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Describe the physiologic effects of acute pain on:
- pulm system
- Pulmonary System
- atelectasis, V/Q mismatch, arterial hypoxemia, hypercarbia, pneumonia
- Cardiovascular System
- Increased catecholamine--> HTN, tachycardia, ischemia, dysrhythmias
- Endocrine System
- hyperglycemia, Na & H2O retention, protein catabolism
↓ Immune Fcn
- ↑platelet adhesion, ↓fibrinolysis, ↑coagulation, ↑ DVTs
- GI/GU Systems
- ↓ peristalsis, urinary retention
Analgesia – absence of pain or perception
Anesthesia – absence of sensation
Neuralgia – pain in a distribution of a nerve or a group of nerves
Paresthesia – abnormal sensation perceived without apparent stimulus
Radiculopathy – functional abnormality of one or more nerve roots
- Allodynia – perception of ordinarily non-noxious stimulus as painful
- Hypoalgesia – diminished response to noxious stimulus
- Hyperalgesia – increased response to noxious stimulus
- Hyperesthesia – increased response mild stimulus
What is the purpose of nociception?
- its processes can be divided into what parts?
Serves to detect, localize and limit tissue damage
Pathway of nociceptive/pain impulses
- involves what type of stimuli?
- when tissues are damaged..
Transduction is the process by which a noxious stimuli --> electrical energy
- Types of stimuli
- When the tissue is damaged exogenous chemicals (NTs) are released
- Substance P
- These substances activate arachidonic cascade -->inflammation
- All these chemicals and inflation lead to the generation of a nerve impulse
Describe transmission in nociception via the first (transmit signals via.. synapse with...) and second order neurons (synapse in...)
- First order neurons transmit signal to SC via the dorsal root ganglia
- First order neurons synapse with second order neurons whose axons ascend to the thalamus via the spinothalamic tract
- Second order neurons synapse in the thalamic nuclei with third order neurons that send signals to the cerebral cortex
Peripheral afferents that conduct pain originate as..
- what are the two types of peripheral afferent pain fibers?
- describe each (myelination, types of pain)
- Oringinate as free (naked) nerve endings
- A-delta fibers
- Transmit “first/fast pain”
- Well localized
- Sharp, stinging, pricking
- C fibers
- Transmit “second/slow pain”
- Burning, aching, throbbing
Describe the layer of the dorsal horn
WRT first order neurons, primary afferents terminate in a ______ fashion in the _____ horn on the _______ side of origin
- - divided in layers (rexed lamina- the first 6 lamina)
- Primary afferents in first order neurons terminate in a highly ordered fashion in the dorsal horn on the ipsilateral (same) side of origin
WRT first order neurons, where to c-fibers terminate?
- interneurons transmite c-fiber impulses to..
how does referred pain occur?
- c-fibers terminate in superficial lamina I and II
- - interneurons transmit c-fiber impulses to lamina V
- Referred pain occurs via WDR/convergent neurons receiving terminal input from both somatic and visceral afferents in the same lamina
FIRST ORDER NEURONS
A-delta fibers terminate in what lamina?
- the major NT released from A-delta fibers are?
- the major NT released from C fibers are?
A-delta fibers terminate in lamina 1, 3-5 after leaving the tract of Lissauer
- - the major NT from A-delta is glutamate (binds to AMPA)
- - the major NT from C is substance P (binds to NK-1 post-synaptic)
Second order neurons:
- where are the cell bodies located?
- what are the types of neurons?
what is the pathway that is most involved in the perception of pain?
- wide-dynamic range (WDR) and NS (Nociceptive specific)
- the spinothalamic tract is the most common ascending pathway involved in normal pain perception
What are the 2 groups of cell in the dorsal horn?
- describe each
- Nociceptive-Specific (NS)
- - located in lamina I
- - responds to noxious stimuli only
- - limited receptive fields and dermatomes
- Wide-dynamic range (WDR)
- - located in lamina V (lesser, I, X)
- - responds to noxious or tactile stimuli
- - contributes to pain perception
- - receives input from A-beta, nociceptive fibers
- - has large, complex receptive fields
- - Stimulation just outside the entire receptive field may produce inhibition
The ascending pathway (Spinothalamic tract) in the second order neurons, what perceptions does it carry?
- describe its physical layout in the SC and brainstem
- describe its modulation
- electrical stimulation of spinal nerve roots will result in..
Major carrier of temperature and pain, but is not the only pathway for it
Ascends the entire length of the cord and the brainstem In the brainstem, separates to terminate in different thalamic and brainstem nuclei.
Capable of excitatory and inhibitory modulation.
Electrical stimulation of spinal nerve roots results in inhibition.
third order neurons- where are most cell bodies located?
- its fibers extend to where in the brain?
Most cell bodies are located in the thalamus
Fibers extend into the somatosensory areas of the parietal cortex, where perception and localization of pain occurs
what 4 areas of the brain is involved in pain perception?
- Reticular Activating System
- -Extensive interconnections with other supraspinal sites
- - The thalamus is the 'central switching station‘ of the brain
- - Third order neurons located here
- Limbic System
- - Emotional aspects of pain, stress, sleep
- Cerebral Cortex
- - Perception of Pain
- - SI region is believed to be the most significant
modulation of pain can occur at ____ sites and can be either ____ or _____
- types of modulation
modulation of pain can occur at multiple
sites and can be either inhibitor or excitatory
- Peripheral modulation
- - Central modulation
- Spinal modulation
- Supraspinal modulation
Describe peripheral modulation
- occurs where?
- what will increase/decrease nociceptive response?
- what will help?
peripheral modulation occurs at the site of tissue damage where the nociceptive receptors are
- Elimination of endogenous mediators of inflammation
- will increase/decrease nociceptive response
- -Lactic acid, H+, K+
ASA, NSAIDs, acetaminophen and steroids work to eliminate these mediators and decrease pain
Central modulation occurs where?
- describe its nature
- Can occur at any
- point in any pain pathway
- Can be inhibitory or
- excitatory in nature
- Can be functional or
What is "wind up?"
- with "wind up" what happens to dorsal horn neurons? flexion reflexes?
- wind up is a phenomena of central modulation (excitatory) d/t repeated firing of WDR neurons even in the absence of C-fiber input
- Dorsal horn neurons increase there receptive field such that adjacent neurons become responsive to stimuli
Hyperexcitability of flexion reflexes
Name and Describe the 2 methods of central modulation inhibition
- Segmental inhibition
- - Occurs when activation of large afferent fibers inhibits WDR neurons and the spinothalamic track
- - Basis of the Gate Theory of pain
- Supraspinal inhibition
- - Several structures send fibers down the spinal cord to inhibit pain in the dorsal horn
supraspinal modulation originates where?
- supraspinal tracts descend via _____ to the ____.
Where do NTs act on 1st and 2nd order neurons?
What does enkephalin do and how?
Supraspinal modulation originates in the periaqueductal gray, reticular formation, and nucleus raphe magnus
Tracts descend via the dorsolateral fasiculus to the dorsal horn
- Neurotransmitters act
- -Presynaptically on 1st order neurons
- -Postsynaptically on 2nd order neurons
Enkephalin decreases transmission of pain signals; it does this via binding to first order neurons and inhibiting substance P