Ma - Nervous Tissue Ii - Glia

Front 1

How many glia are in brain?

Back 1

-Glia outnumber neurons about 10 to 1 in CNS.
-About 10^13 in brain alone and many more in spinal cord, peripheral nerves, ganglia, etc.
-Present in huge numbers in both CNS and PNS

Front 2

Myelin - what produces it, what does it consist of

Back 2

-Myelin produced by glia-insulates and isolates neuronal processes
-Consists of multiple layers of glial cell membrane wrapped around neuron’s processes

Front 3

Nodes of Ranvier - what are they and function (1)

Back 3

-regularly spaced gaps in the myelin sheath around an axon or nerve fiber
-Speeds conduction velocity

Front 4

Myelin in PNS - what is it produced by, where is it found, what does it consist of, and how does it grow

Back 4

-Produced by Schwann cells
-Found around axons of motor neurons and dendrites of sensory neurons
-Consists of many layers of Schwann cell membrane, wrapped around axon. Every revolution of this cell lays down a layer of its membrane
-Grows by elongation of mesoaxon

Front 5

Nodes of Ranvier in PNS

Back 5

Nodes of Ranvier are gaps between adjacent Schwann cells, which is the only place where Axon membrane is directly exposed to extracellular fluid.

Front 6

What are Mobile Schmidt-Lanterman incisures?

Back 6

Mobile Schmidt-Lanterman incisures are conical defects in myelin, filled with Schwann cell cytoplasm, which act to nourish myelin

Front 7

What are Schwann Cells?

Back 7

-Schwann cells are a variety of glial cell that mainly provide myelin insulation to axons in the peripheral nervous system of jawed vertebrates.
-Schwann cells are the peripheral nervous system's analogues of the central nervous system oligodendrocytes.

Front 8

Unmyelinated Nerves and their relation to Schwann cells

Back 8

-Have slow conduction velocity
-Are associated with Schwann cells, often several to a cell
-Do not have multiple layers of Schwann cell membrane

Front 9

Myelin in CNS - what is it produced by, what does it consist of (2)

Back 9

-Produced by oligodendroglia
-Foot-like processes from oligodendroglia associated with several different neurons
-Have nodes of Ranvier and multiple layers of myelin

Front 10

Astrocytes in grey matter vs. Astrocytes in white matter

Back 10

-Protoplasmic astrocytes in gray matter
-Fibrous astrocytes in white matter
-Both associated with blood vessels and neurons
•Protoplasmic astrocytes are leaf-like in structure (looks like stars due to the large number of processes) while fibrous astrocytes have a thinner appearance
•Astrocytes create and maintain boundary layers between the CNS and PNS (barrier of protection)
•Border of astrocyte edge called the glial limitans

Front 11

Blood-Brain Barrier (BBB)

Back 11

-Many substances (including drugs) do not cross from blood vessels into brain parenchyma - thus we speak of a BBB
-Tight junctions at vascular endothelium prevent diffusion by packing the endothelial cells tightly
-Astrocyte foot processes may also play a role in regulating tightness of BBB by surrounding the endothelial cells of the BBB, providing biochemical support to those cells.

Front 12

Microglia - what are they, what activates them, what do they do, what system are they a part of, and what are they derivatives of

Back 12

-Small, pleomorphic phagocytes (pleomorphic means occurs in various forms and shapes). Perform immune surveillance function in CNS
-Recent sophisticated imaging studies show that mouse microglia are highly mobile in normal brains and are activated when BBB is breached
-Clean up debris from cell death and injury in CNS, so active after stroke, in neurodegenerative states, and around tumors
-Part of mononuclear phagocyte system, along with monocytes, macrophages, Kupffer cells, etc. and are bone marrow derivatives rather than neuroepithelial derivatives

Front 13

Satellite Cells - where are they (2), what do they do (3)

Back 13

-Surround neuron cell bodies in Ganglia
-Perhaps functionally isolate and/or support neurons
-Satellite cells serve as boundary capsules
-Present in autonomic ganglia and dorsal root ganglia

Front 14

Müller cells - what do they do

Back 14

-Other type of glia cell
-In neural retina, Müller cells support retinal neurons

Front 15

Bergmann glia - what do they do

Back 15

-Other type of glia cell
-Bergmann glia provide migratory pathways for developing neurons in brain

Front 16

Ependymal Cells - what are they, and what do they have (2)

Back 16

-Cuboidal-Columnar Cells That Line Lumen (central canal of spinal cord and ventricles of brain) in CNS
-Are remnants of proliferative neuroepithelium that produced stratified epithelium of spinal cord and brain (an embryonic remnant)
-Have apical cilia and microvilli

Front 17

Choroid plexus

Back 17

-The remnants of proliferative neuroepithelium are replaced by cuboidal cells with many microvilli in Choroid Plexus, which are patches of specialized tissue, made up of specialized ependymal cells, that produce Cerebrospinal Fluid (CSF)
-Choroid plexus is associated with a large number of blood vessels in lumen of the brain
-The choroid plexus is the area on the ventricles of the brain where cerebrospinal fluid (CSF) is produced by modified ependymal cells.