Lecture 1st Quiz - Electrophysiology of Neurons

Leakage Channels

Membrane channels that are continuously open to allow free movement of ions across the membrane.

Ligand Gated Channels

Membrane channels that respond to chemical stimuli called neurotransmitters.

Voltage Gated Channels

Membrane channels that depend on a change in electrical potential on the cell membrane.

Membrane Potential

The difference in electrical charge across the membrane.

Resting Membrane Potential (RMP)

A difference in electrical potential across the unstimulated membrane of a nerve cell at rest.

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The potential of an unstimulated, resting neuron is about _____millivolts. (mV)

Negative

Living cells are polarized because the charge is more __________ on the inside when at rest.

Potassium Ions (K+1)

These ions have the greatest influence on the RMP, because the plasma membrane is more permeable to them than any other ions.

Local Potential

An electrical potential that is initiated by stimulation at a specific site and spreads passively across the cell membrane, decreasing in strength with time and distance.

Sodium Ions (Na+1)

In a local potential, there is an influx of _________ _____ which diffuses for a short distance.

Trigger Zone

In the local potential of neurons, Na+1 diffuse to the soma and travel towards the ________ _________.

Graded

Local potentials are __________ because they vary in magnitude.

Decremental

Local potentials are ____________ because they become weaker as they spread from the point of stimulation.

Reversible

Local potentials are ____________ because if the stimulation ceases there will be a restoraton of the RMP.

Inhibitory

Local potentials can be excitatory or ____________.

Excitatory

___________ local potentials depolarize a cell and make a neuron more likely to produce an action potential.

Inhibitory

___________ local potentials hyperpolarize a cell and make a neuron less sensitive and less likely to produce an action potential.

Hyperpolarization

When the inside of a nerve cell becomes more negative; results from inhibitory local potentials.

Depolarization

When the inside of a nerve cell becomes less negative; results from excitatory local potentials.

Action Potential (AP)

a.k.a nerve impulse; a brief change in a neuron's electrical charge that is produced at the trigger zone and travels down the axon.

Threshold

For an action potential to happen, a local potential must rise to a critical volatage called the ___________, the minimum needed to open voltage-gated channels. (all or none effect)

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Typically, the threshold for neuronal action potential is ___millivolts (mV).

Influx

The process of flowing in.

Efflux

The process of flowing out.

Sodium Ions (Na+1)

In Step 1 of the AP: voltage-gated channels open at once to allow a massive influx of _______ _____.

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In Step 2 of the AP: Na+1 channels start closing around ___ mV and completely close at peak which is around +___ mV.

Potassium Ions (K+1)

In Step 3 of the AP: By the time the voltage peaks, the _________ _____ channels start to open up and allow an efflux of __________ ______. (same answer)

Repolarizes

In Step 3 of the AP: K+1 exit the cell. This outflow ___________ the membrane, shifting the voltage back into negative numbers.

Hyperpolarization

In Step 4 of the AP: K+1 channels stay opened longer, causing a negative overshoot called _______________.

Continuous Conduction

Transmission of a nerve impulse along the entire length of an unmyelinated axon, relatively slow.

Saltatory Conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one Node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

Myelinated

Most axons are ___________, resulting in a faster spread of action potentials.

Diameter

Myelination and the ___________ of the axon are factors that effect the speed of nerve impulse conduction.

Faster

The greater the diameter of an axon, the _________ the impulse conduction.