What Is an Action Potential

Every time you do something, from taking a step to picking up your phone, your brain transmits electrical signals to the rest of your body. These signals are called action potentials. Action potentials allow your muscles to coordinate and move with precision. They are transmitted by cells in the brain called neurons. Key Takeaways: Action Potential Action potentials are visualized as rapid rises and subsequent falls in the electrical potential across a neuron’s cell membrane.The action potential propagates down the length of a neuron’s axon, which is responsible for transmitting information to other neurons.Action potentials are â€Å"all-or-nothing† events that occur when a certain potential is reached. Action Potentials Are Conveyed by Neurons Action potentials are transmitted by cells in the brain called neurons. Neurons are responsible for coordinating and processing information about the world that is sent in through your senses, sending commands to the muscles in your body, and relaying all the electrical signals in between. The neuron is made up of several parts that allow it to transfer information throughout the body: Dendrites are branched parts of a neuron that receive information from nearby neurons.The cell body of the neuron contains its nucleus, which contains the cell’s hereditary information and controls the cell’s growth and reproduction.The axon conducts electrical signals away from the cell body, transmitting information to other neurons at its ends, or axon terminals. You can think of the neuron like a computer, which receives input (like pressing a letter key on your keyboard) through its dendrites, then gives you an output (seeing that letter pop up on your computer screen) through its axon. In between, the information is processed so that the input results in the desired output. Definition of Action Potential Action potentials, also called â€Å"spikes† or â€Å"impulses,† occur when the electrical potential across a cellular membrane rapidly rises, then falls, in response to an event. The entire process typically takes several milliseconds. A cellular membrane is a double layer of proteins and lipids that surrounds a cell, protecting its contents from the outside environment and allowing only certain substances in while keeping others out. An electrical potential, measured in Volts (V), measures the amount of electrical energy that has the potential to do work. All cells maintain an electrical potential across their cellular membranes. The Role of Concentration Gradients in Action Potentials The electrical potential across a cellular membrane, which is measured by comparing the potential inside of a cell to the outside, arises because there are differences in concentration, or concentration gradients, of charged particles called ions outside versus inside the cell. These concentration gradients in turn cause electrical and chemical imbalances that drive ions to even out the imbalances, with more disparate imbalances providing a greater motivator, or driving force, for the imbalances to be remedied. To do this, an ion typically moves from the high-concentration side of the membrane to the low-concentration side. The two ions of interest for action potentials are the potassium cation (K) and the sodium cation (Na), which can be found inside and outside of cells. There is a higher concentration of K inside of cells relative to the outside.There is a higher concentration of Na on the outside of cells relative to the inside, about 10 times as high. The Resting Membrane Potential When there is no action potential in progress (i.e., the cell is â€Å"at rest†), the electrical potential of neurons is at the resting membrane potential, which is typically measured to be around -70 mV. This means that the potential of the inside of the cell is 70 mV lower than the outside. It should be noted that this refers to an equilibrium state – ions still move into and out of the cell, but in a way that keeps the resting membrane potential at a fairly constant value. The resting membrane potential can be maintained because the cellular membrane contains proteins that form ion channels – holes that allow