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HISTOLOGY CENTRAL NERVOUS SYSTEM

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									           HISTOLOGY: CENTRAL NERVOUS SYSTEM
                     From September 12
1) Neurons, Glia (astrocytes and oligodendrocytes), Ependymal Cells, and CNS macrophages are the
    cells found in the CNS.
2) Cells lining the neural tube which are pseudostratisfied columnar epithelium make up the entire CNS
    (and obviously the cellular components).
3) A specific population of neurons is “born” when they undergo a final mitosis during a defined period
    of embryogenesis.
4) An oligodendrocyte can invest many axons or one axon can be invested by many oligodendrocytes.
    Astrocytes join to form the foot processes that line the BBB. Purkinje cells and pyramidal cells can
    receive many simultaneous stimuli because of their many dendrites. As one, long continuous fiber
    pseudounipolar neurons can conduct impulses through the body very rapidly.
5) Vesicles full of fun stuff like adrenaline and acetylcholine (or maybe just peptides) are formed at trans
    Golgi network. These vesicles are transported down to synaptic terminals along microtubules (usually
    due to an influx of calcium from the extracellular space). The vesicles fuse w/ the membrane at “active
    zones” and release their drugs into the extracellular space.
    transportdockingprimingfusionrecycling
6) A neurotransmitter is a chemical that crosses the synaptic cleft to be bound by receptors on post-
    synaptic membranes, causing channels to open, generating a nerve impulse. There are both excitatory
    synapses and inhibitory synapses. The most common neurotransmitters are acetylcholine (between
    axons and striated muscles) and norepinepherine (between axons and effectors in the autonomic
    nervous system). I’m still not sure if toaster ovens can act as neurotransmitters.
7) Besides neurotransmitters, the CNS makes: v-SNARES (used in the docking of vesicles), MTs (used in
    transport of vesicles down axons), DBH (a protein inserted into the synaptic cleft in an activity-
    dependent manner), NSFs (prepares the vesicles for fusion w/ the neuron’s membrane), NGF
    (attracts/repels axons during development). There are more chemicals, but this is getting tiring.
8) A neuroendocrine hormone usually acts on distant target cells. Neurotransmitters act on cells or tissue
    immediately adjacent.
9) A neuropeptide is an amino acid chain released in large dense-core vesicles. Often, the neuropeptide
    acts as a modulator to the neurotransmitters or simply as a synaptic transmitter.
10) The activity of neurotransmitters and neuropeptides is terminated when they stimulate/destimulate (I
    totally just made up that word) their target organs. Or, when they are reincorporated into vesicles in
    the presynaptic component by endocytosis (this is done so the duration of stimulation of the post-
    synaptic neuron is not excessive). Finally, the neurotransmitter can be incorporated into the post-
    synaptic neuron and packaged in that cell body by the sER for release into the next synapse.
11) The glia cells come in two types. He astrocytes form foot processes that line the blood brain barrier.
    They also buffer extracellular K+ and have uptake machinery for neurotransmitters.
12) The meninges are the three layers that cover the CNS and contain the CSF inside. They are secreted
    by CNS fibroblasts. From superficial to deep they are: the dura mater (dense, irregular CT), arachnoid
    mater (tenuous layer containing the CSF), and pia mater (the innermost layer of connective tissue that
    extends a short distance along blood vessels into the nervous tissue).
13) The blood brain barrier provides a barrier to molecules from blood into the CSF space and vice versa.
    It is formed by endothelial cells with tight junctions, basal laminae, and the foot processes of
    astrocytes.
14) The cerebrospinal fluid is formed continuously by specialized structure inside ventricles called choroid
    plexuses. It is formed by active transport of select ions, glucose and fluid from blood. Cells are
    excluded so CSF is clear. It cushions the spinal cord (and possibly nourishes it as well). It also helps
    us adjust to altitudes. It leaves the CNS by leaking out dural sleeves of the spinal chord. Who cares?
    WHO CARES?!!! I CARE, YOU BASTARD!

								
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