Pain Flashcards
(29 cards)
What is the definition of pain? It is classified into 2 forms - what are they?
an unpleasant sensory & emotional expperience associated with actual or potential tissue damage, or described in terms of such damage
Acute: something correctable, treated with opioids & it’ll subside, or pain that is the result of something SHORT TERM
Chronic: pain that continues OVER TIME, bigger problems, impacts on quality of life
What are the 3 types of pain?
1) Nociceptive pain
2) Inflammatory pain
3) Neuropathic pain
Nociceptive pain
Nociceptive pain is a type of pain caused by the activation of nociceptors, which are sensory receptors responding to potentially harmful stimuli. This pain arises from physical damage or inflammation of tissues, such as skin, muscles, or internal organs. It is typically described as sharp, aching, or throbbing and serves as a protective mechanism, prompting individuals to withdraw from harmful stimuli and seek healing. Common examples include pain from cuts, burns, or fractures.
ACUTE
- diff noxious stimuli can activate specific receptors and/or ion channels on peripheral nociceptors
Inflammatory pain
Inflammatory pain is a type of pain caused by the body’s response to tissue injury or infection, leading to inflammation. This pain results from the** release of chemicals like prostaglandins and cytokines, which sensitize nociceptors. It is typically characterized by redness, swelling, heat, and a persistent aching or throbbing sensation**. Inflammatory pain serves to protect the injured area and promote healing, commonly seen in conditions like arthritis, infections, or injuries.
Neuropathic pain
Neuropathic pain is a type of pain caused by damage or dysfunction in the nervous system, including nerves, spinal cord, or brain. This pain often presents as burning, shooting, or electric shock-like sensations. Unlike nociceptive or inflammatory pain, neuropathic pain arises from abnormal neural activity and may persist without an apparent physical cause. Conditions like diabetes, shingles, and nerve trauma frequently lead to neuropathic pain. Treatment often requires medications targeting nerve activity, as traditional pain relievers are usually less effective.
caused by disease in somatosensory NS
results from injury to peripheral or CNS that causes permanent changes in circuit sensitivity and CNS connections
3 aspects of pain
1) Sensory aspects - location, intensity, duration
2) Motivational-affective aspects - unpleasant feeling associated with pain
3) Emotional response
Arises bc stimuli that produce pain = damage tissue = protective mech.
Pain = subjective + learned
What is nociception?
Nociception is the process by which the nervous system detects and responds to harmful or potentially harmful stimuli. It involves the activation of nociceptors, which are specialized sensory receptors located throughout the body. When these receptors detect damaging stimuli—such as extreme heat, cold, pressure, or chemical irritants—they send signals through nerve fibers to the spinal cord and brain.
Results in perception of pain
Pain sensation / experience is not necessarily implied (can be ‘fake’)
Pathway of pain perception
Nociceptors –> peripheral –> spinal cord –> CNS –> cerebrum –> modulation
How do peripheral nociceptors work?
transduce noxious stimuli into action potentials and transmit to CNS
usually respond to HIGH threshold stimulation
code for intensity for noxious stimulation – tells brain how intense stimulation is
conduct slowly relative to low threshold sensory neurons that relay innocuous touch as pain needs longer time to be aware and temporal resolution is not as good
Explain the overall process for peripheral nociception
Peripheral nociceptors are specialized sensory nerve endings located in tissues such as the skin, muscles, joints, and internal organs. They detect potentially harmful stimuli, including mechanical pressure, extreme temperatures, and chemical irritants. Here’s how they work:
**Activation: **When a harmful stimulus is present, peripheral nociceptors are activated. They contain ion channels and receptors sensitive to specific types of noxious stimuli.
**Signal Transduction: **The activation of nociceptors causes ion channels to open, leading to an influx of ions such as sodium and calcium into the nerve ending. This generates an electrical signal known as an action potential.
Transmission: The action potential travels along the nerve fibers (axons) of the nociceptors towards the spinal cord. Peripheral nociceptors have two main types of fibers: A-delta fibers, which conduct fast, sharp pain, and C fibers, which conduct slow, aching pain.
Processing: The signals are then transmitted to the spinal cord and relayed to higher brain centers, where they are processed and interpreted as pain.
What are the 2 main types of nociceptors?
