Cell basics + neurons
Overview
Basics of Cells and Neurons
Cells are the building blocks of life, and they work together in the nervous system to help us function. The main types of cells to focus on are neurons (nerve cells) and astrocytes (supporting cells).
Structure of Cells
Cell Membrane: This is like the skin of the cell, made of a double layer of fats. It controls what goes in and out of the cell. The cell membrane has special areas called lipid rafts that help organize things inside.
Ion Channels: These are tiny openings in the membrane that let ions (charged particles) move in and out. There are different types:
Sodium/Potassium Pumps: These keep the cell's balance by moving sodium and potassium ions in and out and are super important for neurons.
Ligand-Gated Channels: These open when a chemical messenger (like a neurotransmitter) binds to them, changing what ions can enter the cell—this is important for things like addiction.
Voltage-Gated Channels: These open when there's a change in voltage (electric charge), helping to send signals quickly along the neuron.
G-Protein Coupled Receptors: These are receptors on the cell that, when bound to a molecule, can start other important processes inside the cell, including turning genes on or off.
Neurotransmitters
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Neurotransmitters are chemicals that neurons use to communicate. They are released at synapses (connections between neurons) and bind to receptors on other neurons, causing changes that can lead to signals being sent along.
Vesicles: These are small packages that store neurotransmitters and move them to the cell membrane to be released. This process uses proteins that walk along structures called microtubules, powered by energy from ATP.
Structure of Neurons
Parts of a Neuron: A neuron has several main parts:
Cell Membrane: The outer layer of the neuron.
Cell Body: Contains the nucleus and is where most proteins are made.
Dendrites: Branches that receive messages from other neurons; they usually have a resting charge of around -70 mV.
Axon Hillock: The beginning of the axon where signals are integrated.
Axon: This is a long fiber that carries signals away from the cell body.
Axon Terminals: The end parts that send signals to other neurons.
Myelin Sheath: This is a protective cover around the axon that helps signals travel faster and prevents the loss of electricity. Gaps in this cover, called Nodes of Ranvier, help boost the signal as it travels.
Sending Signals
The process of sending a signal (action potential) through a neuron happens in steps:
Resting State: The neuron is at rest, and the sodium-potassium pumps keep a balance.
Depolarization: When a stimulus is strong enough, sodium channels open, and sodium enters, making the inside of the cell less negative.
Repolarization: Potassium channels open, and potassium leaves the cell, making the inside negative again.
Hyperpolarization: Sometimes the potassium channels stay open a bit too long, making the inside overly negative for a short time.
Return to Resting Potential: Everything goes back to normal.
How Neurons Work Together
Neurons are influenced by the timing and order of the signals they receive. How they process neurotransmitter signals at the dendrites determines if they will send a signal through the axon. Neurons can communicate in many places, not just from dendrites, adding to how complex our nervous system is.
My notes:
people are the outcome of cell cordination
cells we care about
neurons
astrocites
Generic cell (parts)
cell membrain
full of h20 and has a oil layer that doesnt let h2o pass thro, phopholipid bilayer
hydrophpic tail
hydroloving head
lipid rafts
things the channles get plugged into, anchors
allows things to pass thro cell membrain
all stuff foating in raft
Holds ion channles
Ion channles
protien that pass thro the lipid rafts
let charged particles back and forth
sodium/possium pumps
impotant for neruons
active transport, using engry
gated channle closed sometimes but also opens nerotransmiters open them
ligland gated channels
important for addiction
open gate to let ions in when messanger binds to them
ligand means messenger
messanger could be dopamine or something like cokecane or sicsofrina meds
they appear where synapses are
responds to nerotrasmiters
Voltage gated ions channles (class of channles)
senses two electrical state
gate from closed state to open state
doesn’t need a messanger just a range of elctrial differncal on both sides of cells (more postive out side than inside causes it to open)
on axon
stays closed and opens at diff range
volatage gated potssiam
is for repolaltztion
voltage gated calcium
in snapse opens calcium to smoosh vessicle into cell memebrane realsing cell membrane
G protien coupled recptor
have a recption waiting for molecule to bind to it
this opens large complex cascade of proteins to do a bunch of tasks
