Lecture 29 Outline of Last Lecture I. The globus pallidus internal is involved in the direct pathway to the cortex and the globus pallidus external is involved in the indirect pathwaya. Different input to these regions from the putamen results in inhibition or excitation of the thalamus, which projects to the motor cortexb. The substantia nigra also plays a modulatory role in these pathwaysII. The cerebellum also exhibits homuncular organizationa. Lateral and medial hemispheres control different body regionsb. Cerebellar cortex consists of three functionally distinct layersIII. The cerebellum connects to the brainstem via the cerebellar pedunclesa. Spinocerebellar tract provides a pathway for information traveling from the cerebellum to the cortexOutline of Current Lecture I. The spinothalamic tract consists of lateral and dorsal pathwaysII. Pain is an unpleasant sensory and physical experiencea. Responses to pain may be “initial” or “later”b. There are many classifications of pain depending on certain psychological and physiological factorsIII. Nociceptors detect damage or potential damagea. Responsive to mechanical, chemical, or thermal stimuliIV. Perceiving pain occurs in the frontal lobeCurrent Lecture- Spinothalamic tracto Lateral ST tract nociception Also called the “anterolateral system”o Dorsal ST tract hapsis and proprioception Also called the dorsal column medial lemniscus (DCML pathway)- Dorsal spinothalamic tracto First order neurons enter spinal cord, ascend dorsal column fasciculi ispilaterally Synapses in dorsal column nuclei (medulla)o Second order neurons exit dorsal column nuclei and cross over (decussate) to form the medial lemniscus Synapse onto third order neurons in ventrolateral part of thalamuso Third order neurons exit thalamus project to the somatosensory cortex- Lateral spinothalamic tracto First order sensory afferents enter spinal cord, synapse at that level of the spinal cord onto the second order neuronsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. NSCI 110 1st Editiono Second order neurons decussate contralaterally ascending the lateral spinal cord to form the medial lemniscus Synapse onto third order in ventrolateral nucleus (thalamus)o Third order neurons exit thalamus and project to the somatosensory cortexPAIN- Pain is an unpleasant sensory and emotional experience associated with real or potentialtissue damageo Experimental neuroscience shows more than one type of pain acute, inflammatory, visceral, neuropathic, ect.- Responseo Initial (sharp)o Later (burning, soreness)- Psychosomatic pain: emotional components of pain- Neurogenic pain: neurons damages, no specific nociceptor involved- Neuropathic pain: sensitization causes increased perception of paino If persistent, this is referred to as chronic pain- Referred pain: site of cause is not the site of pain perceptiono Visceral organs don’t have existing pain pathways, they are relayed through the limbs (though the primary afferent neurons that extend to the spinal cord from that limb)- Nociceptors detect damage or potential damageo May be responsive to mechanical, chemical, or thermal stimulio Some are responsive to many types of stimuli (polymodal) Thermal extremes, high intensity mechanical stimulation, pain-producing chemicals may all depolarize the same neurono Some harmful stimuli is not detected initially, only a delayed response is- Perceiving pain is a brain function occurring in the frontal lobeo Initial response (damage)o Inflammation (sensitized polymodal neurons, resulting in hyperalgesia) Decreased pain thresholdo How would the experience change if a patient had a frontal lobotomy? Patients perceived less paino Pathways (arising from the lateral ST tract) have extensive connections to carry nociceptive information to… Reticular formation and periaqueductal grey
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