Action potentials are electrochemical waves in the nervous system

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Action potentials:

1. Occur when a neuron’s membrane voltage exceeds its threshold of excitation. This value is approximately negative 55 millivolts.

2. Are all or none signals. This means that action potentials are not “graded” signals, rather, they are binary signals. A neuron will either “fire” and action potential or it will not.

3. Electro-chemical gradients of both potassium and sodium ions, along with the synchronized opening and closing of voltage-gated sodium and potassium ion channels, allow for the generation of an action potential.

Here are some videos that will introduce you to how an action potential is generated in a neuron:

Action Potential: Video #0

Action Potential: Video #1

Action Potential: Video #2

Action Potential: Video #3

Action Potential: Video #4

An action potential is characterizied by 3 phases:

1.  Rising Phase

2. Repolarization

3. Hyperpolarization

Brief explanation of phases:

1. Rising Phase:  Voltage-gated sodium channels open to allow for entry of sodium ions into the cytosol of the neuron. This event increases membrane voltage  from approximately -70 millivolts  to + 50 millivolts.  Activation of voltage-dependent sodium channels triggers opening of voltage-gated potassium channels. As more and more voltaged-gated potassium channels open, more and more voltage-gated sodium channels close. At approximately 1ms, all sodium channels are closed. This state indicates the end of the rising phase and the begining of Repolarization.

2. Repolarization: During repolarization, voltage-gated potassium channels gradually begin to close. Hyperpolarization of the neuron’s membrane is sustained for approximately .25ms. Potassium channel kinetics explain this extended period of hyperpolarization.

3. Hyperpolarization: During hyperpolarization the neuron’s membrane voltage decreases below its resting potential of approximately -70millivolts. This event is called the “undershoot”. During the intial entry into the “undershoot” the neuron’s membrane enters a state called an “absolute refractory period”.  During the absolute refractory period the neuron is not capable of generating an action potential. The “relative refractory period” occurs after the absolute refractory period. During the relative refractory period higher that normal levels of electrical stimulation must be applied in order for the neuron to generate another action potential. The conclusion of the relative refractory period begins when stimulation quantity to generate an action potential returns to “baseline” levels.

What are Quantum Computers?

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What are Quantum Computers?

Quantum computers are not that different from normal computers outwardly, but they are in the sense that quantum theory is the basis on which these computers operate. The end result is that they are put together in a completely different way.
A normal computer operates on the basis of units known as bits. Each byte in a normal computer can only be one of 0 or 1 and nothing else. No matter how many bytes you have, each computer at a single point in time can only occupy one combination of these bytes in order for the programming to actually work.

A quantum computer is different from this because of a principle in quantum mechanics known as superposition. If you think back to your high school science courses, you may have learned about superposition when looking at how waves like light and sound waves move from one point to another. Quanta can also be in superposition with respect to each other and the end result is that the quantum bits that make up the computer can actually be 0, 1 and any superposition of the two.

The more quantum bits (also known as qubits) that you have, the more possibilities they are. Because you are dealing with superposition, it also means that the different positions can be occupied simultaneously. Whereas a simple 8-bit computer can only occupy one of the 256 positions generated by those 8 bits at once, the same 8-bit quantum computer could occupy all 256 qubit positions at once.
The end result is that quantum computers can be much more efficient than their conventional computer counterparts. Although quantum computers are still in their infancy, as the technology improves eventually it will become true that these computers will be able to calculate faster than the computers we have today. When that happens, the 3.0 GHz speed of a personal computer that we brag about now will be nothing in comparison to the new quantum computer models that become available on the market.

General Definition: signal transduction pathway from

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What is a signal transduction pathway?

The steps through which a signal on the cell’s surface is converted to a series of specific cellular responses are called a signal transduction pathway.

The process is described below:
a) Fibroblast growth factors (FGFs) represent one of five classes of peptide growth factors. The binding of FGF-2
to it’s receptor FGFR induces receptor dimerisation and autophosphorylation.
b) These phosphorylated tyrosines act as binding sites for the growth factor receptor bound protein 2 (GRB2).
c) GRB2, with Son of sevenless protein (SOS) bound to it, binds to the RTK, which activates SOS. SOS is a guanine
nucleotide exchange factor (GEF).
d) SOS activates the low-molecular-weight GTPase Ras, by inducing it to release GDP and exchanging it for GTP.
e) GTPase activating proteins (GAPs) accelerate the intrinsic GTP hydrolytic activity of Ras, thereby promoting
the formation of the inactive GDP-bound in the form of Ras.
f) Active Ras triggers a cascade of protein phosphorylation involving mitogen-activated protein kinase kinase
kinase (Raf), mitogen activated ERK activating kinase (MEK) and extracellular signal regulated kinase (ERK).
g) Upon activation, the ERKs phosphorylate cytoplasmic targets translocates to the nucleus, where they stimulate
gene expression through the activation of transcription factors.

