Pain

PAIN

Types of Pain

• Fast pain– felt within about 0.1 second after a pain

stimulus is applied

• Slow pain– begins only after 1 second or more and then

increases slowly over many seconds and sometimes even minutes

Fast pain

‒ sharp pain, pricking pain, acute pain, and electric pain

‒ not felt in most deeper tissues of the body

‒ elicited by the mechanical and thermal types of stimuli

‒ transmitted in the peripheral nerves to the spinal cord by small type Aᵟ fibers at velocities between 6 and 30 m/sec

Slow pain

‒ slow burning pain, aching pain, throbbing pain, nauseous pain, and chronic pain

‒ associated with tissue destruction‒ can lead to prolonged, unbearable suffering‒ occur both in the skin and in almost any deep

tissue or organ‒ elicited by mechanical, thermal, and chemical

pain stimuli.‒ transmitted to the spinal cord by type C

fibers at velocities between 0.5 and 2 m/sec

Dual Pain Pathways in the Cord and Brain Stem

• Neospinothalamic Tract for Fast Pain.

• Paleospinothalamic Pathway for Transmitting Slow-Chronic Pain.

glutamate

glutamatesubstance P

Pain Suppression (“Analgesia”) System in the Brain and Spinal Cord

REFERRED PAIN

branches of visceral pain fibers are shown to synapse in the spinal cord on the same second-order neurons (1 and 2) that

receive pain signals from the skin

Causes of True Visceral Pain

• ischemia of visceral tissue• chemical damage to the surfaces of the

viscera• spasm of the smooth muscle a hollow

viscus• excess distention of a hollow viscus• stretching of the connective tissue

surrounding or within the viscus.

“Parietal Pain” Caused by Visceral Disease

• When a disease affects a viscus, the disease process often spreads to the parietal peritoneum, pleura, or pericardium

• extensive pain innervation from the peripheral spinal nerves

• pain from the parietal wall overlying a viscus is frequently sharp

Localization of Visceral Pain

• Visceral Pathways

• Parietal Pathway