MT - Cell Types of the Nervous System Flashcards
Of the ~20,000 human genes, how many are expressed in the brain? How many are expressed only in the brain?
~14,000! ~6,000 are only expressed in the brain.
What are the 2 classes of cells that make up a nervous system?
- Neurons
2. Glia
What is the main difference between neurons and glia?
Neurons: excitable
Glia: non-excitable
Who Provided evidence to suggest the “neuron theory” of nervous system organization as opposed to the commonly held “reticular theory”?
Santiago Ramon y Cajal.
Who developed the dark stain that was instrumental for the dark staining of individual neurons?
Camillo Golgi.
What was notable about the stain that Golgi produced for his research?
It didn’t stain every neuron, making it easier to visualize the ones that were stained.
Describe “synctitial reticular theory”.
The previously held belief that the nervous system was a single cell web with many processes.
Describe the “neuron doctrine”.
The current understanding that neurons are individual cells which innervate each other.
Give a few characteristics of neurons.
- Electrically excitable cells of the nervous system
- Allow rapid communication on a millisecond timescale
- Communicate at structures called synapses
How many neurons are there in the human nervous system? How many synapses?
10^11 neurons and 10^15 synapses.
What are the 4 main structural elements of a neuron?
- Cell body/Soma
- Dendrites
- Axon
- Presynaptic bouton/terminal
What are the 4 functions/functional zones of the neuron?
- Signal reception
- Signal integration
- Signal conduction
- Signal transmission
Where in the neuron does signal reception occur? What happens?
At the dendrites and the cell body. Incoming signal is converted from chemical to electrical.
Where in the neuron does signal integration happen? What happens?
At the axon initial segment. An electrical signal is converted to an action potential.
Where in the neuron does signal conduction occur? What happens?
At the axon (some with myelin). Action potential travels down the axon.
Where in the neuron does signal transmission occur? What happens?
At the synapse. Signal is converted from electrical to chemical with the release of neurotransmitter.
What is a dendritic spine?
The postsynaptic structures of excitatory glutamatergic synapses. Protrusions on dendrites.
Are all dendritic spines the same shape?
No. They ccan have “mushroom”, “stubby”, “thin”, and “filopodium” shapes.
What is an en-passant synapse?
A synapse that occurs midway along an axon and connects with dendrites from another neuron.
When viewing under a microscope, what kind of synapses would we expect to contain the postsynaptic density?
Glutamatergic synapses.
When viewing under a microscope, what would we call a presynaptic dark line?
The active zone.
What 3 methods are used to categorize neurons?
- Morphology
- Functional properties
- Molecular content
Do all neurons look the same?
No, they can have very different structures/properties but all use the same basic mechanism to send signals.
What are the most prevalent types of neurons in the brain?
Glutamatergic and GABAergic neurons.
What kinds of neurons are only found in the ventral tegmental area, the substantia nigra, and the hypothalamus?
Dopaminergic neurons.
What kinds of neurons produce acetylcholine and are found in the medial septum, striatum, and pedunculopontine tegmental nucleus?
Cholinergic neurons.
What kind of neurons produce serotonin? Where are they localized?
Serotonergic neurons, localized in the Raphe nucleus.
What kinds of neurons produce noradrenaline/norepinephrine? Where are they localized?
Noradrenergic neurons in the locus coerulus.
What kind of neurons contain tyrosine hydroxylase (TH)?
Dopaminergic neurons.
What kind of neurons contain glutamic acid decarboxylase (GAD67)?
GABAergic neurons.
What kind of neurons contain choline acetyltransferase?
Colinergic neurons.
What neurons contain vesicular GABA transporter? Where in the neuron is it located?
GABAergic neurons (duh). Located in the terminals/boutons.
What neurons contain vesicular glutamate transporter? Where in the neuron is it located?
Glutamatergic neurons (duh). Located in the terminals/boutons.
What are the 2 classes of GABAergic neurons? Which one contains parvalbumin?
- Fast-spiking (+Parvalbumin)
2. Non fast-spiking
What is the ratio of glial cells : neurons in the brain?
~10 glial cells per neuron.
What are some examples of glial cell function?
- Modulate synaptic function
- Influence brain metabolism
- Maintain chemical homeostasis
- Regulate blood flow
- Provide “immune” type functions
- Provide scaffold for neurodevelopment
What are the 4 kinds of non-neuronal cells in the vertebrate brain?
- Astrocytes
- Oligodendrocytes + Schwann cells
- Microglial cells
- Emendymal cells (incl. radial glia)
Which non-neuronal cell type is ciliated and lines the ventricles of the brain?
Ependymal cells.
Which adult non-neuronal cell type derives from radial glia during development?
Ependymal cells.
Which non-neuronal cell type can produce cerebrospinal fluid?
Ependymal cells.
Which non-neuronal cell type can serve as a stem or progenitor cell to make more glia/neurons?
Ependymal cells.
Which non-neuronal cell type includes the tanycyte subtype?
Ependymal cells.
What is a tanycyte? Where in the brain are they located?
A subtype of ependymal cell which lines the 3rd ventricle and extends into the hypothalamus.
What is the function of a tanycyte?
To transfer signals from the cerebrospinal fluid to the central nervous system (ex: glucose levels).
Which non-neuronal cell type serves to myelinate axons?
Oligodendrocytes/Schwann cells.
What differentiates the localization of oligodendrocytes from Schwann cells?
Oligodendrocytes: CNS
Schwann cells: PNS
What differentiates the structure of oligodendrocytes and Schwann cells?
Oligodendrocytes: myelinates multiple CNS axons
Schwann cells: 1 motorneuron axon in PNS
What is an “internode”? What subregions does this contain?
The part of the axon under the myelin sheath. Contains the juxtaparanode and the paranode (closest to the node).
Which non-neuronal cell type makes up the main element of the intrinsic immune system?
Microglia.
Which non-neuronal cell type is phagocytic?
Microglia.
Which non-neuronal cell type is involved with synaptic pruning and brain injury?
Microglia.
Which non-neuronal cell type is derived from the hemopoetic stem cells in bone marrow?
Microglia.
Which non-neuronal cell type is implicated in stroke, cognitive disorders, brain injury, inflammation, etc.?
Microglia.
What is the general role of microglia during brain injury?
To limit damage.
Which non-neuronal cell type is closely associated with blood vessels and is an essential element of the blood-brain-barrier (BBB)?
Astrocytes.
Which non-neuronal cell type is responsible for removing glutamate and GABA from synapses?
Astrocytes.
Which non-neuronal cell type provides energy substrate (ex: lactate) to neurons?
Astrocytes.
Which non-neuronal cell type is responsible for maintaining brain water homeostasis and regulating extracellular pH?
Astrocytes.
Which non-neuronal cell type is implicated in cytotoxic brain edema, glioma formation, and stroke outcome?
Astrocytes.
Are astrocytes dividing or non-dividing?
Some retain the capacity to undergo mitosis.
How can astrocytes help regulate blood flow in active brain regions?
by controlling arteriole diameter in response to changes in calcium levels.
Every neuron in the mammalian brain is within ______ of a capillary.
10-20 micrometres.
How is blood flow in the brain regulated?
By astrocytes in response to brain activity and the requirement for oxygen.