B.F. Skinner

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Born in 1904, American Psychologist B. F. Skinner made important contributions to the field of Psychology, in particular to the way we view behavior. Attending Hamiton College, and then Harvard College for a Ph.D., Skinner’s contributions changed the field of psychology with his theory of operant conditioning. The theory holds that when a behavior is followed by a consequence, the likelyhood of that behavior occuring again is influenced by whether the consequence is a reward or a punishment.

One of Skinner’s most famous inventions was called the Skinner box, in which a rat learns that pressing a lever in the cage (operant behavior) releases a food pellet (reward, also called reinforcer). On the other side of this learning process, if a particular behavior is punished, animals and humans alike, learn to not do it because the consequences are unpleasant.

What do you think? Do people behave in certain ways because they will be rewarded for doing good, and punished for the bad or is there more to it?

Media interest in Crush That Test

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Today, we had the first write-up about our little site at Please read if interested:

Best places to study

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If you want a quiet place where you can focus to achieve your study goals:

The library can be an oasis of calm and respite from the hustle and bustle of classes. Find a corner in the “Quiet” area and settle down for a study session.

Find an empty classroom and voila! Your friends and you have an environment tailor-made for discussion, study groups, and quiet studying. Blackboards, seats, projectors are all available in a classroom.

Both at the library and the classroom, you get away from friends, the TV, phone, the fridge and other distractions.

Coffee Shop
The local Starbucks or Peet’s may be just the location to get some studying done. Not too noisy, not too quiet. Have noise-cancelling headphones available in case the espresso machine bothers you. And, of course, you have hot java available on demand.

Barnes and Noble or Borders can be the perfect place to study, with books to browse during breaks and being able to discuss with friends in study groups.

The Biology of Fear

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The emotion known as fear, evolutionary biology claims, is an integral part of a person’s survival instinct. Observing animals can easily confirm this statement. Terror at the prospect of being killed and eaten is the driving force behind the gazelle’s rapid dash across the African savanna. Terror of being pushed out of her fertile hunting grounds pushes the lioness to bite and tear into the flesh of the aforementioned gazelle. Fear is just as omnipresent among humans as it is among animals, and in the past, it was just as crucial to survival. Interestingly enough, recent research is starting to show that there is a lot more science to the sensation of fear than most people would believe.
Science has shown that being afraid triggers the “fight or flight” response in people, but research conducted by the neuroscience department of New York University claim that it does not end there. The body obviously feels the most drastic effects of being terrified or afraid. A host of hormones and biochemicals, like adrenaline, are pumped into every area of the body. These prepare a person, in case the need to physically perform beyond their standard levels are needed. The amygdala, a small section of the brain, is known to be the area that initiates this first response. However, this part of the brain has been shown to react only if the trigger has previously been recognized as a potential threat to status or survival. That implies that another part of the brain is responsible for someone learning fear responses.

According to research, the prefrontal cortex of the brain is responsible for the interpretation of sensory information. There have been some signs that point to this area being responsible for a person learning fear responses. Presumably, all fear is based on sensory information gathered through experience. This would imply that, once a certain stimuli has been interpreted as an unwanted sensation, it causes the person to both subconsciously and actively avoid those sensations. While this does explain why people will avoid being caught in certain situations after having experienced them once before, this does not always equate to a person being afraid of said situation.

The theory also does not explain certain instinctive reactions. Most people grow up afraid of certain things that they have not actually experienced. If the above theory is to be accepted, it must find a way to account for fear responses that appear entirely instinctive and are not explainable simply by previously acquired sensory data. Some experts believe that a combination of several areas of the brain, including the amygdala and the prefrontal cortex, act in conjunction whenever someone is afraid, as well as determining what unknown factors should make a person afraid.

Research done by the University of Wisconsin have revealed that levels of a drenocorticotropic hormone (ACTH) are tied directly to levels of fear. The test used rhesus monkeys as a basis for a human model of the study, which had a notably similar result. The study also shows that there might be a hereditary link between ACTH and fear. The research team found that mothers that were regularly scared, giving them higher levels of ACTH in their bloodstream, had offspring that exhibited the same tendencies. The offspring of the scared rhesus monkeys had higher stress and ACTH levels than others, suggesting a possible genetic link in ACTH production.


