Electrical Neural Communication Flashcards by Simon Blum

Hyperpolarization of dendrites and cell body

IPSP

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These gates open near the peak of the action potential and close during after-hyperpolarization

Vg potassium channels

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A measure of a difference in electrical potential

volt

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What are some different ion pumps?

Sodium-potassium pump

Calcium pump

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Tool that visualizes voltage change over time

oscilloscope

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Can measure or record activity and can deliver electrical current (stimulate)

microelectrodes

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When is electrochemical equilibrium achieved?

When the electrical force and concentration force are balanced. The net flux is 0

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Combines input to same location over time. Changes how fast the input is

Temporal summation

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Electrical force and concentration force want this ion to go in the cell, but the cell doesn’t want it

Sodium

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Usually due to the inward flow of chloride ions or outward flow of potassium ions (rare)

IPSP

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Dendrites do not have this

Myelination

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Is the inside of an axon positive or negative?

negative

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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

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If the membrane potential becomes more positive than its is at the resting potential, the membrane is said to be this

Depolarized

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Protein structure in cell membrane that uses energy (ATP) to move ions across the membrane. Like a salmon swimming upstream

Ion pump

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What are the different types of ion channels?

Voltage-dependent (electrical)
Ligand-gated (chemical)
Mechanically-gated (physical)

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Ratio of intracellular ions

Large amounts of potassium ions. Small amounts of sodium and chloride

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The decision point of the cell

Axon hillock

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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

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What cations are involved with axons?

Potassium, sodium, and calcium

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Increase in electrical charge across a membrane (more negative)

IPSP

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Limits how frequently a neuron can fire, maintains unidirectionality of signals

Refractory period

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A device that measures the difference in electrical potential between two bodies

voltmeter

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Small analogue signals summed over time and space

EPSP/IPSP integration

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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