Pain pathways Flashcards
Pain is a complex phenomenon that includes two components, what are they?
1) Sensory discriminative
2) Motivation Affective responses
What is sensory discriminative?
What is the pathway of this?
Ascending pathways
spinothalamic & trigemino-thalamic tracts –> cerebral cortex –> perception of pain
Motivation- affective responses to painful stimuli include? (4 things)
`1) Attention and arrousal
2) somatic and autonomic reflexes
3) Endocrine responses)
4) Emotional changes
The international association for the study of pain emphasizes the complex nature of pain as _____, _______, _______.
Physical, emotional, Psychological
What is “The experience of pain with a series of complex neurophysiologic processes?”
Nociception
What are the 4 places that medications target to treat pain?
Transduction, transmission, interpretation and modulation in CNS and PNS
Does the degree of damage to tissue that is present always correlate with patient’s experience of pain?
No!
Chronic pain in ____ % of adult population.
40%
Low back ___% to ____ % in 45 to 60 yr olds.
8% to 37%
____ million with MS pain condition.
40 million
Annual cost of pain in society?
40 billion!!! This doesn’t factor in surgeries and lost day of work.
What part of nociception? “Nerve/electrical impulses start at the nerve endings”
Transduction
**Travel **of nerve/electrical impulses to the nerve body connecting to the dorsal horn of the spinal cord.
Transmission
Process of altering (inhibitory/excitatory) pain transmission mechanisms at the dorsal horn to the PNS and CNS
Modulation
Thalamus acting as the central relay station for incoming pain signals & the** primary somatosensory cortex** serving for discrimination of specific sensory stimuli.
Perception
What step in nociception do local anesthetics work on for peripheral nerve blocks?
TRANSMISSION
What is the central relay station in the brain?
Thalamus
What is the primary area serving for discriminiation of specific sensory stimuli?
Sematosensory cortex
Where do the modulation of pain impulses occur?
Dorsal Horn
Location of Nociceptors at the peripheral level? (5)
Skin, muscles, joints, viscera, vasculature
What is the pathway of the peripheral nerve pain?
Stimulus –> Nociceptor: Resting Threshold –> Transmission –> Modulation –> Interpretation
Unmyelinated pain fibers?
What type of pain?
How fast does it travel?
Acute or chronic?
C- Fibers
Burning pain from heat and pressure from sustained pressure.
SLOW pain: 2 m/s
Chronic
Myelinated fibers?
types?
what kind of pain do they transmit?
Speed of transmission?
Acute or chronic?
- A fibers
- type 1 A-beta and A -delta: heat, mechanical, chemical
- Type 2 fibers: A- delta: heat
- FAST PAIN: > 2 m/s
- Acute pain
Name the main groups of chemical mediators. (7)
Peptides
Eicosanoids
Lipids
Neutrophins
Cytokines
Chemokines
Extracellular proteases and protons
What are specific peptide chemical mediators?
Substance P
Bradykinin (1st released)
CGRP
What are the specific lipid mediators?
Prostaglandins
Thomboxanes
Leukotrienes
Endocannbinoids
What drug that we commonly use acts on the lipids ?
NSAIDS
What chemical mediator does cannabis act on?
Endocanninoids
What group of chemical mediators is targeted by spinal/ epidural anesthetics?
Peptides
What are the Receptors and Ion Channels Dorsal root ganglion & peripheral terminals?
Purinergic
Metabotropic
Glutamatergic
Tachykinin
TRPV I
Neurotrophic
Ion channels
What is sensitization?
the increased responsiveness of peripheral neurons responsible for pain transmission
What is acute pain?
acute pain is short term and limited to days to weeks after injury. Provides important protective mechanism signaling body to protect the area.
What is chronic pain?
pain that persists even after the tissue healing is complete and extends beyond the expected period of healing. Chronic pain receptors fire even in the absence of tissue damage.
What is Hyperalgesia?
Increased pain sensations to normally painful stimuli.
What is allodynia?
perception of pain sensations in response to normally non-painful stimuli.
What is primary Hyperalgesia?
increased pain sensation at the original site of injury from heat and mechanical injury.
Primary hyperalgesia causes an ____ in pain threshold.
Decrease!
It’s easier for them to experience pain, they have a more exaggerated response
____ response to suprathreshold stimuli.
INCREASED
They have an expansion of their receptive field
Does primary or secondary hyperalgesia cause spontaneous pain?
Primary hyperalgesia
What is secondary hyperalgesia?
This can only occur from what type of stimuli?
increased pain sensation to the unijured skin surrounding the injury.
Mechainal stimuli
What is the Relay center for nociceptive & other sensory activity?
Spinal Dorsal Horn
Where do the Ascending pathways take information?
To brainstem and forebrain (SI and SII) for determination of perception of pain location & intensity
Lamina 1 is also called?
What fibers go here?
Marginal layer
Afferent C fibers
What is another name for lamina 2?
What fibers are here?
What drugs work specifically in this lamina?
Substantia gelatinosa
C fibers
Opioids
Lamina I, IV, VII, and Ventral Horn have what fibers there?
Which innervate what kind of structures?
Myelinated fibers (A- beta, A-delta)
Muscles and viscera
Lamina III and IV have what receptor which is stimulated by what chemical mediator?
NKI receptor stimulated by substance P
Describe the gate control theory of pain.
When gate is open what fibers are acting?
When gate is closed what fibers are acting?
