Pain and Neuropathy (Physiology) - Block 2 Flashcards
What is pain?
Unpleasant sensory and emotional experence associated with actual or potential tissue damage
* subjectively defined
How does pin initiate a stress response?
- hormonal and metabolic change
- HPA axis and sympathetic NS
- Neuroendocrine response induces catabolic state
- Increases oxygen delivery and organ perfusion
- Increased plasma glucose, proteins , and free fatty acids
- Water retention by kidnes
What are the negative effects of stress response?
- HTN and tachycadia
- Hyperglycemia, negative nitrogen, immunosuppression
- Hypercoag state
What is nociceptive pain?
Physiologic response to heat, cold, viration, stretch, or chemicals released from damaged cels that may cause tissue damage
* a protective biological response
What is the difference between somatic and visceral pain?
Somatic: aching, throbbing, dull pain from skin, muscle, and joints
Visceral: squeezing, cramping, dull, and deep pain from organ
What is neuropathic pain?
Nerve cell dysfunction in the PNS and/or CNS
What is the difference between acute and chronic pain?
Acute: hours-weeks
Chronic: occurs after resolution of an acute infury or inflammation
What is transduction?
COnversion of noxious thermal, mechanical, chemical stimulus into a nerve impulse
What is transmission?
Transfer of a noxious peripheral stimulus to the CNS
What is modulation?
Peripheral and central neurotransmitters and other substances that enhance or dampen the transduction and transmission of noxious stimulus
What is perception?
Cognitive appreciation of a noxious stimulus
What is the function of afferent neurons?
Detection of a noxious thermal, mechanical, or chemical stmulus
What is a nociceptors?
Free peripheral endings of sensory neurons
What is the difference between somatic and visceral nociceptors?
Somatic: Respond to thermal, mecanical, chemical stimulus
Visceral: Stimulated by inflammation, ischemia, dilation, stretch, and spasm
What is the function of afferent nociceptive fibers with VGSCs?
Transmission of noxious stimulus to the CNS
What are A delta fibers?
Large myelinated fibers that have a low stimulation threshold and a fast conduction velocity
Differentiate the typws of A delta fibers?
Type 1: High-threshold mechical nociceptors that respond to both chemical and mechanical stimuli (first and fast and ends when the stimulus is removed)
Type 2: Low-heat threshold and high mechanical threshold (fast for heat stimulus)
What are C fibers?
Smaller unmyelinated, polymodal, mechno-heat-responsive nociceptors that have a slow conduction velocity (second or slow pain such as throbbing, burning, aching)
What happens if a pain threshold of fibers is reached?
Action potetial is generated
How is an action potential produced by nociceptors?
- Nociceptor carries the noxious stimulus to the CNS
- Conscious percepton of pain
- Nociceptors show no adaptation and depolarize in portion to the intensity and frequency of the stimulus
- Activation of:
* VOltage gated sodium and potassium channels -> generation and conduction of action potential
* VOltage gated calcium channels -> release of neurotransmitters for transmission of pain or mediation
What is the roles of upregulation of calcium channels in C fibers?
Hyperalgesia: exaggerated and prolonged response to pain
Allodynia: perception of pain from a stimulus that doesn’t usually cause pain
Describe the structure of a-delta and c afferents?
- cell bodies from the trunk and limbs located in the dorsal root ganglion
- cell bodies from the fce are located in the trigeminal ganglion
- Both have a peripheral branch and central axonal branch
What are the layers of gray matter in the spinal cord called?
Rexed laminae
* dorsal horn contains laminae I-VI
What are the first-order neurons invlved with transmission of pain?
Aδ fibers synapse with second-order neurons.
C fibers primarily synapse with interneurons that synapse with second-order neurons.
Aβ fibers may be involved in the transmission of chronic pain.
What are the second-order neurons invlved with transmission of pain?
nociceptive-specific neurons: small receptive fields and respond only to nociceptive stimuli
Wide dynamic range (WDR) neurons: Have complex receptive fields and respond to nociceptive and tactile input.
Excitatory neurotransmitters in the dorsal horn
What are the receptors used for glutamate signalling?
AMPA
NMDA
What is the inhibitory neurotransmitter?
GABA adn glycine
What are the excitatory neurotransmitters?
GLutamate, aspartate, VIP, substance P, CCK, CGRP
What are the tracts that ascend second-order neurons to the thalamus?
- Spinothalmic tract (STT)
- Spinoreticular tract (SRT)
- Spinomesencephalic (SMT)
What are thrid order neurons?
Transmit novious impulses from the thalamus to the primary somatosensory areas of the cortex for the perception of pain
What are the primary neurotransmitters?
NE, seratonin
What stimulates the releae of supraspinal and spinal endogenous opiods?
