PS215 Unit 2 Neural Signaling Explanation Example

Reviewed by Romilly Dunmore, MEd Neuroscience Purdue University Global Free custom sample in 24 to 48h

How a neuron rests, fires and passes its signal on is explained in this PS215 Unit 2 neural signaling explanation, and the same steps show why neurons in Harold's stroke stopped working within minutes. The sodium-potassium pump, which spends ATP to move three sodium out for two potassium in, keeps the membrane near minus 70 millivolts; threshold opens sodium gates; calcium at the terminal releases glutamate. When the clot cut off oxygen, the pump stopped, cells depolarized and excess glutamate damaged neighbors, which is why treatment races to save the edge of the injury. Purdue Global PS 215, Neuroscience, assigns this explanation in the BS in Psychology course.

CoursePS215 Neuroscience
UnitUnit 2
Paper typeNeural signaling explanation
LengthAbout 560 words, 5 pages double-spaced
FormatAPA 7 student paper
SchoolPurdue University Global
ProgramBS in Psychology
UpdatedOctober 2026

Free sample paper for PS215 Unit 2

1

Why Neurons Stop Firing When Blood Stops Flowing: A PS215 Unit 2 Neural Signaling Explanation

[Student Name]

Purdue University Global

PS215: Neuroscience

Unit 2 Neural Signaling Explanation

[Instructor Name]

[Date]

The stroke case is composite; the physiology and studies cited are real.

What this part is doingTying each signaling step to what fails in a stroke in the lead shows the explanation is applied, not memorized.
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The Neuron at Rest

A neuron at rest holds an electrical charge across its membrane, about 70 millivolts more negative inside than outside. Two features create this resting potential. Ion channels let potassium leak out more easily than sodium leaks in, and the sodium-potassium pump continually moves three sodium ions out and two potassium ions in for each molecule of ATP it uses (Kandel et al., 2021). The result is a membrane that is charged and ready, with sodium concentrated outside and potassium inside.

The pump is the key to the stroke case. It runs constantly and consumes a large share of the brain's energy, which is why the brain, about two percent of body weight, uses about a fifth of the body's oxygen at rest.

The Action Potential

When a neuron receives enough excitatory input to raise its membrane voltage to a threshold, around minus 55 millivolts, gates in the membrane that respond to voltage swing open for sodium, which pours inward until the cell's interior turns briefly positive. About a millisecond later the sodium gates shut, slower potassium gates swing open, and the outward potassium current pulls the voltage back down. Hodgkin and Huxley (1952) worked out these currents in the giant axon of the squid, measuring how sodium and potassium conductances change with voltage. Size does not vary: crossing threshold produces the same full spike every time, and that spike regenerates along the axon at undiminished strength.

An action potential always fires at full strength; what changes with a stronger stimulus is how often it fires.

Passing the Signal On

When the impulse reaches the terminal button, calcium floods in, and that influx makes small packets of transmitter fuse with the membrane and empty into the gap, where it binds receptors on the next neuron. Glutamate, the brain's main excitatory transmitter, opens channels that let positive ions in and pushes the next neuron toward its own threshold. The signal is then cleared by reuptake into surrounding cells, a step that also depends on energy.

What this part is doingNoting that neurotransmitter clearance needs energy prepares the explanation of why stroke damage spreads.
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What Happens in a Stroke

When a clot blocked an artery in Harold's left hemisphere, the neurons it supplied lost oxygen and glucose. Without ATP, the sodium-potassium pump stopped. Sodium built up inside the cells and potassium leaked out, the resting potential collapsed and the neurons depolarized. Depolarized terminals released glutamate, and the energy-dependent systems that normally clear it failed. The excess glutamate overstimulated neighboring neurons, letting in calcium that triggers enzymes and processes that destroy cells, a chain called excitotoxicity (Lai et al., 2014).

This sequence explains why speed matters. Neurons in the core of the blocked territory die within minutes, but a surrounding zone of tissue receives some blood from other vessels and stays salvageable for a few hours if circulation comes back. The clot-dissolving drug Harold received in the emergency department worked by reopening the artery before that surrounding zone was lost.

Why the Explanation Matters

Understanding signaling turns the phrase time is brain into mechanism. Every minute without flow lets the pump failure and glutamate cascade spread outward, and treatment aims to stop it at the edge.

