PSY280 Unit 5

types of touch senses

tactile, temperature, pain, body sensations

tactile senses are caused by

the mechanical displacement of skin

proprioception

perception of the body mediated by kinesthetic and vestibular receptors

vestibular system tells us the location of our body within the

gravity field

somatosenation

all sensory signals from the body which includes all the components of touch

sensory organ for touch

skin

touch receptors are embedded in the ___ and ____

epidermis and dermis

each touch receptor has these 3 attributes

type of stimulation that the receptor responds to, size of the receptive field, and rate of adaptation (how quickly it fatigues)

4 tactile receptors in the skin

Meissner corpuscles, Merkel cell neurite complexes, Pacinian corpuscles, and Ruffini nerve endings

Meissner receptors are

fast adapting with small receptive fields (FA 1)

Pacinian receptors are

fast adapting with large receptive fields (FA 2)

Merkel receptors are

slow adapting with small receptive fields (SA 1)

Ruffini receptors are

slow adapting with large receptive fields (SA 2)

where is the Merkel cell neurite complex located

at boundary between epidermis and dermis

Merkel cell neurite complexes respond best to 

steady downward pressure

Merkel cell neurite complexes important for

texture and pattern perception, fine spatial details

Merkel cell neurite complexes sensitive to

very low frequency of vibrations, < 3Hz

Meissner corpuscles located at

boundary between epidermis and dermis

Meissner corpuscles sensitive to

low frequency vibrations between 3 and 40 Hz

Meissner corpuscles important for

detecting slip of objects across skin to properly grip objects

Ruffini endings are located

deeply in the dermis

Ruffini endings respond best to

sustained downward pressure and lateral skin stretch

Ruffini endings are important for

finger position and grasp

Ruffini endings have a ___ sensitivity to vibrations

low

Pacinian Corpuscles located in

subcutaneous tissue

Pacinian Corpuscles respond best to 

high frequency vibrations between 40-700 Hz

Pacinian corpuscles are active when

object makes first contact with skin

kinesthetic receptors 

play a role in our sense of where the limbs are and what kinds of movements they make

spindles

convey the rate at which muscle fibers change in length

type 1a sensory fibers

wrap around muscles to detect and signal change in muscle stretch

type ___ sensory fibers adapt while type ____ sensory fibers do not

1a, 2

type 2 sensory fibers

interact with the neuromuscular junctions to signal amount of muscle stretch/position of fibers

thermoreceptors

sensory receptors that signal information about changes in skin temperature

2 types of thermoreceptors

warmth fibers and cold fibers

hot is a sensation of ____, not ___

pain, temperature

nociceptors

sensory receptors that transmit information about painful stimulation that potentially causes damage to the skin

2 groups of nociceptors

A-delta fibers and C fibers

A-delta fibers respond to

initial and quick sharp bursts of pain, strong pressure (crushing) and heat

C fibers respond to 

throbbing sensation that evolves after initial surge of pain with sustained stimulation

___ fibers have fast transmission to the brain while __ fibers have slower response 

A-delta, C

pain responses can be moderated by

anticipation, religious belief, prior experience, watching others respond, excitement

analgesia

decreasing pain sensation during conscious experience

natural pain relieving effects are caused by

endogenous opiates (block uptake of neurotransmitters that are sending pain sensations to the brain)

gate control theory

a system that transmits pain that incorporates modulating signals from the brain (top down)

gate control theory includes a feedback circuit that is located in the

substantia gelatinosa of the dorsal horn of the spinal cord

pain sensitization

damage to body tissue leaves site being more sensitive to pain

hyperalgesia

an increase in pain sensation

neuropathic pain is pain as a result of

damage to or dysfunction of nervous system

part of the brain corresponding to more cognitive aspects of painful experiences and signalling something is wrong

anterior cingulate cortex

emotional response to prolonged suffering is associated with the

prefrontal cortex

social touch is mediated by

unmyelinated peripheral C fibers aka C tactile afferents

social touch is processed in the

orbitofrontal cortex rather than the somatosensory cortex

C tactile afferents respond best to

slowly moving, lightly applied forces (ex. petting)

touch sensations travel as far as ____ to get from skin of feet to the brain

2 meters

the first synapse for touch sensation occurs at the

spinal cord

first connection occurs at the _____ of the spinal cord

dorsal horn

2 major pathways for touch information once in the spinal cord

spinothalamic, dorsal-column-medial-lemniscal

which touch pathway is slower

spinothalamic

what is the spinothalamic pathway for

pain, temperature, crude touch

what is the dorsal-column-medial-lemniscal pathway for

tactile and proprioceptive information

which pathway has fewer synapses

dorsal-column-medial-lemniscal

spinothalamic pathway

dorsal horn → lateral spinothalamic tract → ventral posterior nucleus of thalamus → cerebral cortex

spinothalamic pathway also provides mechanisms for

pain inhibition

dorsal-column-medial-lemniscal pathway

dorsal horn → Gracile nucleus → medial lemniscus →ventral posterior nucleus of thalamus → somatosensory cortex 

primary somatosensory cortex is located on the

postcentral sulcus

how are touch sensations represented

somatotopically, meaning adjacent areas on skin connect to adjacent areas on the brain

phantom limb

perceived sensation from a physically amputated limb of the body

phantom limbs can be felt in areas that are

adjacent to the areas of the amputated limb on the homunculus

2 point threshold

minimum distance at which 2 simultaneous touches are perceptible as separate

typical resolution for temporal details of 2 different touches is

5 ms

auditory temporal resolution is

0.01 ms

haptic perception

knowledge of the world derived from sensory receptors using active exploration/interaction with the environment

exploratory procedure

typical hand movement pattern used to touch objects in order to perceive their properties

lateral motion used to determine

texture

pressure used to determine

hardness

static contact used to determine

temperature

unsupported holding used to determine

weight

enclosure used to determine

global shape/volume

contour following used to determine

global shape/exact shape

fingerprint ridges selectively amplify frequencies from ___ to _____ by a factor of

200-300, 100

ridged fingerprints may help maintain

grip in the presence of moisture

Jack Loomis experiment showed that

accuracy of touch when feeling a raised stimulus is similar to blurry vision

what happens to tactile acuity for sighted people

it gets worse with age

tactile agnosia

inability to identify objects by touch

tactile agnosia is caused by

lesion to parietal lobe

where system of touch

knowing where objects are in the environment when only using touch perception

frame of reference in the where system of touch

coordinate system used to define locations in space

egocenter in the where system of touch

center of a reference frame used to represent locations relative to the body

is there a consistent location of the egocenter?

no

body image

impression of our body in space

tadoma method

method of touch for speech perception for deaf and blind people

physical stimulus for olfaction

odorant

odorant

any specific aromatic chemical that is volatile (able to float through air), small, and hydrophobic

primary purpose of nose

filter, warm, and humidify air we breathe

3 parts of the nose

small ridges (turbinates), olfactory clef, and olfactory epithelium

olfactory cleft

narrow space at the back of the noise where air flows in, where the main olfactory epithelium is located

olfactory epithelium

secretory mucosa whose primary function is to detect odorants

3 types of cells in the olfactory epithelium

supporting, basal, olfactory sensory neurons

supporting cells

provide metabolic and physical support for olfactory sensory neurons

basal cells

precursor cells to olfactory sensory neurons