NROB60H3 Chapter Notes - Chapter 2: Franz Nissl, Golgi'S Method, Camillo Golgi
11 Jun 2018
School
Department
Course
Professor
Chapter 2- Neurons and Glia
• Neurons- sense changes in the environment, communicate these changes to other neurons and
oad the od’s resposes to these sesatios
• Glia/glial cells- contribute to brain function mainly by insulating, supporting and nourishing
neighbouring neurons
• The Neuron Doctrine
o Scientists had to overcome the obstacle of studying the small neurons and for this they needed
the compound microscope
o To study the brain tissue, you need to make extremely thin slices of the brain tissue which is
diffiult, ut this a e doe hardeig/ fiig the tissues i foraldehde ad the used a
irotoe to ake thi slies
o Thus the foratio of the field histolog- the microscopic study of the structure of tissues
o But another issue was that all the structures had similar colouring so you could not tell them
apart
o Franz Nissel came up with a dye that would stain the nuclei of all cells along with clumps of
material surrounding the nuclei called the Nissl stain
▪ This stain distinguishes between the neurons and the glia and it helps histologists to
study the arrangement of cytoarchitecture
➢ The Golgi Stain
o The Nissl stained neuron looked like a protoplasm with a nucleus
o Camillo Golgi- thought of soaking the brain tissue in silver chromate (called Golgi stain),which
makes a small percentage of neurons darkly coloured and this showed that the neuronal cell
body is actually only a small section of what the nissl stain showed us
o This stain showed that there is a central region of the cell nucleus and a lot of thin tubes that
radiate away
o The cell body can be referred to as soma, perikaryon
o The neurites are split into 2 categories; axons and dendrites
o The cell body gives rise to a single axon, axons act as wires that carry outputs (very long) and
dendrites that are short and they come in contact with many axons (input)
➢ Cajal’s Cotriutio
o He used the golgi stain to the greatest degree trying to work out the circuitry of many of the
brain regions
o Golgi viewed neurites as different cells that were fused to work continually (similar to the
circulatory system)
▪ If this was true then the brain would be a exception to the rule that and individual cell
works as a functional unit of tissue
o Cajal believed that neurites of different neurons are not continuous with each other but they
communicate through contact (called neuron doctrine)
o The electron microscope showed that different neurons are not continuous with one another
o Neurites are in contact not continuity
• The Prototypical Neuron
o The neuron/nerve cell consists of different parts: soma, dendrites, and axon
o Inside of the neuron is separated from the outside by the neuronal membrane
➢ The Soma
o Soma is the spherical central part
o Watery fluid in the cell is called cytosol (salty, potassium-rich solution)
o Within the soma there are enclosed structures called organelles: nucleus, rough E.R., Golgi
apparatus, mitochondria
o Everything excluding the nucleus is referred to as the cytoplasm
find more resources at oneclass.com
find more resources at oneclass.com
o The Nucleus
▪ Spherical, centrally located, and it is contained within a double membrane called the
nuclear membrane called a nuclear envelope
▪ In the nucleus there are chromosomes that contain a genetic material called DNA
▪ DNA that are used to assemble a cell is referred to as genes
▪ The readig of the DNA is alled gee epressio ad he gee epressio is
complete the final product are proteins
▪ Protein synthesis is when protein molecules are assembled in the cytoplasm
▪ The mRNA carries genetic messages (DNA) from the nucleus to the site of protein
synthesis in the cytoplasm
▪ Assembling a piece of mRNA fro information from genes is called transcription and the
result of this is called a transcript
▪ One end of a gene contains the promote when RNA polymerase binds to start
transcription, this binding is done by transcription factors
▪ On the other end of the DNA there is a section called the terminator/stop sequence that
lets the RNA polymerase know when the end of transcription is
▪ The non coding regions of the DNA are introns (removed by RNA splicing) and the coding
regions of the DNA is called exons
▪ The remaining exons are fused together; in some cases, the exons can be accidently
removed to create new proteins (alternatively spliced)
▪ The building blocks of protein consist of amino acids (20 kinds) and the assembly of
proteins of amino acids is called translation
o Neuronal Genes, Genetic Variation, and Genetic Engineering
▪ Neurons are different from the other body cells because they express specific genes as
proteins differently
▪ Human genome- the entire length of DNA that comprises the genetic information in our
chromosomes
▪ Gene copy number variation- when long stretches of DNA either have genes missing or
duplicated leading to overexpression of some proteins
• This gene variation is sometimes also seen in autism and schizophrenia
(psychiatric disorders)
▪ Some nervous system disorders could be caused by mutations in a gene or regions of the
DNA that regulate gene expression
▪ Single nucleotide polymorphism-small mutations caused by a change in a single letter,
soe ould affet the protei odig soe ould’t
▪ Genetic engineering- ways to change organisms by design with gene mutations or
insertions
▪ We use mice because they reproduce quickly and they have similar nervous systems
▪ Knockout mice-when one gene is deleted to study the progression of the disease and
find ways to cure it
▪ You could also generate transgenic mice, where genes have been introduced and
overexpressed (these new genes are called transgenes)
▪ Knock-in mice-when the native gene is replaced with a modified transgene
o Rough Endoplasmic Reticulum
▪ Neurons make proteins using information from genes through globular structures called
ribosomes
▪ Ribosomes are attached to stacks of membrane called rough endoplasmic reticulum
▪ Rough E.R. exist in large numbers around the neurons more so than glia and other non
neuronal cells
find more resources at oneclass.com
find more resources at oneclass.com
