Pain Flashcards
Nociceptors
free nerve endings present in most types of tissue that are activated by thermal, mechanical, or chemical stimuli. They are the terminal portions of two types of afferent neurons, A-delta and C fibers.
Afferent neurons
sensory neurons that carry info from sensory stimuli towards the CNS
Efferent neurons
motor neurons that carry info from the CNS to the muscles to cause a reaction
A-delta fibers
afferent neurons that transmit detailed info rapidly from peripheral cutaneous (skin) structures. Transmit pain signals that are sharp and localized.
C-fibers
afferent neurons that transmit info from deep tissues (e.g. joints, viscera) and do so more slowly than A-delta fibers. Transmit pain signals that are dull, aching, and diffuse.
A delta and C- fibers send their impulses…
A delta and C- fibers send their impulses to the dorsal horn of the SC, where the impulses then travel to the thalmus via the spinothalamic tracts. The nerve signal is then projected to the sensory cortex to be interpreted and become a conscious pain sensation.
Gate control theory
A theory that helps to explain the regulation of pain, and how other stimuli can help to decrease the painful stimulus. A-delta and C-fibers synapse with secondary neurons, which sends pain signals to the brain, however, they also synapse with inhibitory interneuron at the same junction. A-alpha and A-beta afferent fibers also synapse at this junction and function to excite the inhibitory neurons located there. Therefore, nerve signals from A-alpha and A-beta can activate the inhibition of pain signals (closing the gate). E-stim and massage stimulate A-alpha and A-beta fibers.
Endogenous Opiates
Pain regulation is also controlled by endogenous opiates known as opiopeptins (also known as endorphins). These substances bind to opiod receptors located throughout the nervous system resulting in pain inhibition.
Endogenous opiates (opiopeptins/endorphins) method of function
Opiopeptins have a direct effect on nerve signals by controlling the amount of calcium and potassium that move into and out of the cell during depolarization. They also have an indirect effect on nerve signals by inhibiting release of GABA, a substance that normally inhibits the activity of pain control structures, such as A-beta fibers.
Numerical pain rating scale
pain rating on a scale of 0-10 or 0-100
Visual Analogue Scale
a tool used to assess pain intensity using a 10-15 cm line with the left anchor indicating no pain and the right anchor indicating max pain.
Viscerogenic pain
pain that results from pathology of an internal organ, which can refer to a site distant from the organ. Viscerogenic pain does not change based on movement or positioning of the body part, as would musculoskeletal pain. Because the organs have innervation from multiple spinal cord levels and a low density of nerve receptors, the pain is often diffuse and poorly localized and may be accompanied by other systemic symptoms, such as NV, weight loss, pallor, profuse sweating, fever, and abnormal VS.
Common sites for viscerogenic pain
shoulder, scapula, back, chest, pelvis, sacroiliac joint, groin, and hip.
MI viscerogenic pain
The heart is innervated by C3-T4 spinal segments and thus cardiac pathology can result in referred pain to a variety of areas. A pt experiencing an MI may experience pain on the left side of the body in the chest, shoulder, neck, arm, mid-back, or jaw.
Kehr’s sign
Blood that accumulates in the abdominal cavity, often secondary to rupture of the spleen, can cause irritation of the diaphragm and refer pain to the left shoulder. Pain is referred to this region due to the innervation of the phrenic nerve (C3-C5). Kehr’s sign is positive when pressure to the upper abdomen or supine positioning results in left shoulder pain.
