Chapter 12: Glial Cells

Flashcards covering vocabulary, cell types, functions, and structures associated with glial cells and cerebrospinal fluid.

Glial Cells (Neuroglia)

Non-excitable cells found in both the CNS and PNS that are smaller and outnumber neurons, capable of undergoing mitosis, and function to protect, nourish, and physically support neurons.

Microglia

Small, rare phagocytic cells of the immune system in the CNS that replicate during infection, engulf infectious agents, and remove debris from damaged CNS tissue.

Astrocytes

The most abundant CNS glial cells, characterized by a star shape and perivascular feet, which form the blood-brain barrier, regulate interstitial fluid, provide structural support, assist in neuronal development, and replicate to fill space left by dying neurons.

Blood-Brain Barrier (BBB)

A protective mechanism formed by astrocyte perivascular feet wrapping around brain capillaries with tight junctions and a thickened basement membrane to strictly regulate substance entry into the CNS.

Perivascular Feet

Astrocyte extensions that wrap around capillaries in the brain to form the blood-brain barrier and regulate the chemical environment by soaking up excess $K^+$ ions and neurotransmitters.

Ependymal Cells

Ciliated simple cuboidal or simple columnar epithelial cells lining the brain ventricles and central canal of the spinal cord that form and circulate cerebrospinal fluid (CSF).

Brain Ventricles

Cavities within the brain lined with ependymal cells that contain cerebrospinal fluid and connect with each other and the central canal of the spinal cord.

Cerebrospinal Fluid (CSF)

A clear, colorless liquid surrounding the CNS that provides buoyancy (reducing apparent brain weight by cushions tissue, and transports nutrients and wastes

Choroid Plexus

A specialized tissue located in each brain ventricle consisting of ependymal cells and blood capillaries that actively produces cerebrospinal fluid.

CSF Composition

Filtered and modified blood plasma containing higher concentrations of $Na^+$ and $Cl^-$ and lower concentrations of $K^+$, $Ca^{2+}$, and glucose compared to blood plasma.

Subarachnoid Space

A space in the tissue layers surrounding the brain through which cerebrospinal fluid flows after exiting the fourth ventricle.

Arachnoid Villi

Extensions through the tissue layers of the brain that drain cerebrospinal fluid from the subarachnoid space into the dural venous sinuses.

Dural Venous Sinuses

Venous spaces located between the two layers of the dura mater into which cerebrospinal fluid drains.

Myelination

The process of wrapping an axon with a lipid-rich myelin sheath to insulate the neuron and increase signal propagation speed via saltatory conduction.

Neurolemmocytes

PNS glial cells, also called Schwann cells, that encircle individual axons to form a myelin sheath up to $1\,mm$ long and push their cytoplasm and nucleus to the periphery.

Neurilemma

The peripheral outer layer of a neurolemmocyte containing its cytoplasm and nucleus, formed during myelination in the PNS.

Neurofibril Nodes

Also known as nodes of Ranvier, these are the unmyelinated gaps along an axon between adjacent neurolemmocytes or myelin segments.

Oligodendrocytes

Large CNS glial cells with slender extensions that wrap around and myelinate $1\,mm$ segments of multiple axons without forming a neurilemma.

Satellite Cells

PNS glial cells arranged around neuronal cell bodies in a ganglion that electrically insulate the cell body and regulate nutrient and waste exchange.

Unmyelinated Axons

Axons that lack a myelin sheath and propagate nerve signals more slowly; associated with Schwann cells without myelin in the PNS and unassociated with oligodendrocytes in the CNS.