MCDB 322 Quiz 1 Questions and Answers Fully Solved
astrocytes - Answers have processes that interface with neurons and blood vessels. They help
maintain the concentration of chemicals in the extracellular space, remove excess NT, react to
tissue damage, and maintain the BBB
Oligodendrocytes - Answers have processes that branch of from the cell body to wrap around
the axons of neurons, this provides insulation for the axons in the form of myelin
Neurons - Answers have a process called an axon that carries info to other neurons, and
processes called dendrites that receive input from other neurons. neurons send messages
between brain areas using electrochemical signals. These encode sensory information and
generate motor commands.
Microglia - Answers serve neuroimmune (removing cell debris and other waste) functions in the
brain
How do we know about these cell types? - Answers - microscopy
- neurons are small
-compound light microscopes invented in the 1600s
- optical theory advancements allowed them to reach their diffraction resolution limit by the
1800s
Historical challenges and solutions - Answers - living tissue rots quickly when take out of an
animal
- solution: chemical fixatives preserve tissue
- discovered in late 1800s
- alcohols precipitates proteins, aldehydes crosslink them
- also gives tissue mechanical strength to allow thin sections to be cut
- methods to visualize the cell structure in living animals have now been developed
- in mammals, neurons are translucent; there is too little contrast to seee them: cell specific
staining methods, fluorescence microscopy
Golgi Method for Neuronal Structure Visualization - Answers - invented by Golgi and optimized
by Santiago Ramon y Cajal
- fix tissue, soak for several days in potassium dichromate, then add silver nitrate
-a black precipitate stains a few cells completely, and most not at all
,- although they shared a Nobel prize, the had a huge disagreement about what the images they
obtained meant
- Golgi's nobel essay rejected the neuron doctrine
-cajal's nobel essay argued that the neuron doctrine was the key to understanding the function
of the brain (correct)
Golgi labeling is sparse - Answers - most neurons have one axon:
-runs a long distance before branching
-ends in fine terminal branches
-constant diameter
-sometimes covered by myelin
-presynaptic to other cells
-most neurons have many dendrites:
-branch extensively close to cell body
-taper as they branch
-some are covered with fine spines
- postsynaptic to axon terminals
-the Golgi method can also label glial cells:
-recognized by absence of an axon and short processes that look different than dendrites
Dendritic trees are diverse - Answers - not all neurons have dendrites
Limitations of Golgi staining - Answers - can only be done on dead, fixed tissue that has been
sectioned:
- cannot obtain physiological data from neurons
- cannot map long distance, 3d projections as the region the axon terminates in is seldom the
same section
-no ability to control which cells will be stained:
- it is possible that some cells are never stained and some are overrepresented
- very low rate that both partners at synapses are stained
, Fluorescent labeling of neurons and glia - Answers - a fluorescent molecule absorbs photons at
a specific wavelength and releases lower energy photos (longer wavelength):
- specific wavelengths depend on chemical structure
-with appropriate filters, one gets brightly colored specimen on a black background
- can be used on living cells or on fixed tissue:
- a variety of methods are available for specifying which cell has a fluorescent molecule
Intracellular staining - Answers -penetrate cell(s) with glass micro electrode filled with a
fluorescent molecule ( inject dye into neuron):
- characterize physiology
- view structure during, or at the end of experiment
Indirect immunocytochemistry to define cell classes biochemically - Answers - commonly used
to look at strcuture
- procedures:
- fix and section material so reagents can penetrate
- make or buy a primary antibody that reacts with a specific target molecule (mouse antibody (lg)
against SMI32)
-detect it by binding a secondary antibody chemically linked to a fluorescent tag that recognizes
the primary antibody:
-in this case, green fluorescent-labeled Goat antibodies against mouse legs
Dil and DiO labeling - Answers - fluorescent lipid analogs that spread throughout the cell
membrane in neurons (inject dye)
-moves only by diffusion in the lipid bilayer:
- faster over a few hundred mu-m
- take days or weeks to move to end of long axon fiber pathways
- also works in fixed tissue, so can be used to map human brains (fixed and live)
Green Fluorescent Protein (GFP) - Answers - part of a two protein system that makes Puget
Sound jellyfish glow green:
-Shimomura identified GFP protein
astrocytes - Answers have processes that interface with neurons and blood vessels. They help
maintain the concentration of chemicals in the extracellular space, remove excess NT, react to
tissue damage, and maintain the BBB
Oligodendrocytes - Answers have processes that branch of from the cell body to wrap around
the axons of neurons, this provides insulation for the axons in the form of myelin
Neurons - Answers have a process called an axon that carries info to other neurons, and
processes called dendrites that receive input from other neurons. neurons send messages
between brain areas using electrochemical signals. These encode sensory information and
generate motor commands.
