Nociception

Question 1

What is pain ?

Answer 1

Submodality of somatic sensation
- nocer : to injure / hurt
- nociceptive : sensitive to noxious stimuli (elicit tissue damage & activate nociceptors)

Question 2

Nociceptors definition

Answer 2

Sensory receptors that detect the signals from damaged tissue or threat of damage / chemicals released from damaged tissue

Question 3

Types of nociceptors

Answer 3

• Skin nociceptor
  • Threshold mechanonociceptors ( respond only to
  intense mechanical stimulation such as pinching, cutting or stretching )
  • Thermal nociceptor ( above stimuli as well as to thermal stimuli )
  • Chemical nociceptors ( which respond only to chemical substances )
  • Polymodal nociceptors ( to high intensity stimuli such as mechanical, thermal and to
  chemical substances )
• Joint nociceptor ( The joint capsules and ligaments contain high-threshold mechanoreceptors, polymodal nociceptors, and “silent” nociceptors )
• Visceral nociceptor ( Visceral organs contain mechanical pressure, temperature, chemical and silent nociceptors. The visceral nociceptors are scattered, with several millimeters between them, and in some organs, there are several centimeters between each nociceptor )
• Silent nociceptor ( In the skin and deep tissues there are additional nociceptors called “silent” or “sleep” nociceptors. These receptors are normally unresponsive to noxious mechanical stimulation, but become “awakened” (responsive) to mechanical stimulation during inflammation and after tissue injury )

Question 4

Factors activate nociceptor

Answer 4

• Globulin and protein kinases
• Arachidonic acid
• Histamine
• Nerve growth factor (NGF)
• Substance P (SP) and calcitonin gene-related peptide (CGRP)
• Potassium - K+
• Serotonin (5-HT), acetylcholine (ACh), low pH (acidic) solution, and ATP
• Muscle spasm and lactic acid

Question 5

Classification of pain

Answer 5

1.Pricking pain
- caused by a needle, pin prick, skin cut

2.Burning pain or soreness pain
- caused by inflammation, burned skin

3. Aching pain
   - sore pain

Question 6

Opioid

Answer 6

Endogenous peptides
- endorphine, dynorphins, enkephalins

Opioid analgesics
- morphine, diamorphine, oxycodone

Question 7

Non-steroidal anti-inflammatory drugs (NSAIDs)

Answer 7

• aspirin
• diclofenac
• etoricoxib
• paracetamol
• ibuprofen

Question 8

Fever definition

Answer 8

complex physiologic response triggered by infectious or aseptic stimuli.

Question 9

Antipyretic action

Answer 9

• Paracetamol acts at least partly by reducing cytoplasmic peroxide tone: peroxide is necessary to activate the haem enzyme to the ferryl form.
• In areas of acute inflammation, paracetamol is not very effective because neutrophils and monocytes produce high levels of H2O2 and lipid peroxide, which overcome the actions of the drug
• However, paracetamol is an effective analgesic in conditions in which leucocyte infiltration is absent or low