| Course | PSY 340 Biological Foundations in Psychology (PSY/340) |
|---|---|
| Week | 1 |
| Paper type | Neural communication paper |
| Length | about 1,020 words, 4 double-spaced pages plus title page and references |
| Format | APA 7 student paper |
| School | University of Phoenix |
| Program | BS in Psychology |
| Updated | October 2026 |
Free sample paper for PSY 340 Week 1
When the Signal Slows: Neurons, Myelin and Synapses Explained Through a Case of Multiple Sclerosis
[Student Name]
University of Phoenix
PSY/340: Biological Foundations in Psychology
Week 1 Assignment
[Instructor Name]
[Date]
The person described is a composite written for a model paper; research findings come from the sources listed.
Every thought, movement and feeling depends on neurons signaling to one another. When that signaling falters, the effects show up in behavior and experience. This paper explains how neurons communicate and uses a case of multiple sclerosis to show what happens when one part of the process is damaged.
The Case
Teresa is thirty-four and teaches seventh-grade science in Tucson, Arizona. Last spring she woke with blurred vision and pain when moving her left eye. A few months later, her right hand began to tingle and feel clumsy while she wrote on the whiteboard. A neurologist ordered a magnetic resonance scan, which showed several small areas of damage in the white matter of her brain and spinal cord, and she was diagnosed with relapsing multiple sclerosis. She has also been treated for depression with sertraline for two years.
The Scale of the System
Azevedo et al. (2009) counted cells in human brains by dissolving tissue and counting nuclei, a method that avoids estimating from small samples. They found about 86 billion neurons and a similar number of nonneuronal cells, correcting earlier claims of 100 billion neurons and a tenfold excess of glia. Each neuron may connect with thousands of others, so even small disruptions in signaling can spread across networks.
Structure of a Neuron
A typical neuron has dendrites that receive input, a cell body that integrates it and an axon that carries output to terminals, where chemical messengers are released. Many axons are wrapped in myelin, made in the brain and spinal cord by oligodendrocytes, with small gaps called nodes of Ranvier between segments.
The Resting Potential
At rest, the inside of a neuron is negative relative to the outside, at about minus seventy millivolts. This resting potential results from an uneven distribution of ions: more sodium outside, more potassium inside, maintained by the sodium-potassium pump and by the membrane's greater permeability to potassium.
The Action Potential
Hodgkin and Huxley (1952) used the giant axon of the squid to measure the currents flowing across the membrane during a nerve impulse and built a mathematical model that explained it. When inputs push the membrane past a threshold, voltage-gated sodium channels open, sodium rushes in and the inside briefly becomes positive. Sodium channels then close, potassium channels open, potassium flows out and the membrane returns to rest, briefly overshooting. Their model, built from these measurements, predicted the shape and speed of the impulse and remains the foundation of the field.
The action potential is all or none: once threshold is reached, it fires at full strength. Stronger stimuli produce more frequent action potentials, not bigger ones.
How Myelin Speeds the Signal
In an unmyelinated axon, the action potential must regenerate at every point along the membrane, which is slow. In a myelinated axon, current flows quickly under the insulated segments and the action potential regenerates only at the nodes, appearing to jump from node to node. This saltatory conduction can be many times faster and uses less energy.
What Goes Wrong in Multiple Sclerosis
Compston and Coles (2008) reviewed multiple sclerosis as a disease in which the immune system attacks myelin in the central nervous system, producing areas of inflammation and scarring, along with damage to axons themselves. Where myelin is stripped away, conduction slows or fails entirely, and the effects depend on which pathways are affected. Most patients begin with a relapsing course, in which symptoms appear and then improve as inflammation subsides and some repair occurs.
Teresa's symptoms map onto this mechanism. Inflammation of the optic nerve slowed signals from her left eye, causing blurred vision and pain on eye movement. A lesion in the spinal cord disrupted sensory and motor pathways to her right hand, producing tingling and clumsiness. Heat, such as a warm classroom in an Arizona May, can worsen conduction through damaged segments temporarily, which is why some patients notice symptoms more on hot days.
Teresa's hand works and her eye works; what fails is the speed of the message traveling between them and her brain.
Chemical Communication at the Synapse
When an action potential reaches the axon terminal, it opens calcium channels. Calcium entry causes vesicles to release neurotransmitter into the synapse, the small gap between neurons. The neurotransmitter binds to receptors on the receiving neuron, opening ion channels or triggering chemical cascades that raise or lower the chance the receiving neuron will fire. Transmission stops once the neurotransmitter is broken down or taken back into the sending neuron by transporters, a process called reuptake.
How Teresa's Antidepressant Works
Sertraline belongs to the antidepressant class known as SSRIs. The drug occupies the transporter that would normally pull serotonin back out of the synapse, so serotonin lingers there longer. The blocking happens within hours, yet mood usually improves only after weeks, suggesting that the benefit depends on slower adaptations, such as changes in receptor sensitivity and in the growth of connections, rather than on serotonin levels alone. This is one reason the phrase "chemical imbalance" oversimplifies depression.
