Lec 8 Pain

Question 1

Receptive fields of pain/temp neurons are ____ (larger/smaller) than mechanosensory.

Answer 1

larger, bc detecting presence of pain more impoartant than exact location of pain

Question 2

A-delta: myelinated or not? Responds to?

Answer 2

lightly myelinated.

dangerously intense.

Question 3

C fibers: myelinated or not? responds to?

Answer 3

unmyelinated.

several types of stimuli.

Question 4

A-delta mechanosensitive detect…

Answer 4

dangerous mechanical (e.g. crrush)

Question 5

A-delta mechanothermal detect…

Answer 5

dangerous thermal (e.g. burns)

Question 6

Types of C-fibers

Answer 6

Polymodal - respond to several types of stim.

Non-Nociceptive Thermo - nonharmful thermal stim.

Question 7

Channel receptor in A-delta & C

Answer 7

Vanilloid (VR-1)

Question 8

VR-1 is activated by what? What happens when activated?

Answer 8

Activated by heat, [H+], capsaicin.

Opens pore & allows influx of Na+ & Ca2+ = AP.

Question 9

Inflammatory response: damaged tissues release…

Answer 9

Prostaglandins
Histamine
Bradykinin
ATP
Substance P

Question 10

Inflammatory response: peripheral sensitization

Answer 10

released substances = increased nociceptor responsiveness = reduced threshold for depolarization

Question 11

Inflammatory response: hyperalgesia

Answer 11

enhanced sensitivity to stimulation around area of damaged tissue (e.g. mild heat on a sunburn hurts worse)

Question 12

Anti-inflammatory agents act where?

Answer 12

injury site

Question 13

Opiate drugs act where?

Answer 13

CNS

Question 14

Local anesthetic acts where?

Answer 14

on nociceptor neurons (blocks Na channels)

Question 15

Segregation: A-delta & C go where?

Answer 15

Lateral division of dorsal root

Question 16

Segregation: A-beta, I, & II go where?

Answer 16

medial division of dorsal root

Question 17

Lissaur’s tracts

Answer 17

incoming spinothalamic axons branch into ascending/descending collaterals.
run up/down 1-2 spinal cord segments before synapsing on N2.

Question 18

Rexed lamina

Answer 18

gray matter in spinal cord is split into 10 different sections (each section is a rexed lamina). Cell body of N2 is in one of these lamina.

Question 19

Name some of the Rexed lamina

Answer 19

Marginal Zone
Substantia Gelatinosa
Nucleus Proprius

Question 20

Spinothalamic projects where?

Answer 20

Reticular Formation (medulla).
Parabrachial Nucleus (pons).
Intralaminar Nuclei (thalamus).

Question 21

Parabrachial projects where?

Answer 21

Hypothalamus & amygdala.

Periaqueductal grey matter (midbrain).

Question 22

Intralaminar Nuclei (thalamus) project where?

Answer 22

frontal lobe
insula
cingulate cortex

Question 23

Brown Sequard Syndrome results from what?

Answer 23

exactly half of spinal cord segment damaged.

Question 24

Brown Sequard Syndrome: loss of mechanosensory on what side?

Answer 24

Affected

Bc mechano ascends ipsi.

Question 25

Brown Sequard Syndrome: loss of pain/temp on what side?

Answer 25

Contralateral to injury.

Bc crosses over before ascending up spinal cord.

Question 26

Descending Modulatory Pathways originate from what structures? (5)

Answer 26

Periaqueductal
Somatosensory cortex
Hypothalamus
Raphe Nuclei
Rostral Medulla

Question 27

Gate Theory

Answer 27

activating mechanoreceptors = activates interneurons that inhibit ascending nociception.
This is why rubbing a painful area can make it feel better.

Question 28

How do endogenous opioids modulate pain?

Answer 28

synapse on ascending N2, reducing activity of ascending noci (N1)

Question 29

Name 3 endogenous opioids

Answer 29

Enkephalins
Endorphins
Dynorphins

Question 30

Where are enkephalins located?

Answer 30

Periaqueductal
Rostral Medulla
Spinal Cord

Question 31

Where are dynorphins located?

Answer 31

Periaqueductal
Rostral Medulla
Spinal Cord

Question 32

Where are endorphins located?

Answer 32

Periaqueductal