Nociception I-III

Question 1

What tract carries temperature and pain information?

Answer 1

the anterolateral system

Question 2

Where are the cell bodies for temperature receptors?

Answer 2

in the dorsal root or trigeminal nerve (for the head)

Question 3

Each primary sensory temperature neuron has an axon that _____.

Answer 3

bifurcates

Question 4

Where do each of the axon limbs in a primary sensory neuron go?

Answer 4

one goes to the skin and one goes to the CNS (the central axon)

Question 5

Cool receptors are associated with ____ fibers.

Answer 5

Aδ

Question 6

_____ (temperature) receptors are associated with Aδ fibers.

Answer 6

Cool

Question 7

Warm receptors are associated with ____ fibers.

Answer 7

C

Question 8

____ (temperature) receptors are associated with C fibers.

Answer 8

Warm

Question 9

Where is the first synapse for the DRG neurons?

Answer 9

the dorsal horn of the spinal cord

Question 10

What is the spinothalamic tract?

Answer 10

the relay of info thru the thalamus to the somatosensory cortex

Question 11

What is the spinoreticular tract?

Answer 11

relay of info via the reticular formation to the hypothalamus for regulation of temperature and ANS function

Question 12

This is tract relay of info via the reticular formation to the hypothalamus for regulation of temperature and ANS function.

Answer 12

spinoreticular tract

Question 13

What tracts does the ALS system include?

Answer 13

spinoreticular

spinomesencephalic

Question 14

The _____ pathway refers to the axons of the dorsal hor second order neurons that cross the midline and ascend anterolaterally.

Answer 14

ALS

Question 15

With respect to site of origin of sensory info, info about temp and pain ascends _____ in the spinal cord.

Answer 15

contralaterally

Question 16

The ____ is a principal pathway that conveys pain info to the ventrobasal thalamus (including the VPL).

Answer 16

spinothalamic tract

Question 17

The spinothalamic tract is a principal pathway that conveys ____ info to the _______.

Answer 17

pain; ventrobasal thalamus (including the VPL)

Question 18

The _____ pathway conveys pain inputs that lead to forebrain arousal and elicits emotional/behavioral responses from the limbic system.

Answer 18

spinoreticular tract

Question 19

The spinoreticular tract pathway conveys ____ inputs that lead to ______ and elicits _____.

Answer 19

pain; forebrain arousal; emotional/behavioral responses from the limbic system

Question 20

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

Answer 20

spinoreticular

Question 21

The spinoreticular tract projects to the_____ and is important for ______.

Answer 21

midbrain periaqueductal gray region (PAG); descending control of pain

Question 22

How does the cingulate gyrus contribute to pain?

Answer 22

it is the emotional component

Question 23

How does the insular cortex contribute to pain?

Answer 23

processes info related to the ANS component of pain

Question 24

Intense pressure activates ____ receptors.

Answer 24

Aδ

Question 25

Damaged cells release what 4 items?

Answer 25

K ATP PGs acids (H+)

Question 26

Name 4 compounds that lead to direct activation of nociceptors.

Answer 26

bradykinin potassium acid 5-HT

Question 27

Name 5 compounds that sensitize nociceptors.

