Neurons Flashcards
Nissl stain
Franz Nissl made a dye that stains only the nucleus and some surrounding clumps (nissl bodies)
- shows the difference between glia and neurons but didnt show real shape
Golgi stain
- 1837
- camillo golgi made a stain that showed all parts of the neuron (axons/dendrites and soma)
- made of silver chromate solution
parts of the neuron
- soma
- dendrite
- axon
cell membrane
- cell skin with a lipid bilayer made of hydophilic heads and hydrophobic bodies
- has pores/channels/pumps in it
Soma
- cell body
- around 20um but can vary
- filled with cytoplams
cytoplasm
the organelles and cytosol
- not including nucleus
cytosol
slaty potassium rich aquous fluid where organelles float
Dendrites
receive input signals from other cells
- can be many
- not as long as axon
Axon
- typically longest branch but can vary
- sends output signals
- can branch into axon collaterals
- no protein synthesis (no er/ribosome)
Nucelus
sphere at the center of the soma
- abut 5-10 um
- contains chromosones with dna
Nuclear envelope
membrane with small pores that contains the nucleus
genetic code
blueprint for making proteins
DNA
- would be 2 meter
- contains in 46 chromosones
- each cell has the same dna but uses different parts
complementary chromosome pairs
adenine and thymine
guanine and cytosin
rough endoplasmic reticulum
maze of mebrane dotted with ribosomes
ribosomes
where proteins are assembled
- not all of them are in the ER
Golgi apparatus
- modifies proteins and packages them for export
smooth ER
folding of proteins and regulates internal concentration of calcium
Mitochondria
produces ATP from pyruvic acid and O2
Cytoskeleton
maintains the shape of the cell
- contains microtubules, neurofilaments, microfilaments
- dynamic
microtubules
- large and hollow
- made of tubulin
- run down the neurites
- biggest
Neurofilaments
- very strong
- coiled
- medium
microfilament
- built from actin
- dynamically adjust cell shape
- smallest
gene expression
- reading the DNA
if cells have the same DNA how are they different?
Because of proteins
function of proteins
- determine structure (cytoskeleton) (actin/tubulin are proteins)
- determine the function of neurons
- chemical reactions
- properties of cell membrane
protein properties of cell membrane
- neuroreceptors on dendrites
- channels on axons
Structure of proteins
- proteins are made combinations of 20 amino acids
- can be primary, secondary, tertiary or quartiary
- shape determines its function
- shape destroyed by heat
polypeptides
long chains of amino acids
amino acids
has a central carbon, amino group, carboxyl group and a residue (R group)
- residue affects it shape because can be hydrophillic or phobic
- order of amino acid determined by DNA
what is a gene made up of
- its a sequence of codons that make up a given protein
Transcription
- copying of DNA onto RNA because it cant leave nucleus so it need a copy
- Adenine with Uracil
- goes to ribosomes (mRNA)
translation
making the protein from the ribosomes
- each amino acid is coded by 3 bases
- to make a protein which is sometimes cut from larger pieces
ER vs free ribosomes
- proteins made from free riosomes stay in cytosol (enzymes) and on the ER will go to organelles or membrane
Fragile X syndrome
mutation of the FMR1 gene on the X chromosone which should make a protein called FMRP
- but too many CGG repeats turns this gene off and will not make FMRP which causes intellectual delays
- males more affected
Axon terminal
end of axon (terminal button)
- contains vesicles
- no microtubules
- many mitochondria
Anterograde Axoplasmic transport
Kenesin legs move the vesicles down microtubules (uses ATP)
- fast
retrograde
- transport protein from terminal to soma to tell about metabolic changes
- uses dynein legs
types of dendrites
shape: pyramidal or stellate
spine: spiny or aspynous
- spines add surface areas
classifying neurons
- number of neurites (unipolar, bipolar or multipolar)
- dendrite types (shape/spine)
- connections (motor/sensory/internueron)
- axon length (short/long –>golgi I/II)
- NT type
Glia
- supporting cells
- make up 50% of cells in the brain
- some can modulate communication between neurons
- many types with different functions
Glia in the CNS
- astrocytes
- ependymel
- oligodendrocytes
- microglia
Glia in PNS
- satelite cells
- Shwan cells
Astrocytes
- star shapes
- physical support to neurons
- support neuronal metabolism (carries nutrients from capillaries)
- regulate extracellulare fluid
- help with BBB
- carry Nt receptors
oligodendrocytes
- myelinate in the CNS
- one cell insulates many axon segments
- anchoring of the axons
Schwan cells
- also myleinate but in the PNS
- one cells insulates one axons
Microglia
- smallest of the glia cells
- active immune defense in the CNS
- protect from invaders and clean up waste
neuron doctrine
each neuron is its own entity and is separated from other by small spaces
- Cajal
- took 50 years to prove him right
Reticular theory
- neurons are not distinct. they are fused and act as a whole
- Golgi
- can kinda be right if we look at gap junctions