Descending tracts
What are the peripheral influences of modulaing pain?
- injuredtissue releases substance p and glutamate which activate nociceptors
- mediators are released to tissue -> inflammation
- peripheral sensitization -> primary heperalgesia
What are the functions of glial cells?
decreases the effectiveness of the inhibitory function of te descending tracts
What is central sensitization?
Increased excitability of the dorsal horn -> amplification of the novious stimulus
Excessive or continued activation of the dorsal horn -> abnormal response to sensory input and secondary hyperalgesia
What influences the perception of pain?
- Emotional or psychological stress
- Cultural and religious beliefs
- Prior experience with pain
What is a pain threshold?
The minimum intensity of a noxious therma, mechanical, or chemical stimulus that activates nociceptors and is perceived as painful
How is the pain threshold modulated in the periphery?
Increased release of chemical mediators that increase/decrease the threshold
How is the pain threshold modulated in the central?
Exictaory/inhibitory neuortransmitters that increase/decrease the threshold in the dorsal horn and thalamus
What is an increased excitability of neurons?
Sensitization
What is central sensitization?
Increased excitability of neurons in the CNS
What responses results from central sensitization?
- Tactile allodynia
- Secondary hyperalgesia
What is pain tolerance?
Amount of pain an individual can take or tolerate
How do you increase pain tolerance?
Activation of large somatic fibers
What is the gate control theory of pain?
Nnpainful input closes a pain gate to painful input in the dorsal horn and prevents the transmission of pain to the CNS
When there is no imput from A-delta and C fibers what happens?
inhibitory interneurons in the dorsal horn block activation of second-order neurons, closing the pain gate
Why is it important for large somatic nerve fibers to activate inhibitory interneuorons?
To prevent smaller pain fibers from activating second-order neurons
What type of pain is difficult to pinpoint?
Visceral pain
What are the types of acute nociceptive pain?
Somatic and visceral
What is a soft tissue injury?
Damages of muscles, ligaments tendons, joint structure (pain, swelling, bruising, damage)
What are the types of soft-tissue injuries?
- Strains
- Sprains
- Contusions
- Bursitis
- Tendonitis
- Synovitis
What is the difference between the strain and sprain?
Strain: Injury to muscle or muscle-tendon unit from overstretching (extend beyond capacity)
Sprain: ligaments around th joint are stretched or torn
What is the most common site for strains?
Lower back and neck
What is the most common site for sprains?
ankle
Sx of strain?
- Immediate pain
- reduced ROM
- Musle spasm
- Edema
- Muscle weakness
- Partial tearing in muscle
Sx of sprain?
- ROM severly hindered
- Pop or rip
- Bruising, pain, immediate swelling
- Pain exacerbated with movement
What is a bursae?
Enclosed fluid-filled sacs that act as cushions between muscles, tendons, and bony prominences
Inflammation of the bursa
Busitis
What is a tendon sheath?
Elongated bursa that wraps around tendons
What is inflammation of the tendon?
Tendonitis
What is the synovial membrane?
Surrounds the inner lining of joints that creates synovial fluid for nourishment and lubrcation
What is inflammation fo synovial mmbrane?
Synovitis
What is the common areas of bursitis, tendonitis, synovitis?
Shoulder, hips, knees, elbows
What are the causes of Bursitis, Tendonitis, and Synovitis?
- Overuse of joint, direct trauma to joint
- Constant friction between bursa and tissue around sac -> inflammation, irritation, and edema
What are te sx of Bursitis, Tendonitis, and Synovitis?
Warm, red, swollen, tenderness, pain with extention and flexion
How is a contusion formed?
Direct blow to the body that causes damage to the skin surface forcing BV to rupture
What is chronic pain?
Pain that lasts longer than 12 weeks
What are the types of chronic pain?
- Recurrent
- Intractable benign
- Progressive
What is chronic recurret pain?
Repeated and intense episodes of pain separated by pain-free periods (migraine)
What is chronic intractable benign pain?
Continuous pain with varying levels of intensity (low back pain)
What is chronic progressive pain?
Continuous pain that increases in intensity (cancer pain)
What is break through pain?
Occurs randomly and suddnely
What is osteoarthritis?
Wear and tear on joints breaks down cartilage in joint , causing bone to rub on bone
What is the most common site of OA?
Hands, knees, and hips
What is the greatest risk factor of oA?
older age
What are the forms of idiopathic OA?
Localized: affects one or two joints
Generalized: affects three or mor joints
What is secondary OA?
OA caused by underlying conditions
What are bone spurs?
Particles that break off joint to ittirate synovial tissue
Describe the progression of OA?
- Chanes to joints synovium, subchondral bone, and cartilage slowly develop
- Joint no longer moves smoothly
What are the manifestations of OA?
