Lecture 2 - Nerve Cell Structure and General Anatomy (Neurons and Glia) Flashcards
What type of macroglia are developmentally transient (last for a short period of time)? Are there any exceptions to this transientness?
The radial glia are developmentally transient with the exception of the Muller glia in the retina and the Bergmann glia in the cerebellum.
What words are the term “synapse” derived from?
Syn (together) and Haptein (clasp)
Both dendrites and axons have a microtubule network, but axons have more filamentous actin than dendrites (though dendritic spines are highly enriched in actin).
True
What type of neuron is pictured below?
Pseudounipolar Cell
If you pick up a hot coffee cup, why do you feel that you’ve picked up the cup long before you’ve realized how hot it is?
Large-diameter sensory neurons tend to be myelinated while small-diameter pain fibers tend to not be myelinated. As such, the sensory neuron that tells you you’ve picked up the cup transmits its signal much faster than the pain fiber that tells you how hot it is.
What are the 3 components of the tripartite synapse?
- Presynaptic Axon
- Postsynaptic Dendrite
- Associated Glial Astrocyte Process
What is block face electron microscopy?
Rather than sectioning the brain, you take a chunk of tissue and put it on the EM. You take a scan of the surface of the chunk, burn off a layer (just a few molecules thick), and then repeat.
What are the 4 compartments in neurons?
- Input Compartment
- Integrative Compartment
- Conductile Compartment
- Output Compartment
What 3 things do astrocytes do at synapses?
- Neurotransmitter Uptake, Processing, & Recycling: Pump excess glutamate into glia and away from synapses to improve temporal and spatial resolution of chemical neurotransmissions and prevent excitotoxicity.
- Responding to Neural Activity: Use their own neurotransmitter receptors (for glutamate, GABA, and ATP) to increase increase [Ca2+] in response to neural activity.
- Releasing Neuromodulatory Factors: Release gliotransmitters (D-serine, ATP, and glutamate) to modulate neuronal responses and influence synaptic plasticity.
True or False?:
Neurons with small, simple dendritic arbors can integrate large amount of information, such as for learning associations or storing memories.
False
Neurons with large, complex dendritic arbors can integrate large amount of information, such as for learning associations or storing memories.
True or False:?
Cajal proposed the Reticular Theory.
False
Golgi proposed the reticular theory.
What theory did Golgi propose and what did it dictate?
Golgi proposed the reticular theory which stated that the nervous system is made up of a network of fibres which are all fused into an interconnected mesh that function as a single unit.
True or False?:
Bipolar and unipolar cells tend to transmit information with high fidelity, such as in sensory transmission.
True
What are microtubules composed of?
Microtubules consist of helices of 13 tubulin dimers (alpha & beta). The end with beta-tubulin exposed is the end that can add more dimers and is called the (+) end.
True or False?:
Microglia are derived from ectoderm rather than yolk sac.
False
Microglia are derived from yolk sac rather than ectoderm.
Is glycine an excitatory or inhibitory neurotransmitter?
Inhibitory
What part of the neuron is the conductile compartment?
Axon
What disease is a result of CNS demyelination?
Multiple Sclerosis
What is the role of non-myelinating Schwann cells?
Non-myelinating Schwann cells bundle small-diameter (C-fibers) axons into Remak bundles and help maintain peripheral synapses.
True or False?:
Spine synapses are often times inhibitory and shaft synapses are excitatory.
False
Spine synapses are excitatory and shaft synapses are often times inhibitory.
What are the four main classes of microglia?
- Oligodendrocytes
- Astrocytes
- Ependymal Cells
- Radial Glia
What cells serve as dedicated immune cells in the CNS?
Microglia
What happens at the conductile compartment?
Action potentials are conducted.
What method of staining did Golgi use and how was it discovered?
Golgi used a silver impregnation stain. It was discovered by accident when he threw out a chunk of leftover brain along with chemicals used for photo reactions. The next day when he went to throw out his trash, he noticed the silver stain.
What cells myelinate in the CNS?
Oligodendrocytes
What theory did Cajal propose?
Cajal proposed the Neuron Doctrine.
What are dendritic spines?
Spines are filopodial protuberances that are studded along dendrites. At the tip of each spine is a postsynaptic density. Each of these can act as postsynaptic sites for a neuron as they are innervated with presynaptic cells.
What happens at the input compartment?
Excitatory (dendrites/spines) and inhibitory (soma) inputs are received.
True or False?:
Spines are the primary sites for excitatory synapses onto pyramidal neurons.
