Electrical Neural Communication Flashcards
Hyperpolarization of dendrites and cell body
IPSP
These gates open near the peak of the action potential and close during after-hyperpolarization
Vg potassium channels
A measure of a difference in electrical potential
volt
What are some different ion pumps?
Sodium-potassium pump
Calcium pump
Tool that visualizes voltage change over time
oscilloscope
Can measure or record activity and can deliver electrical current (stimulate)
microelectrodes
When is electrochemical equilibrium achieved?
When the electrical force and concentration force are balanced. The net flux is 0
Combines input to same location over time. Changes how fast the input is
Temporal summation
Electrical force and concentration force want this ion to go in the cell, but the cell doesn’t want it
Sodium
Usually due to the inward flow of chloride ions or outward flow of potassium ions (rare)
IPSP
Dendrites do not have this
Myelination
Is the inside of an axon positive or negative?
negative
The neuron can fire with a stronger stimulus, AP less likely. K channels are still open, effluxing out; too much K comes out making it go beyond resting
Relative refractory period
If the membrane potential becomes more positive than its is at the resting potential, the membrane is said to be this
Depolarized
Protein structure in cell membrane that uses energy (ATP) to move ions across the membrane. Like a salmon swimming upstream
Ion pump
What are the different types of ion channels?
Voltage-dependent (electrical)
Ligand-gated (chemical)
Mechanically-gated (physical)
Ratio of intracellular ions
Large amounts of potassium ions. Small amounts of sodium and chloride
The decision point of the cell
Axon hillock
Features of the resting potential
Neuron is polarized
Charge is around -70 mV
Selectively permeable membrane
Uneven distribution of ions on the inside vs the outside
What cations are involved with axons?
Potassium, sodium, and calcium
Increase in electrical charge across a membrane (more negative)
IPSP
Limits how frequently a neuron can fire, maintains unidirectionality of signals
Refractory period
A device that measures the difference in electrical potential between two bodies
voltmeter
Small analogue signals summed over time and space
EPSP/IPSP integration
These negatively charged molecules are unable to pass through channels and pumps
Proteins
What is the resting potential value for most neurons?
-70 mV
This toxin is found in pufferfish and block VG Na channels and prevents the flow of sodium. It prevents the rising phase of AP and causes death by paralysis
Tetrodotoxin (TTX)
Charge of the threshold
Around -60 mV
Selectively binds to VG Na channels to stop the flow of NA. Prevents the rising phase of AP. No sensory or motor function
Local anesthetics. Novocaine, lidocaine, -caine
What happens at leak channels?
Some sodium ions enter the cell through these leak channels
Internal resistance to flow (how big is the diameter?)
Axial resistance
Tells the neuron not to fire
Inhibitory postsynaptic potentials (IPSPs)
Electrical forces want this ion to go in the cell and concentration forces want this ion to move out of the cell
Potassium
Rank the membrane permeability to the ions at rest
None - Proteins and calcium
Less permeable - Sodium
In between less and more - Chloride
More permeable - Potassium
Junction of the cell body and axon that contains many voltage-gated channels
Axon hillock
When molecules move from areas of high concentration to areas of low concentration
moving down the concentration gradient
What is the resting potential?
Electrical charge across the cell membrane in the absence of stimulation that has a store of negative every on the intracellular side relative to the extracellular side. Inside at -70 mV
Are electrical signals from neurons large or small?
very small
Fewer open channels leads to this which leads to this
Higher resistance to longer length constants
Electrical force wants this ion to move out of the cell and concentration forces want it to go in the cell
Chloride
Depolarization of dendrites and cell body
EPSP
Which ion channel deals with neurotransmitters?
Ligand-gated
These gates open at threshold and close at the peak of the action potential
Vg sodium channels
What are the different parts of an ion channel?
Channel domains (number varies per channel), outer vestibule, selectivity fiber, diameter of selectivity fiber, phosphorylation site, and the cell membrane
Combines input from multiple different locations. Different places giving the same input make it stronger
Spatial summation
Larger diameter axons have this
Longer length constants
Ratio of extracellular ions
Large amounts of sodium and chloride. Small amounts of potassium
What anions are involved with axons?
Chloride and protein anions
Where are the ion channels and pumps mostly located on the axons
In between the myelin sheaths in the nodes of Ranvier
Lambda is equal to what
The distance where a graded potential has decreased to 37% of original amplitude
Graded potentials need to do this in order to not decay as they travel from point to point
Active regeneration
Tells the neuron to fire
Excitatory postsynaptic potentials (EPSPs)
Graded potentials decay
The signal sent decays and no longer counts for anything
What is the equilibrium potential for potassium?
-90 mV
Characteristics of action potential
Initiated at axon hillock at threshold of excitation, large brief reversal in polarity of an axon, intracellular fluid becomes positive relative to extracellular fluid, lasts 1-2 milliseconds, mediated by opening and closing of vg ion channels, size and shape of AP remain constant along the axon, all or none, frequency coding
Because there is a potential difference across the cell membrane, the membrane is said to be this
Polarized
If threshold is reached, these open and this happens
Voltage-gated sodium channels and an action potential is initiated
Depolarization is caused by these
Excitatory postsynaptic depolarization
Decrease in electrical charge across a membrane (more positive)
EPSP
This moves ions against the concentration and electrical forces
Ion pump
Membrane potential necessary to trigger an action potential
Threshold
As a result of sodium leaking into the cell during resting potential, how does the cell maintain resting potential and polarization?
The cell uses active transport to move against concentration gradients. It moves 3 sodium ions out of the cell and 2 potassium ions in the cell
Protein structure in cell membrane that allows ions to pass without the use of additional energy. Like a lazy river
Ion channel
Used in lethal injection cocktails. Increases concentration of K in extracellular fluid. Raised the resting potential, cells become inactive, death occurs by cardiac arrest
Potassium Chloride
Hyperpolarization is caused by these
Inhibitory postsynaptic potentials
How long does the action potential last
1-2 milliseconds
If the membrane potential becomes more negative than it is at the resting potential, the membrane is said to be this
Hyperpolarized
Properties of water
Polar, hydrogen bonding, and hydrophilic
This ion wants to enter the cell because the inside is negative
Sodium
What does the selectivity filter in ion channels do?
Allows some ions to pass through and some to not
Potentials can travel over longer distances in these before dying out
Large myelinated axons
What is decay described by?
Length constant (lambda)
When value is the peak of the action potential usually at?
40 mV
There are low amounts of this ion both inside and outside, but there are more outside
Calcium
What is the charge of the inside of an axon?
-70 mV
What is the equilibrium potential for sodium?
65 mV
Number of open channels (how leaky is the membrane?)
Membrane resistance
These are poor at improving potential longevity
Thin unmyelinated axons
Usually due to the inward flow of sodium, but can also be done by calcium
EPSP
Decreases likelihood of action potential
IPSP
Facilitates likelihood of an action potential
EPSP
What are the two types of postsynaptic potentials?
Excitatory (EPSPs) and Inhibitory (IPSPs)
What can you change about an action potential?
How often it occurs (frequency coding) only
Which presynaptic inputs will have the greatest effect on the axon hillock and ATP generation
The ones close to the axon hillock
Why is the resting potential value for a neuron slightly less negative than the equilibrium potential for potassium?
Other ions are involved
What is net flux?
The amount going in and out of the membrane
The neuron cannot fire again under any circumstances. The VG Na channels are closed and are not capable of opening again
Absolute refractory period
What is it called when the membrane returns to resting potential after depolarization?
Repolarization