How we started Crush That Test

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Struggled with Bio courses at UT…made flashcards…concept maps…drew all diagrams in textbook…read aloud to ourselves…100 hours per course to create study materials BEFORE we could even START studying…
Lots of us got weeded out. We were fed-up and wanted to create a website to help students study for any subject online with flash cards and study guides.
Started with Bio 101 and AP Bio. Took a bunch of us 2.5 months on our spare time…Crush That Test was off and running…we created a website from scratch and then…launched it several months later. Its been an amazing journey and we are all so happy to give students a cost-effective solution to study all subjects.

Learning a language with flashcards

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Research shows that “repetition is the mother of skill”, then it comes to learning a new language. How many of us can afford 100s and 1000s of dollars for Rosetta Stone or a college course to learn a language.

Yet, we can learn a new word or two every day , and then use it in a sentence with a native speaker. The native speaker might correct us, and that is great. The reason it is good is that we feel a little ashamed when this happens. That sense of shame might push us to learn more and do better in the future.

Learning a few sentences in a language like Spanish can greatly help in the United States. Our culture has absorbed many aspects of the spanish language and latino culture. The ability to at least speak a few sentences in Spanish, the language natively spoken by 15% of the US population, is useful. It allows us to communicate and share ideas with people on a daily basis. Even if the sentences we might use are simple, the native speaker appreciate the effort and might reward us with a cheerful smile, better service or even a job opportunity.

Crush That Test flash cards for Hindi have been well-received by native Hindi speakers who want to learn English and students of South Asia study programs in the US, who wish to learn Hindi.

We will be releasing our Spanish flashcards with 1000 of the most commonly used words and phrases in mid-may 2010.

Happy studying!

Crush That Test Announces the release of eStudyguides and eFlashCards for AP subjects

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Redwood City, Calif., May 2, 2010 – Building on the foundation of deep research into learning styles and adaptive learning, Crush That Test is launching online eFlashcards and eStudyguides at designed for high school students to ace their preferred Advanced Placement tests.

The revolutionary eFlashcards are designed to be more appealing, interactive and engaging to capture and keep the attention of media savvy high-schoolers who are often exposed to a wide array of online learning solutions. Relevant content, a study mode and test mode, and illustrations that appeal to the 16-18 age group are incorporated into the new online learning solution. Crush That Test eFlashcards for Biology, for instance, assist students study faster and retain more biology concepts, particularly among those who struggle with memorization.
“The AP tests have become a requirement, not an option, for admission into the top colleges. We are very excited about our eFlashcards and their potential to help students succeed in their quest for AP success,” said Crush That Test’s Chief Knowledge Officer Jay Jackson. “We have received rave reviews of our eFlashcards from students at a top University in Texas, who have said that they saw a direct improvement in their academic achievement. Early adoptions by school districts all over the country will allow us to work with experienced AP teachers who will help us demonstrate online learning’s clear strengths.”
Using research-based methodologies, eFlashcards and eStudyguides at engage all learners with media-rich content and comprehensive knowledge in Biology, Chemistry, Psychology and US History. Organic Chemistry, Physics, and US Government will follow in the coming weeks. The new web-based courseware also provides anytime, anywhere access and empowers students to choose their preferred learning approach, thereby making lessons more personalized and has the greatest educational impact for each student.
“Numerous national studies show that the U.S. is experiencing near crisis proportions of students who are not proficient in the sciences as they enter college” said Crush That Test’s President and CEO Sundar Nathan. “We built the new AP Chemistry and AP Biology solutions specifically to help students, schools and districts meet the challenges of college admissions and the instructional demands of No Child Left Behind. Based on our initial feedback from pre-launch demonstrations, educators and students are finding that it does that very well.”
More than 500 teachers and 3000 students recently participated in customer advisory panels to review the new Crush That Test eFlashcards and eStudyguides. Among those were a group of students whose feedback can be seen at

About Crush That Test®
Crush That Test, LLC. has offices in Redwood City, California, Austin, Texas and Chennai, India. The company is a cutting-edge publisher of online learning solutions to make learning easier and more efficient with our patented and scientifically proven tools. Our eFlashcards and eStudyGuides cover every essential concept for a growing list of courses. At a fraction of the cost of a textbook, you can have access to over 1000 flashcards per subject. With online flashcards, you can quickly learn all of the important material while skipping the fluff. You can then test yourself – all the while tracking your progress with dynamic charts and graphs. CrushThatTest can identify the specific areas where you need more work, and will design tests and quizzes targeted to those specific concepts.
As a part of the Destination AP Success® solution, Crush That Test® combines content correlated to College Board standards with powerful tools that allow students to target their individual areas of challenge. For more information, visit

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