Chapter 14 Touch and Pain

Week 12

epidermis vs dermis

outer layer of the skin vs inner layer of the skin (houses touch receptors)

mechanoreceptors

transduce physical movement on the skin into neural signals

→ send to the brain

SAI mechanoreceptors

slow adapting receptors using Merkel cells

• small receptive fields

• densely packed near the surface of the skin

SAII mechanoreceptors

slow adapting receptors using Ruffini endings

• large receptive fields

• widely distributed

• deeper in skin

FAI mechanoreceptors

fast adapting receptors with Meissner corpuscle endings

• smaller receptive fields

• densely packed near the surface of the skin

FAII mechanoreceptors

fast adapting receptors with Pacinian corpuscle endings

• large receptive fields

• widely distributed

• deeper in skin

meissner corpuscles

specialised transduction cells in FAI mechanoreceptors

Pacinian corpuscles

specialised transduction cells in FAII mechanoreceptors

Merkel cells

specialised transduction cells in SAI mechanoreceptors

Ruffini endings

specialised transduction cells in SAII mechanoreceptors

proprioception

perception of the movements and positions of our limbs

muscle spindles

receptors in the muscles that sense info about muscle length

• if you can figure out muscle length, you therefore know muscle action (stretched out, resting)

joint receptors

receptors found in each join that sense info about the angle of the joint

golgi tendon organs

receptors in the tendons that measure the force of a muscle contraction

afferent fibres

neural fibres that carry sensory information to the central nervous system

thermoreception

ability to sense changes in temperature on the skin

thermoreceptors

sensory receptors that signal info about the temp as measured on the skin

cold fibres

thermoreceptors that fire in response to colder (30c and below) temps on the skin

warm fibres

thermoreceptors fire to warmer temps (36c and above) on the skin

pain

perception and experience of actual or threatened tissue damage

nociceptive pain

pain from tissue damage that causes nociceptors in the skin to fire

nociceptors

sensory receptors that when activated cause us to feel pain

• found in dermis and epidermis

A delta fibres

myelinated nociceptors that conduct signals rapidly

• respond to heat and pressure

c fibres

NON-myelinated nociceptors that are slower

• respond to pressure, extreme cold or heat, and toxic chemicals

dorsal root ganglion

node on the spine where nerve cells carry signals from sensory organs toward the somatosensory areas of the brain

dorsal root

end of the spinal nerve where sensory information enters the spinal cord

ventral root

the end of the spinal cord where motor info leaves the spinal cord

dorsal

toward the back of the body

top of the head

remember: shark’s dorsal fin is right on the top of their back

ventral

toward the front of the body

bottom of head

remember: in fishies, ventral fin is on the belly/in front of them

dorsal column medial lemniscal pathway

mechanoreceptors (touch) and proprioceptors (muscle position) travel up the spinal column on the ipsilateral side and cross to the contralateral side in the medulla

ipsilateral

same side of the nervous system as it entered

ex. feel on right, travel up right side

contralateral

sensory info is on opposite side of the nervous system that it entered

ex. feel on right side, info travels to left side

somatosensory cortex

in the parietal lobe of the cerebral cortex (outermost layer of the brain)

• all about processing info coming from skin senses

ventral posterior nucleus of the thalamus

area in thalamus that gets input from dorsal column medial lemniscal pathway AAAAANDD spinothalamic pathway

spinothalamic pathway

path for the nociceptors (pain) and thermoreceptors (temp)

• travels up contralateral side of the spinal column

• doesn’t synapse in brain until ventral posterior nucleus of the thalamus

somatotopic map

skin of body maps onto the surface of the primary somatosensory cortex in a systematic way

homunculus

horrifying drawing of a human but the proportions of the body parts match the relative sides of each body part with the somatotopic map

gate control theory

model that allows for top down control of the pain signal coming up the spinal cord

substantia gelatinosa

region of the dorsal horn where neurons meet

dorsal horn

area of spinal cord that receives input from nociceptors and feedback from the brain

anterior cingulate cortex

region in prefrontal lobe

• emotional experience of pain

endogenous opioids

chemicals produced by the body that reduce pain

analgesia

processes that act to reduce pain perception

pruriceptors

receptors that respond to mild skin irritants by making the dreaded ITCH

haptic perception

how we use touch to actively identify objects

(hmm this is round and fuzzy, must be a kiwi)

• must have to read braille

exploratory procedures

hand movements made in order to identify an object

tactile agnosia

inability to identify objects by touch

(man I know this is smooth and long but I have no idea what it could be!!)

vestibular system

sensory system in charge of perception of balance and acceleration

• in the semicircular canals and otolith organs (beside the inner ear)

semicircular canals

3 tubes in the inner ear that signal head rotation

otolith organs

detect acceleration of the head and can tell you when the head is tilted at an angle

endolymph

fluid that fills the semicircular canals

ampulla

at the base of each semicircular canal

• holds the crista

crista

in the ampulla of each semicircular canal

contains receptors

macula

in the otolith organs

contains the receptors

vestibular complex

area of brain stem

receives input from vestibular nerve and sends info to the forebrain

parietal insular vestibular cortex

in the parietal lobe (shocker)

gets input from vestibular nerve

• all about perception of balance and orientation

electroception

ability to detect electric fields

• fishies

passive electroreception

can only detect electric fields

active electroreception

generate electric fields (woah!) and then detect changes to those electric fields causes by external events

ex. someone is messing with my electricity rn

phantom limb syndrome

illusory sensory reception in a missing appendage

ex. my hand is gone but I feel it still..

phantom limb pain

pain in a limb that has been amputated

ex. god my ankle hurts but I actually have nothing below the knee

visual capture

visual input can dominate the input from other senses when they conflict

ex. ventriloquism and those freaky puppets