Firstly nociceptors have un-specialized, free nerve endings and are classified according to their AXON-CONDUCTING PROPERTIES
- A-fibre axons - thinly myelinated, conduction velocities (5-30m/s), FAST (SHARP) PAIN
- C fibre axons - unmyelinated, conduction velocities (<2m/s), SLOW BURNING PAIN
3 types of nociceptors (classified according to modality i.e. what sensory stimulus activates them)
- Mechanical - noxious mechanical stimuli (cutting, crushing, pinching)
- Thermal - noxious temps
- Polymodal - combinations of above, and / or chemicals or inflammatory mediators
POLYMODAL NOCICEPTORS CAN EXPRESS (CORNEA) TRPV1 AS SPECIFIC COMBINATIONS OF ION CHANNELS OR RECEPTORS MAY BE INVOLVED IN TRANSDUCTION FOR EACH TYPE OF NOCICEPTOR
Which region of the spinal cord receives input from nociceptors (pain receptors)? And where is the signal ransferred to?
dorsal horn –>
2nd order neurons originate in diff lamina (layers) of dorsal horn and ascend towards brain –>
interneurons - communicate b/w diff lamina and contribute to processing pain signals
Interneurons can shape the signal by dampening it or modifying it depending on the context, integrating input from many neurons
Pathway for body pain and temperature
Tract/system of axons: for body pain and temp, the pathway involves 2nd order neurons that receive input in the dorsal horn,
cross over (decussate) to the opposite side of the spinal cord,
and ascend in the anterolateral part of the spinal cord (spinothalamic tract)
Ascending pathways for face pain/temp
TRIGEMINAL system - pain and temp signals from face travel through the trigeminal nerve system
these signals also cross over to opposite side and then ascend via a diff pathway compared to body
Visceral pain
alternative pathways – visceral pain (from internal organs) may travel through diff pathways, such as post-synaptic dorsal column pathway, which is separate from the ain spinothalamic tract used for somatic (body) pain
Where do the 2nd order neurons synapse to?
In the thalamus, they synapse with 3rd order neurons
These 3rd order neurons project to the somatosensory cortex of the cerebrum, where the sensory information is processed and perceived as pain, temp, or crude touch
What is the difference in how the anterolateral system (which includes the spinothalamic tract for pain & temp) & the dorsal column-medial lemniscal system (for fine touch & proprioception) process and transmit sensory info.
The anterolateral system (pain and temp) –> fibers cross midline at level of spinal cord shortly after entering it, which means that pain and temp info from ONE siDE OF BODY IS PROCESSED by other side of brain
Dorsal column-mediated lemniscal system (fine touch, vibration, proprioception i.e. mechanoreceptors) –> do not cross midline immediately but ascend IPSILATERALLY (on same side) in dorsal columns of spinal cord
–> cross over at medulla in brainstem
This means that fine touch and proprioception information is processed on the same side of the body until it reaches the medulla, where it then crosses over to the opposite side of the brain.
Because these pathways cross at different points, a lesion at different levels of the nervous system will have . . . .
distinct effects on sensory perception
A lesion in one side of the spinal cord will affect the spinothalamic tract’s ______ pain and temp sensaions below the level of the lesion
The same lesion will affect the dorsal column-medial lemniscal system’s ______ fine touch and proprioception below the level of the lesion
contralateral (opposite side)
ipsilateral (same side)
Since both pathways have crossed by the time they reach the brainstem, lesions above the medulla will affect contralateral sensation for both systems.
Where does pain perception occur?
in the cerebrum
Somatosensory cortex via ventral posterior nucleus is where sensory-discriminative info is processed and generated
Affective-motivational responses are generated from thalamus and variety of brain structures
Sensory discriminative vs affective motivational
Sensory-discriminative: ventral posterior nucleus –> somatoensory cortex
Affective-motivational: midline thalamic nuclei –> anterior cingulate cortex + insular cortex
What’s the neuraxis?
Pain modulation involves several complex mechanisms operating at diff levels of the nervous system
Pain modulation involves several complex mechanisms operating at different levels of the nervous system, often referred to as the neuraxis. These mechanisms include:
1) Neurogenic inflammation
2) Sensitization
3) Descending inhibition
4) Analgesics
