# L4 Neural Signaling: Electrical Propagation of Neurons

## 26 terms

### What is a parallel RC circuit?

A parallel RC circuit is a circuit that has both resisters and capacitors. it is like the model neuron. as current is applied, it will slowly rise to max voltage, then when current is taken away, it will leak energy and return to baseline

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### What is the resistance of an axon proportional to?

inversely proportional to the diameter of an axon. the larger the diameter, the larger the cross sectional area and the lower the resistance will be. the smaller the diameter, the higher the resistance

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### What is Lambda?

the smaller the lambda, the quicker the decay, the more rapidly the curve falls back to 0. the higher the lambda, the more likely that that potential will have a shot at helping summativly create an action potential

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### Why do we have 63% as the number Tau represents?

63% is just an arbitrary number created by the constant e, which we have to use to calculate curves. accept that the larger Tau is, the longer it takes to reach 63%

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### What is Tau?

it is a number that is mathematically equal to the membrane resistance X the membrane capacitance. it tells you when you reach 63% of your ultimate change. it also tells you how long that postsynaptic value hangs around

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### What does Tau tell you?

whether you have a rapidly rising curve, a medium rising curve or a high rising curve. the smaller the Tau the steeper the curve

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steeper

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### Which synaptic potential would have a better chance at summating, one with a tau of 2.0 sec, or one with a tau of .02 seconds

the one with 2.0 seconds

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### Is the tau for a neuron variable?

no, the neuron determines Tau, and since that neuron doesn't chance, the tau will not either

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### What is the only way a neuron with a very high tau could mount an action potential?

cranking up it's frequency of input

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### How does resistance effect lambda?

the greater the resistance, the smaller the lambda, the faster the current will decay. the smaller the resistance, the greater the lambda, the slower the current will decay.
they are inversely proportional

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### Walk through axon diameter as it pertains to resistance and lambda.

the greater the diameter, the less resistance there will be. (bigger highway, more traffic can pass)
the smaller the resistance, the easier it is for the current to flow, thus it will be able to cover more ground (have a higher lambda) before it decays

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### What is the signature event of an action potential?

it is the rapid depolarization and then a rapid repolarization

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### What causes an active membrane response?

the function of the voltage gated ion channels. they are what allows the axon to generate propagate the action potential.

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### What is the difference between a passive conductance property and an active one?

passive is just doable. it just happens, it can be predicted. active response is not predicted by the electrical equations. there is participation of the membrane.

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### What is a voltage clamp?

it allows us to measure the votlage in an axon preparation and to cause current changes with a stimulator. we could also set a current, or 'clamp' it

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### What is the importance of the invention of the voltage clamp?

it allows us to observe what underlying processes that are occurring before the action potential

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### What are the relevant things to the propagation of an action potential?

conc gradients of Na, K and Cl and integral membrane proteins

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### How are permeability and conductance related?

conductance is proportional to permeability. it's just that one is an electrical measure and one is a chemical measure, they describe the ease of current flow

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OHM

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### What is the unit of conductance?

since the conductance is the recipricol of resistance, they named the MHO

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Na

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### What are some properties of Na channels that set it apart from the other ion channels?

that they facilitate a rapid increase in Na conductance, which terminates on it's own despite the prolonged depolarization.

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### What are some properties of K channels that set it apart from Na channels?

K channels, unlike Na channels, are much slower to open, but once they're open, they stay open, as long as the depolarization that caused it persists

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### How many controls are there on a Na voltage gated ion channel?

there are 2. the middle core can squeeze shut, this is the usual closed form. then, while the middle pore is open and ions are rushing in, there is another gate that swings suddenly shut. this is the inactivated form. the pore squeezes shut again, and the gate swings open, leaving the 'closed' form of the voltage gated ion channel

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