Neurocytology Flashcards
What are the features of a typical vertebrate neuron?
Cell body, dendrite, axon, terminal branches of axon
What is the cell body?
Region of integration of incoming information and metabolic center of the cell. Large amount of condensed rER. Nissl Substance
What is a Dendrite?
Major area of reception of incoming information. Apical and basal locations on cell body. Tend to taper in diameter. Cell can give rise to many dendrites from soma.
What is a Axon?
Specialized for carrying information away from the cell body to other parts of the circuit. Cell tend to give rise to only one axon but it branch extensively.
What are the axon terminals?
Also known a boutons/varicosities)
Location of synapse
What is a characteristic of dendrites on axons found in the cerebellum?
Form tree like structure. Extensive network of dendrites
Neurons found in the cerebellum are called?
Purkinje cell
Neuron found in the cortex are called?
Pyramidal cell
How can you tell a dendrite from a axon?
Dendrites are thick and axons are small
What are nissl bodies and how do they stain?
They are rER and free ribosomes and they stain dark`
Where are motor neurons located?
Spinal cord
This neuron has one axon and several dendrites. It can be found in most vertebrates
Multipolar neuron
This neuron has one axon and one dendrite. It can be found in the retina (photoreceptors) and the olfactory epithelium.
Bipolar Neuron
This neuron contains central and peripheral axons. No dendrites. Can be found in the dorsal root ganglia.
Pseudo-unipolar Neuron
The peripheral axon of the pseudo-unipolar neuron behaves like what?
Like a dendrite
This neuron has on axon with dendritic branches and is found in the autonomic system and invertebrates
Unipolar Neuron
What is the Neuron doctrine?
Explains that together neurons form a network of interconnected cells, but not through a syncytial arrangement.
What is the structure of a synapse?
It is where the synaptic knob meets the target cells (postsynaptic neuron)
What is the state of synaptic knob when the nerve terminal is at rest?
Voltage Gated calcium channels are closed. Neurotransmitter is within a synaptic vesicle
What is the state of the synaptic knob when the nerve terminal is activated by an action potential?
Voltage Gated Calcium channels are open. Vesicle fuses with membrane releasing Neurotransmitter into synaptic cleft. Neurotransmitter binds to receptors on postsynaptic cell
What is the order of synaptic transmission?
- Vesicle “dock” at active site
- Action potential leads to influx of calcium
- Rise in Calcium triggers vesicle fusion and release of transmitter
- Transmitter diffuses across cleft and binds to receptors
- Membrane retrieved by coated vesicles for reuse
What is a characteristic of the neuromuscular junction?
Deep invagination on the postsynaptic cell (muscle cell)
How are synaptic vesicles (SV) formed?
- Delivery of SV components to PM
- Endocytosis of SV components to form new SV directly or endocytosis of SV components and delivered to endosome
- Budding of synaptic vesicle from endosome
- Loading of neurotransmitter into vesicle
- Excocytosis in response to AP
Where can synaptic vesicles be found?
Only in nerve cells and some endocrine cells.
What is the order of the synaptic vesicle cycle?
- Docking at the plasma membrane
- Priming - done by ATP
- Fusion Exocytosis (activated by calcium)
- Endocytosis (also activated by calcium)
- Translocation (takes in hydrogen ions)
- Endosome fusion
- Budding
- Loading of NT
- Translocation to plasma membrane
What are the vesicle membrane proteins involved in exocytosis?
Snyaptobrevin and synaptotagmin.
What is the v-snare?
Synaptobrevein (located on vesicle) - involved in targeting and docking
What is the t-SNARE?
Synataxin (located on pre-synaptic PM). Bound by accessory proteins SNAP-25
What is Synaptotagmin?
Believed to be a calcium-sensitive regulatory protein in the complex that binds to syntaxin. Allows fusion of vesicle with membrane (located on vesicle)
What is Neurexin?
Presynaptic protein that help to connect neurons at the synapse. Focuses on alignment
Neurexin works with what other membrane bound protein?
Neuroligin. Post synaptic neuron. Assist in binding as well
What is the effect of Tetanus Toxin?
It blocks the release of inhibitory neurotransmitters. Which can lead to muscle spasms.
What are the four types of dendritic spines?
Stubby, Spine (thin), Mushroom, and Filopodium
Gap junctions for what type of synapse?
Electrical synapses
What makes the electrical synapse different?
No synaptic cleft
No neurotransmitter being released
What are microglia?
Macrophages of the CNS Invade the brain during fetal development and maintain residence in parenchyma. Stain poorly migrate actively Important in neuropath
A glial cell responsible for response to injury to trauma by proliferation and phagocytosis of debris. Spider like cells
Microglia
What are the differnt type of macroglia?
Myelin forming Cells 1. Oligodendrocytes 2. Schwann Cells Supporting cells 1. Astrocytes 2. Satalite
Oligondendrocytes and Astrocytes belong to which part of the nervous system?
Central
Schwann cells and Satellite cells belong to which part of the nervous system?
Peripheral
How were scientist able to begin seeing the glial cells in the lab.
They used Golgi preparations
What is the function of astocytes?
Interface between neurons and pia, ependyma, and blood vessels. Structural support take up NT Ionic balance Guide axons (radial glia) immune response
Thsi cell forms glia scars after a CNS injury. Covering the portion of the damage neuron preventing regeneration.
Astrocyte
What are ependymal cells?
Cells that line the ventricles of the brain and help produce and move CSF. Are also supported by astrocytes
Remnants of embryonic neuroepithelium
What are the physiological aspects of ependymal cells?
Cuboidal or columnar epithelial
Microvilli and cilia on luminal surface
What stain is used to identify ependymal cells.
Nissl Stain
What two cells are going to found in the spinal cord?
Astrocyte and Oligodendrocyte
in the periphery both myelinated and unmyelinated axons are covered by?
Schwann cells
One Schwann cells covers ______ _________ axon
One, myelinated
(can wrap around muliple unmyelinated axons.
T/F In the CNS unmyelinated axons are wrapped by oligodendrocytes
False
What is the function of oligodendrocytes?
Each on can wrap around several axons but only a short portion of that axon is myelinated.
How does myelin form around and axon?
Newest layer is closer to the axon. Layers are tucked under as they form
What form due to the tightness and squeezing of the cytoplasm in the myelin?
Paranoadal pockets
Areas where axon bulges out and that are unmyelinated are called what?
Node of Ranvier
Axoplasmic membrane at each node posses high concentrations of what?
Voltage gated Na+ channels
How does the wave of depolarization go down the axon?
It jumps from node to node (saltatory conduction) rather than proceeding along the entire membrane of the axon.
What is MS?
Mutiple Sclerosis
Oligodendrocytes are affected.
Repeated episodes of inflammation of nervous tissue. Inflammation destroy myelin -> scar tissue
