Chemosensation & Pain

Question 1

Gustatory pathway

Answer 1

1st order: CN ganglia (cell bodies) synapse @ solitary nucleus
2nd order: Solitary nucleus synapse @ VPM
3rd order: VPM synapse @ Gustatory Cortex

Question 2

Olfactory System Tract

Answer 2

bundle of axons connecting the mitral (MAIN OUTPUT cells) and tufted cells of the olfactory bulb to several target regions in the brain, including piriform cortex, amygdala, and entorhinal cortex.

Question 3

Capsaicin

Answer 3

principle ingrediant responsible for heat in hot peppers

activtes receptors on C-Fibers which normally respond to heat

repeated applicaiton desencitizes pain fibers

Question 4

4 mechanical primary sensory receptors

Answer 4

Superficial– small receptive fields

1) Meissners (light touch, fast, unmeyelinated)
2) Merkels (2 point discrimination)

Deep– lare receptive fields

3) Ruffinis (SLOW, sustained pressure, slow and large, allow modulation of grip of object)
4) Pacinian (FAST, vibration and pressure)

Question 5

Referred Pain

Answer 5

pain in one region signifying damage in another

Dorsal Horn neuron in Lamina V recieves affarent signals from viceral nociceptors and cutaneous nocicpetors

Question 6

Lamina V

Answer 6

recieves input from Alpha-gamma + C-fibers (nociceptive) as well as ABeta

Question 7

Gate control theaory

Answer 7

larger diameter A-Beta fibers going through lamina inhibit transmission of smaller nerves carrying pain signla.

Question 8

lamina II

Answer 8

where C-fibers synapse (dorsal horn)

Question 9

Thalamic Pain syndrome (Dejenrine-Roussy)

Answer 9

chronic pain resulting from lesions in posterior thalamus

first get numbness and then tingling

Question 10

nociceptive pain fibers

Answer 10

A-delta = fast, thin, myelinated. Carries Afferent info about localized, intense pain
C= slow, throbbing, long lasting pain (Glut and Sub P)

Terminate in Dorsal Horn of spinal cord
Lamina V (although C fibers synapse at II)

Question 11

“Wind Up Theory” –Nueropathic pain

Answer 11

repeated activation of NMDA rectpors
causes increased response to same stimulus nerve damage can produce this

C fibers release GLUT and SUB P

stimulus that is usually nonpainful becomes painful (Allodynia)

Question 12

Anti-inflammatory (NSAIDs

Answer 12

ASA and Ibuprofen

Question 13

Acetaminophen

Answer 13

blocks TRPV1 (vallinoid receptors) and COX inhibitor
no effect on inflammation

Question 14

Prednisone (glucocorticoid)

Answer 14

inhibits PG and Leukotriene synthesis by acting on hormone receptors (transcription factors)

reduces inflammation

Question 15

Morphine and Codeine

Answer 15

morphine (moderate to severe)
Codeine (weaker)

ascending pathway– hyperplarizes postynaptic neurons by opening presynaptic K+ channels and close voltage gated Ca2+ channels (inhibits NT release)

Descending pathway: Inhibit GABA actions, disinhibit NT modulating pain in dorsal horn (NE)

Question 16

Amitriptyline

Answer 16

Monoamine reuptake inhibitor: tricyclic anti-depressant

blocks reputake of serotonin and NE (used for neuropathic pain, no sedation)

Question 17

Duloxetine

Answer 17

selective NE and serotonin reuptake inhibitor SNRI

used for pain associated iwth cancer and peripheral diabetic neuropathy

Question 18

gabapentin
pregabalin
carbamazepine

Answer 18

gaba and pre– ion channel modulator. bind to alpha-2-delta- subunit of ca ion channels to block ca ion influx and relase NT, glutamate and sub P. approved for peripheral diabetic neuropathy

carb– blocks voltage gated Na ion channels. for epilepsy and trigeminal neuralgia

Question 19

lidocaine

Answer 19

blocks neuronal firing– slow rapid firing of voltage gated Na+ ion channels (Na+ channel blocker). can be applied as cream

Question 20

capsaicin

Answer 20

blocks neuronal firing- stimulates C fibers causing an AP.

Sub P released –> TRPV1. damages nerve endings reducing ability to send pain signals

causes pain but followed by relef from pain for several weeks

Question 21

Ketamine

Answer 21

blocks glutamate NTs by blocking Ca2+ influx.

Question 22

Thermal and Pain receptors

Answer 22

Free nerve endings

sense injurious forces,

Question 23

Proprioception afferent axons

Answer 23

A-alpha (large, myelinated, transpit porpioceptive form skeletal muscles)