ions to flow into and out of cells – and sodium/potassium pumps which can pump ions in and out of the cell. Ion channels are not always open; some types of channels only open up in response to specific conditions. These channels are thus called â€Å"gated† channels. A leakage channel opens and closes at random and helps maintain the resting membrane potential of the cell. Sodium leakage channels allow Na to slowly move into the cell (because the concentration of Na is higher on the outside relative to the inside), while potassium channels allow K to move out of the cell (because the concentration of K is higher on the inside relative to the outside). However, there are many more leakage channels for potassium than there are for sodium, and so potassium moves out of the cell at a much faster rate than sodium entering the cell. Thus, there is more positive charge on the outside of the cell, causing the resting membrane potential to be negative. A sodium/potassium pump maintains the resting membrane potential by moving sodium back out of the cell or potassium into the cell. However, this pump brings in two K ions for every three Na ions removed, maintaining the negative potential. Voltage-gated ion channels are important for action potentials. Most of these channels remain closed when the cellular membrane is close to its resting membrane potential. However, when the potential of the cell becomes more positive (less negative), these ion channels will open. Stages of the Action Potential An action potential is a temporary reversal of the resting membrane potential, from negative to positive. The action potential â€Å"spike† is usually broken into several stages: In response to a signal (or stimulus) like a neurotransmitter binding to its receptor or pressing a key with your finger, some Na channels open, allowing Na to flow into the cell due to the concentration gradient. The membrane potential depolarizes, or becomes more positive.Once the membrane potential reaches a threshold value—usually around -55 mV—the action potential continues. If the potential is not reached, the action potential does not happen and the cell will go back to its resting membrane potential. This requirement of reaching a threshold is why the action potential is termed an all-or-nothing event.After reaching the threshold value, voltage-gated Na channels open, and Na ions flood into the cell. The membrane potential flips from negative to positive because the inside of the cell is now more positive relative to the outside.As the membrane potential reaches 30 mV – the peak of the action potential – voltage-gated potassium channels open, and K leaves the cell due to the concentration gradient. The membrane potential repolarizes, or moves back towards the negative resting membrane potential.The neuron becomes temporarily hyperpolarized as the K ions cause the membrane potential to become a little more negative than the resting potential.The neuron enters a refractory period, in which the sodium/potassium pump returns the neuron to its resting membrane potential. Propagation of the Action Potential The action potential travels down the length of the axon towards the axon terminals, which transmit the information to other neurons. The speed of propagation depends on the diameter of the axon—where a wider diameter means faster propagation—and whether or not a part of an axon is covered with myelin, a fatty substance that acts similar to the covering of a cable wire: it sheaths the axon and prevents electrical current from leaking out, allowing the action potential to occur faster. Sources â€Å"12.4 The Action Potential.† Anatomy and Physiology, Pressbooks, opentextbc.ca/anatomyandphysiology/chapter/12-4-the-action-potential/.Charad, Ka Xiong. â€Å"Action Potentials.† HyperPhysics, hyperphysics.phy-astr.gsu.edu/hbase/Biology/actpot.html.Egri, Csilla, and Peter Ruben. â€Å"Action Potentials: Generation and Propagation.† ELS, John Wiley Sons, Inc., 16 Apr. 2012, onlinelibrary.wiley.com/doi/10.1002/9780470015902.a0000278.pub2.â€Å"How Neurons Communicate.† Lumen - Boundless Biology, Lumen Learning, courses.lumenlearning.com/boundless-biology/chapter/how-neurons-communicate/.

