Exploring Neuron Function Using NeuroSim

Neurons and muscle fibers communicate using two types of electrical signals: _____ potentials, for _____-distance communication, and _____ potentials, for _____-distance communication.

Graded; short; action; long

Both graded potentials and action potentials involve changes in _____/_____, where refers to a _____.

Membrane potential; voltage; difference in electrical charge across the plasma membrane

Neurons and muscle fibers are _____ cells. Electrical excitability refers to the ability to _____ and generate an _____. This triggers the release of _____, which allow for communication with _____, _____, and _____.

Excitable; respond to a stimulus; action potential; neurotransmitters; other neurons; muscles; glands

Graded potentials refer to _____ changes in membrane potential. These occur when a stimulus opens or closes _____/_____-gated channels. These typically occur in the _____ or _____.

Small; mechanically; ligand; dendrites; cell body

Depolarization refers to when the membrane potential becomes _____.

Less negative

Hyperpolarization refers to when the membrane potential becomes _____.

More negative

Graded potentials vary in strength/amplitude/size depending on the _____. _____ movement across the membrane results in a signal.

Strength of the stimulus; ion

Graded potentials spread by local current flow, which refers to the _____.

Passive movement of charges from one region of the membrane to adjacent regions

Graded potentials display decremental spread, which mean they _____.

Decay over distance

Summation refers to when _____.

Two or more graded potentials are added together

The passive conduction model simulates _____ potentials, allowing you to investigate the effects of stimulus _____, _____, and _____.

Graded; strength; duration; distance

In order to generate an action potential, a threshold voltage of _____ must be reached. This means that the stimulus must be strong enough to _____ the membrane to threshold. Subthreshold stimuli are _____, while suprathreshold stimuli are _____ and act to _____. Action potentials are considered _____.

Threshold; -55 mV; depolarize; not strong enough; stronger than necessary; increase the frequency of action potentials; all-or-none

Action potentials have three phases. During the depolarizing phrase, the membrane potential _____ to _____. During the repolarizing phase, membrane potential _____ to _____. During the hyperpolarizing phase, membrane potential _____ to _____.

Increases; +30 mV; decreases; -70 mV; undershoots; -90 mV

Before a stimulus, the activation gates of voltage-gated Na+ channels are _____ and inactivation gates are _____. This means that the channels are in a _____ state.

Closed; open; ready

After receiving a stimulus, the activation gates of voltage-gated Na+ channels are _____ and inactivation gates are _____. This means that the channels are in an _____ state, contributing to the _____ phase and _____.

Open; open; active; depolarizing; Na+ influx

During the repolarizing phase, the activation gates of voltage-gated Na+ channels are _____ and inactivation gates are _____. This means that the channels are in an _____ state, conttributing to _____ becoming more significant in membrane potential.

Open; closed; inactive; K+ efflux

The hyper-polarization phase is characterized by _____. At this time, voltage-gated Na+ channels _____, meaning that activation gates are _____ and inactivation gates are _____.

K+ efflux; reset to ready; closed; open

The refractory period refers to the _____.

Period of time after an action potential begins when an excitable cell cannot generate another action potential in response to a normal threshold stimulus

During the absolute refractory period, _____. This coincides with the period of _____ channel activation and inactivation, as _____ channels cannot reopen before they return to the _____ state.

Even a very strong stimulus cannot initiate a second action potential; Na+; inactivated; resting

During the relative refractory period, _____. This coincides with the period when the _____ channels are still open after some _____ channels have reset. The relative refractory period takes place from _____ to _____.

Larger-than-normal stimuli can initiate a second action potential; K+; Na+; end of repolarization; hyperpolarization

The Hodgkin-Huxley model allows for the simulation of _____, where you can measure the _____ and _____ of spikes. By adjusting the _____ between stimuli, you can determine the _____ and _____. You can also investigate the effects of _____, _____, and _____.

Action potentials; amplitude; timing; delay; absolute refractory period; relative refractory period; TTX; scorpion toxin; hyperkalemia

Hyperkalemia causes a _____ in the K+ concentration gradient across the plasma membrane, causing _____ to leave the neuron, which causes the neuron to _____.

Decrease; less; depolarize

When stimulus strength increases, respond amplitude _____. This is because _____.

Increases; the strength of a stimulus is directly proportional to the strength of a graded potential

In graded potentials with longer duration, it takes relatively _____ for the response to reach the maximum amplitude as well as decrease back to baseline.

Longer

Increasing stimulus duration in a graded potential tends to _____ the magnitude of the response because _____.

Increase; the response from the first stimuli does not decay as much before receiving the second stimuli

TTX appears to produce _____ despite the input of a stimulus. This indicates that TTX appears to block the action of _____, likely by preventing the _____, preventing _____ into the neuron and therefore _____.

No action potential; votlage-gated Na+ channels; opening of the activation gates; Na+ influx; depolarization

Scorpion toxin appears to cause the action potential to _____. This indicates that scorpion toxin appears to block the action of _____, likely by preventing them from _____, preventing _____ out of the neuron and therefore _____.

Fail to repolarize following depolarization; voltage-gated K+ channels; opening; K+ efflux; repolarization

Hyperkalemia results in multiple action potentials occurring after a single stimulus because the rate of _____ is slower, _____ the membrane potential _____ threshold and keeping the neuron in a _____ state, which makes it easier to fire an action potential.

K+ efflux; raising; closer to; depolarized