What this part is doingEnding on the mechanism behind a familiar slogan shows the explanation reaches the case.
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References

Hodgkin, A. L., & Huxley, A. F. (1952). A quantitative description of membrane current and its application to conduction and excitation in nerve. The Journal of Physiology, 117(4), 500-544. https://doi.org/10.1113/jphysiol.1952.sp004764

Kandel, E. R., Koester, J. D., Mack, S. H., & Siegelbaum, S. A. (2021). Principles of neural science (6th ed.). McGraw Hill.

Lai, T. W., Zhang, S., & Wang, Y. T. (2014). Excitotoxicity and stroke: Identifying novel targets for neuroprotection. Progress in Neurobiology, 115, 157-188. https://doi.org/10.1016/j.pneurobio.2013.11.006

Reading the PS 215 Unit 2 instructions

Unit 2 in PS215 typically asks you to explain how a neuron generates and transmits an action potential and what can disrupt it. Work in order: the resting potential and what maintains it, the events at threshold, the return to rest and transmission across the synapse. Use accurate values and name the channels and ions involved. Then apply the mechanism to a disruption, such as a drug, a toxin or an injury, showing exactly which step fails and what follows. A classic study, such as Hodgkin and Huxley's work on the squid axon, adds depth when described correctly. Keep the explanation clear enough for a reader without a biology background, and cite a neuroscience text along with any primary sources.

Inside the PS215 Unit 2 example

The explanation begins with the resting membrane, leak channels and the pump, and notes the brain's large share of the body's oxygen. The action potential section covers threshold, sodium entry, the later potassium current and Hodgkin and Huxley's squid measurements, under a highlighted line that strength changes firing rate, not spike size. A synapse section follows calcium entry, transmitter release and glutamate's excitatory action, adding that clearing it needs energy. The stroke section traces pump failure, depolarization and glutamate buildup into excitotoxicity with Lai and colleagues, and distinguishes the dying core from the salvageable surrounding zone that the clot-dissolving drug protected. A closing line turns the phrase time is brain into the mechanism just described.

Reading the PS215 Unit 2 grading rubric

Explanations in this unit are graded on accuracy and sequence. Instructors check that the resting potential, the events at threshold and the return to rest are described correctly, with the right ions moving the right way. Including synaptic transmission follows the signal to the next cell. Applying the mechanism to a disruption, and naming the exact step that fails, shows understanding rather than memorization. Accurate description of a classic experiment adds credit. Clear prose that a nonspecialist could follow is valued, since PS215 is an introductory course. A neuroscience textbook and any primary sources should be cited correctly, and diagrams, if included, should match the text. Linking the explanation to a case the reader can picture also earns credit for application.

Common PS215 Unit 2 mistakes, and how to avoid them

The most frequent error reverses the ions, saying potassium rushes in during the rising phase. Another common slip describes the action potential as getting stronger with a stronger stimulus, when firing rate changes instead. Students often stop at the axon terminal and leave out synaptic transmission. Applications are sometimes vague, saying a drug affects neurons without naming the step. Explanations copied from a textbook in technical language lose the clarity instructors want. Before submitting, check each ion's direction at each phase, add one sentence on what happens at the synapse, name the exact step your example disrupts and read the paper aloud to see whether a classmate could follow it.

Get a PS215 Unit 2 example written to your instructions

Share the instructions and the rubric. A custom explanation walks through resting potential, the action potential and synaptic transmission with an example. Turnaround is 24-48h, free the first time. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.

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PS215 Unit 2 questions, answered

What is the resting potential?

The voltage difference across a neuron's membrane at rest, about minus 70 millivolts, maintained partly by the sodium-potassium pump.

What causes an action potential?

Voltage-gated sodium channels open when the membrane reaches threshold, letting sodium rush in.

Should the paper include an example?

Yes; a drug, toxin or injury that disrupts signaling makes the mechanism concrete.

Where can I find a free PS215 Unit 2 sample paper?

This page carries the complete PS215 Unit 2 explanation of the action potential and synapse, applied to why neurons die in a composite stroke.

Why do neurons stop firing in a stroke in the PS215 Unit 2 sample?

Without oxygen the sodium-potassium pump fails, cells depolarize and excess glutamate overstimulates neighboring neurons.