Microanatomy: neurons Domina Petric, MD
Cell types in central nervous system Neurons are primary processors of neural signals. Neuroglia supports the electrical and chemical functions of neurons. Vascular endothelium provides for the supply of blood to brain tissue.
Neurons I.
Neurons fundamental unit of the function in the central nervous system metabolically similar to other somatic cells Distinctions from other somatic cells are: rich diversity of morphology unique bioelectrical properties specialisations for intercellular communications
Main parts of the neuron Input zone: dendrites and cell body. Conducting zone: axon. Output zone: axon terminals. http://interactive-biology.com/wp-content/uploads/2012/04/canstockphoto472954612-779x1024.jpg
Dendritic spines Increase surface area of the dendrite and provide a place for synaptic contact from other neurons. Cells with dendritic spines are excitatory cells. Wikipedia.org
There are cells with smooth dendrites (without spines). Inhibitory cells There are cells with smooth dendrites (without spines). Those cells have an inhibitory effect on the surrounding cells.
Pyramidal neuron Basal dendrite Can be found in cerebral cortex. Cell body is shaped like a pyramid. This neuron has one thick and long, apical dendrite among other thinner dendrites, that grows from the apex of the pyramidal neuron towards the surface of the brain. Shorter and thinner dendrites are called basal dendrites. Apical dendrite Wikipedia.org
Axons Some of the axons can be long up to half a meter or even more. Other axons are short as 100 microns or less. Axons generate action potential which propagates from cell´s body towards the synapse.
En passant or in-passage synaptic connections Synaptic boutons En passant or in-passage synaptic connections www.raosyth.com
Classes of neurons cortical pyramidal neuron or projection neurons (often excitatory) cortical stellate neuron or interneuron (excitatory, inhibitory) retinal bipolar neuron retinal ganglion cell retinal amacrine cell cerebellar Purkinje cells ....
Non-neuronal cells of the CNS II.
Neuroglia supports the metabolic and signaling functions of the neurons participates in neuron circuit formation and synaptic plasticity makes myelin contributes to the formation of blood-brain barrier participates in inflammatory response in injured neural tissue, including phagocytosis of cellular debris contributes to the formation of the scar tissue in damaged brain and spinal cord
Wikipedia.org It is found primarly in grey matter. Astrocyte It is found primarly in grey matter. It is closely associated with neuronal cell bodies, dendrites and synapses. Wikipedia.org
Astrocyte functions are: Helps maintain ionic ballace of extracellular fluid. Takes up and processes neurotransmitters from synaptic clefts. Assists in the formation of new synapses and circuits. Contributes to formation of blood-brain barrier and brain-ependymal (ventricular) barrier. Contributes to the formation of scars in necrotic neural tissue following injury.
Oligodendrocytes Wikipedia.org
Oligodendrocyte It is found in white matter and forms myelin. Schwann cells form myelin in peripheral nerves. Myelin aids in the propagation of neural signals along myelinated axons. Oligodendrocytes present antigens that influence the outgrowth of axons in developing and recovering brain. Oligodendrocytes present antigens that are subject to immunological attack in diseases of the CNS (multiple sclerosis).
Myelin Insulates axons by generating layers of membraine that wrap around axon segments. Decreases ionic leakiness of the membrane. Nodes of Ranvier allow for the economical concentration of ion channels and ion pumps that are necessary for electrical signaling in axons.
Microglial cell http://www.brainfacts.org/-/media/Brainfacts/Article-Multimedia/Brain-Basics/Neuroanatomy/3D-Microglia.ashx
Microglial cell It is special type of mononuclear phagocyte that resides in the CNS. It is derived from hematopoetic precursor cells that migrate into the brain during development. In the dormant state it is called a remified cell. Active form is ameboid cell (injury, inflammation) engaged in phagocytic activity of the cellular debris. Activated microglia secrete signaling molecules (cytokines) that modulate local inflammatory responses.
Located near the ventricles, often adjecent to blood vessels. Glial stem cells Located near the ventricles, often adjecent to blood vessels. They may give rise to more stem cells, mature astrocytes or mature oligodendrocyte or mature neurons. They exibit key properties of somatic stem cell like proliferation, self-renewal and potency to make all the cells of a given tissue (neural tissue).
Mature oligodendrocytes Glial stem cells Glial stem cells More stem cells Mature astrocytes Mature oligodendrocytes Mature neurons
Oligodendroglial precursors They are scattered throughout the white matter. Mainly give rise to mature oligodendrocytes, but may also generate astrocytes and neurons.
Blood-brain barrier It is specialised permeability barrier between the capillary endothelium and the extracellular space in neural tissue.
Literature https://www.coursera.org/learn/medical- neuroscience/lecture: Leonard E. White, PhD, Duke University interactive-biology.com Wikipedia.org www.raosyth.com BrainFacts.org