16. White Matter Anterior Funiculus (Anterior White Column) Posterior Funiculus (Posterior White Column) Fasciculus Gracilis & Fasciculus Cuneatus Lateral Funiculus (Lateral White Column) Gray Matter Anterior Horn ------------ --- motor Posterior Horn -------------- sensory Lateral Horn ----------------- autonomic (sympathetic) Gray Commissure -------- anterior and posterior Spinal Cord Internal Structure
17. Lamina I Posteromarginal Nucleus Lamina II Substantia Gelatinosa of Rolando Lamina III Lamina IV, V, VI ----- Nucleus Proprius Lamina VII - Intermediate Gray - I ntermediolateral cell column (ILM) - Clarke’s column (Nucleus dorsalis) - I ntermediomedial cell column (IMM) Lamina VIII Lamina IX ---------- Anterior Horn (Motor) Cell Lamina X ----------- Gray Commissure Lamina of Rexed
39. Pain Transmission Acute Pain Noxious Stimulus travel Via A-Delta and C-delta Fibers to Dorsal Horn (spinal Cord) Doral Horn A-Beta C-Delta Pain Transmitted to Higher Brain Centers Acute Pain STT (Spinal thalamic Tract) Thalamus and Cortex location and discrimination Retinacular Formation & Periaquductal Gray (PAG) Motor, sensory and autonomic Response Discrimination and Location of pain occurs during this sequence Limbic System & Cortex Descending Control Mech. Activated here once noxious stimuli reaches higher centers of brain. Incoming stimuli can be inhibited at various levels and endogenous opiates released
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46. Specificity theory: specific stimulus has a specific receptor which goes to a location in the brain The specific location identifies the pain’s quality. Thus any noxious stimulus applied to the surface of the skin results in a pain sensation. The evaluation of the type of pain occurs in the brain.
47. Pattern Theory: a pattern or coding of sensory information is created by different sensations. This theory is faulty due to the number of different types of receptors proven to exist.
64. Gate-Control Theory Gate is open Gate is closed Brain Spinal Cord Gating Mechanism Transmission Cells From pain fibers From other Peripheral fibers To brain Brain Spinal Cord Gating Mechanism Transmission Cells From pain fibers From other Peripheral fibers To brain
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72. Pain originating in the heart may feel as if it is coming from the skin because sensory impulses from those two regions follow common nerve pathways to the brain.
Algogenic substances include seretonin, histamine, and bradykinin – promote immune function activity, cause inflammation at the injured site.
Myelination increases the speed of transmission and so sudden, sharp pain gets transmitted to the cerebral cortex faster than dull or aching pain. This may be important for survival. The motivational and affective elements of pain appear to be influenced strongly by the C-fibers. They project onto the thalamus, hypothalamus, and amygdala. The A-delta fibers project onto particular areas of the thalamus and sensory areas of the cerebral cortex. Neurotransmitters are also involved, in particular, substance P.
Episodes of neuralgia occur suddenly and without apparent cause. Someone with causalgia may report that it feels like my arm is pressed against a hot stove. Typically follows a traumatic injury like a gun shot wound or stabbing and occurs at the site of injury. Is experienced well after the wound has healed. Phantom limb pain – example might be burning sensation in your toes after the limb and foot has been amputated. Person can experience a sense of their limb moving. Can persist for months and years. Pain can be felt as shooting, burning, or cramping (e.g., feel like hand is clenched with finger nails digging into the hand).
Pain signals arrive from the pain fibers (A-delta and C) at the spinal cord, along with signals from other peripheral fibers (A-beta) and the brain. The solid arrows depict stimulation conditions that tend to open the gate and send pain signals through. The dotted arrows indicate inhibition conditions. Pain signals enter the spinal cord and pass through a gating mechanism before activating transmission cells, which send impulses to the brain (from text by Sarafino EP. Health Psychology, Biopsychosocical Interactions, Third Edition. John Wiley & Sons, Inc. New York: 1998.)
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