Chapter Fourteen 

Outside Intervention 

Oligodendrocytes are the myelinating cells

Myelination is formation of the myelin sheath around a nerve to allow for improved conduction

of the central nervous system

They are the end product of a cell lineage

the pattern of cell divisions during its development

which has to undergo a complex and precisely timed program:

neurons are believed to have permanently blocked their capacity to proliferate once they are differentiated

migration,

migration during development brings different classes of neurons together so that they can interact appropriately

differentiation,

 a complex process requiring the regulation of proliferation, cell death (apoptosis), differentiation and maturation

the nervous system matures to connect and shape the neuronal circuitry and to keep it functional

and myelination

form a membraneous sheath surrounding axons called myelin, thereby insulating the axon. This myelination, as it is called, can greatly increase the speed of signals transmitted between neurons

glial cells:

Schwann cells,

support cells of peripheral neurons

That deliver messages 

astrocytes,

 a sub-type of glial cells in the central nervous system. Star-shaped, their many processes envelop synapses made by neurons

 They perform metabolic,

the process of glucose and lipid metabolism in the brain, which is critical for:

neurotransmitter synthesis

endogenous chemicals that allow neurons to communicate with each other throughout the body

synthesis of small-molecule neurotransmitters occurs within presynaptic terminals 

at the end of an axon and is the place where the electrical signal (the action potential) is converted into a chemical signal (neurotransmitter release)

The enzymes needed for transmitter synthesis are synthesized in the neuronal cell body and transported to the nerve terminal 

maintaining balance in neural systems.

structural,

structurally-based neurons, which include:

unipolar,

A unipolar neuron only has one nerve process extending from the cell body: an axon that extends into dendrites

Dendrites comprise numerous cytoskeletal structures and they collect and store all incoming information from axon terminals

multipolar,

a type of neuron that possesses a single axon and many dendrites 

bipolar,

defined as a type of neuron that has one dendrite and one axon, with the cell body located between these two structures

and pseudo-unipolar neurons

a cell that only occurs as a sensory neuron. In a pseudounipolar neuron, the nerve process extending from the cell body splits into two branches or axons. As a result, the neuron has two separate axons that independently divide into dendrites at the ends.

homeostatic,

the purpose of homeostasis is to maintain the established internal environment without being overcome by external stimuli that exist to disrupt the balance

and neuroprotective

relative preservation of neuronal structure and/or function. It includes neuroprotective agents that protect against neuronal injury 

tasks such as clearing excess neurotransmitters, stabilizing and regulating

the blood-brain barrier,

Is a selective semi-permeable membrane

thin biological sheets of material that allow certain molecules to pass through them more easily than others

between the blood and the interstitium of the brain, allowing cerebral blood vessels to regulate molecule and ion movement between the blood and the brain.

and promoting synapse formation

 a highly regulated process resulting in morphologically distinct subcellular structures

morphologically meaning in a way that relates to the structure and form 

subcellular meaning contained within the cell 

in the pre and postsynaptic sites to transmit and receive signals

The presynaptic terminal is at the end of an axon and is the place where the electrical signal (the action potential) is converted into a chemical signal (neurotransmitter release)

microglia,

Microglia are resident cells of the brain that regulate brain development, maintenance of neuronal networks, and injury repair

and ependymal cells 

regulate what flows in and out of the brain to maintain overall brain health

to finally produce the insulating sheath of axons