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This 4 page Class Notes was uploaded by Sam Stegelmann on Sunday February 8, 2015. The Class Notes belongs to Bil 268 at University of Miami taught by Dr. Zhongmin in Fall. Since its upload, it has received 73 views. For similar materials see Neurobiology in Biology at University of Miami.
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Date Created: 02/08/15
Neurons and Glia Understanding the individual and concerted actions of brain cells will allow us to understand the origins of our mental abilities Glial cells mainly support neurons through insulation support and nourishment o The term glia came from quotgluequot in Greek The Neuron Doctrine Cells are roughly 001005 mm in diameter Formaldehyde was used in the early 19th century to harden the soft brain tissue so it could be sliced and observed under a microscope o A quotmicrotonequot would then slice the brain Histology The microscopic study of the structure of tissues Franz Nissl introduced the Nissl Stain which only stained Nissl bodies rough ER 0 Distinguishes neurons from glia o Allows for the study of the brain39s cytoarchitecture The Golgi stain uses silver chromate and stains the entire neuron Cell bodysomaperikaryon Neurites axons and dendrites Cajal said that neurons communicate by contact not continuity neuron doctrine o Golgi advocated the neural net The Prototypical Neuron The Soma 0 Contains cytosol which is potassium rich and organelles o The nucleus contains all the genetics stuff 0 The rough ER has large concentrations of ribosomes With free polyribosomes existing in the cytoplasm Proteins are synthesized usually where they will be used 0 The smooth ER is thought to help fold proteins and regulate the internal concentrations of substances such as calcium 0 The Golgi apparatus is where the quotposttranslationalquot chemical processing of proteins occurs Believed to sort proteins that are destined for various areas of the neuron o Mitochondria cellular respiration Cristae folds two membranes and matrix inside 0 Neuronal membrane The composition of proteins on the membrane varies depending on whether it is the soma the dendrites or the axon o Cytoskeleton Scaffolding or bones of the cells 0 Microtubules Large and run longitudinally down neurites Microtubules are hollow and made from the tubulin protein small and globular Microtubuleassociated proteins MAPs participate in the regulation of microtubule assembly and function 0 Anchor microtubules to one another and elsewhere 0 The tau MAP when pathologically changed can lead to Alzheimer39s disease Alzheimer39s disease This condition arises when the tau microtubule becomes over prevalent due to abnormal secretion of an amyloid protein and begins to rapidly replicate These quotneurofibrillary tanglesquot grow and grow until they displace all the neurons39 organelles and even the entirety of the cytoplasm killing the cells 0 Micro laments Made of actin molecules and particularly prevalent in neur es Help provide structural help 0 Neuro laments Present in other cells as quotintermediate filamentsquot Structure is slightly different however Analogous to bones and ligaments of the skeleton The Axon 0 Three parts Axon hillock Axon proper The middle of the axon Axon terminal terminal bouton Where the axon comes in contact with other dendritescell bodies 0 The collective term is terminal arbor 0 Contains no rough ER and very few if any free ribosomes No protein synthesis 0 Axonal membrane protein composition is fundamentally different than that of the soma membrane Proteins in the axonal membrane originate from the soma o Axonal branches are known as axon collaterals Those that return to communicate with the same cell that gave rise to the axon are known as recurrent collaterals o The larger the axon diameter the faster the action potentialnerve impulse o Sends signals through the synapse Synaptic cleft Area between neurons Presynaptic and postsynaptic membranes Neurotransmitters sent through the synapse o Innervation is the process of making synaptic contact 0 Differences in axon terminal cytoplasm No microtubules are present in the cytoplasm Contains many synaptic vesicles Contains many mitochondria and many membranous proteins 0 Axoplasmic Transport The movement of material down the axon Material is enclosed within vesicles which is then walked down the microtubules by Kinesin protein quotlegsquot 0 All movement of material down the axon is known as anterograde transport as opposed to retrograde transport towards the soma o Retrograde transport uses dynein proteins Wallerian degeneration is the degeneration of axons when disconnected from the soma Dendrites o Collectively known as a dendritic tree 0 Individually known as dendritic branches 0 Receptors detect neurotransmitters in the synapse o Dendritic spines are specialized structures that receive some types ofsynapUcinput Abnormal dendritic spines can be associated with mental retardation o Herpes Herpesvirus is taken in through the axon terminals in the lips and mouth and is moved through retrograde transport to the soma where it remains dormant until a trigger usually stress causes the virus to replicate and return to the nerve ending causing cold sores o The composition of dendritic cytoplasm is very similar to axonal but poyribosomes are present in the dendrites Classifying Neurons Glia Neurons can be classi ed according to the total numbers of neurites o Unipolar bipolar or mutipoar In the cerebral cortex cells can be stellate star shaped or pyramidal pyramid shaped Neurons can be spiny or aspinous depending on whether their dendrites have spines Connchons 0 Primary sensory neurons Those that take in sensory information 0 Motor neurons Those whose axons command movements 0 lnterneurons Those that form connections with other neurons Axon Length 0 Golgi type projection neurons Those that have a long axon Pyramidal cells 0 Golgi type II local circuit neurons Those with short axons Stellate ces Astrocytes Most numerous glia that probably in uence whether a neurite can grow or retract 0 These cells regulate the chemical content of the extracellular space 0 Actually have membrane proteins that remove neurotransmitters from the synaptic cleft and regulate the concentration of potassium ions in the extracellular uid Myelinating Glia o Oligodendroglial and Schwann cells provide layers of insulating myelin to axons Myelin sheath denotes the entire covering of an axon Nodes of Ranvier are the exposed regions where the membrane proteins propagate action potential Oligodendroglia are found only in the CNS Schwann cells are found only in the PNS Ependymal cells provide the lining of uid lled ventricles within the brain 0 Also help direct cell migration during brain development Microglia act as phagocytes to remove dead debris
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