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54 Cards in this Set
- Front
- Back
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What three considerations simplify the task of studying connections? |
1) Individual neurons aren't unique 2) Different types of neurons aren't randomly distributed (clustered into layers or nuclei) 3) We now have a clearer idea of the functional importance of key nuclear groups |
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What is contained in gray matter? |
Cell bodies and dendrites of neurons and glial cells |
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What is contained in white matter? |
Axons grouped into tracts |
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What is contained in the dorsal horn of the spinal cord? |
Sensory nuclei that are relay sites for somatosensory information |
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What is contained in the ventral horn of the spinal cord? |
Motor nuclei that innervate skeletal muscles |
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What is the intermediate zone of the spinal cord? |
Between dorsal and ventral horns Contains neurons whose axons terminate either in the ventral horn or the brain stem and cerebellum Preganglionic sympathetic neurons (intermediolateral cell column) |
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What connects the gray matter on the two sides of the spinal cord? |
Central canal |
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What are the three columns in the spinal cord white matter? |
1) Dorsal columns: primary afferent axons that carry somatic sensory information to the brain stem 2) Lateral columns: axons that ascend to higher levels and axons that project from nuclei in the brain stem and cortex upon motor neurons and interneurons in the gray matter 3) Ventral columns: axons that relay information about pain and thermal sensation to higher levels and descending motor axons that control posture |
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What is the ventral commisure? |
Cross spinal cord contains axons with information about pain and axons for posture |
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What are the four major regions of the spinal cord? |
1) Cervical 2) Thoracic 3) Lumbar 4) Sacral |
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What two important features determine the organization of the spinal cord? |
1) Axons from the periphery are added successively from the lower region, so sacral has little white matter compared to gray and vice versa 2) Regions of spinal cord that innerate limbs have larger ventral and dorsal horns than the thoracic region |
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Where are the cells of neurons that relay information from the skin, muscles, and joints? |
Dorsal root ganglion within the vertebral column immediately adjacent to the spinal cord |
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Describe dorsal root ganglion neurons. |
Pseudo-unipolar neurons with a central and a peripheral branch |
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What cells carry somatosensory information from the head and neck? |
Cranial sensory ganglia |
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Where do the central processes of the DRG enter the spinal cord? |
The dorsal tip of the dorsal horn |
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What are the three types of connections that determine how the sensory signal is used? |
1) Connections with interneurons and motor neurons are for reflex activity 2) Connections with neurons whose output ascends through the thalamus are for perception of sensory stimuli 3) Connections with neurons of the reticular formation are for behavioral arousal and awareness |
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How are central axons of DRG arranged in the dorsal column? |
Somatotopically |
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Describe the path of neurons that convey tactile sensation. |
Project central axons into the spinal cord where the axon ascends rostrally in the dorsal columns |
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Where are axons that enter the cord in the sacral region found? |
Near the midline |
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What is the principal pathway for somatosensory perception? |
The dorsal column-medial lemniscal system |
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Where do axons in the DCML system synapse? |
Dorsal column nuclei in the medulla |
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Where do axons in the DCML system decussate? |
Medulla |
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What do pontine nuclei do? |
Cross the midline and run to the contralateral half of the cerebellum Cerebellar control of movement and posture |
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What is contained in the pons? |
Pontine nuclei Corticospinal tract |
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What are thalamocortical connections made through? |
The internal capsule |
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What is the internal capsule? |
A large fiber bundle that carries most of the axons running to and from the hemisphere |
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What are the two functional groups of the thalamic nuclei? |
Relay nuclei Diffuse-projection nuclei |
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What are three features of relay nuclei? |
1) Each processes either a single sensory modalitiy or input from a distinct part of the motor system 2) Each projects to a specific local region of cortex 3) Each receives recurrent input from the region fo the cortex to which it projects |
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Describe diffuse-projection nuclei. |
More widespread connections Influence cells both in the cortex and in the thalamus itself Govern the level of arousal of the brain |
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What are the groups of nuclei in the thalamus? |
Lateral Medial Anterior Intralaminar Midline Reticular |
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What is the largest thalamic nucleus? |
Pulvinar, projects to the parietal-temporal-occipital association cortex |
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What does the lateral nucleus do? |
Receives sensory and motor input and projects to specific regions of sensory, motor, and association cortex |
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What do the medial nuclei do? |
Relay nuclei |
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What do the anterior nuclei do? |
Emotion |
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What is the only nucleus with inhibitory output and that doesn't project to cortex? |
Retricular |
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What is the name for cortex that isn't laminated? |
Allocortex |
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What the two main types of cortical neurons? |
Pyramidal cells Several types of nonpyramidal cells |
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Describe pyramidal cells. |
Cell body shaped like a pyramid, apex pointed towards brain surface Apical dendrite from the apex Basal dendrites from the base that course laterally Axon may have several collateral branches and termines in a different area of cortex Projection interneuron |
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Describe nonpyramidal cells. |
Round, smaller cell bodies Often stellate in shape Dendrites may arise from all aspects of the cell body Axon branches profusely and stays local Local interneurons |
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How many layers in the neocortex? |
6 |
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Describe the layers of the neocortex. |
1: few cell bodies, axons that run laterally, close to pia mater 2: small pyramidal neurons 3: large pyramidal neurons, output 4: rich in nonpyramidal cells, afferent input from thalamus 5: largest pyramidal cells, give rise to long axons that descend to basal ganglia, brain stem and spinal cord 6: pyramidal cells, many of which project back the thalamus, white matter below carries axon |
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What causes variation in laminar structure in different regions? |
1) Layer four expanded in primary sensory areas because there are so many inputs 2) Layer 5 is prominent in motor areas |
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How many Brodmann areas are there? |
50 |
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What is the direct pathway for voluntary movement? |
Corticospinal tract |
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What is the origin of the CST? |
Layer 5 of primary motor cortex |
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What is the pathway of the CST?
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Layer 5 of primary motor cortex descend through white matter, internal capsule, medullary pyramids, decussate in the medulla, 10% cross over at the level of termination
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What is another name for the CST? |
Pyramidal tract |
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What does bulbar mean? |
Medulla |
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What two structures have an important role in motor integration? |
Cerebellum and basal ganglia |
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What are the three deep cerebellar nuclei? |
Fastigial Interposed Dentate |
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What does the corpus striatum do? |
Regulating speed of movements |
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What mediates the control of movement by the cerebellum and basal ganglia? |
Brain stem and thalamic motor nuclei |
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What happens with damage to the cerebellum? |
Delays the onset of movements Affects the timing and trajectory of movements |
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What happens with damage to the basal ganglia? |
Slows voluntary movement Results in uncontrolled, involuntary movements |
