
- has free nerve endings (noci/thermo) that send signals to the CNS
dermis
has mechanoreceptors and thermoreceptors
Merkel’s disks
mechanoreceptors that provide info about the shapes of the things you touch, and about how much pressure is being applied to the surface of your skin.
- found in dense clusters in fingertips and mammary glands
Meissner’s corpuscles
mechanoreceptors; seem to react to light touch on the fingertips and the lips
- respond to the onset of touch, adapt quickly
hair follicle receptors
mechanoreceptors that transmit info whenever the hair is moved
hypodermis
where fat is stored, also sweat and mammary glands - - contains Pacinian and Ruffini corpuscles
Pacinian corpuscles
about a mm long and are visible to the naked eye (with opening)
-mechanoreceptors; sensitive to vibrations, adapt quickly, not sensitive to constant pressure
Ruffini corpuscles
mechanoreceptors that adapt slowly to pressure that results in stretching of the skin, so they record the sustained presence of pressure on the skin
touch receptors can be categorized by 3 criteria
- type of stimulation to which receptor responds
- size of the receptive field
- rate of adaptation (fast vs. slow)
SA I (MERKEL)
respond best to steady and downward pressure
-texture and pattern perception (braille)
SA II (Ruffini)
respond best to lateral skin stretch
-good for knowing the position of fingers when grasping
FA I (Meissner)
respond best to low-frequency vibes,
-like slipping objects
FA II (Pacinian)
respond best to high-frequency vibes,
-when an object contacts another
Somatic reflex
an involuntary contraction of the skeletal muscles in response to stimuli
2 major pathways from the spinal cord to the brain
- spinothalamic pathway
- dorsal column- medial lemniscal (DCML) pathway
spinothalamic pathway
carries most of the info about skin temperature and pain (slower of the two)
dorsal column- medial lemniscal (DCML) pathway
carries signals from skin, muscles, tendons, joints
somatosensory cortex
this is the end of the path
“soma”= BODY
why doesn’t the brain itself get any space in the somatosensory cortex?
the brain cannot feel pain
insula
associated with processing affect
C-tactile fibres
project to the insular cortex and code specifically for gentle caresses
social touch hypothesis
- proposes that social touch is a distinct domain of touch
- C-tactile afferents form a special pathway that distinguishes social touch from other types of touch by selectively firing in response to touch of social-affective relevance
- socially relevent touch stands out from the rest as having positive emotional value and is processed further in affect-related brain areas such as the insula
