Nerves Part 2 Flashcards
What is the difference between a glial cell and a Oligodendrocyte?
A single oligodendrocyte wraps around and ensheathes many different axons.
What is Dysmyelination/Hypomyelination?
Inherited myelin disease in which there is failure t myelinate axons during fetal life or early infancy.
What is demyelination?
The breakdown of pre-existing myelin; Slows down the conduction velocity and can make it impossible for the AP to proceed.
Describe Gullain-Barre syndrome.
Autoimmune damage to myelin and nodes of ranvier of peripheral neurons; Weakness or paralysis
Describe Multiple Sclerosis.
Autoimmune disease attacks oligodendrocytes; Resulting in demyelination of CNS neurons.
Describe Schwann cell function in the PNS.
Regulate environment of the axons but do NOT insulate axons electrically.
Where are unmyelinated axons in the CNS?
Within grooves made by folding of oligodendrocyte cytoplasm.
Describe the variability of synapses.
- Axon-dendrite
- Axon-Soma
- Axon-Axon
- Dendrite-Dendrite
What is the fate of a neurotransmitter?
Either degraded in the cleft or taken back up (active transport) into the presynaptic ending; Could also go into glial cells.
Discuss the Motor end plate.
The skeletal muscle cell membrane at the motor end plate has junctional folds that contain receptors for Ach (Nicotinic cholinergic receptors); These receptors keep the Ach confined to the region.
What is the fate of Ach?
It is degraded by acetylcholinesterase and transported to the basal lamina in the synaptic cleft; Made by the skeletal muscle cell.
Describe in general how ligand-gated ion channels work.
- First messenger binds to outward facing, ligand binding domain of receptor.
- Ligand binding cases a conformational change in receptor and opens the channel.
- Ions flow through via passive transport.
- Target cell depolarizes.
- Depolarization initiates an event in the cell.
What do gap junctions allow to happen?
They allow the flow of ions between cytoplasms of adjacent cells.
How do molecules and organelles get transported along the axon?
Microtubules; Microtubule associated proteins (MAPs) use ATP to genereate changes in shape which produces movement along the microtubule.
What are the two directions of axon transport?
Anterograde: From the soma, towards the axon terminal
Retrograde (Dyenin): From the axon terminal to the soma.
Discuss Anterograde transport.
Uses the Kinesin family of MAPs.
- Fast: Used to transport components of membranous organelles.
- Slow: Transports some proteins of the cytoskeleton and various enzymes.
Describe mixed nerves.
Mixed nerves have more than one type on nerve; Some are afferent axons, some are efferent. Some axons are myelinated, some are not.
What is the perineurium?
A protective barrier that surrounds and defines a bundle of axons (fasicle); Forms the blood-nerve barrier.
What is the Epineurium?
Dense Ct surrounding several fascicles to form a nerve trunk; Made by fibroblasts.
What is the Endoneurium?
Loose CT surrounding each myelinated axon or collection of unmyelinated axons; External to myelin and Schwann cell basal lamina.
What is a ganglion?
A cluster of neuronal cell bodies and glial cells outside the CNS; All derived from the neural crest.
Discuss the myelination of pre-ganglionic and post-ganglionic neurons.
Pre-ganglionic neurons are myelinated; Post-ganglionic neurons are unmyelinated.
Describe post-ganglionic neurons.
Numberous dendrites with a single unmyelinated axon.
What are satellite cells?
Glial cells that surround, support and sustain the post-ganglionic cell bodies
Whats the difference between a Schwann cell and an oligodendrocyte?
A single Oligodendrocyte provides myelin to more than one internode segment and to more than on neuron.