are dependent on internal state of cell being in certain state
can open up ion channle or can effct what DNA gets transcribed and turned into protein
binding site for transmiter and may do many things
where do recptors, enzymes and proteins come from
necleus membrane has DNA inside it
so based on the sate of rest of cell the double helex of DNA get unattched and make opposite copy in RNA
RNA gets sent out to determe order of amino acids to make strands of protein
protien is the formation of everything
Zinc finger proteins- attach to DNA so that certian genes can be turned into protiens and other parts do not (the expresion is very locailised, very regionally specific and tied to certian functions)
Protien are evrything
amino acids in a row are as meaningfull as bunch of random letters in a row
amino acids get turned into words and then more meaningful sentances and then get combined into even more soecific until useful/has disired effect
complexity in maping DNA to functionlal protiens
Variety in protein assmbly leads to variety of function
depening on sub units that make up ligated gated channel, but depending on assembly changes what activates the channel to let cholride thro
ligengated channel in ex
so basically proteins are made slighly differntly to provide slighlt diff function
like diff emphasis on diff words in a sentance
vessicles
pakage made of phospholipid bilayer and get shipeed to cell membrane from golgi appartus
could have nerotansmiters to cross snyaptic cleft, enzymes, or lots of other things
cellular trabnsport
kinisn protiens walk down microtuble by ATP to where they need to be
PARTS OF NEURON
cell membrane, defines what is the neuron
cell body, where protiens are generated
dendrites, where info is summerized via chemical electrical
if you plug elsctrode in dendrite its - 70 mV
nerotransmiters (messenger) bind to lingated ion channle recrptors
lets in sodium which causes small excitory potential
the total amount of sodium let in over space and time is what triggers action potential
every time the dendrite lets a little sodium in causes a tiney excitory response
the sodium doedn’t just stay put it moves to disspate across electrical and concentraition gradent, which brings its pos charge to other parts of cell
so the lowest dendrite branch that is closest to recording site has a higher concentraition of charge but the further the branch is rom the recording site the more diluted it is
axion hillock begining of axon
axon, action potential is tranfered to axon terminal
semaptic end blubs, where info is realsed to next cell
geial cells, glue of nervous system and mylanate the axon
mylin sheath, procetion of axon and allows info to process quickly
gaps in between mylin sheath are premiable
Membraine poteintal
as you move elctrode closer to cell there is no diff but once you go thro cell membrane it goes down to neg 70 mV
this means that there is action poteial in membraine, which is maintained by sodium potaium pumps
Generaly excitory
Ca+2 or Na+
Generaly inhibitory
K+ (pos thing going out of cell causes neg change inside) or Cl-
Intro to nurons
steps of chemical messaging
reception
intagration
electric switch
signal progation
signal trasduction of chemical messangers
Dendrites- order and timing of nerutransmites matter
if you get a bunch of nerotransmiter responses at bottom better reation
Axon Hillock
Gated ion channles switch electeric and fires action potential
if up to threshold we get same set of steps:
resting, basic cell sate
depolarazation, postive charge changes differnachel so then the postive ions come in, it then gors under the -50 as it takes postive ions
repolarazation, potasium voltage gated channels take cell and make sure it goes to -50
Hyperpolarization, channles stay open too long and dips below neg 70
resting, return back to resting potential
Myelin sheath
insulates the action potienal
makes it travel faster
stops ions from escaping had sodium move through very quickly till it hits the next patch of tissue and depolarizes it
Node of ranvier
influx of sodium travels down mylinsheath and the depolarozes, happens over and over and over again
Sypnaptic terminal
travels down side of this to volatage gated chanel
calicum binds vessicles to neruotransmiter to cellular membrane
Snyapes aren’t exclusive with dendrites
they can be lots of places
axon holloic (if there it causes a response faster)
right at the start of another synapse (if there trigger nerotranmiter realses faster without travling down axon, or it would cause an ecetrical or chemical gradient)
gap juniction- direct contact between cells that are formed so that they can share electrical charge
chemical to electrical to chemical
post synaptic potentals at the dendrites intergated at the soma
Presnaptic is realsing NT
Postsnyaptic is receving NT
frequancy of action poteintals not the magnitude is how info is encoded.