Depression and Multiple Sclerosis
Depression is common in people with multiple sclerosis, more common than in many other chronic illnesses. It may reflect both the stress of living with an unpredictable disease and the effects of lesions on brain circuits involved in mood. For Teresa, the two conditions are linked, and treating her depression supports her ability to manage the disease.
Treatment and Outlook
Teresa's neurologist has started a disease-modifying therapy that reduces immune attacks on myelin and lowers the rate of relapses. Corticosteroids may shorten an acute relapse. Physical and occupational therapy help her adapt her writing, and cooling strategies help on hot days. Many people with relapsing multiple sclerosis continue working for years.
Conclusion
Neurons communicate through an electrical signal within the cell and a chemical signal between cells. Myelin makes the electrical signal fast, and its loss in multiple sclerosis explains Teresa's blurred vision and numb hand. Her antidepressant acts at the chemical stage, and its delayed benefit shows that behavior emerges from changes across networks, not from a single molecule.
References
Azevedo, F. A. C., Carvalho, L. R. B., Grinberg, L. T., Farfel, J. M., Ferretti, R. E. L., Leite, R. E. P., Jacob Filho, W., Lent, R., & Herculano-Houzel, S. (2009). Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. Journal of Comparative Neurology, 513(5), 532-541. https://doi.org/10.1002/cne.21974
Compston, A., & Coles, A. (2008). Multiple sclerosis. The Lancet, 372(9648), 1502-1517. https://doi.org/10.1016/S0140-6736(08)61620-7
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
What the PSY 340 Week 1 instructions ask
Week 1 work in PSY 340 typically centers on how neurons are built and how they pass signals along. Typical requirements include describing dendrites, cell body, axon, myelin and terminals, explaining the resting potential and action potential, describing synaptic transmission and the roles of major neurotransmitters and discussing how drugs or disorders affect these processes. Some versions ask for a diagram or a case application. Use accurate physiological terms, explain each step in order and connect the biology to an observable behavior or symptom. Back each step with the course text and journal research cited in APA style, and avoid oversimplified phrases such as "chemical imbalance" without explaining the mechanism.
How this PSY 340 Week 1 example is built
Our worked paper follows Teresa, a middle school teacher who notices blurred vision in one eye and tingling in her right hand. Tests show areas of damaged myelin in her brain and spinal cord, and she is diagnosed with relapsing multiple sclerosis. The paper explains how ions create the resting and action potentials, drawing on the classic experiments that first described them, and how myelin speeds conduction by letting signals jump between gaps. A review of multiple sclerosis links her symptoms to slowed and blocked signals. Her prescribed antidepressant illustrates synaptic transmission and reuptake, and research on the number of cells in the human brain puts the scale of the system in view.
PSY 340 Week 1 grading rubric: where the points go
Neural communication papers are usually graded on accurate terminology, a correct sequence of events and clear links between biology and behavior. Instructors look for the action potential to be explained with ion movement, for the difference between electrical signaling within a neuron and chemical signaling between neurons to be clear and for neurotransmitter roles to be described without oversimplifying. Credit goes to applying the mechanisms to a real case or drug, to citing primary and review research and to diagrams labeled correctly. APA formatting is expected. Graders also value papers that note what remains uncertain, such as why myelin is attacked in multiple sclerosis, rather than presenting every mechanism as settled.
PSY 340 Week 1 help: mistakes to avoid
A common mistake is mixing up the electrical and chemical stages, describing neurotransmitters traveling down the axon or ions crossing the synapse. Another is explaining the action potential as a gradual signal, when it is all or none, with intensity coded by firing rate. Students also describe myelin as insulation without explaining how it speeds conduction, or list neurotransmitters with single, simplistic jobs such as "serotonin is the happiness chemical." Some papers describe a drug's effect without saying which step it changes. Follow the signal in order, name the ions and receptors involved and tie each mechanism to a symptom. A tutor can help you check each step of the sequence.
Related PSY 340 sample papers
Other PSY 340 week samples
- PSY 340 Week 2: Brain Structure and Research Methods
- PSY 340 Week 3: Sensation, Perception and Movement
- PSY 340 Week 4: Sleep, Eating and Motivation
- PSY 340 Week 5: Learning, Memory and Emotion
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PSY 340 Week 1 questions, answered
What does PSY 340 Week 1 usually cover?
It usually covers neuron structure, the resting and action potentials, synaptic transmission and neurotransmitters.
Where can I find a free PSY 340 Week 1 sample paper?
The PSY 340 Week 1 paper explaining neural signals through a case of multiple sclerosis is free above.
What is an action potential?
A brief, all-or-none electrical signal that travels down the axon when the neuron's membrane reaches its threshold.
What does myelin do?
It wraps the axon and lets signals jump between gaps, making conduction much faster and more efficient.
How do SSRIs work?
They block the reuptake of serotonin into the sending neuron, leaving more serotonin available in the synapse.
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