Answer 27

``` PGs substance P ATP ACh 5-HT ```

Question 28

___ increases the synthesis of prostaglandins from neighboring cells, which then sensitize nociceptors.

Answer 28

Bradykinin

Question 29

How does aspirin work as an analgesic?

Answer 29

inhibits COX to prevent PG synthesis and prevent nociceptor sensitization

Question 30

____ is known as primary hyperalgesia.

Answer 30

Sensitization of nociceptors

Question 31

Sensitization of nociceptors is known as _____.

Answer 31

primary hyperalgesia

Question 32

What is allodynia?

Answer 32

when pain sensitization is extreme enough to allow non-noxious stimuli to trigger a painful sensation

Question 33

This is the term for when pain sensitization is extreme enough to allow non-noxious stimuli to trigger a painful sensation.

Answer 33

allodynia

Question 34

What is the triple response?

Answer 34

a bradykinin mediated reddening, wheal, and flare due to tissue injury

Question 35

This is a bradykinin-mediated reddening, wheal, and flare due to tissue injury.

Answer 35

the triple response

Question 36

How does bradykinin cause pain?

Answer 36

it activates C fiber nociceptors --> depol --> APs --> substance P is release

Question 37

What does substance P do?

Answer 37

causes vasodilation/pain; closes K+ channels --> depolarization --> enhancement, prolongation of glutamate action

Question 38

Substance P is a sensitizer that ______ of nociceptors and collaterals in the exposed region.

Answer 38

reduces threshold for activation

Question 39

_____ is a sensitizer that reduces threshold for activation of nociceptors and collaterals in the exposed region.

Answer 39

Substance P

Question 40

Where in the brain do C fibers terminate?

Answer 40

in the substantia gelatinosa

Question 41

On what fibers do C fibers terminate? Where are these fibers found?

Answer 41

in the Rexed's laminae in the dorsal horn of the spinal cord (substantia gelatinosa)

Question 42

Where do visceral and somatic pain inputs converge?

Answer 42

at the dorsal horn neuron

Question 43

Why is injury to internal organs often perceived as cutaneous pain?

Answer 43

bc visceral and somatic pain pathways converge at the dorsal horn neuron, but cutaneous input dominates, and the two are perceived as the same

Question 44

Name 2 types of glutamate receptor in the dorsal horn. Are they fast or slow?

Answer 44

NMDA (slow) | AMPA (fast)

Question 45

Why does pain persist, even after glutamate is taken back up?

Answer 45

substance P persists bc it's not removed by reuptake

Question 46

What neurons process info related to the localization of pain?

Answer 46

the VPL

Question 47

What is the pathway of the anterolateral system?

Answer 47

skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> specific tract in the brain (spinoreticular, spinomesencephalic, or spinothalamic)

Question 48

Where does the ALS decussate?

Answer 48

immediately (in the spinal cord)

Question 49

What is nociceptive pain?

Answer 49

detection of an acute, painful stimulus

Question 50

What is neuropathic pain?

Answer 50

injury to the nervous system --> chronic pain

Question 51

What is the pathway of the spinoreticular tract?

Answer 51

skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> medulla --> reticular formation --> hypothalamus and thalamic nuclei

Question 52

Name the system that uses this pathway: skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> specific tract in the brain (spinoreticular, spinomesencephalic, or spinothalamic)

Answer 52

the anterolateral system

Question 53

What is the pathway of the spinomesencephalic tract?

Answer 53

skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> midbrain --> mesencephalon

Question 54

What is the pathway of the spinothalamic tract?

Answer 54

skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> thalamus --> somatosensory cortex

Question 55

Name the tract: skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> medulla --> reticular formation --> hypothalamus and thalamic nuclei

Answer 55

spinoreticular

Question 56

Name the tract: | skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> midbrain --> mesencephalon

Answer 56

spinomesencephalic

Question 57

Name the tract: | skin --> dorsal root ganglion --> dorsal horn of the spinal cord --> decussate --> thalamus --> somatosensory cortex

Answer 57

spinothalamic

Question 58

A brain region that is particularly sensitive to opioids is the _____.

Answer 58

PAG

Question 59

What happens if the dorsal lateral funiculus is cut bilaterally?

Answer 59

stimulation-produced and systemic opiate-induced analgesia are blocked

Question 60

Stress leads to increased activity in the limbic system, which in turn leads to activation of the ____.

Answer 60

PAG

Question 61

Activation of the PAG ultimately leads to ____ in the pain pathway.

Answer 61

inhibition of 2nd order neurons of the dorsal horn

Question 62

How do we know that endogenous opioids are involved in the placebo affect?

Answer 62

giving naloxone blocks the placebo affect

Question 63

What are the 2 types of sodium channels that sensory afferents have?

Answer 63

TTX sensitive | TTX resistant

Question 64

What does the TTX-resistant channel do?

Answer 64

plays a role in setting inflammatory pain thresholds

Question 65

Following nerve damage, the expression, distribution, and function of _____ is altered, leading to spontaneous discharge of pain primary afferents.

Answer 65

Na+ channels

Question 66

Why aren't Na+ channel blockers used to treat pain?

Answer 66

they're nonselective (CNS, CV SEs would occur)

Question 67

What happens in the substantia gelatinosa following injury of C fibers?

Answer 67

Aβ afferents begin to invade it

Question 68

How do glial and immune cells contribute to pain?

Answer 68

astrocytes develop and maintain neuropathic pain macs secrete TNF that activates TTX-resistant Na+ channels microglia secrete BDNF --> reverse potential so GABA becomes excitatory --> hyperalgesia