Flashcards in Chapter 48 Deck (64):
What is the time span for slow pain?
begins only after 1 second or more and then increases slowly over many seconds and sometimes even minutes
What are the characteristic Sx of slow pain?
slow burning pain, aching pain, throbbing pain, nauseous pain, and chronic pain
What causes slow pain?
What is the time span for fast pain?
pain felt within about 0.1 second after a pain stimulus is applied
What are the characteristic Sx of fast pain?
sharp pain, pricking pain, acute pain, and electric pain. not felt in most deeper tissues of the body
What causes fast pain?
when a needle is stuck into the skin, the skin is cut by a knife, when the skin is acutely burned, or when skin is subject to electric shock
Where are pain receptors?
Pain receptors (nociceotors) are free nerve endings and are widespread in superficial skin as well as periosteum, arterial walls, joint surfaces, and the falx and tentorium in cranial vault
What are the 3 different stimuli to cause pain?
mechanical, thermal, and chemical pain
Slow pain is caused by which stimuli?
Slow pain is elicited by all three mechanical, thermal and chemical pain
What types of substances cause chemical pain?
bradykin, serotonin, histamine, potassium ions, acids, acetylcholine, and proteolyic enzymes
Fast pain is caused by which stimuli?
just mechanical and thermal
true or false: there is a great deal of pain R adaptation
Why is failure of pain receptors to adapt important?
because it allows the person to be aware of the tissue damaging stimulus as long as it persists
What is the role of pain perception?
pain is a protective mechanism that tells the body that tissues are being damaged and causes the individual to react to remove the pain stimulus
What degree of temperature (C) causes tissue destruction and pain?
What is the most painful chemical in tissues?
Which 2 susbtances correlate to the intensity of pain felt in a local area of pain?
K ions or proteolytic enzymes
Tissue ischemia causes pain by the release of what substance?
lactic acid in the tissues formed from the cells use of anaerobic metabolism
Slow pain uses what type of fibers to sense pain?
CV of C fibers?
Fast pain uses what type of fibers to sense pain?
small type Aδ fibers
CV of Aδ fibers?
Both fast and slow pain fibers enter the spinal cord from the dorsal spinal root and the pain fibers terminate on relay neurons where in the spinal cord?
Neospinothalamic and paleospinothalmic are part of which pain tract?
What type of pain is neospinothalamic tract used for?
for fast pain and the fast type Aδ fibers transmit mainly mechanical and acute thermal pain
Where does the neospinothalamic tract terminate in the dorsal horn?
Where do the fibers cross in the neospinothalamic tract?
immediately after synapsing in lamina I through the anterior white commisure and go up to the brain in the ALS
neospinothalamic tract uses what NT?
What type of pain is paleospinothalamic tract used for?
for peripheral slow-chronic pain type C pain fibers
Where does the paleospinothalamic tract terminate in the dorsal horn?
terminate in the spinal cord almost entirely in laminae II and III of the dorsal horns together it’s called the substantia gelatinosa
After synapsing in lamina II and III, where do the short fibers enter for the paleospinothalamic tract?
Lamina V and then up to the brain through the ALS
What are the 3 places the 2nd-order neurons terminate for the paleospinothalamic tract?
(reticular nuclei of the medulla, pons and midbrain) or (tectal area of midbrain) or (PAG)
What are the indications for surgical intervention for pain pathways?
when a person has severe and intractable pain (sometimes resulting from rapidly spreading cancer) necessary to relieve pain
What procedure in the thoracic region of the spinal cord often relieves the pain for a few weeks to months?
Cordotomy (contralateral to pain to disrupt the ALS)
Why might a cordotomy be unsuccessful?
o Many pain fibers from the upper part of the body do not cross to the opposite side of the spinal cord until they have reached the brain so cordotomy doesn’t touch them
o Pain usually returns several months later partly as a result of sensitization of other pathways that normally are too weak to be effectual
Why might slow pain cause chronic arousal? (giggity)
reticular formation of the brain stem and the intrelaminar nuclei constitute part of the brains principal arousal system so if you have chronic pain stimulating the reticular formation of brain stem and intralaminar nuclei you are also going to cause nervous system arousal and the inability to sleep
What are 3 components to the analgesia system?
PAG, raphe nucleus in upper medulla, dorsal horn of spinal cord
What are the 2 NT's for the analgesia system?
enkephalin and serotonin
Where is enkephalin secreted?
periventricular nuclei and PAG
What is the role of enkephalin?
believed to cause both presynaptic and postsynaptic inhibition of incoming type C and type Aδ fibers where they synapse in the dorsal horns
Where is serotonin secreted?
