Week 9 ch 49 Flashcards
Somatic sensations II. Pain, headache, thermal sensations
Fast pain examples
sharp, prickling, acute, electric feeling
Slow pain examples
burning, aching, throbbing, nauseous, chronic
3 types of nociceptors
- mechanical
- thermal
- chemical
Fast pain nociceptors:
Mechanical, thermal
Slow pain nociceptors:
Mechanical, thermal, chemical
Chemicals that do NOT cause AP (examples and what they do)
- prostaglandins
- substance P
enhance sensitivity but do not excite (do not cause action potential)
Pain receptors and adaptation
do not adapt, excitation becomes progressively greater
Tissue damage does what
activates nociceptors
Pain correlates with
rate at which damage to the tissue is occuring
Tissue ischemia and pain correltaion
greater rate of metabolism, more rapidly pain appears
i.e. blood pressure cuff on still arm or exercising forearem
Pain and metabolism correlation
more metabolic tissue = more pain from ischemia
i.e. muscle spasm: muscle spasm causes compression of blood vessels and causes ischemia, muscle spasm is a high rate of metabolism in that muscle
Fast pain pathway fibers:
A delta
Slow pain pathway fibers;
C
Fast sharp pain signals are elicited by
mechanical or thermal pain
Sudden painful stimulus gives pain sensation on what fibers?
A delta AND C
(“double” pain sensation)
i.e glucose prick = sharp, then dull throbbing pain
Pain fibers terminate on
relay nuerons in DORSAL HORNS
Fast pain signals take the ___ pathway
neospinothalmic tract
Slow pain fibers take the ____ pathway
Paleospinothalmic tract
Fast pain fibers terminate in
lamina I of the dorsal horns
2nd order neurons in the fast pain pathway terminate in
- brain stem
- ventrobasal complex (in thalamus)
What neurotransmitter is at type A delta pain nerve fiber endings?
glutamate
Type C fibers are transmitted via thw
paleospinothalmic pathway
Type C pain fibers terminate in
spinal cord laminae II and III (substantia gelatinosa)
Type C pain fibers cause release of
substance P
Slow, chronic paleospinothalmic pathway terminates in
brainstem
Pain still felt without cerebral cortex =
lower brain centers cause conscious perception of pain
Cordotomy
surgical interruption of thoracic region of spinal cord
Built in analgesia system
- neurons send signals to lower pons and medulla
- second order neurons transmit to inhibitory complex in dorsal horns
3.Nervous system secretes opiate-like substances
Neurtotransmitters in pain suppression/built in analgesia system: (examples and role)
- enkephalin
- serotonin
role: pre and post synaptic inhibition of type C and A delta pain fibers
opiate-like substances secreted by nervous system at end of pain supression pathway:
endorphins
enkephalin byproducts
dynorphin
What depresses transmission of pain signals?
Tactile stimulation of large type A beta sensory fibers
i.e. rubbing a painful spot
i.e. pressing/pinching an area before a stick
Mechanism of referred pain
Visceral pain fibers synapse on teh same second-order neurons that receive pain signals from the skin
Examples of diffuse stimulation of pain nerve endings(4):
- ischemia
- chemical stimuli
- Spasm
- Overdistention
Insenstive viscera (2):
- parenchyma of the liver
- alveoli of the lungs
Parietal pain (definintion and cause)
Friction form membranes rubbing together
often from inflammation
Parietal pain areas
Peritoneiuum, leura, pericardium
Visceral pain is localized
poorly, localized to dermatomal segment from where visceral organ originated
Hyperalgesia
hypersensitivity to pain
Primary hyperalgesia
excessive sensitivty of receptors
Secondary hyperalgesia
additional neurons firing to move neuron towards AP (facilitation of transmission)
Herpes zoster is an infection of
dorsal root ganglion
Herpes zoster pain in
dermatomal segment affected
Pan in herpes zoster thought to be from
infection of pain neuronal cells
Tic douloureux is
trigenimal neuraglia
Tic Doulreux presentation
Sudden severe pain on one side of face - set off by very sensitive trigger areas (mechanoreceptive)
requires surgical treatment
Brown-sequard syndrome
Spinal cord transected on one side
weaknessor paralysis on same side of transection
loss of pain, heat, and cold sensation on oposite side of body
Intracranial Headache MOA (3)
- tugging of venous sinuses around brain –>damage tentorium –> stretching of dura
- traumatizing stimulus to blood vessels of meninges
pain receptors in cerebral vault above tentorium cause
front half of head pain
pain receptors located below tentorium cause
occipital head pain
Headache types of intracranial origin:
- meningitis inflammation
- low CSF fluid pressure
- MIgraine
- alcohol headaches
Migraine MOA
vasospasm of arteries of head = ischemia to meninges
Extracranial headache types:
- Muscle spasm
- Nasal
- Eye disorders
Muscle spasm HA MOA
Emotion tension causes muscles of head to become spastic
Nasal HA MOA
infection or irritative process (HA behind eyes)
Eye disorder HA MOA (2)
excessive contraction of eye ciliary muscles trying to focus eyes
Excessive irradiation (sun or welder)
Types of thermal receptors (4)
- Cold - pain
- Cold - receptors
- Warmth receptors
- Heat - pain
Cold receptor nerve is
Type A delta (myelinated)
thermal sensations travel
up anterolateral pathway
Thermal sensation - how?
gradation determined by degree of stimulation of different type of nerve endings
Thermal sensation adaptation
cold receptors are fast to adapt but never completely
Temp signals terminate in
laminae I, II, III of dorsal horn—>brain stem and thalamus