- Tenderness
- Effuion: swelling related to excess fluid
- Crepitus: crackling or grating of joint
- Bone spurs
- Decreaed ROM
What is are the complications for OA?
Risk of falling from joint pain, stiffness, unsteady gair, and effects of medication
What is the difference between neurtis and neuralgia?
Neuritis: inflammation of a nerve
Neuralgia: pain that follows the distribution of a nerve
What is radiculopathy?
Pain or loss of sensory and/or motor function as a result of impaired conduction block in a spinal nnerve or its roots
What is neuropathy?
a disease or disorder of the PNS or CNS
What is peripheral neuropathy?
Constant or intermittent burning, aching, lancinating limb pain due to lesions or dysfunction of peripheral nerves
* Motor, sensory, autonomic fiber lesions or dysfunction
What are central neuropathies?
Results from:
* Injury
* Stroke
* Disease
* Congenital condition in the brain or spinal cord
What are the causes of neuorpathic pain?
- Traumatic injuries
- Surgical procedures
- Repetitiatve stress
- Metabolic and endocrine disords
- Autoimmune diseases
- Chemo
- Viral/bacterial infections
- Deficiencies
- Alcohol
- Environmental exposures
A pathologic disorder that occurs without obvious tissue injury or disease and serves no protective biological function.
Neuropathic pain
What are the sx of neuropathic pain?
- Paresthesias
- Allodynoa
What is paresthesias?
Numbness, tingling, pricking sensation
What is allodynia?
Area of the body become abnormally sensitive
* innocuous stimulus
* Sensitzation of peripheral nocicetors
What are descriptors of neuropathic pain?
- Burning
- Electric shock
- Shooting
- Numbness
- Throbbing
Diminished pain response to a normally painful tactile and/or thermal stimulus.
Hypoalgesia
Unpleasant sensation?
Dysesthesia
Increased sensitivity to tactile or thermal stimulation.
Hyperesthesia
Decreased sensitivity to tactile or thermal stimulation?
Hypoesthesia
What is the characteristic of pain in the PNS and CNS?
Neuroplasticity
What is the result of lesions or damage of primary sensory neurons?
Increased number of abnormal sodium channels that spontaneously or ectopically depolarize
What are the manifestations of neuropathic pain?
- Loss of sensory input to the dorsal hron from increase neurotransmission and input from C fibers results in windup
- Release of inflammatory cytokines from central flial cells
- INcreased growth of alpha-adrenoreceptors on nociceptors
What is the most frequent form of peripheral neuorpathy?
Diabetes
What is diabetec PN?
Progressive loss of nerve fibers in both autonomic and peripheral NS from diabetes
What is the cause of diabetic PN?
Microvascular complications
Windup of the WDR neurons in lamina V
What are the manifestation of diabetic PN?
- Pain and paresthesia
- Dyin back pattern
- Stocking glove pattern
- Vasomotor changes: pallor, cyanosis, mottling
Wht are the branches of trigeminal neuralgia?
Opthalmic: supplies sensation to the scalp, forehead, and the front of the head
Maxillary: supplies sensation to the cheek, upper jaw, top lip, teeth, gums
Mandibular branch: supplies snsory and motor innervation to the lower jaw, teeth, gums, bottom lips
What is the cause of trigeminal neuralgia?
Pathophysiology involves segmental demyelination of trigeminal sensory fibers in the nerve root or brainstem:
Compression of the nerve root -> demyelination -> ephaptic communication stimulates trigeminal nerve
What are the manifestations of trigeminal neuralgia?
- Sudden burning or shock-like paroxysms of facial pain
- Pain in motor activities: chewing, speakig, yawning, eating, brushing teeth
- Unilateral pain in V2 and V3 branches
What is postherpetic neuralgia?
Painful peripheral neuralgia that is a sequela of herpes zoster infection
What is herpes zoster?
Shingles caused by varicella zoster virus
What is the cause of postherpetic neuralgia?
Reactivated herpes zoster
What are the manifestations of postherpetic neuralgia?
- Thoracic dermatomes innervated by the T1-L2 ganglia and ophthalmic branch of the trigeminal nerve
- Hyperesthesia
- Allodynia
- No reliable predicotr ofprogression
What are the RF of postherpetic neuralgia?
- Older age
- Compromised immune system
What is the most common cause of widespread musculoskeletal pain?
Fibromyalgia
What is FM?
widespread areas of tenderness distributed symmetrically on the trunk and proximal limbs
* Sympathetically mediated and sensitive to catecholamines
* Tender points
* Central sensitization
How do you diagnose FM?
- 3 month duration
- 7 of the 18 trigger points
- Fatigue
- Absence of other disorders