What is the role of serotonin?
causes local cord neurons to secrete enkephalin
What is referred pain?
when a person feels pain in a part of the body that is fairly remote from the tissue causing the pain
What is the mechanism of referred pain?
• Branches of visceral pain fibers synapse in the spinal cord on the same second order neurons that receive pain signals from the skin
• When the visceral pain fibers are stimulated pain signals from the viscera are conducted through at least some of the same neurons that conduct pain signals from the skin
How can ischemia cause visceral pain?
causes visceral pain because of the formation of acidic metabolic end products or tissue degenerating products like bradykin or proteolyic enzymes
How can chemical stimuli cause visceral pain?
damaging substances leak from the GI tract into the peritoneal cavity
Example-duodenal ulcer allows proteolytic acidic gastric juice to leak through and this causes widespread digestion of the visceral peritoneum stimulating broad area pain fibers
How can a spasm of a hollow viscus cause visceral pain?
spasm of a portion of the gut, gallbladder, a bile duct, a ureter, or any other hollow viscus can cause pain by stimulating the mechico stimulation of nerve ending. Can also cause diminished blood flow Often can occur as cramps with pain increasing to a high degree of severity and then subsiding. Happens each time a peristaltic wave travels along an overly excitable spastic gut
How can overdistention of a hollow viscus cause visceral pain?
extreme overfilling of a hollow viscus can result in pain b/c of overstretch of the tissues themselves. Can also collapse the vessels that encircle the viscus
What are insensitive viscera?
a few visceral areas are almost completely insensitive to pain if any type. Includes the parenchyma of the live and the alveoli of the lungs
What is hyperalgesia?
A pain nervous pathway that becomes excessively excitable and leads to hypersensitivity to pain
What is 1o and 2o hyperalgesia?
Primary hyperalgesia- excessive sensitivity of the pain receptors themselves
Secondary hyperalgesia- facilitations of sensory transmission
What are the Sx of brown-sequard syndrome (unilateral spinal cord transection)?
• All motor functions are blocked on the side of the transection in all segments below the level of transection
• Sensations of pain, heat, and cold sensations served by the spinothlamic tract are loss on the contralateral side of the transection 2-6 dermatomes below the transection (b/c already crossed in the anterior commissure)
• Kinesthetic and position sensation, vibratory touch, discrete localization and two point discrimination are lost on the ipsalateral side in all dermatomes below the level of the transection (posterior columns)
How can a headache result from meningitis?
one of the most severe headaches of all causes inflammation of the meninges including the sensitive area of the dura and the sensitive area around the venous sinuses Such intense damage can cause extreme headache pain referred over the entire head
How can a headache result from low CSF?
removing as little as 20ml of fluid from the spinal canal especially if the person remains in an upright position. Happens b/c removing that much fluid removes part of the floatation for the brain that CSF provided and the weight of the brain stretches and distorts dural surfaces which causes the pain
What causes a migrane?
from abnormal vascular phenomena exact mechanism is unknown. One theory is that prolonged emotion or tension causes reflex vasospasm of some of the arteries of the head including the ones that supply the brain
How can a headache result from a hangover?
alcohol b/c its toxic to tissues directly irritates the meninges and causes the intracranial pain
Dehydration may also play a part in the hangover that follows an alcoholic bender
How can a headache result from muscle spasm?
emotional tension often causes muscles of the head and especially those attached the scalp and the neck muscles attached the occiput to become spastic and is one of the most common causes of headache
How can a headache result from irritation of the nasal cavity?
mucous membranes of the nose and nasal sinuses are sensitive to pain but not intensely.
How can a headache result from eye disorders?
difficulty in focusing one’s eyes clearly may cause excessive concentration of the eyes cillary muscle in an attempt to gain clear vision. The tonic contraction of them can causes retro-orbital headaches
Excessive focusing can also cause spasm in various facial and extra ocular muscles and can cause headaches
What are the 3 different sensory receptors for temperature?
cold receptors, warmth receptors, and pain receptors.
When are pain receptors stimulated by temperature?
are only stimulated by extreme degrees of heat or cold
What are the fibers associated with heat receptors?
are believed to be type C nerve fibers at transmission velocities of only 0.4 to 2m/sec
What are the fibers associated with cold receptors?
is a special small type Aδ myelinated nerve ending that branched many times transmitted at 20 m/sec