Term
| How many neurons are in each of the two major somatosensory pathways? (they form a chain from the receptors to the cerebral cortex) |
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Definition
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Term
| 3 neurons that form the major somatosensory pathway chain from the receptors to the cerebral cortex |
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Definition
1. primary sensory neuron (cell body in a spinal ganglion or in a cranial nerve ganglion)
2. secondary sensory neuron (has its cell body in the gray matter of the spinal cord or in the brain stem)
3. tertiary sensory neuron (cell body in the thalamus) |
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Term
| What does it mean that both somatosensory pathways are "crossed"? |
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Definition
| signals from one side of the body are brought to the cerebral hemisphere of the other side |
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Term
| What does it mean that somatosensory pathways are "somatotopically organized"? |
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Definition
| neurons that conduct signals from different parts of the body are kept separate |
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Term
| What type of fibers continue without synaptic interruption rostrally in the dorsal columns, without synaptic interruption in the cord? |
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Definition
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Term
| Where does the first synaptic interruption occur for thick dorsal root fibers? (it is also where the cell bodies of the secondary neurons lie) |
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Definition
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Term
| What forms the medial lemniscus? |
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Definition
| the secondary axons crossing in the medulla to end in the thalamus on the opposite side |
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Term
| Where do tertiary neurons of the dorsal-medial lemniscus pathway send their axons from the thalamus? (it is in the post-central gyrus) |
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Definition
| primary somatosensory cortex |
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Term
| 5 things that the dorsal column-medial lemniscus pathway is important for perception of (hint: it has a prevalence of thick fibers conducting from low-threshold mechanoreceptors) |
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Definition
1. touch
2. pressure
3. vibration
4. kinesthesia
5. discrimination aspects (most important!!) (the ability to distinguish differently placed & different kinds of stimuli) |
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Term
| Does the central pathway followed by signals conducted in thin dorsal root fibers follow the one that the thick fibers take? |
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Definition
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Term
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Definition
| the axons of secondary neurons in the thin dorsal root pathway cross to the other side of the spinal cord |
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Term
| 2 things that the spinothalamic tract is important for perception of (hint: it transmits information mainly from A delta & C dorsal root afferents) |
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Definition
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Term
| posterior parietal cortex |
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Definition
| the location of further analysis & integration with other sensory modalities after sensory information reaching the SI is processed |
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Term
| 3 major subdivisions of the thalamus (hint: they are delimited by the Y-shaped internal medullary lamina) |
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Definition
1. anterior nuclear group
2. medial nuclear group
3. lateral region/part (made up of a dorsal & a ventral nuclear group) |
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Term
| intralaminar thalamic nuclei |
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Definition
| several less clearly defined groups of neurons that lie within & close to the internal medullary laminae |
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Term
| Why are specific thalamic nuclei called "specific"? |
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Definition
| most of them are relays in precisely organized, major pathways that reach only certain parts of the cerebral cortex |
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Term
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Definition
| the fibers occupying the medial part of the dorsal columns; conduct signals from the lower part of the trunk & legs |
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Term
| Where do gracile fascicle fibers end? |
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Definition
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Term
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Definition
| the lateral part of the dorsal columns; conduct signals from the upper part of the trunk & the arms |
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Term
| Where do fibers of the cuneate fascicle terminate? |
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Definition
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Term
| How does organization of the spinal fibers of the dorsal columns change along the cord? |
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Definition
| initially, they are arranged segmentally, but as they ascend, the fibers rearrange themselves so that they are organized somatotopically |
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Term
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Definition
| a particular cytoarchitectonic subdivision where the primary afferent fibers ascending in the dorsal columns end; part of the dorsal column nuclei |
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Term
| Where does the medial lemniscus end? |
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Definition
| ventral posterolateral nucleus (VPL) |
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Term
| ventral posteromedial nucleus (VPM) |
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Definition
| where fibers from the sensory trigeminal nucleus end; located most medially in a separate nucleus from the VPL |
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Term
