neurophysiology Flashcards
What is diffusion?
ions flowing from high concentration to low concentration, a long concentration gradient.
What is electrostatic pressure?
negatively charged ions repel, oppositely, charged ions attract.
Semi permeable membrane explanation.
Screen door keeps mosquitoes out but let’s air get through.
What are neurons just like?
Batteries – the store charge to use when needed.
What if there is no charge in a neuron?
It’s dead.
What charge is it outside axon?
Positive
What charge is the inside axon?
Negative
What is voltage?
Difference in potential
Cell membrane is a what?
Lipid bilayer.
What are the ion channels?
Protein spinning the membrane so ions can pass in and out
What is important about the ion channels?
It doesn’t open to everybody.
What are the gated channels?
Open/close in response to voltage changes, chemicals(drugs) and mechanical actions
What can pass through the ion channels?
Sodium potassium chloride and calcium.
Why can’t proteins leave the cell?
They are too fat and the membraned are too small– proteins are negatively charged
What does the neuronal cell membrane do to water?
Repels water, so membranes need ion channels
Since ions are surrounded by water, what must they do?
They can enter a cell only through a channel
Why does potassium enter the cell?
Attracted to the negatively charged proteins.
What can move in and out of the cell freely?
Potassium
What happens if there is proteins in the bloodstream?
the cell is damaged
When does potassium reach equilibrium?
When ion movement out is balanced by ion movement in.
What happens when there’s too much potassium in the cell?
Other potassium ions, lose interest and leave
What is the resting membrane equilibrium?
-60
If they suck in what is the membrane slightly permeable to?
Sodium ions
Why do sodium ions want in?
They are positive.
What does the sodium potassium pump do?
pumps out 3 sodium and pumps in 2 potassium to maintain resting potential
How is the sodium potassium pump powered
ATP
What charge makes the cell useless
0
What does tetrodotoxin block nerve action?
Binding to/blocking pores of voltage gated sodium channels in neuron membranes
where is sodium
outside
where is potassium
inside
where is chlorine
outside
where is calcium
outside
where are proteins
inside
what do tetrodotoxins do
blocks nerve action by binding to/blocking pores of voltage gated, sodium channels in neuron mems
What does sodium do to the neuron?
Makes the neuron fire.
what is the job of a neuron
take info to pt A to pt B
WHat receives the info
dendrites
Where does the action potential spark?
Axon hillock
Where does the graded potential occur?
The dendrites
What happens as you inject negative ions?
Becomes more than negative inside.
What happens as graded potential spread across membranes?
They diminish like a ripples in a pond
What number is the threshold?
-40
What can graded potentials transform into?
Action potentials
What happens when the membrane reaches threshold?
It triggers an action potential, inside the cell becomes briefly positive
What happens once it hits -40?
The neuron jumps to +40.
How can the cell be positive with negative components in the cell?
-40 voltage opens up so sodium rushes into the cell and then door slam shut
What speed is an action potential?
One speed -> all or nothing
What starts an action potential?
Incoming positive charge coming from the dendrites to axon hillock
What happens in response to the initial depolarization?
Voltage gated sodium channels open.
What happens as soon as the cell reaches the threshold?
voltage gated sodium ions flood into cell until membrane potential hits +40
What happens after membrane potential hits +40?
Voltage gated sodium channels close and voltage gated potassium channels open
What happens after vg potassium channels open
repolarization as K+ moves out and resting potential is restored
When does sodium potassium pump come in during AP
during repolarization (3 Na+ out and 2 K+ in)
how is the concentration gradient like at peak (action potential)
gradient pushing Na+ out is equals charge pushing Na+ in
where does information enter nerve cell
at the synaptic site on the dendrite
What is the absolute refractory phase
no more action potentials can be made
What is the relative refractory phase
only a strong stimuli can cause another AP
Why can’t there be another action potential during the AR phase
the activation gate locks
what does sodium do to neurons(think of putting salt on worms)
it causes neuron to fire
how many action potentials are there in one axon
many
why do action potentials travel in one direction
the refractory state of the membrane
what does myelin do
speeds up the process
what is periodic paralysis
genetic defect in Na+ channels - so neuron doesn’t fire the way it needs to
what happens after the action potential travels down to the axon terminal
voltage gated calcium channels open
When do APs stop
no more voltage gates
What does Calcium do
gives enzymes that make it active-controls everything
What happens after Calcium enters
synaptic vesicles fuse with membrane and release transmitter into the cleft
What happens after the fusion
transmitters bind to postsynaptic receptors- EPSP or IPSP
what may transmitters bind to instead
presynaptic autoreceptors, decreasing release
what are neurotransmitters inactivated by
degradation or reuptake
what is Excitatory postsynaptic potential
makes cell more likely to fire because it is more positive
what is inhibitory postsynaptic potential
makes the cell less likely to fire because it is more negative
how are epsp and ipsps decided
the axon hillock
what is a reuptake
reabsorptions of a neurotransmitter
what is a degradation
breakdown/inactivation of transmitter by an enzyme
What is an electrical synapses
ions flow DIRECTLY through large channels into neuron w out delay
What are the benefits an electrical synapses
faster, allow neurons to synchronize saves energy
what happens when neurons fire at the same time
a seizure
what are ligands
receptors to activate or block(lock and key)
endogenous ligands
neurotransmitters and hormones
exogenous ligands
drugs and toxins from outside the body
the number of receptors in a neuron what
varies over time
what is up-regulation
sensitization-increase number of receptors-more of a response over time
what is a down-regulation
tolerance- decrease in receptors-less of an effect over time
what is electroencephalogram(EEG)
recording of brain activity- used for seizures