Dqs Example

Essays on Dq's Assignment Responses to Posts al Affiliation Responses to Posts Response to Post One shares similar contentionsto the relevance of the three (3) key insights which were selected: due care in the performance of professional responsibilities, responsibilities to clients, and ethics and tax services. As emphasized in the AICPA Code of Professional Conduct, accounting practitioners are expected to adhere by the guidelines and principles expected of the profession. The observance and knowledge of ethical standards, in addition to the basic rules, govern the ability for effective application in diverse situations. As noted, knowledge of applied business models that conform to accounting standards should have been integrated in the theoretical frameworks learned to ensure that false entries are ultimately avoided. The experience at HealthSouth illumined the importance of acknowledging diversity in applied business models which should not be presumed as already conforming to accounting principles. The case highlighted the need for auditors to be more vigilant in discerning the application of business models which could hide erroneous entries and ultimately cause their reputations to be at stake. Response to Post# 2 The conflict of interests which were highlighted as one of the key insights learned was also affirmed as relevant. In contemporary settings, one observed that despite knowledge of accounting practitioners to the governing rules stated in the AICPA Code of Professional Conduct, there still exists tendencies for lapses in application of some practices which lead to conflicts of interests. The rationale clearly explained the separation in duties and responsibilities was paramount due to the nature of accountability that the professional holds. These accountants and auditors should focus on financial duties to avoid situations where their professional interests are questioned as to the integrity and viability of accountability. As to the understanding on the concept of tax shelters, it is actually a legal technique, not only for the wealthy; but for individuals and businesses, to reduce or minimize taxable income. One strongly believes that the techniques are varied depending on the res pective accounts and expenses which could be eligible for minimization before the tax shelter concept could be applied. Response to Post #3 It was commendable to have recognized that the contents of the audit report was a key insight in this week’s reading. A comprehensive understanding of the components assist in appreciating the importance of an auditor’s job in the light of accountability for ensuring that the organization being examined conforms to accounting principles and standards. One affirms the need to avoid violations, especially in recording false statements or maliciously intended transactions that aim to provide a padded financial condition than what the actual situation is. Like in the case of Tyco, the manner by which Kozlowski structured some transactions to be private to higher members of the echelon contributed to fraudulent activities. If external auditors were more vigilant of examining related financial transactions undertaken by board members and those from the executive management team, the extensive amounts of money stashed away by these officers should have been checked and preven ted. One believes that there could be apprehension to question the owners, senior management, or members of the board, since they are expected to adhere to codes of ethical standards and are least expected to use the organization’s financial resources for their own selfish interests. Response to Post #4 Acknowledging learning more on the topics of internal auditing, code of ethics, and corporate governance from the Institute of Internal Auditors (2014) is shared as paramount since these concepts form the theoretical frameworks for conformity to accounting principles and standards; especially in ensuring transparency and accountability of reported transactions. The strongly recommended sections were likewise reviewed for an in-depth understanding of information contained in the position papers, practice advisories, as well as from the practice guides. One affirms that for interested practitioners who would like to learn more on internal auditing and corporate governance, they could learn from experiences from actual cases of contemporary corporations. Just like the cases of HealthSouth, Tyco, and others where whistleblowing led to discoveries of violations are interesting to know. As such, one recognizes the importance of giving protection, and even incentives or encouragement, to w histleblowers, so that fraudulent activities would be ultimate abated. Reference The Institute of Internal Auditors. (2014). Code of Ethics. Retrieved from na.theiia.org: https://na.theiia.org/standards-guidance/mandatory-guidance/Pages/Code-of-Ethics.aspx

Autobiography of Frederick Douglass Free Essays

Frederick Douglass’s Autobiography, Narrative of the Life of Frederick Douglass, An American Slave, is situated in a context that was not open to, or fond of the straightforwardness of his writing style. His open identity in an anonymous world of anti-slavery literature thrust him into international fame. His writings are often compared with that of Thomas Jefferson, and Benjamin Franklin. We will write a custom essay sample on Autobiography of Frederick Douglass or any similar topic only for you Order Now Unlike Jefferson and Franklin, however, Douglass’s Narrative was inspired by much more than a harsh, but removed king-figure. Instead, violence and the difficulty of obtaining a worthwhile education spawned Douglass’s quest for freedom. After compelling and continual praise from Garrison and Wendell Phillips in the Preface to the Narrative, Douglass begins his story immediately addressing the ignorance expected from slaves. They were not allowed to know their ages, they were often taken from their mothers at a very early age. Even Douglass admits that upon his mother’s death, it meant nothing more to him than the death of a stranger. From a very early age, Douglass felt the need to learn. He recognized that a major distinction between slaves and their white masters was education. He recalls his master saying that education could do him (Douglass) no good, but instead â€Å"a great deal of harm. It would make him discontented and unhappy† (1776). At that moment, Douglass realized what he had to do to escape the bonds of slavery to achieve freedom. â€Å"These words sank deep into my heart, stirred up sentiments within that lay slumbering, and called into existence an entirely new train of thought† (1776). Diligently, Douglass learned to read and became an eloquent speaker. Upon his escape to freedom, the opportunity to share his experiences with multitudes of others that were unaware of the abilities of a Negro to think deeply and speak powerfully opened up. He led a revolution of thought and made available to the public a new perspective on universal and all-inclusive humanity. In addition to education, violence also played an important role in Douglass’s efforts to prove himself an equal. He offers disturbing accounts of starvation and depravation of the most essential things in life. Numerous descriptions of violent beatings that were indicative of any given day on a plantation drew sympathy from those who read the Narrative. Douglass’s stories offer a view of the brutality of slavery that was rarely seen or heard in that time, especially from a black man. His descriptive and graphic words grabbed hold of the hearts of readers and listeners. Douglass used his personal experiences, as painful as they were, to inspire a revolutionary new idea: the idea that Negroes were as capable (if not more capable to be able to endure those methods of punishment) as the whites. To Douglass, education would bring him out of oppression, and the violence he witnessed and endured left him no choice but to escape from that oppression. In his Narrative, the visual imagery of emaciated slave girls fighting for offal thrown into the street and women being beaten until too exhausted to even stand provided a foundation for events as critical as the Emancipation Proclamation. He showed courage beyond that which was called for by standing, as a former slave, against those who would oppress a person because of the color of their skin. His narrative is powerful and moving and it a cornerstone of the civil rights we have today. How to cite Autobiography of Frederick Douglass, Papers

