Cell types and Myelination

Nervous tissue is composed of?

Neurons and glial cells

What are neurons?

high specialized single nerve cell

What are neuroglial?

supports, nourish, and protect neurons, and maintain the interstitial fluid that bathes them 

What are the neuroglial cells?

Schwann cells, satellite cells, astrocytes, oligodendrocytes, microglial cells, and ependymal cells

What are the cells of the PNS?

schwann cells and satellite cells 

(PNS) What are schwann cells?

form myelin sheath around a single axon in the PNS

(PNS) What are satellite cells?

flat cells that surround and provide structural support, and the exchange of materials between the ganglia and the interstitial fluid

(PNS) What is the ganglia?

clusters of nerve cell (neuronal) bodies of the PNS

What are the neuroglial of the CNS?

astrocytes, oligodendrocytes, microglial cells, ependymal cells

(CNS) What is the function of astrocytes? (3)

1) microfilaments provide support 

2) processes of astrocytes surround capillaries and filter what neurons need, maintaining the BBB

3) maintain the chemical environment for the generation of nerve impulses

(CNS) What are the functions of oligodendrocytes?

form and maintain the myelin sheath of multiple CNS axons 

(CNS) What are the functions of microglial cells?

phagocytize debris and microbes around neurons

(CNS) What are the functions of ependymal cells?

produce, maintain, and assist with the circulation of cerebrospinal fluid

form the blood cerebrospinal fluid barrier

What cells perform myelination?

Schwann cells (PNS) and oligodendrocytes (CNS)

What is the myelin sheath?

layer of phospholipids and proteins that insulates and protects axons

What are the functions of myelin sheaths?

sheath electrically insulates axons (prevents electrical signals from stopping) and increases the speed of conduction (nerve impulse)

Schwann cell: Myelin sheath formation (3)

1) schwann begins to wrap itself around an axon

2) cytoplasm of SC gets thinner and pushed out 

3) layers of the PM (phospholipid and proteins) form the myelin sheath 

Schwann cell: What is the neurolemma?

outer nucleated cytoplasmic layer of the SC, which encloses myelinated and unmyelinated axons 

The neurolemma is only found in?

PNS

(M) What are the nodes of Ranvier?

gaps in the myelin sheath that conduct impulses faster

(M) How do the nodes of Ranvier conduct faster?

They are central spots for channels to open and close, allowing the AP to “jump“ node to node

Differences with oligodendrocytes

neurolemma is not present

nodes of Ranvier are fewer in number

What is multiple sclerosis?

breakdown of the myelin sheath in the CNS, stops signals from transmitting 

What is Tay-Sachs disease?

inherited disorder, death of neurons in brain and spinal cord