True
Where do microglia originate?
Microglia are born in the yolk sac during development and migrate into the brain early on.
True or False?:
One Schwann cell wraps many axons, but one axon is wrapped by just one Schwann cell.
False
One Schwann cell wraps jut one axon, but one axon is wrapped by many Schwann cells.
Where are ependymocytes found?
Ependymocytes line the ventricle are are foudn in the choroid plexus (which makes CSF).
What happens at the output compartment?
Action potentials cause the release of chemical neurotransmitters.
Is serotonin an excitatory or inhibitory neurotransmitter?
Excitatory
What are located at the postsynaptic density?
Neurotransmitter Receptors
What is the main role of ependymocytes?
The main role of epdenymocytes is to cirulate cerebrospinal fluid through beating their cilia.
What is pictured below?
Dendritic Spines
What do astrocytes look like?
They look like stars (hence astro-).
What is an action potential from a presynaptic cell converted into in a postsynaptic cell?
An EPSP or IPSP
True or False?:
Light microscopy provided clear morphological evidence of the synapse in the 1950s.
False
Electron microscopy provided clear morphological evidence of the synapse in the 1950s.
True or False?:
Genetic engineering can reveal neuronal pathways. For example, GPF can be expressed exclusively in one cell type to give Golgi-like morpholohical detail of identified cells.
True
Is glutamate an excitatory or inhibitory neurotransmitter?
Excitatory
True or False?:
Some early investigators thought that all transmissions in the nervous system were chemical.
False
Some early invertigators thought that all transmission in the nervous system was electrical and even proposed that although “gaps” did exist between cells there might be sparks of current that could cause one cell to excite the other.
True or False?:
Synaptic vesicles filled with neurotransmitters are found in the presynaptic terminal of the presynaptic neuron.
True
What molecular motor is responsible for fast retrograde transport?
Dynein
True or False?:
Spine size appears to correlate with functional efficacy. In general, a large synapse is a strong synapse.
True
Is noradrenaline an excitatory or inhibitory neurotransmitter?
Excitatory
What is the ratio of glia to neurons like in C. elegans relative to that of humans?
C. elegans have a ratio of 1:6 while humans have a ratio of >1:1. Humans have much more glia relative to neurons than C. elegans.
Is GABA an excitatory or inhibitory neurotransmitter?
Inhibitory
True or False?:
Retrograde transport occurs in the direction towards the plus-end.
False
Retrograde transport occurs in the direction away from the plus-end.
True or False?:
An axon will have one bouton that forms an “en passant” synapse.
False
One axon can have many boutons like beads on a string. These form “en passant” synapses.
How many times do Schwann cells wrap around an axon?
Around 100
Are neuroactive peptides excitatory or inhibitory neurotransmitters?
Excitatory
What syndrome is due to peripheral demyelination?
Guillain-Barré Syndrome
What markers are used to identify astrocytes?
Glial Fibrillary Acidic Protein (GFAP) and Aldehyde Dehydrogenase (ALDHL1)
Oligodendrocytes can only myelinate one axon.
False
Oligodendrocytes can myelinate many axons.
True or False?:
Einstein had a significantly lower glia:neuron ration in his associational cortex than the average man.
False
Einstein had a significantly higher glia:neuron ration in his associational cortex than the average man.
What type of neuron is pictured below?
Unipolar Cell
What type of neuron is pictured below?
Bipolar Cell
What gene mutation resulted in “the elephant man” and what does it do?
The NF1 gene mutation causes non-myelinating Schwann cells to form massive, grotesque tumours like those of “the elephant man”.
What type of cells have a highly complex morphology with many fine processes that interact with neurons, synapses, and blood vessels?
Astrocytes
What is the function of a myelinating Schwann cell? What kind of conduction do they lead to?
Schwann cells myelinate an axon by wrapping around it many times to act as an insulator. Due to the myelination, axons will propogate an action potential through saltatory conduction, which is when action potentials “jump” from one node of Ranvier to the next due to generation of action potentials only at these sites.
*(Saltare - Latin - To Hop or Leap)*
True or False?:
Smooth dendrites receive synapses on the shaft while spiny dendrites receive synapses on the shaft as well as on dendritic spines.
True
Who coined the term “synapse” and when?
The great British physiologist Charles Sherrington coined the term “synapse” in 1897.
What antigens are expressed by both oligodendrocytes and myelinating Schwann cells?
Myelin Basic Protein (MBP) and Proteolipid Protein (PLP)
What are boutons?