Big City Description Stone Cold free essay sample

I knew I shouldnt have done this, not like this, not today Not any day. I cant turn back now, its too late for that, and in fact it was too late 3 hours ago, sitting on the plane I stare out of the window trying to look at the New York streets, but the shapes are a meaningless blur. Theres hardly any green, I notice every color of the rainbow, but no green. Its nothing like home -Snap out of alt- I tell myself sternly. I look at the hole that I dug in the tired upholstery of the worn seat, Thatll be 24 dollars, doll, the cabin says, his tone of voice clearly Implying that this wasnt the iris time he was trying to get through to me but his face Is a mask of nonchalance and amusement, its like he has two personalities that are fighting to show In one way or another Stiffly and without looking him In the eyes, I put a $50 bill In his hand and leave, not waiting for change. We will write a custom essay sample on Big City Description: Stone Cold or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page The pungent smell of car fumes was unbearable; so was the amount of people.To be quite honest, the whole city came as a huge surprise, the Images In books lied, or maybe they hadnt and I made It out to be more perfect than It actually was.. . Most people were thankfully keeping to themselves, though some were openly staring; their icy glares like knives on my back. Others were something Id call rather eccentric, one woman with a homeless sign looked up and smiled, a toothless genuine smile, I would have given her money, if not for her eyes; they looked like grey polished stones, dead eyes in a live body -Dont look into nobodys eyes- I remind myself.Another man laughed at a joke that only he seemed to hear. Right then I realized I had stayed in this street for far too long As I elk I look up into the bruised sky, its dotted with grayish clouds; I have the sudden urge to clear them away to see nothing but the flares of the celestial sun casting a dreamy haze upon the sky, announcing the arrival of twilight. I cant hear crickets- I didnt expect to, though I guess it would be nice to think I was back -You dont even have a home- I think bitterly.I hadnt realized I walked this far but I find myself face to face with the Empire State Building My mind starts to wonder what it would be like to step out one of the highest windows, Just floating, flying at peace like a sightless bird. The last seconds of my life, stretched to minutes, but then would one feeling be worth hitting the ground in the end? Its not like I would mind dying, not now, with no family or a place I could call home without thinking twice about It. Stop It right now! My inner voice tells me. -Happiness lays somewhere in your future- it carries on, but I dont listen, I have made up my mind, and there was only one road I could take now. I Cyan Oclock, had a mission.. . I had to prove them wrong. Big City Description: Stone Cold By Lockjaw I knew I shouldnt have done this, not like this, not today Not any day. I cant turn rainbow, but no green. Its nothing like home -Snap out of it- I tell myself sternly.I dollars, doll, the cabin says, his tone of voice clearly implying that this wasnt the first time he was trying to get through to me but his face is a mask of nonchalance and amusement, its like he has two personalities that are fighting to show in one way or another Stiffly and without looking him in the eyes, I put a $50 bill in his hand reprise, the images in books lied, or maybe they hadnt and I made it out to be more perfect than it actually was Most people were thankfully keeping to themselves, into anybody eyes- I remind myself. Another man laughed at a Joke that only he didnt expect to, though I guess it would be nice to think I was back -You dont even now, with no family or a place I could call home without thinking twice about it. -Stop it right now! My inner voice tells me. -Happiness lays somewhere in your future- it carries on, but I dont listen.