NSCI 110 1st Edition 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 pathway a Different input to these regions from the putamen results in inhibition or excitation of the thalamus which projects to the motor cortex b The substantia nigra also plays a modulatory role in these pathways II The cerebellum also exhibits homuncular organization a Lateral and medial hemispheres control different body regions b Cerebellar cortex consists of three functionally distinct layers III The cerebellum connects to the brainstem via the cerebellar peduncles a Spinocerebellar tract provides a pathway for information traveling from the cerebellum to the cortex Outline of Current Lecture I The spinothalamic tract consists of lateral and dorsal pathways II Pain is an unpleasant sensory and physical experience a Responses to pain may be initial or later b There are many classifications of pain depending on certain psychological and physiological factors III Nociceptors detect damage or potential damage a Responsive to mechanical chemical or thermal stimuli IV Perceiving pain occurs in the frontal lobe Current Lecture Spinothalamic tract o 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 tract o 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 thalamus o Third order neurons exit thalamus project to the somatosensory cortex Lateral spinothalamic tract o First order sensory afferents enter spinal cord synapse at that level of the spinal cord onto the second order neurons These 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 o 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 cortex PAIN Pain is an unpleasant sensory and emotional experience associated with real or potential tissue damage o Experimental neuroscience shows more than one type of pain acute inflammatory visceral neuropathic ect Response o 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 pain o If persistent this is referred to as chronic pain Referred pain site of cause is not the site of pain perception o 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 damage o May be responsive to mechanical chemical or thermal stimuli o Some are responsive to many types of stimuli polymodal Thermal extremes high intensity mechanical stimulation pain producing chemicals may all depolarize the same neuron o Some harmful stimuli is not detected initially only a delayed response is Perceiving pain is a brain function occurring in the frontal lobe o Initial response damage o Inflammation sensitized polymodal neurons resulting in hyperalgesia Decreased pain threshold o How would the experience change if a patient had a frontal lobotomy Patients perceived less pain o Pathways arising from the lateral ST tract have extensive connections to carry nociceptive information to Reticular formation and periaqueductal grey arousal
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