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| The growth cones on initial azons that are later joined by other axons to create a large axon bundle |
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| Intermediate targets that influence the growth of a pioneering growth cone. They attract or repel the growth cone |
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| Bundling together of axons into tracts (a means of contact mediated growth. Previous axons can act as a guidance cue to some new axons) |
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| Effect the outgrowth of developing axons. They can be: local v long range, attactive v. repulsive, and targeted derived signals)--> sends growth cone in the correct directions towards its target |
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| Positional info is encoded in the form of gradients of signaling molecules at the target which would be detected by complementary gradients of receptors on the axons. (So positional info can be encoded by a small number of molecules) |
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| Neuroal Cell Adhesion Molecules. A member of the immunoglobulin superfamily where N-CAM binds to N-CAM via homophilic binding (Ca 2+ independent) |
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| (Ca 2+ dependent) Adhension between individual cadherins is by homophilic binding |
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| Transmembrane proteins that are involved in adhension of cell surfaces. Adhesive interactions between integrins and other macromolecules is by heterophilic binding |
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| Ventral Midline (and Guidance Cues) |
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Definition
| Acts as an important intermediate target for axons. Growth cones are able to sense specific cues at the midline that influence their decision to cross or not to cross |
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| Diffusable messanger that binds to Robo and tells growth cone to turn around and go back! |
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| Receptor for Slit, Robo is downregulated when axons cross the ventral midline and upregulated to prevent axon from crossing |
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| Function to modulate or guide axon growth. Found on axons and allow the axon to respond to various growth factors in the local environment |
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| Family of secreted proteins that are diffusable and cell associated. They bind to axonal receptors (DOC/UNC 40 (attractive) and UNC 5 (repulsive)). These receptors determine whether the actions of netrin is attractive or repulsive. |
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Definition
| Repulsive factors for axonal guidance. (p33) The receptors are the plexins |
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| A nerve derived factor. It helps clustering of receptors ACh and other components of the NMJ for efficient synaptic transmission. It organizes postsynaptic differentiation. |
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| Contains signals for presynaptic differentiation and postsynaptic differentiation |
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| Nerve Growth Factor (NCF) |
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Definition
| Survival of certain neurons depends on NGF. NGF has three protein subunits. It is a retrograde survival factor...when NCF reaches the soma it affects transcription and tranlation |
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Definition
Due to a large role of trophic factors (NGF related chemicals such as BDNF, NT3, etc)
For example: If NGF is present in a cut postsynaptic neuron, then regeneration and reinnervation occurs. |
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Definition
| Molecule that depolarizes microtubules (Blocks the retrograde transport of NGF from target cell to soma--> regeneration of damaged neuron thereby inhibited) |
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| The loss of the distal segment due to degeneration of an axon |
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| List the 3 major chances that occur during neuronal degeneration |
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Definition
1) RER breaks down and moves to periphery of the cell body
2) Increase in free polyribosomes, mRNA transcription and protein synthesis (trying to rebuild the broken)
3) A damaged nueron's regeneration success is largely dependent on finding the appropriate target to innervate |
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| List 3 major components of Reinveration |
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Definition
1) Axon's proximal segment forms sprouts and regrowth begins
2) Axonal sprouts migrate into the conduit formed by the residual endoneural sheath that surrounded the previous axon
3) Axon sprouts migrate to find a target--> if suitable target found-->survivial occurs |
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| contain bundles of microtubules, neurofilaments and scattered mitochondria |
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| Microtubule associated protein. Found in the dendrites and axons. Those in the microtubule have a higher molecular weight than those found in the axon |
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| provide termendous increase in surface area available for synaptic contacts |
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| AKA Trigger Zone--> region of action potential intiation that is more reliable guide to understanding the functional focal point of the cell |
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| Multipolar cell that is small neuron that usually is an interneuron |
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| A type of intermediate filament found in nerve cells. They are composed of 3 10nm diameter tubules. They are more abundant than microtubules in axons whereas microtubules are more amount in dendrites. They undergo modification in Alzheimer's disease. |
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1) Do not form synapses
2) Have one type of process
3) Retain the ability to divide
4) Are less electrically excitable than neurons |
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| A type of macroglia and are found primarily in gray matter. Nucleus is ellipsoid with flecks of chromatin |
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| Found primarily in white matter and have smoother cell body than protoplasmic ones |
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| Support neurons in their immediate vicinity. Provide a physical barrier between cells, maintain ionic and pH equilibrium. Proliferate and phagocytize dead cells. Often form glial scars. Metabolize neurotransmitters by removing them from synaptic cleft. |
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| Located in gray and white matter. Interfascicular oligodendroglia- found in white matter and form and maintain myelin nearby |
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| Myelin in between nodes p 68 review |
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| Derived from early germinal epithelium. They line the ventricles of the brain and central canal of spinal cord. The cilia of these cells move CSF in the ventricles |
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| From mesoderm. Throughout the nervous system and are responsible for proliferating ad migrating to the site of injury via phagocytosis. |
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