Microglia - Answers serve neuroimmune (removing cell debris and other waste) functions in the
brain
How do we know about these cell types? - Answers - microscopy
- neurons are small
-compound light microscopes invented in the 1600s
- optical theory advancements allowed them to reach their diffraction resolution limit by the
1800s
Historical challenges and solutions - Answers - living tissue rots quickly when take out of an
animal
- solution: chemical fixatives preserve tissue
- discovered in late 1800s
- alcohols precipitates proteins, aldehydes crosslink them
- also gives tissue mechanical strength to allow thin sections to be cut
- methods to visualize the cell structure in living animals have now been developed
- in mammals, neurons are translucent; there is too little contrast to seee them: cell specific
staining methods, fluorescence microscopy
Golgi Method for Neuronal Structure Visualization - Answers - invented by Golgi and optimized
by Santiago Ramon y Cajal
- fix tissue, soak for several days in potassium dichromate, then add silver nitrate
-a black precipitate stains a few cells completely, and most not at all
,- although they shared a Nobel prize, the had a huge disagreement about what the images they
obtained meant
- Golgi's nobel essay rejected the neuron doctrine
-cajal's nobel essay argued that the neuron doctrine was the key to understanding the function
of the brain (correct)
Golgi labeling is sparse - Answers - most neurons have one axon:
-runs a long distance before branching
-ends in fine terminal branches
-constant diameter
-sometimes covered by myelin
-presynaptic to other cells
-most neurons have many dendrites:
-branch extensively close to cell body
-taper as they branch
-some are covered with fine spines
- postsynaptic to axon terminals
-the Golgi method can also label glial cells:
-recognized by absence of an axon and short processes that look different than dendrites
Dendritic trees are diverse - Answers - not all neurons have dendrites
Limitations of Golgi staining - Answers - can only be done on dead, fixed tissue that has been
sectioned:
- cannot obtain physiological data from neurons
- cannot map long distance, 3d projections as the region the axon terminates in is seldom the
same section
-no ability to control which cells will be stained:
- it is possible that some cells are never stained and some are overrepresented
- very low rate that both partners at synapses are stained
, Fluorescent labeling of neurons and glia - Answers - a fluorescent molecule absorbs photons at
a specific wavelength and releases lower energy photos (longer wavelength):
- specific wavelengths depend on chemical structure
-with appropriate filters, one gets brightly colored specimen on a black background
- can be used on living cells or on fixed tissue:
- a variety of methods are available for specifying which cell has a fluorescent molecule
Intracellular staining - Answers -penetrate cell(s) with glass micro electrode filled with a
fluorescent molecule ( inject dye into neuron):
- characterize physiology
- view structure during, or at the end of experiment
Indirect immunocytochemistry to define cell classes biochemically - Answers - commonly used
to look at strcuture
- procedures:
- fix and section material so reagents can penetrate
- make or buy a primary antibody that reacts with a specific target molecule (mouse antibody (lg)
against SMI32)
-detect it by binding a secondary antibody chemically linked to a fluorescent tag that recognizes
the primary antibody:
-in this case, green fluorescent-labeled Goat antibodies against mouse legs
Dil and DiO labeling - Answers - fluorescent lipid analogs that spread throughout the cell
membrane in neurons (inject dye)
-moves only by diffusion in the lipid bilayer:
- faster over a few hundred mu-m
- take days or weeks to move to end of long axon fiber pathways
- also works in fixed tissue, so can be used to map human brains (fixed and live)
Green Fluorescent Protein (GFP) - Answers - part of a two protein system that makes Puget
Sound jellyfish glow green:
-Shimomura identified GFP protein
