Chapter 3 - Sensory Receptors/Pain Theories

Question 1

Touch

Answer 1

1) superficial pressure = crude touch or light touch
2) vibration
3) discriminative touch

Question 2

discriminative touch

Answer 2

what is being touched or manipulation

• have to have an intact parietal lobe to distinguish
  1) two-point
  2) stereognosis
  3) graphesthesia

Question 3

two-point touch

Answer 3

ability to discriminate between two different points

• 2mm for finger tips
• 4-7cm on back

Question 4

stereognosis

Answer 4

ability to identify an object by touch

Question 5

graphesthesia

Answer 5

ability to identify things written on skin

Question 6

Proprioception

Answer 6

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

Question 7

How information is conveyed

Answer 7

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)

Question 8

Mechanoreceptors

Answer 8

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

Question 9

Chemoreceptors

Answer 9

responds to chemical released by cells

- pain

Question 10

thermoreceptors

Answer 10

respond to warmth and cool

Question 11

nociceptors

Answer 11

cause pain

- extreme high and low temps

Question 12

Slowly adapting receptors

Answer 12

Tonic

• static or slow
• responds as long as stimulus is maintained

Question 13

Rapidly adapting receptors

Answer 13

Phasic

• dynamic or rapid
• adapt to constant stimulus and stop firing

Question 14

Classification of axons

Answer 14

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

Question 15

Type 1 joint receptor

Answer 15

Ruffini = slowly adapting(constant)

• located in superficial capsule
• discharge altered by posture, motion, muscle tension changes
• can inhibit pain

Question 16

Type 2 joint receptors

Answer 16

large pacinian-type cluster(rapidly adapting)

• located in deep capsule
• inactive when joint immobile
• discharge altered by active and passive motion of joint

Question 17

Type 3 joint receptor

Answer 17

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

Question 18

Type 4a joint receptor

Answer 18

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

Question 19

Type 4b joint receptor

Answer 19

free nerve endings

• located in all joint capsules, ligaments and fat pads
• dull aching pain or burning sensation when provoked

Question 20

Fine touch

Answer 20

carried in the CNS in the dorsal columns/medial lemniscus to the thalamus

Question 21

Meissner’s corpuscles

Answer 21

light touch or vibration(superficial)

• stroking or fluttering feel
• rapidly adapting(steady state = no firing)

Question 22

Merkel’s disks

Answer 22

pressure or texture(superficial)

- slowly adapting

Question 23

hair follicle receptors

Answer 23

from hair displacement(superficial)

- rapidly adapting

Question 24

Pacinian corpuscles

Answer 24

touch and vibration(deep)

- tuning fork response

Question 25

Ruffini's corpuscles

Answer 25

stretching of skin(deep) | - allows us to feel edges of objects

Question 26

receptor fields

Answer 26

Rapid superficial = Meissner's and Hair follicle Slow superficial = Merkel's Rapid Deep = Pacinian Slow Deep = Ruffini's

Question 27

Course touch

Answer 27

carried in the CNS in the spinothalamic system or anterolateral system - pleasant touch or pressure and sensations of tickle and itch - free nerve endings

Question 28

Nociceptors

Answer 28

pain - fibers are As and C, carried in the CNS in the spinothalamic system and anterolateral system - free nerve endings

Question 29

Thermal receptors

Answer 29

temperature - fibers are As and C, carried in the CNS in the spinothalamic system or anterolateral system - free nerve endings

Question 30

nociception

Answer 30

refers to the reception of signals in the CNS evoked by activation of specialized sensory receptors(nociceptors) that provide information about tissue damage

Question 31

pain

Answer 31

the perception of an aversive or unpleasant sensation that originates from a specific region of the body

Question 32

Types of pain

Answer 32

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

Question 33

pain pathways

Answer 33

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

Question 34

analgesic system

Answer 34

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

Question 35

Gate control theory

Answer 35

stimulation of A-beta afferents results in the blocking of impulses(closing of the gate) carried along the pain fibers

Question 36

Central biasing theory

Answer 36

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

Question 37

endogenous opiod model

Answer 37

stimulation of pain fibers causes the release of endogenous opiods(beta endorphins)

Question 38

counter irritant theory

Answer 38

enkaphalins | - inhibition of nociceptive signals by stimulation of non-nociceptive receptors occurs in the dorsal horn