Nervous System 2 Flashcards
What are bundles of nerve fibres called?
fascicles
What forms myelin
Schwann cells and oligodendrocytes
Where does action potential occur?
Nodes of Ranvier
What makes up a single segment of myelin sheath?
Schwann cell
What is grey matter?
contains most of neuronal cell bodies and dendrites
What is white matter?
Contains most of the axons (myelinated)
What is the most abundant cells in the CNS?
Glial cells @ 90%
Where are ependymal cells found?
lining ventricles and spinal canal of spinal cord
What is the function of ependymal cells?
- Secrete CSF
2. Possess cilia to help with flow
What do ependymal cells look like?
simple, cuboidal, ciliated cells
What is the most abundant glial cell?
Astrocytes
What is the function of astrocytes?
- Control blood brain barrier (BBB)
2. Metabolic support
What are microglia?
Resident immune cells of the brain
What are the different shapes of microglia?
Ramified
Amoeboid
What is the function of microglia?
- Release nerve growth factors in resting state (stationary)
- Activated by infection/injury:
a. Alter shape (amoeboid)
b. Become phagocytic
c. Release chemicals
What is the function of oligodendrocytes?
Form myelin sheath around axons
When does myelin sheath formation begin in CNS?
About 4mths
What is the function of the BBB?
Protect brain from chem fluctuations in blood
What makes the BBB?
Endothelial cells with tight junctions
How does saltatory conduction work?
- Active node at peak of action potential (Na+ moves in)
- Adjacent inactive node into which depolarisation is spreading will soon reach threshold
- Remainder of nodes are still @ resting potential
- Previous active node returns to resting potential and no longer active
- Adjacent node that was brought to threshold by local current flow is active 2 peak of action potential
- New adjacent inactive node into which depolarisation is spreading will reach threshold
What is the cellular basis for myelination?
- Aid in debris removal and regeneration of peripheral nerves
- Providing fast conductance