When the gate is open A- delta and C fibers transmit pain to the brain. But by applying pressure to the site of injury it closes the gate and A-beta fibers deliver information about the pressure and touch information, while inhibiting the A delta and C fiber pain transmission.
What area is responsible for perception of motivational- affective pain components?
Limbic cortex and thalamus
What area is responsible for depression or facilitating the integration of info in the spinal dorsal horn to the thalamus to be relayed to the sematosensory cortex?
Periaqueductal gray - rostral ventromedial Medulla system
(PAG-RVM)
Name the 7 Neuromodulators of the CNS.
Substance P
Glutamate
CGRP
NMDA (specific neuromodulator to ketamine)
AMPA
BDNF
Cytokines
Which neuromodulator is specific to ketamine? and what is the full name?
NMDA
N-methyl-d-aspartate
What are two major CNS neuromodulators that are important to anesthesia?
Substance P and NMDA
Tissue injury releases what chemical mediators?
Substance P and Glutamate
Damaged cells, mast cells and platelets release what chemical mediators? (6)
Bradykinin
Histamine
prostaglandins
Serotonin
Hydrogen ion
Lactic acid
Primary excitatory impulse mediator?
Glutamate
E or I?
Glutamate
excitatory
E or I?
Calcitonin
Excitatory
E or I?
GABA
Inhibitory
E or I
Glycine
Inhibitory
E or I?
Enkephalins
Inhibitory
E or I
Norepinephrine
Inhibitory
E or I
Calcitonin
Excitatory
E or I
Neuropeptide Y
Excitatory
E or I
Dopamine
inhibitory
E or I
Aspartate
Excitatory
E or I
Substance P
Excitatory
What are the four ascending pathways of Nociception information
Spinothalamic
Spinomedullary
Spinobulbar
Spinohypothalamic
Spinothalamic transmits what type of pain?
What fibers?
what laminae?
Pain, temp, itch
ALL fibers (a beta, a delta, C fibers)
Laminae I, VII, VIII
Spinobulbar pathways detemines what?
What laminae?
Behavior towards pain
Laminae I, V, VII
Spinohypothalamic determines what 3 aspects of pain?
Laminae?
Autonomic, neuroendocrine, and emotional aspects of pain.
Laminae: I, V, VII, and X
What part of the brain determines Location and intensity of pains?
Forebrain S1 and S2 (somatosensory 1 and somatosensory 2)
What parts of the amygdala determine the emotinal and motivational aspects of pain?
Anterior cingulate cortex (ACC) and
Insular Cortex (IC)
What other parts of the brain are mentioned that deal with pain? (he didn’t say anything specific about these, just read them off the slide..)
Prefrontal cortex
Thalamus (RELAY CENTER)
Cerebellum
Describe the descending inhibitory pain pathway.
What NT’s are involved?
What is the end result of the pathway?
The periaqueductal gray is where this pain pathway originates. It passes through the Rostral VentroMedial Medulla, then through the dorsolateral funiculus and synapses at the Dorsal horn.
NT’s : endorphins, enkephalins, serotonin
Hyperpolarization of A-delta and C-fibers which decreases the release of Substance P through opening of K+ channels and inhibition of Ca+ channels.
Where does the pain impulse originate if it is pertaining to the descending inhibitory tract?
PAG-RVM
What is neuropathic pain?
Who’s at increased risk for this pain?
What is treatment?
Persists after the tissue has healed, allodynia and hyperalgesia
Increased risk: Cancer patients d/t chemo and radiation therapy
Treatment: symptomatic (opioids, gabapentin, amitryptiline, cannabis)
What is visceral pain?
What are causes?
Diffuse & poorly localized (referred to somatic sites: muscle & skin)
Causes: ischemia, stretching of ligamentous attachments, spasms, distention
what is Complex regional pain Syndrome?
What are symptoms of this?
A variety of painful conditions following injury in a region with impairment of sensory, motor, and autonomic systems
Symptoms include: Spontaneous pain, allodynia, hyperalgesia, edema, autonomic abnormalities, active and passive movement disorders, and trophic changes of skin & SQ tissues.
What is the earliest pain is felt in gestation?
23 weeks
Pain in neonates and infants has __ threshold and ____ pain responses.
Decreased,
increased
Cardiovascular responses to pain?
Hypertension
Tachycardia
Myocardial irritability
↑ SVR
Could compromise LV function and lead to decreased CO and MI
Pulmonary response to pain?
Increased total body oxygen consumption and CO2 production.
Increased minute ventilation
Decreased movement of chest wall d/t pain can lead to?
Atelectasis and intrapulmonary shunting
Physical manifestations of pain r/t pulm system?
Splinting, decreased movement of chest wall, imparied coughing
GI/GU response to pain?
and complications?
Enhanced sympathetic tone…↑ sphincter tone, and ↓ motility
causes ileus and urinary retention
Hypersecretion of acid
Causes Stress ulceration and Aspiration
N/V
Abdominal distention
Endocrine Response to pain?
↑ catabolic hormones
Catecholamines
Cortisol
Glucagon
↓ anabolic hormones
Insulin
Testosterone
Effects
Negative nitrogen balance
Carbohydrate intolerance
Increases renin, aldosterone, angiotensin
Hematologic response of pain?
(effects on platelets, fibrin, and coagulation?)
Platelet adhesiveness
Reduced fibrinolysis
Hypercoagulability
Emotional responses?
anxiety, sleep distrubances, and depression
