Nociception-Pain-Temperature

Question 1

Spinothalamic Tract path

Answer 1

C and Ad (cell body in DRG)  Ipsilateral Spinal Gray Matter Decussates in Anterior white commissure (spine) Ascends contralateral VPL- thalamus sensory cortex

Question 2

Spinothalamic Tract carries?

Answer 2

pain and temp

Question 3

Warm fiber?

Answer 3

C

Question 4

Cool Fiber?

Answer 4

Ad

Question 5

Touch/ proprioception fiber?

Answer 5

AB

Question 6

Extreme cold fiber?

Answer 6

C

Question 7

Extreme Hot fiber?

Answer 7

Ad

Question 8

First a tolerable, localized, “pricking” pain is detected (___ fiber first pain).

Answer 8

Aδ

Question 9

Then, a burning,

intolerable, diffusely localized, “burning” pain is experienced (____ fiber second pain).

Answer 9

C

Question 10

Aδ and C fibers differ. The receptive fields associated with Aδ fibers are _____ than those associated with C fibers.

Answer 10

smaller

Thus, information carried by Aδ fibers will be better localized leading to better
spatial discrimination

Question 11

Pressure Block of pain

Answer 11

AB (first pain) –> Ad –> finally C (in order)

Question 12

Local Anesthetics block of pain

Answer 12

C (second pain) –> Ad –> AB

Question 13

Polymodal nociceptors have C fibers as their

Answer 13

afferents

Question 14

______ is expressed on polymodal

nociceptors.

Answer 14

VR-1

Question 15

A __________ is a sensory neuron that responds to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain.

Answer 15

nociceptor

Question 16

Polymodal nociceptors can be activated by ________________

C fibers as their afferents.

Answer 16

high-intensity mechanical,

chemical or thermal stimuli

Question 17

Polymodal activation

Answer 17

↑ E-stim: AB stim–> Ad–> finally C (repetitive stim needed)

Question 18

chemicals that act as pain activators

Answer 18

Bradykinin, acid, K+, serotonin. Depolarize to threshold creating AP

Question 19

Activators

Answer 19

direct activation of nociceptors

Question 20

Bradykinin produced by cleavage of an inactive precursor, ___________ (a serum protein).

Answer 20

kininogen

Question 21

Upon ___________, cytoplasmic proteases are released –> degrade serum proteins–> bradykinin.

Answer 21

tissue damage

Question 22

Bradykinin directly activates pain receptors of :

Answer 22

Aδ and C fibers.

Question 23

vanilloid receptor (VR)

Answer 23

The receptor is part of an ion channel complex. When the receptor is activated,
the associated non-selective cation channel opens, thereby leading to a depolarization.

Question 24

VR-1, is known as the capsaicin receptor. VR-1 is strongly activated by capsaicin and weakly activated by ______

Answer 24

acids and extreme heat

Question 25

nociceptors that signal extremely cold temperatures (

Answer 25

C fibers.

Question 26

warm receptors tend to be on

Answer 26

C fibers

Question 27

C fibers are coated w/

Answer 27

nothing, unmyelinated

Question 28

information carried by __________ ( lightly myelinated) will reach the CNS before that carried by C fibers.

Answer 28

Aδ fibers

Question 29

projects to the midbrain periaqueductal gray region (PAG) and is important for descending control of pain.

Answer 29

spinomesencephalic tract

Question 30

pathway conveys pain inputs that lead to forebrain arousal and elicits emotional/behavioral responses via connections to the emotional circuits of the brain

Answer 30

spinoreticular tract p

Question 31

a principal pathway and conveys pain information to the thalamus. This tract projects to the nuclei of the ventral posterior thalamus, which includes VPL. Neurons in these nuclei process information related to localization of pain and project to somatosensory cortex.

Answer 31

spinothalamic tract

Question 32

Release of Substance P at the dorsal horn synapse produces central sensitization:

Answer 32

(hyperalgesia)

Question 33

Activation of non-nociceptive fibers leads to activation of dorsal horn interneurons that in turn inhibit synapses activated by:

Answer 33

nociceptive fibers non-nociceptive afferent pathways (e.g., touch receptors and Aβ fibers). Rubbing a wound helps

Question 34

The synthetic drug, __________, blocks the action of opiates.

Answer 34

naloxone

Question 35

A brain region that is particularly sensitive to opiate actions is the

Answer 35

PAG.

Question 36

Opiates also inhibit transmission in the _________ of the spinal cord

Answer 36

dorsal horn

Question 37

brains own opiate-like compounds.

Answer 37

enkephalins, β-endorphin and dynorphins and are collectively known as endorphins

Question 38

Stress Activates PAG --> inhibition of 2o neurons of the dorsal horn. _______ blocks some but not all of the analgesia produced by stressful situations

Answer 38

Naloxone

Question 39

In the dorsal horn of the spinal cord, _______ is the major inhibitory transmitter.

Answer 39

GABA

Question 40

Following injury of C fibers, Aβ afferents sprout and invade the normally forbidden territory of the:

Answer 40

substantia gelatinosa second-order neurons in the substantia gelatinosa that are normally activated only by pain input are now also activated by non-noxious stimuli.

Question 41

Nervous systems of patients experiencing | chronic pain are__________ from those who have not had the same experience.

Answer 41

functionally and structurally different changes are diverse and range from changes in excitability, neurotransmitter content, synaptic efficacy, to circuitry.

Question 42

A very telling observation is that administration of naloxone blocks the

Answer 42

placebo effect.

Question 43

Stress can activate:

Answer 43

PAG

Question 44

DOes Nalaxone block stress analgesia?

Answer 44

Only partially. | THC does the other bit

Question 45

Thus, stress–induced analgesia involves both ____________________ mechanisms

Answer 45

opioid and nonopioid mediated

Question 46

spinomesencephalic tract projects to the midbrain ___________ and is important for descending control of pain

Answer 46

periaqueductal gray region (PAG)

Question 47

Stimulation of the periaqueductal gray region (PAG) in the midbrain produces a powerful:

Answer 47

analgesia Touch, pressure and temperature sensations persist and only pain sensation is attenuated.

Question 48

PAG neurons project to the __________ in the medula

Answer 48

nucleus raphe magnus

Question 49

nucleus raphe magnus neurons in this medullar region are:

Answer 49

serotonergic (i.e., use serotonin as their neurotransmitter)

Question 50

In the spinal cord, serotonin will lead to inhibition of second-order neurons of the dorsal horn by exciting an inhibitory interneuron.

Answer 50

This interneuron uses enkaphalin

Question 51

enkephalin mechanism

Answer 51

presynaptically (block of voltage-gated calcium current) postsynaptically (opening of potassium channels).