Review of Cellular Neuroanatomy Flashcards
What are glia
They provide physical support to neurons (the other of the two principal cell types in the nervous system).
Also provide electrical insulation for impulse conductance
Provide metabolic exchange between the the vascular system and the Nervous sytem
Cell Body of a Neuron called?
Soma
Name the two types of processes that extend from a soma?
Axon and Dendrites
Electrical input for the cell comes trhough?
Dendrites
Electrical output for a cell comes through
Axon
Gray Matter =
unmyelinated tissue
Primaruly somas and dendrites
White matter=
tissue containing myelinated axons
Myelin=
lipid wrapping on axons
Soma of Neurons is especially rich in what cell organelle?
rER…because of the large amount of proteins it produces
What stain is used to look for Neuronal somas and proximal dendrites
A Nissl stain
What is a Nissl stain
A stain which preferentially stains Nissl substance made up of Nissl bodies…basophillic mass that is made up primarily of rER and ribosomes (protein synthesis bundles).
Nissl stain typically stains what parts of a neuron?
Cell body (stroma) and proximal dendrites…does not extend into the axon
rER stacks appear as islands in the Nissl stain
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Axons usually form where?
the soma at the axon hillock specifically
What is the axon Hillock
An area that is free of cell organelles. The beginning of an axon.
Axonal initial segment is?
The area of the axon that originates at the hillock and goes to the beginning of the myelination line
What are dendritic spines?
Places where dendrites receive information from other Neurons via synapses. This is especially true for excitatory inputs
Which part of the axon is generally the site of action potential initiation?
Axonal initial segment
What are axon collaterals
major branches of an axon
Neurons whose axons contact muscle or glands are known as?
motor neurons
Neurons are classified based on what?
Dendritic structure (number and pattern of dendrites)
What are principal cells
Projection neurons, meaning they integrate information and send axons to other brain areas.
Golgi Type 1 cells are
Principal cells…just means they have a long projection axon
Interneurons are
cells that do not send their axon out of the local brain area. Also called local circuit neurons
Interneurons are also classified as
Golgi Type 2 cells
Synapses are
specialized junctions that allow neural signals to be communicated from one cell to another
Two types of synaptic transmissions and they are?
Chemical and Electrical
Electrical synapses are formed as direct connections from one cell to another via gap junctions.
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Chemical synapses = electrical signal in the presynaptic neuron is transduced into release of a chemical transmitter that traverses a synaptic cleft to bind to receptors on the postsynaptic neuron
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Synapses classified how?
By their subcellular target (axosomatic - synapse between axon and soma)
Most excitatory synapses are what
formed on dendritic spines…called axospinous
Vertebrate chemical synapses are
Unidirectional…they only transmit info from the presynaptic neuron to the postsynaptic
Know the pattern of sending a signal via a synapse
1) The presynaptic bouton contains membranous synaptic vesicles that contain neurotransmitter
2) On an incoming nerve impulse, the entry of calcium causes synaptic vesicles to release their contents into the synaptic cleft
3) Specialized receptor proteins located in the postsynaptic density bind the neurotransmitter and generate another electrical signal in the postsynaptic cell.
On the basis of their function, neurotransmitters can be divided into three classes:
excitatory- these types of synapses increases the probability that the postsynaptic neuron will fire an action potential. Examples are synapses containing acetylcholine ( at nicotinic receptors) or glutamate
inhibitory- reduces the probability that the postsynaptic neuron will fire an action potential. Examples are synapses with glycine or GABA
modulatory - influences how excitatory and inhibitory signals are integrated.
Excitatory means
Inhibitory means
something that increases the probability of an action potential
Inhibitory means something that decreases the probability for an action potential
Gray’s type 1 synapse
Excitatory
Gray’s type 2 synapse
Inhibitory
Gray’s type 1 synapses (excitatory) are found mostly on what?
Dendrites
Type II synapses (inhibitory) are found where?
Somas mostly
In electrical synapses, passive flow of electrical current from one cell to the next is achieved via?
Gap junctions
Gap junctions are made up of what
Connexons (6 connexins make a connexon). These pores form a connection between the cytoplasm of two opposing cells
ELectrical synapses can be bi-directional
whereas chemical synapses are uni-directional
How are proteins made in the soma transported out of the soma and through processes (axons and dendrites)
- Packed into cargo vesicles and transported along microtubules toward their destination via ratchet-like action.
- Remember, there are separate engines for movement to the soma and away from the soma
- To the soma= Dynein…moves vesicles retrograde (to the soma)
- Away from the soma (anterograde)- Kinesin
Schwann cells do what?
Provide myelination in the PNS
Oligodendrocytes do what
myelination in the CNS
Astrocytes do what
Provide general support and serve as part of the blood brain barrier in the CNS.
Two types of astrocytes are?
Fibrous:
Protoplasmic
Microglia do what?
They mediate phagocytosis and response to inflammation in the CNS… The immune cells of the brain
Schwann cells, oligodendrocytes, astrocytes, and microglia are all what type of cells
Neuroglia—-supporting cells
Schwann cells provide myelination in the PNS. Myelination does what
electrical insulation
Node of Ranvier is what?
The area in between two schwann cells…an unmyelinated area. This is the area where action potentials regenerate
Endoneurium
Thin connective tissue layer that surrounds each nerve fiber
Perineurium
Surrounds the nerve fascicle itself
One oligodendrocytes has several processes and each process myelinates one axon, therefore one oligodendrocyte myelinates several axons
know
Astrocytes do what
move metabolites to and from neurons
Perineural feet?
Perivascular feet
processes from astrocytes that make ocntact with neurons
processes from astrocytes that make contact with blood vessels and myelin
What are satellite cells
small cuboidal cells of neural crest origin….function as the astrocytes of teh PNS
Ependymal cells
Line the ventricles of the braina nd the central canal of the spinal cord…cells are often cilliated and form simple cuboidal or low columnar epithelium.
