Lecture 1 - Neurons Flashcards
What are the the two foundational units of brain function?
Neurons and Circuits
True or False
There are different types of neurons
True
How many methods are there to identify neurons?
Six
1. Golgi stain
2. Dye injection
3. Genetically-encoded fluorescent proteins
4. Immunohistochemistry
5. Electron microscopy
6. Brain clearing
1830’s : What is the Cell Theory?
Matthias Jakob Schleiden theorized that plants are made up of inidivual cells
Theodor Schwann then applied the same idea to the brain
1873 : What is the Reticular Theory?
Camillo Golgi developed the Silver Stain (now called the Golgi stain), and theorized that the brain is all interconnected
1889 : What is the Neuron Doctrine?
Ramon Y Cajal formed the Neuron Doctrine and theorized that
- Neurons are not interconnected, they have spaces in between
- Neurons communicate in a certain way
1950’s : What is the Electron Microscopy and what did it confirm about the Neuron Doctrine?
The Electron Microscopy is new microscopic technology that shows a higher resolution when looking at neurons.
It confirmed that
- Neurons communicate via snynapses and individual cells by releasing neurotransmitters
How many different types of neurons are there?
4 types
1. Unipolar Cell
2. Bipolar Cell
3. Pseudo-unipolar Cell
4. Multipolar Cell (has 3 different types under its category)
Unipolar Cell
- A neuron that has one end/pull
- Sends signals right through without the help of a cell body
Bipolar Cell
- A neuron with two ends
Pseudo-unipolar Cell
- Like a Unipolar cell as it can send signals right through without it on the way. Uniquely , it’s cell body is pushed to the side
Multipolar cells (and its types)
Multipolar cells have lots of branches coming off the cell body and going in different directions. There are 3 types:
- Motor Neuron - Ends on a muscle where the neuromuscular junction is, and influences many parts of the brain.
- Pyramidal Cell - contains spines on dendrites which causes lots of contact (shaped like a pyramid)
- Purkinje Cell - Specific to the Cerebral cortex. Known for the long and intricate dendrites
Motor Neuron
Ends on a muscle where the neuromuscular junction is, and influences many parts of the brain
Pyramidal Neuron
contains spines on dendrites which causes lots of contact (shaped like a pyramid)
Purkinje Cell
Specific to the Cerebral cortex. Known for the long and intricate dendrites
4 Basic zones of a neuron
- Input: receives input/signals
- Integrative: Where action potential can occur. Signal gets added, subtracted, goes against, etc
- Conductive: Where electrical signals spread
- Output: Where the neuron influences another cell type/neuron
Sensory Neuron
Comes from the sensory cells to the Thalamus
Local Interneuron
connects two different neurons (usually inhibitory)
Projection Interneuron
has a longer axon and can travel further
Neuroendocrine cell
Ends up on capillaries and blood vessels. Can influence blood pressure through widening or dilation, etc.
Connectome
Connectome is the wiring/synaptic connectivity of all neurons.
Connectome is the goal of neuroscientists, to know how neurons interact and to map every circuit
The Golgi Stain
- chemical processes that causes silver impregnation in neurons
- only a small amount of neurons are labelled
- only dead tissue allowed due to slicing
- very easy, tried and true technique
Dye Filling/Dye Injection Neurons
- injects a fluorescent dye on live or dead tissue (through trial and error)
- isolates cells from others
- combining anatomical and electrophysiological measures determines neurons functions
Immunohistochemistry
- uses antibodies to determine certain proteins
- some antibodies stains ALL neurons so finding a specific antibody for a specific neuron is important
- only on dead tissue
- cheap
Genetically-encoded fluorescent proteins
aka GFPs
- artificially expressing genes using a cell specific promoter so you can get a cell specific gene expression
- this method is exploited to visualize neurons
Brain Clearing (Clarity)
- requires dissolving all the fat, mucus, lipids, in the brain that scatter light using hydrogelmonomer
- hydrogelmonomer will harden and replace the fats etc
- once thats removed, we are left with all the neurons in the brain, and see their pathways
- dead tissues only
2 photon microscopy
- micrsocope that takes image deep into tissue
(the whisker mice experiment)
Electron Microscopy
- very expensive (micrscope and technician)
- emebeds tissue in a resin and makes thin cuts (60 nanometer)
- no vibrations in the room
- time consuming
Fluorescent Microscopes
All light from the tissue is directed to the eyepiece.
Confocal Microscope
Uses a pinhole to block out-of-focus light, enabling clear visualization of a single focal plane. Can reconstruct images from multiple focal planes.
Thy 1 promotor
active in a fraction of all types of neurons, can do in-vivo imaging, no tissue treatment and chemicals since cells naturally produce the GFP
L7 promotor
Active only in cerebellar Purkinje neurons
Doublecortin
(as mentioned in Immunohistochemistry): it is immature neurons, usually used as a marker for labeling
Iba1 promotor
microglia cells
GFAP promotor
only in astrocytes
DAPI neurons
type of stain, stains all neurons
