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mcb 163 lec#5
Spinothalamic System
| Question | Answer |
|---|---|
| the protopathic alerting system | Spinothalamic system for pain and temperature |
| functions of the spinothalamic | Perceiving pain, Temperature, Immuno cascades |
| thermal noniceptors | 45oC or <5oC; Aδ, C, thinly, myelinated or unmyelinated |
| mechanical nociceptors | intense pressure, Aδ |
| polymodal nociceptors | high intensity of both thermal and mechanical, chemical |
| Viscera | silent nociceptors |
| Viscera | normally depolarize from chemical insults and/or inflammatory response. Typically, not activated by noxious stimuli |
| nociception | "the neural processes of encoding and processing noxious stimuli" |
| noxious stimuli | "an actually or potentially tissue damaging event." |
| pain-BURNING | Aδ(thermal-mech) |
| pain-FREEZING | C (thermal-mech) |
| pain-slow murning... | C |
| I-“marginal zone” | Aδ, nociceptive-specific, some wide dynamic range neurons |
| II-“substansia gelatinosa” | C, interneurons (excite and inhib), mix of nociception and nonnoxious |
| V-Aβ and Aδ | wide dynamic range; to the brainstem, various thalamic nuclei. Many visceral afferents (nociceptive) |
| Melzack's "Gate control theory" | the idea that the perception of physical pain is not a direct result of activation of nociceptors, but instead is modulated by interaction between different neurons, both pain-transmitting and non-pain-transmitting. |
| gate control theory | "pain is in the brain"; afferent regulation |
| Gate control theory thus explains how stimulus that activates only nonnociceptive nerves can inhibit pain | The pain seems to be lessened when the area is rubbed because activation of nonnociceptive fibers inhibits the firing of nociceptive ones in the laminae |
| lissauer tract (posterolateral tract) | contains centrally projecting axons carrying non-discriminative pain and temperature information (location, intensity and quality), |
| substantia gelatinosa | gelatinous substance consists mainly of neuroglia, but contains a few nerve cells and fibers; |
| ischemia | brought on by a myocardial infarction (heart attack) where pain is often felt in the neck, shoulders, and back rather than in the chest, the site of the injury. |
| phantom limb | is the sensation of pain from a limb that has been lost or from which a person no longer receives physical signals |
| VPL (ventral posterolateral nucleus) | nucleus of the thalamus. |
| spinoreticular tract | ascending pathway in the white matter of the spinal cord, positioned closely to the lateral spinothalamic tract. The tract is from spinal cord---to reticular formatiom--- to thalamus. |
| spinoreticular tract is responsible for | pain such as waking up, affective and vegatative functions |
| centromedian nucleus of the thalamus | physiological role involves attention and arousal, including control of the level of cortical activity |
| Fast pain travels via type Aδ fibers to terminate on the dorsal horn of the spinal cord where they synapse with the dendrites of ___________ | neospinothalamic tract |
| paleospinothalamic tract involves... | Slow pain is transmitted via slower type C fibers to laminae II and III of the dorsal horns, together known as the substantia gelatinosa. |
| degree of pain can be modified by the | Central gray |
| central gray | is the gray matter located around the cerebral aqueduct within the midbrain. It plays a role in the descending modulation of pain and in defensive behaviou |
| raphe nuclei | main function is to release serotonin to the rest of the brain |
| Reticular formation | attention and vigilance |
| Interlaminar thalamic nuclei | diffuse sensory/motor cortex involvement |
| Hypothalamus | ANS (para) |
| Autonomic Nervous System (ANS) | is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions |
| Cingulate Gyrus | limbic, vast array of projections, integral part of the limbic system |
| cingulate gyrus | is involved with emotion formation and processing, learning, and memory |
| Central gray or periaqueductal gray (PAG) | incoming emotional. Outgoing (descending) projections to the midline of the medulla. |
| Raphe nuclei | project to dorsal horn and depress nociception. |
| spinomesencephalic tract | fibers originate in the spine and terminate in the mesencephalon, another name for the midbrain, the part of the brain in which the PAG resides. |
| Enkephalins | endogenous ligands, or specifically endorphins, as they are internally derived and bind to the body's opioid receptors |
| dynorphins | class of opioid peptides that arise from the precursor protein prodynorphin; addiction... |
| endorphins | are endogenous opioid polypeptide compounds. They are produced by the pituitary gland and the hypothalamus in vertebrates during strenuous exercise, excitement, pain and orgasm and they resemble the opiates |
| Hyperalgesia | heightened sensitivity |
| Phantom limb | combination of referred pain and plasticity concepts |
| (DC v. ST)Fine touch, vibration | DC |
| (DC v. ST)Small receptive field | DC |
| (DC v. ST)Little overlap | DC |
| (DC v. ST)Narrow range | DC |
| (DC v. ST)No presyn inhibition | DC |
| (DC v. ST)Heavy mye=rapid | DC |
| (DC v. ST)Prominent in higher vert. | DC |
| (DC v. ST)evolutionary history=New | DC |
| (DC v. ST)main ascending target=VP of the thalamus | DC |
| (DC v. ST)pain, temp, crude touch | ST |
| (DC v. ST) large receptive field | ST |
| (DC v. ST)great overlap | ST |
| (DC v. ST) presynaptic inhibition | ST |
| (DC v. ST)light myelination | ST |
| (DC v. ST)prominent in lower vertebrates | ST |
| (DC v. ST)evolutionary history=old | ST |
| (DC v. ST)main ascending targets=VP, CM, medial nuclear group, posterior thalamus, central gray | ST |
| first synapse of spinothalamic system (ST) | dorsal horn |
| anterolateral system | is an ascending pathway that conveys pain, temperature (protopathic sensation), and crude touch from the periphery to the brain |
| second synapse of the spinothalamic system | posterior thalamus |
| third synapse of ST | indirect targets are the central gray, reticular formation,and hypothalamic centers |
| interlaminar thalamic nuclei can activate | large expanses of sensory and motor cortex |
| central gray participates in | the descending control of nociception |
| reticular formation helps to direct | attention and vigilance |
| hypothalamus is a source of | preganglionic parasympathetic synaptic drive for the autonomic nervous system |
| fourth synapse of the ST | cerebral cortex, where the representation of nociception is surprisingly diffuse |
| brain stem systems can regulate | the excitability of C fibers |
| central gray in the midbrain projects | to the raphe nucleus in the pons |
| raphe-spinal (serotonergic) projections descend through | the spinal cord near the zone of Lissauer |
| presynaptic inhibition alters | the perception of pain due to the central neural adjustments of set point |
| nature of nociceptive reflexes after loss of supraspinal modulating systems | withdrawal is spasmodic, poorly coordinated, and involuntary |
| flexor reflex afferent pathways in the spinal cord can modulate | crude withdrawal from nociceptive stimulation even after severe cortical damage or spinal trauma |
| strategy for reducing intractable (chronic) pain | reducing ganglion cell output with subdural anesthetic injections |
| strategy for reducing intractable (chronic) pain | anterolateral cordotomy to interrupt spinothalamic lemniscal axons ascending toward the brain stem |
| strategy for reducing intractable (chronic) pain | medullary tractotomy to sever trigeminothalamic lemniscal fibers in cases of trigeminal neuralgia |
| strategy for reducing intractable (chronic) pain | direct electrical stimulation of spinothalamic areas in the dorsal horn with implanted electrodes |
Created by:
greerbaby
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