Pain physiology and assessment Flashcards
Define Pain
an unpleasant sensory and emotional experience arising from actual or potential tissue damage
Define acute pain
the normal, predicted physiologic response to an adverse chemical, thermal, or mechanical stimulus. associated w/surgery, trauma, or acute illness
What is the biologic purpose of acute pain?
alerts person to a noxious environment and activates fight/flight mechanisms
Define chronic pain
Pain that persists or progresses over a long period of time and is resistant to medical treatments
What is the biologic purpose of chronic pain?
no biological usefulness. becomes disease in its own right
Define hyperalgesia
increased response to a stimulus that normally is painful
Define hypoalgesia
diminished response to a normally painful stimulus
Define analgesia
absence of pain in response to stimulation that normally is painful
Define paresthesia
an abnormal sensation, whether spontaneous or evoked (pins/needles)
Define allodynia
pain resulting from a stimulus such as light touch that doesn’t normally elicit pain
What are the 4 physiologic processes associated with pain?
transduction, transmission, modulation, perception
Describe the onset and quality of fast pain
felt within 0.1s, is sharp in character
Describe the onset and quality of slow pain
begins after a second or more, is throbbing/aching in nature
Describe characteristics of pain receptors and their stimulation
all pain receptors are free nerve endings. they do not adapt to the stimulus. can by stimulated by mechanical (stretch), thermal, or chemical factors
What do prostaglandins and substance P do in relation to pain stimulation?
they enhance the sensitivity of pain endings but do not directly excite them
What causes pain?
the rate of tissue damage
What is the role of bradykinin in relation to pain?
causes the most pain and is the most responsible for causing the tissue damage type of pain.
What are the two classifications of pain?
nociceptive or neuropathic
Define nociceptive pain
involves the normal neural processing of pain that occurs when free nerve endings are activated by tissue damage or inflammation (somatic/visceral)
Define neuropathic pain
involves the abnormal processing of stimuli from the PNS or CNS, and is thought to serve no useful purpose.
What is an example of neuropathic pain?
peripheral neuropathy in diabetics
Define transduction as a part of the pain pathway
The conversion of a noxious stimulus. Transferred into electrical activity in the peripheral terminals of nociceptor sensory fibers
Define transmission as a part of the pain pathway
transmits info
Define modulation as a part of the pain pathway
refers to the alteration (augmentation or suppression) of sensory input
Define perception as a part of the pain pathway
refers to the decoding of afferent input into the brain that gives rise to the individual’s specific sensory experience
What type of fibers and tract transmit fast pain?
Type Adelta fibers, transmitted in the neospinothalamic tract
What type of fibers and tract transmit slow pain?
Type C fibers, transmitted in the paleospinothalamic tract
Describe 1st order neurons as a mechanism of pain
detect stimuli that threaten the integrity of innervated tissue. Get AP to dorsal horn
Describe 2nd order neurons as a mechanism of pain
located in the spinal cord and process nociceptive info. Get AP to the brain
Describe 3rd order neurons as a mechanism of pain
project pain info to the brain. Get AP to the cortex
Where do fibers of the neospinothalamic tract terminate in the spinal cord?
can travel up or down 1-3 segments and terminate on neurons in the dorsal horn.
What do fibers of the paleospinothalamic tract terminate in the spinal cord?
terminate in the laminae II or III of the spinal cord. they make 1-2 local connections before giving rise to 2nd order neurons
What is the pathway of 2nd order neurons in both the neospinothalamic and paelospinothalamic tracts?
the 2nd order neurons cross to the opposite side and pass to the brain in the anterolateral columns
Where do 2nd order neurons of the neospinothalamic tract terminate?
some terminate in the reticular substance, but most go to the ventrobasal complex of the thalamus
Where do 2nd order neurons of the paleospinothalamic tract terminate?
some terminate in the thalamus, but most terminate diffusely in the reticular nuclei of the medulla, pons, mesencephalon, tectal area of the mesencephalon, or the periaqueductal gray region
Where do the neurons go from the lower reticular areas of the paleospinothalamic tract?
project to the intralaminar nuclei of the thalamus, hypothalamus, and other basal brain regions
How would the removal of the somatic sensory areas of the cortex affect pain?
still able to perceive pain because pain impulses to lower areas can cause conscious perception of pain
What does the cortex determine with pain?
the quality of pain
What do nerve fibers in the periventricular nucleus and periaqueductal gray nuclei secrete at their nerve endings?
enkephalin
What do nerve fibers from the raphemagnus secrete at their nerve endings?
serotonin
What does serotonin do in relation to pain suppression?
causes local neurons to secret enkephalin
What is the fxn of enkephalin?
causes both pre- and post- synaptic inhibition of type C and type Adelta pain fibers where they synapse in the dorsal horns
What are the three large molecules that opoid substances originate from?
proopoimelanocortin, proenkephalin, prodynorphin
What are the major opiate substances?
B-endorphin, met-enkephalin, leu-enkephalin, dynorphin
Where are the enkephalins and dynorphin found?
brain stem and spinal cord
Where is B-endorphin found?
hypothalamus and the pituitary
What is the fxn of the opiate system?
pain suppression during times of stress. an important part of an organism’s response to an emergency is a reduction in the responsiveness to pain
What are the different types of pain?
Cutaneous, somatic, visceral
Describe cutaneous pain
superficial structures such as skin and subQ. sharp, bright pain, localized accurately
Describe somatic pain
deep body structures, more diffuse than cutaneous, various stimuli (pressure on bone, ischemia to a muscle, tissue damage)
Describe visceral pain
pain from an internal organ that’s perceived to originate from a distant area. viscera have few sensory fibers except for pain fibers. highly localized damage to an organ may result in little pain, widespread damage can lead to severe pain
Where is visceral (referred pain) localized to?
the dermatome of embryological origin
What are causes of visceral pain?
ischemia, chemical irritation, spasm of hollow viscus, overdistension of hollow viscus
Define pain threshold
closely associated with the pt at which a stimulus is perceived as painful
Define pain tolerance
relates more to the total pain experience, it’s the maximum intensity or duration of pain that a person is willing to endure
How is inflammation related to pain?
It’s used to promote healing. Sensitivity increased so that stimuli to the affected part that wouldn’t normally cause pain now cause pain.
What is the fxn of algogenic substances?
increases the permeability of capillaries and edema formation when a tissue is damaged/inflammed
What is the biocultural model of pain?
society influences an individual’s pain experiences
What are the consequences of untreated acute pain?
increased metabolic rate and blood clotting, impaired immune fxn, negative emotions, and pain receptors become sensitive/long lasting changes