Boutons are axonal swellings that correspond to the presynaptic sites of neurotransmitter release. They form “en passant” synapses.
Is dopamine an excitatory or inhibitory neurotransmitter?
Excitatory
What happens at the integrative compartment?
Passively propagated signals are integrated in the soma and action potentials are generated at the axon initial segment (axon hillock).
What type of neuron is pictured below?
Purkinje Cell (of Cerebellum)
True or False?:
Astrocytes link neuronal activity to local blood flow.
True
Cajal and Sherrington were awarded the Nobel Prize in 1906.
False
Cajal and Golgi were awarded the Nobel Prize in 1906.
What do radial glia turn into?
Radial glia turn into an astrocytic cell type.
What are the two main types of cells in the nervous system?
Neurons and Neuroglia
Approximately how wide is the synaptic cleft?
20 nm
What part of the neuron is the integrative compartment?
Soma & Axon Initial Segment
What type of cell are known as “foreigners in the brain”?
Microglia (due to their origin in the yolk sac.)
True or False?:
The microtubule associated protein (MAP) Tau is found exclusively in dendrites while MAP2 is found exclusviely in axons.
False
Tau is found exclusively in axons and MAP2 is found exclusively in dendrites.
True or False?:
Unipolar cells are typical of vertebrate nervous systems, but some invertebrate neurons can adopt a pseudounipolar morphology.
False
Unipolar cells are typical of invertebrate nervous systems, but some vertebrate neurons can adopy a pseudounipolar morphology.
What type of cells express myelin associated growth inhibitors?
Oligodendrocytes
True or False?:
Glia’s only function is to structually support neurons like glue.
False
There are many classes of glia that all have important jobs.
What are the two types of actin?
Actin exists in free monomer (G-actin) or filamentous (F-actin) forms.
True or False?:
Astrocytes are interconnected through gap junctions to form networks that function off of intracellular calcium signals. In many ways, they are closer to a reticular system than neurons are.
True
True or False?:
Schwann cells are found in the CNS.
False
Schwann cells are found in the PNS.
What is the role of the radial glia?
Radial glia give rise to new neurons and macroglia through cell division and serve as scaffolding for radially migrating neurons.
True or False?:
Microglia are small migrating cells that scavenge debris in the CNS. Due to the blood-brain barrier, the CNS is isolated from the immune system, so microglia serve as an immune system for the CNS. They respond to infection or injury by producing rapid morphological and biochemical changes and release pro-inflammatory cytokines.
True
What molecular motor is responsible for fast anterograde transport?
Kinesin
Is acetylcholine an excitatory or inhibitory neurotransmitter?
Excitatory
True or False?:
There are very few en passant synapses in the PNS.
True
What three lines of evidence argued for chemical transmission at the synapse?
- Information appears to flow in one direction from axon to dendrite.
- Some interactions appear to be inhibitory rather than excitatory.
- A delay of several milliseconds is present even in very simple reflex arcs made up of just a few synaptic links.
How do anterograde & retrograde anatomical tracing work?
Neurons will take up certain substances and transport them preferentially in either the anterograde or retrograde directions. PHA-L (anterograde) and fluorescenct microspheres or the rabies virus (retrograde) can be used to visualize the microtubule networks within neurons.
What are the four principles of the Neuron Doctrine?
- The brain cell (neuron) is the unit of the nervous system.
- Neurons are separated by “gaps” through which they communicate.
- Each neuron contacts only specific target cells.
- Impulses travel in one direction in a neuron.
What part of the neuron is the input compartment?
Dendrite & Soma
Is ATP/adenosine an excitatory or inhibitory neurotransmitter?
Excitatory
What is the name of the gaps on an axon between myelinating Schwann cells?
Nodes of Ranvier
What is the main stem cell in the brain?
Radial Glia
True or False?:
During development, oligodendrocytes release factors like cholesterol and throbospondins that help promote synapse formation.
False
During development, astrocytes release factors like cholesterol and throbospondins that help promote synapse formation.
Compare the orientation of microtubules in axons and dendrites.
In axons, the orientation of microtubules is plus-end distal (away from cell body) while in dendrites, the orientation of microtubules is both plus-end distal and minus-end distal. The reason for this is that the dendritic compartment is treated as part of the somatic compartment whereas the axon is thought to be a represenative of the cell that extends very long distances in many cases. As such, you need to be able to carry materials out to the tips of the axon terminals. You can’t just have random diffusion, it needs to be organized.
What part of the neuron is the output compartment?
Axon Terminal
