Physio CHAPTER 49
Pain has been classified into two major types
(1)Fast pain (sharp pain, pricking pain, acute pain, and electric pain)
– is felt within about 0.1 second after a pain stimulus is applied
– Fast-sharp pain is not felt in most deep tissues of the body.
(2)slow pain (slow burn- ing pain, aching pain, throbbing pain, nauseous pain, and chronic pain)
– begins only after 1 second or more and then increases slowly over many seconds and
sometimes even minutes.
– This type of pain is usually associated with tissue destruction.
– It can lead to prolonged, almost unbearable suffering.
– Slow pain can occur both in the skin and in almost any deep tissue or organ.
PAIN RECEPTORS AND THEIR STIMULATION
Pain Receptors Are Free Nerve Endings.
They are widespread in the superficial layers of the skin & in internal tissues:
-the periosteum,
-the arterial walls,
-the joint surfaces, and
-the falx and tentorium in the cranial vault
Mechanical, Thermal, and Chemical Stimuli Excite Pain Receptors.
fast pain is elicited by the mechanical and thermal types of stimuli,
slow pain can be elicited by all three types.
Some of the chemicals that excite the chemical type of pain are bradykinin, serotonin, histamine,
potassium ions, acids, acetylcholine, and proteolytic enzymes.
prostaglandins and substance P enhance the sensitivity of pain endings but do not directly excite
them.
Nonadapting Nature of Pain Receptors.
-Pain receptors adapt very little and sometimes not at all.
-Excitation of pain fibers becomes progressively greater, especially for slow, aching, nauseous
pain, as the pain stimulus continues.
-This increase in sensitivity of the pain receptors is called hyperalgesia.
Rate of Tissue Damage as a Stimulus for Pain.
Pain has been classified into two major types
(1)Fast pain (sharp pain, pricking pain, acute pain, and electric pain)
– is felt within about 0.1 second after a pain stimulus is applied
– Fast-sharp pain is not felt in most deep tissues of the body.
(2)slow pain (slow burn- ing pain, aching pain, throbbing pain, nauseous pain, and chronic pain)
– begins only after 1 second or more and then increases slowly over many seconds and
sometimes even minutes.
– This type of pain is usually associated with tissue destruction.
– It can lead to prolonged, almost unbearable suffering.
– Slow pain can occur both in the skin and in almost any deep tissue or organ.
PAIN RECEPTORS AND THEIR STIMULATION
Pain Receptors Are Free Nerve Endings.
They are widespread in the superficial layers of the skin & in internal tissues:
-the periosteum,
-the arterial walls,
-the joint surfaces, and
-the falx and tentorium in the cranial vault
Mechanical, Thermal, and Chemical Stimuli Excite Pain Receptors.
fast pain is elicited by the mechanical and thermal types of stimuli,
slow pain can be elicited by all three types.
Some of the chemicals that excite the chemical type of pain are bradykinin, serotonin, histamine,
potassium ions, acids, acetylcholine, and proteolytic enzymes.
prostaglandins and substance P enhance the sensitivity of pain endings but do not directly excite
them.
Nonadapting Nature of Pain Receptors.
-Pain receptors adapt very little and sometimes not at all.
-Excitation of pain fibers becomes progressively greater, especially for slow, aching, nauseous
pain, as the pain stimulus continues.
-This increase in sensitivity of the pain receptors is called hyperalgesia.
Rate of Tissue Damage as a Stimulus for Pain.
