Chapter 3 - Sensory Receptors/Pain Theories Flashcards
Touch
1) superficial pressure = crude touch or light touch
2) vibration
3) discriminative touch
discriminative touch
what is being touched or manipulation
- have to have an intact parietal lobe to distinguish
1) two-point
2) stereognosis
3) graphesthesia
two-point touch
ability to discriminate between two different points
- 2mm for finger tips
- 4-7cm on back
stereognosis
ability to identify an object by touch
graphesthesia
ability to identify things written on skin
Proprioception
muscle and joint receptors
- some from skin receptors
1) stretch of muscles
2) tension of tendons
3) position of joints
4) sense of passive movement
How information is conveyed
1) receptors encode the stimulus into receptor potentials(pseudounipolar neuron)
2) if exceeds threshold will have an action potential
3) conducted along the peripheral nerve to a cell body in the dorsal root ganglion and then into the spinal cord(dorsal horn of spinal cord)
4) then the information ascends to the cortex
- other part goes to brain to process heat and pain
- can go back through ventral horn and produce a motor effect(touching a hot stove)
Mechanoreceptors
mechanical deformation(indention in skin)
- fires initially but does not continue to fire, if object is not moving
1) touch
2) pressure
3) stretch
4) vibration
Chemoreceptors
responds to chemical released by cells
- pain
thermoreceptors
respond to warmth and cool
nociceptors
cause pain
- extreme high and low temps
Slowly adapting receptors
Tonic
- static or slow
- responds as long as stimulus is maintained
Rapidly adapting receptors
Phasic
- dynamic or rapid
- adapt to constant stimulus and stop firing
Classification of axons
speed of transmission and place it projects 1) 1a(130 m/sec) 2) 2a(120 m/sec) 3) II (AB) (90 m/sec) 4) As(45 m/sec) 5) C(2 m/sec) 1&2 fastest 4&5 slowest
Type 1 joint receptor
Ruffini = slowly adapting(constant)
- located in superficial capsule
- discharge altered by posture, motion, muscle tension changes
- can inhibit pain
Type 2 joint receptors
large pacinian-type cluster(rapidly adapting)
- located in deep capsule
- inactive when joint immobile
- discharge altered by active and passive motion of joint
Type 3 joint receptor
ligament receptor
- large, thinly encapsulated end organs(Golgi-like)
- short and at end of ROM
- located in surface of joint ligaments(slowly adapting)
- sense tension and are active at extremes of joint motion
- dynamic sensation
- reflex inhibition of muscle tone at end of ROM
Type 4a joint receptor
plexiform, lattice-like receptor
- located in entire thickness of joint capsule but not in muscle and nerve tissue
- nociceptor, non-adapting
- evokes pain sensation when heat or stretch
Type 4b joint receptor
free nerve endings
- located in all joint capsules, ligaments and fat pads
- dull aching pain or burning sensation when provoked
Fine touch
carried in the CNS in the dorsal columns/medial lemniscus to the thalamus
Meissner’s corpuscles
light touch or vibration(superficial)
- stroking or fluttering feel
- rapidly adapting(steady state = no firing)
Merkel’s disks
pressure or texture(superficial)
- slowly adapting
hair follicle receptors
from hair displacement(superficial)
- rapidly adapting
Pacinian corpuscles
touch and vibration(deep)
- tuning fork response
Ruffini’s corpuscles
stretching of skin(deep)
- allows us to feel edges of objects
receptor fields
Rapid superficial = Meissner’s and Hair follicle
Slow superficial = Merkel’s
Rapid Deep = Pacinian
Slow Deep = Ruffini’s
Course touch
carried in the CNS in the spinothalamic system or anterolateral system
- pleasant touch or pressure and sensations of tickle and itch
- free nerve endings
Nociceptors
pain
- fibers are As and C, carried in the CNS in the spinothalamic system and anterolateral system
- free nerve endings
Thermal receptors
temperature
- fibers are As and C, carried in the CNS in the spinothalamic system or anterolateral system
- free nerve endings
nociception
refers to the reception of signals in the CNS evoked by activation of specialized sensory receptors(nociceptors) that provide information about tissue damage
pain
the perception of an aversive or unpleasant sensation that originates from a specific region of the body
Types of pain
1) fast, localized
- neospinothalamic pain pathway(As)
- emerges right when injury occurs
2) slow, aching pain
- paleospinothalamic pain pathway(C)
- usually lasts longer
- buring, throbbing, sometimes nauseous
pain pathways
1) neospinothalamic pathway(As) - fast and localized
2) paleospinothalamic pathway(C) - slow and aching pain
3) spinomesoencephalon pathway - to midbrain(periaqueductal gray)
4) spinoreticular pathway - runs along entire length of brain stem
- Raphe nuclei and locus ceruleus receive pain information
analgesic system
1) periaqueductal gray - stimulating can abolish pain
2) Raphe magnus nucleus - release serotonin to release enkephalin in dorsal horn to suppress pain
3) pain inhibitory complex
4) chemicals
- enkephalin
- serotonin
Gate control theory
stimulation of A-beta afferents results in the blocking of impulses(closing of the gate) carried along the pain fibers
Central biasing theory
descending pathways synapse in the dorsolateral part of the spinal cord on pain fibers results in a blocking of the impulses carried along the pain fibers
- peraqueducatal gray and raphe nuclei
endogenous opiod model
stimulation of pain fibers causes the release of endogenous opiods(beta endorphins)
counter irritant theory
enkaphalins
- inhibition of nociceptive signals by stimulation of non-nociceptive receptors occurs in the dorsal horn
