What was the magnification of the slides?
40x
For silver-stained tissue, what can be visualized neuronally?
the cell body and dendrites that are proximal to the cell body
distal dendrites often cannot be seen
Why can’t the distal dendrites often be seen? (for silver stained tissue)
because the tissue was sliced very thinly, often so thin that the three-dimensional structure of the dendrites, which radiate away from the cell body, was cut off during the sectioning process
What will axons appear as (for silver-stained tissue)?
- very fine, black, thread-like processes
- will often not be directly connected to a cell body that you can see (they may have been connected to a cell body found in a different part of the brain), but they will often surround neurons because axons synapse onto neurons at this location
What are the key differences between gray and white matter? Specifically, what cellular components do you find in each?
- grey matter contains the “neuropil” (dendrites and cell bodies/soma of neurons) as well as astrocytes
- white matter contains axons of neurons, often myelinated by surrounding oligodendrocytes
- microglia found in both compartments
What is a very specialized structure in the temporal lobe?
the hippocampus
What is the strip of tissue that is above the hippocampus and runs horizontally across the top of the tissue section?
the cerebral cortex
What forms the exterior most tissue of the brain that can be seen as soon as you remove the meninges?
- the cerebral cortex
- it is a sheet of tissue of roughly equivalent depth/width that surrounds the inner brain structures
If the cerebral cortex is removed, flattened, and depicted as a 2-D sheet, how thick would it be at all points?
1-2mm thick
What separates the cerebral cortex from the hippocampus?
a strip of white matter
What is meant by “pial surface”?
the amter would normally be adhered to this part of the tissue
What are the differences between the cells that are closer to the pial surface, as compared to those closer to the white matter?
- pyramidal cells in the superficial layers (closer to pia) are smaller and more densely packed then the pyramidal cells in the depper (closer to white matter) layers
What are most of the cells in layers 2-3 of the cortex?
recognizably pyramidal neurons
What characterizes pyramidal neurons?
- cell body is 3-dimensional pyramid
- most have one “apical” dendrite that travels towards layers 2-3
- have multiple “basilar” dendrites that leave the base of the cell body and travel horizontally (the denderites of these neurons would typically extend across far longer distances than what you can see in the image)
What do pyramidal neurons do?
- play a major role in receiving information from other brain structures, processing it and then communicating with other brain regions
- axons may often leave the brain region in which their cell body is located and travel long distances before amaking a synapse
- the axons of layer 2, 3, 5, and 6 neurons tend to travel to different locations
Pyramidal neurons utilize and release th neurotransmitter glutamate, which means that they are ____ neurons?
excitatory
Pay close attention to the pyramidal cells that you see in layers 2 and 3 (closer to the pial surface) vs. layers 5 and 6 (closer to the white matter). Are the cell bodies of layer 2-3 cells, on average, larger than those of layer 5-6 cells?
No
What is the “empty space” to the right of the hippocampus? And is fully enclosed by tissue. What is its’ purpose?
- a ventricle, contains CSF
- the ventricle has a primarily protective purpose by allowing the brain to move and give if pressure is applied to it.
- CSF provides the water and electrolytes neurons need to function
Immediately to the right of the ventricle is an egg-shaped structure, with diagonal strands of white matter running through it at the lower aspects of the field of view. What are the dark thread-like structures running through the white matter?
axons
The hippocampus has defined neural pathways that are critical to what?
memory
What is the C-shaped structure in the “lower” part of the hippocampus?
the dentate gyrus
What type of cells is the dentate gyrus made of?
- very small, densely aggregated cells called “granule cells”