| Neurons of the dorsal column nuclei that send their axons in the medial lemniscus most likely use _____ as transmitter |
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Definition
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Term
| 2 structures that send their axons to the postcentral gyrus after the internal capsule |
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Definition
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Term
| secondary somatosensory area (SII) |
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Definition
| where some fibers from the VPL & VPM end; situated in the upper wall of the lateral central fissure |
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Term
| What is the response to electrical stimulation of SI or SII? |
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Definition
| sensory phenomena such as tingling, itching, numbness, etc. |
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Term
| What type of mechanoreceptors are primarily in the dorsal columns in the skin, muscles, & joints? |
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Definition
| low-threshold mechanoreceptors |
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Term
| Are there more rapidly-adapting or slowly-adapting sensory units in the dorsal columns? |
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Definition
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Term
| Do the dorsal column sensory units have large or small receptive fields? |
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Definition
| small (mostly in the distal parts of the extremities) |
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Term
| post-synaptic dorsal column neurons |
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Definition
| axons that end in the dorsal column nuclei but do not belong to primary sensory units; neurons with their cell bodies in the dorsal horn |
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Term
| 2 types of receptors that activate post-synaptic dorsal column neurons |
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Definition
1. low-threshold mechanoreceptors
2. visceral nociceptors |
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Term
| Most studies indicate that acute damage to the dorsal columns produces _____ |
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Definition
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Term
| What response is characteristic of the lesions that affect the dorsal column-medial lemniscus system? |
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Definition
| disturbances of voluntary movements |
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Term
| tract of Lissaur (zona terminalis) |
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Definition
| the thinnest among the ascending & descending branches of the dorsal root fibers that form a small bundle immediately dorsal to the dorsal horn |
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Term
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Definition
| fibers that ascend without interruption as far as the thalamus |
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Term
| 2 things that collaterals to the brain stem nuclei off of the spinothalamic fibers are involved in |
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Definition
1. autonomic control
2. behavioral responses to signals from nociceptors |
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Term
| The majority of spinothalamic tract fibers are located in the _____ (anteriorly within the lateral funiculus) |
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Definition
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Term
| The major group of spinothalamic cells is located in _____, particularly in those parts that receive A delta fibers from the dorsal roots |
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Definition
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Term
| The second major population of spinothalamic cells are located in _____ |
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Definition
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Term
| Are spinothalamic cells found in laminae VII & VIII? |
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Definition
| yes! more ventrally & scattered |
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Term
| Where do the numerous small neurons in lamina II which are contacted by dorsal root C fibers send their axons? |
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Definition
| dorsally into lamina I (where spinothalamic cells can be influence) & ventrally in the dorsal horn to contact other interneurons (which form synapses on spinothalamic cells in laminae V, VII, & VIII) |
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Term
| Are there a lot or a few very small interneurons & neuroactive substances in the dorsal horn? |
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Definition
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Term
| 4 classifications of the spinothalamic cells in the cord (based on their response properties) |
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Definition
1. low-threshold units (neurons that react only to light mechanical stimuli)
2. wide dynamic range units (neurons that react to stimuli of high intensity & to light stimuli)
3. high-threshold units (neurons that respond only to stimuli of an intensity sufficient to activate nociceptors)
4. thermosensitive units (neurons that respond only to either warming or cooling of the skin) |
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Term
| What is the goal of cordotomy? |
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Definition
| to alleviate intense pain |
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Term
| 3 structures that receive signals from nociceptors & participate in autonomic behavioral responses to nociceptor activation |
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Definition
1. reticular formation
2. PAG
3. parabrachial nucleus |
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Term
| Are nociceptive neurons easily sensitized by prolonged stimulation? |
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Definition
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Term
| 3 types of components of the stress response |
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Definition
1. autonomic
2. somatic
3. endocrine |
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Term
| Signals from proprioceptors are conveyed to the _____ |
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Definition
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