1. Microanatomy: neurons
Domina Petric, MD

2. 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.

3. Neurons I.

4. 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

5. Main parts of the neuron
Input zone: dendrites and cell body.
Conducting zone: axon.
Output zone: axon terminals.

6. 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

7. 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.

8. 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

9. 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.

10. En passant or in-passage synaptic connections
Synaptic boutons
En passant or in-passage synaptic connections

11. 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
....

12. Non-neuronal cells of the CNS
II.

13. 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

14. 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

15. 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.

16. Oligodendrocytes
Wikipedia.org

17. 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).

18. 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.

19. Microglial cell

20. 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.

21. 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).

22. Mature oligodendrocytes
Glial stem cells
Glial stem cells
More stem cells
Mature astrocytes
Mature oligodendrocytes
Mature neurons

23. Oligodendroglial precursors
They are scattered throughout the white matter.
Mainly give rise to mature oligodendrocytes, but may also generate astrocytes and neurons.

24. Blood-brain barrier
It is specialised permeability barrier between the capillary endothelium and the extracellular space in neural tissue.

25. Literature
neuroscience/lecture: Leonard E. White, PhD, Duke University
interactive-biology.com
Wikipedia.org
BrainFacts.org