Viscerosomatic Sensation 1

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Principal sensations

Touch (Mechanosensation and Thermosensation), Prorioception, Nociception

Activation of peripheral receptor results in a generator potential

Graded response, Sums to reach threshold and fire an action potential, Conversion of peripheral stimuli (mechanical or heat) to electrical current

Nerve fiber that's not myleinated

C (axons in Group IV)

Cutaneous mechanical receptors can detect what types of stimuli

Location, intensity and duration

Mechanoreceptors (encapsulated) types

Slowly adapting (SA) - I, Slowly adapting (SA) - II, Fast adapting (FA) - I, Fast adapting (FA) - II

Thermoreceptors

Respond to warming and cooling

Thermoreceptors are spontaneously active at

normal tempuratures

Thermoreceptors have _____ receptive fields

Spot-like (1 mm diameter)

Proprioceptors Sense

joint position in space

Proprioceptors Important for

normal coordinated movement

Muscle Spindles Type Ia responds to

dynamic, rate of change

Muscle Spindles Type II responds to

static, muscle length

Muscle Spindles Excite

alpha motor neuron

Muscle Spindles Increase

muscle tension

Golgi Tendon Organs are type

Ib sense stretch on tendon (muscle contraction)

Golgi Tendon organs Inhibit

alpha motor neuron

Golgi tendon organs are involved in Compliance which is

"give of muscle"

Nociceptors respond when there is

Damage/threatened damage to skin

Principal nociceptors

Aδ- mechanonociceptors, C polymodal nociceptors, Silent (sleeping) nociceptors

Defining characteristic of nociceptors

they sensitize, this is unique to nociceptors and means that the rate of firing increases after injury

Joint Nociceptors are found in

Joint capsule and ligaments

Joint Nociceptors include

Group III (Aδ) and group IV (C) axons

Muscle Nociceptors are found in

Connective tissue surrounding joint

Muscle nociceptors are involved in

Aching and cramping

Muscle nociceptors include

Group III (Aδ) and group IV (C) axons

Silent Nociceptors

Do not respond to noxious mechanical/thermal stimuli before injury, After tissue injury, begin to respond to mechanical/thermal stimuli

Where are silent nociceptors Found?

in cutaneous, joint, and visceral tissues

Visceral Receptors Sensations

discomfort and pain

Visceral receptor types

Chemoreceptors, Mechanoreceptors, Thermoreceptors

Microneurography Used to

record and stimulate nerves in human subjects

Microneurography helps us Understand

sensations related to specific receptors

FA I (Meissner's corpuscle) sense

Tapping at 1 Hz, flutter at 10 Hz and vibration at 50 Hz

FA II (Pacinian corpuscle) sense

Tickle/vibration over 20-50 Hz

SA I (Merkel's disk) sense

Sustained pressure over 5 - 10 Hz

SA II (Ruffini endings) sense

No sensation

Aδ mechanical nociceptors sense

Sharp pain

C polymodal receptors sense

Dull, burning pain or itch

Muscle nociceptor (Group IV) sense

Cramping pain

Touch-pressure receptor, spinal termination, major ascending pathway

SA I receptor, hair follicle, Lamina III-IV, Dorsal columns

Flutter-vibration receptor, spinal termination, major ascending pathway

FA I receptor, FA II, hair follicle, Lamina III-IV, Dorsal columns

Proprioception receptor, spinal termination, major ascending pathway

Muscle spindle, Golgi Tendon, Type II join, Lamina IV-VII, X, Dorsal columns

Cold receptor, spinal termination, major ascending pathway

Aδ and C receptors, Lamina I, II, V, STT*

Warm receptor, spinal termination, major ascending pathway

C, Lamina I, II, V, STT

Nociception

Aδ/ Group III, and C/ Group IV receptors, Lamina I, II, V, X, STT (and others)**

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