1. Touch

Mechanosensation

Thermosensation

2. Proprioception

3. Nociception/Pain

Classification of Nerve Fibers:

Axons in Skin

A beta

A delta

C

Classification of Nerve Fibers

Axons in Muscle/Joint

Group I-myelenated-fastest conducting

Group II: A beta-myelenated-fast conducting

Group III: A delta-myelenated- slower

Group IV: C- not myelenated-slowest

Group I: afferent-deep tendon reflexes

Group II: touch fibers

Group III & IV: nociceptors

RF=area in skin/muscle/etc. that can be activated

Multiple primary afferent neurons terminate on a single 2nd order neuron (RF made up of all these primary order neurons)

Central neurons have inhibitory/excitatory regions-can narrow down stimulus to tell where it's coming from

Cutaneous Mechanical Receptors

Thermoreceptors

Proprioceptors

Nociceptors

Visceral Receptors

respond to mechanical stimuli

tell location, intensity, and duraction of stimulus

Mechanoreceptors

1. Slowly adapting (SA) I

2. Slowly adapting (SA) II

3. Fast adapting (FA) I

4. Fast adapting (FA) II

Slow adapting: respond continuously to stimulus (continues firing)

Better at telling INTENSITY & LOCATION b/c respond in a graded manner

Fast adapting: turn on when apply stimulus, turn off when take it away

Better at telling DURATION of stimulus

slwoing conducting but NOT nociceptors

respond to warming/cooling

spontaneously fire at normal temperatures (fire differently depending the temp to tell what the temp is)

Spot-like receptive fields

A-delta & C fiber axon

Sense joint position in space & joint movement

Muscle Spindles & Golgi Tendon Organs

Coordinates movement

TYPE Ia

dynamic, rate of change

tells what's changing

TYPE II

static, muscle length

responds in a static manner & to muscle length

Excit alpha motor neuron-Increase muscle tension

Protect against movements at extreme ROM & coordinates movement

TYPE Ib

respond to stretch on tendon (muscle contraction)

if really shortened muscle-won't respond & fire

inhibit alpha motor neuron-

Compliance "give of muscle"

respond to damage/threats to the skin

They sensitize

Principal nociceptors

A delta mechanonociceptors

C polymodal nociceptors

Joint nociceptors

Muscle nociceptors

Silent nociceptors

respond to mechanical, chemical, and temperature stimulus

innervate joint capsule & ligaments

extreme ROM would activate them

Group III (A delta) and Group IV (C) axons

innervate connective tissue & surrounding joint

activated by really strong mechanical pressure, ischemic muscle

Activation causes cramping/aching (in skin activation=sharp pain)

Group III (A delta) and Group IV (C) axons

17% of cutaneous receptors

do not resond to noxious mechanical/thermal stimuli before injury

After tissue injury-begin to respoind to m/t stimuli

Found in cutaneous, joint & visceral tissues

A delta & C fibers

Sensations-discomfort & pain

I.e. if cut viscera down the middle-they won't respond, but will to distention

Chemoreceptors

Mechanoreceptors

Thermoreceptors

stick a recording electorde into a nerve & then apply a stimuluis to characterize individual nerve fibers & find out where their sensations are

an unpleasant sensory & emotional experience associated with actual or potential tissue damage

Is subjective

Have to have cortex to process pain

activation of a nociceptor

introduced to distinguish b/t the detection of a noxious stimulus & the psychological & other responses related with pain

NO PAIN WITHOUT THE PAIN

activation of nociceptors does not necessarily result in pain-don't get pain until get to the cortex

nociceptive (withdrawal) reflex

autonomic reflex

pain (not without a brain)

noxious stimuli activate specific sesnory receptors-nociceptors-and evoke nociceptirve (withdrawal) and autonomic reflexes and pain (in the intact organism)

1. Sensory-discriminative dimension

Quality, Location, Duraction, Intensitdy (2/10)

2. Affect Dimension

amount of unpleasantness can vary

how much does the pain bother you

Spinal Cord Organization

Laminae

Dorsal horn-laminae I-VI

Intermediate zone-laminae VII, X

Ventral horn-laminae VIII, IX

1. Nociceptive specific

only input from nociceptors

2. Wide dynamic range

input from nociceptors & A-beta fibers=large afferent fibers

increased sensitivity or responsiveness after tissue injury

Nociceptors even after injury, only respond to noxious stimuli

Non-nociceptor primary afferent fibers NEVER change their response properties, even after injury

Increased responsivenss to innocuous stimuli occurs

Response magnitude (# of action potentials fired) to noxious stimuli increases-->

Response threshold to noxious stimuli may decrease-->

Spontaneous activity may increase-->

Receptive field size incresaes

(small increase for nociceptors-PNS

large increase for central neurons-CNS)

Response magnitude (# of action potentials fired) to noxious stimuli increases-->

Response threshold to noxious stimuli may decrease-->

Spontaneous activity may increase-->

Receptive field size increases

(Large increases for nociceptors-PNS)

Response magnitude to innocuous stimuli incresaes-central neurons only