Lecture 1 - Neurons

Question 1

What are the the two foundational units of brain function?

Answer 1

Neurons and Circuits

Question 2

True or False

There are different types of neurons

Answer 2

True

Question 3

How many methods are there to identify neurons?

Answer 3

Six
1. Golgi stain
2. Dye injection
3. Genetically-encoded fluorescent proteins
4. Immunohistochemistry
5. Electron microscopy
6. Brain clearing

Question 4

1830’s : What is the Cell Theory?

Answer 4

Matthias Jakob Schleiden theorized that plants are made up of inidivual cells

Theodor Schwann then applied the same idea to the brain

Question 5

1873 : What is the Reticular Theory?

Answer 5

Camillo Golgi developed the Silver Stain (now called the Golgi stain), and theorized that the brain is all interconnected

Question 6

1889 : What is the Neuron Doctrine?

Answer 6

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

Question 7

1950’s : What is the Electron Microscopy and what did it confirm about the Neuron Doctrine?

Answer 7

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

Question 8

How many different types of neurons are there?

Answer 8

4 types
1. Unipolar Cell
2. Bipolar Cell
3. Pseudo-unipolar Cell
4. Multipolar Cell (has 3 different types under its category)

Question 9

Unipolar Cell

Answer 9

• A neuron that has one end/pull
• Sends signals right through without the help of a cell body

Question 10

Bipolar Cell

Answer 10

• A neuron with two ends

Question 11

Pseudo-unipolar Cell

Answer 11

• 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

Question 12

Multipolar cells (and its types)

Answer 12

Multipolar cells have lots of branches coming off the cell body and going in different directions. There are 3 types:

1. Motor Neuron - Ends on a muscle where the neuromuscular junction is, and influences many parts of the brain.
2. Pyramidal Cell - contains spines on dendrites which causes lots of contact (shaped like a pyramid)
3. Purkinje Cell - Specific to the Cerebral cortex. Known for the long and intricate dendrites

Question 13

Motor Neuron

Answer 13

Ends on a muscle where the neuromuscular junction is, and influences many parts of the brain

Question 14

Pyramidal Neuron

Answer 14

contains spines on dendrites which causes lots of contact (shaped like a pyramid)

Question 15

Purkinje Cell

Answer 15

Specific to the Cerebral cortex. Known for the long and intricate dendrites

Question 16

4 Basic zones of a neuron

Answer 16

1. Input: receives input/signals
2. Integrative: Where action potential can occur. Signal gets added, subtracted, goes against, etc
3. Conductive: Where electrical signals spread
4. Output: Where the neuron influences another cell type/neuron

Question 17

Sensory Neuron

Answer 17

Comes from the sensory cells to the Thalamus

Question 18

Local Interneuron

Answer 18

connects two different neurons (usually inhibitory)

Question 19

Projection Interneuron

Answer 19

has a longer axon and can travel further

Question 20

Neuroendocrine cell

Answer 20

Ends up on capillaries and blood vessels. Can influence blood pressure through widening or dilation, etc.

Question 21

Connectome

Answer 21

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

Question 22

The Golgi Stain

Answer 22

• 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

Question 23

Dye Filling/Dye Injection Neurons

Answer 23

• 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

Question 24

Immunohistochemistry

Answer 24

• 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

Question 25

Genetically-encoded fluorescent proteins

aka GFPs

Answer 25

• artificially expressing genes using a cell specific promoter so you can get a cell specific gene expression
• this method is exploited to visualize neurons

Question 26

Brain Clearing (Clarity)

Answer 26

• 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

Question 27

2 photon microscopy

Answer 27

• micrsocope that takes image deep into tissue
  (the whisker mice experiment)

Question 28

Electron Microscopy

Answer 28

• very expensive (micrscope and technician)
• emebeds tissue in a resin and makes thin cuts (60 nanometer)
• no vibrations in the room
• time consuming

Question 29

Fluorescent Microscopes

Answer 29

All light from the tissue is directed to the eyepiece.

Question 30

Confocal Microscope

Answer 30

Uses a pinhole to block out-of-focus light, enabling clear visualization of a single focal plane. Can reconstruct images from multiple focal planes.

Question 31

Thy 1 promotor

Answer 31

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

Question 32

L7 promotor

Answer 32

Active only in cerebellar Purkinje neurons

Question 33

Doublecortin

Answer 33

(as mentioned in Immunohistochemistry): it is immature neurons, usually used as a marker for labeling

Question 34

Iba1 promotor

Answer 34

microglia cells

Question 35

GFAP promotor

Answer 35

only in astrocytes

Question 36

DAPI neurons

Answer 36

type of stain, stains all neurons