The Synapse & Myelination

Synapse

the structure that allows neurons to pass signals to other neurons, muscles, or glands

presynaptic neuron

sends information towards synapse

postsynaptic neuron

the neuron on the receiving end of the synapse

Chemical Synapse

release and reception of neurotransmitters

Synaptic vesicles

Membrane-bounded compartments in which synthesized neurotransmitters are kept.

Unidirectional

moving in only one direction

Electrical Synapse

Connected by gap junctions, allowing action potentials to spread cell to cell

Bidirectional

functioning in two directions

Anterograde

away from cell body

What moves Anterograde?

mitochondria, enzymes

Retrograde

Toward cell body

What moves Retrograde

viruses, signal molecules

Myelination

the formation of a fatty sheath around the axons of a neuron

What does a myelin sheath do?

protects and electrically insulates axon (helps w/ speed)

Myelination - PNS

Schwann cells wraps around axon like a jelly roll

One cell forms one segment of myelin sheath

Neurilemma

bulge containing nucleus and most of cytoplasm

Nodes of Ranvier

gaps in the myelin sheath

Myelination - CNS

Oligodendrocytes can wrap up to 60 axons at once, but no neurilemma

White matter

regions of brain and spinal cord with dense collections of myelinated fibers

Gray matter

mostly neuron cell bodies and nonmyelinated fibers