Touch

Touch

pressure against the surface of the skin sufficient to change or move its surface

Slow adapting receptors

fires constantly while the stimulus is active. impulses are continuous and slowly ramps up

rapid adapting receptors

only fires when a stimulus starts and ends. Localizes things in time and space which allows us to build a spatial world model

Mechano Receptors

• Merkel receptors

• Meissner’s corpuscles

• Pacinian corpuscles

• Ruffini ending

Merkel Receptors

near the surface of the skin, are slow adapting, are all along the skin, and are responsible for fine details

Meissner’s Corpuscles

just under the dermis, extensively distributed, and rapid adapting to respond to change

Pacinian Corpuscles

deep within glabrous (naturally hairless) skin, within joints to sense movement pressure, and are rapid adapting

Ruffini endings

are sensitive to stretching and pays attention to motion and positioning of the body, monitors slippage across skin, detects temperature changes, and is slow adapting

2 point threshold

the bare minimum separation between 2 point that can still be distinctly identified as such and is the metric for sensitivity across the body

Somatosensory cortex

the part of the brain that processes sensory information, it is contralateral (goes from left to right), and plans motor responses

Posterior parietal cortex

important for spatial perception and is involved in touch

Homonculus problem

demonstrates the topographic representation of the somatosensory cortex which uses more space for more sensitive parts of the body

Specific receptor theory

suggests we perceive hot and cold as distinct stimulus. Hot stimulants are detected by the Ruffini endings and cold stimulants are detected by the Krause end bulbs

Non-specific receptor theory

suggests temperature detection is a pattern of nerve activation (this is likely in most cases)

Pain

anything that causes tissue damage. Has physical, cognitive, and emotional aspects

Nociception

body’s knowledge of an injury

free nerve endings

pain receptors that also activate to regular touch suggesting we have a threshold for pain.

detects pressure, temperature, chemical damage, and electric shock

S fibers

• A-delta fibers

• C-fibers

A delta fibers

rapid adaption, myelinated axons that detect mechanical stimuli such as a slap

C fibers

slow adapting, unmyelinated axons that process all types of pain such as “ghost” or throbbing types of pain

Pain Gating Theory

the transmission of pains partially controlled and moderated by other cutaneous stimulation. Proposes that there is a mechanism that lets pain signals through or blocks/cancels them out

Endorphins

opiates block emotional aspects of pain and are very addictive

a runners high/adrenalin keeps you going by mitigating the pain

Pain/stress induced analgesia

the fight or flight adrenalin rush that blocks pain and the central nervous system level. it is effective in the moment but doesn’t last forever

cognitive aspects of pain

Expectations - if people expect pain they are prepared for it

Shifting attention - reduces pain with pleasant distractions

Individual differences - resistant to frequently experienced types of pain (sports)

Congenital Insensitivity to Pain and Anhidrosis

a “color blindness” for pain. problematic because you could be injured and in need of medical help and not know until it’s too late

Referred Pain

when we feel pain in locations where damage hasn’t happened or isn’t happening such as with heart attack pain. your organs don’t have pain localization so pain appears elsewhere

Phantom limbs

the sensation an amputated limb is still present. lasts longer when the limb was lost traumatically/unexpectedly

Phantom limb pain

pain in amputated limbs, can be treated with compelling illusions like with the mirror box

Kinesthesis/proprioception

the sense of where of body parts are located and how they’re moving

Pacinian corpuscles

in the joints of the body and are major receptors for kinesthesis. most sensitive in the hips, shoulders, wrists, and knuckles

Vestibular sense

the ability to detect changes in motion as well as balance gained from the semicircular canals