What does EPSP stand for in neural communication?

Excitatory PostSynaptic Potential

Enhanced PostSynaptic Potential

Electrostatic PreSynaptic Potential

What is the main difference between neurons in the brain and liver cells?

Neurons have specific functions while liver cells generally perform the same function.

Liver cells are more interconnected than neurons

Neurons are larger than liver cells

Neurons are responsible for digestion

What is an EPSP in neural transmission?

Excitatory Postsynaptic Potential

Excitatory Pre-synaptic Potential

Enhanced Postsynaptic Potential

What distinguishes an action potential from graded potentials?

Action potentials occur in an all-or-none fashion.

Action potentials are weaker than graded potentials.

Action potentials are graded responses.

Action potentials can vary in size.

What can cause an inhibitory postsynaptic potential (IPSP)?

Activation of an inhibitory neuron

Release of neurotransmitters from glial cells

Depolarization of the postsynaptic neuron

Activation of an excitatory neuron

What is frequency coding in the nervous system?

Increasing stimulus strength leads to more action potentials.

All action potentials are the same regardless of stimulus.

The size of the action potential increases with stimulus strength.

Frequency coding refers to the type of neurotransmitter released.

What role does lateral inhibition play in visual perception?

Enhances the perception of edges.

Reduces the clarity of images in the brain.

Prevents signal transmission between photoreceptors.

Increases overall brightness perception.

What is one major characteristic that distinguishes neurons in the brain from liver cells?

Neurons have specific jobs or functions.

What is a characteristic of action potentials in nerve cells?

They are elicited in an all-or-none fashion.

They can change based on the type of neuron.

They only occur in muscle cells.

They can vary in size depending on the stimulus.

What is the role of an inhibitory postsynaptic potential (IPSP)?

Decreases the likelihood of an action potential.

Has no effect on the postsynaptic neuron.

Causes a neuron to fire immediately.

Increases the likelihood of an action potential.

In the context of neural circuits, what is convergence?

When multiple neurons connect to a single postsynaptic neuron.

When one neuron connects to multiple postsynaptic neurons.

When neurons are isolated from each other.

What is the result of a feed-forward inhibition in neural circuits?

It decreases the activity of a following neuron.

It connects two excitatory neurons.

It increases the activity of neighboring neurons.

It has no effect on neuron activity.

What is the function of the suprachiasmatic nucleus in the brain?

Regulation of circadian rhythms.

Processing of visual information.

Intro to Neuro | Quizalize

Intro to Psychology Vocabulary--Central Nervous System and the Neuron

Chemical Synaptic Transmission: Neurotransmitters are released from the presynaptic neuron into the synaptic cleft, where they bind to receptors on the postsynaptic neuron, causing a change in membrane potential. Signal Summation: Graded potentials from multiple synapses can summate, reaching threshold and initiating an action potential. Muscle Function: Functions of Skeletal Muscle: Responsible for voluntary movement, posture maintenance, and heat production. Muscle Structure and Packaging: Skeletal muscle fibers are bundled into fascicles, surrounded by connective tissue layers including epimysium, perimysium, and endomysium. Cardiac Muscle: Intercalated discs contain gap junctions and desmosomes, allowing for coordinated contraction and electrical coupling. Smooth Muscle: Dense bodies anchor thin filaments, allowing for contraction. Muscle Contraction: Involves the sliding filament theory, where actin filaments slide past myosin filaments, shortening the sarcomere. Excitation-Contraction Coupling: Action potentials trigger the release of calcium ions from the sarcoplasmic reticulum, initiating muscle contraction. Muscle Contraction and Relaxation: Contraction: Cross-bridge formation between actin and myosin filaments. Relaxation: Reuptake of calcium ions into the sarcoplasmic reticulum, allowing for muscle relaxation. Comparison of Skeletal and Smooth Muscle Contraction: Skeletal muscle contraction is voluntary and striated, while smooth muscle contraction is involuntary and lacks striations.

Learning is brain change (1) Everybody has a brain, but not many people know how the brain works. Some people believe that the brain is like the hard disk of a computer. We use it to store files-images, language (words, texts, sounds) and other data. Others compare the brain to a huge container or cupboard with lots of little drawers, shelves and boxes in it. We put information into these boxes and hope to find it again later. (2) The brain is not a computer disk, and it isn't a container. Look at the picture here. It looks a bit like weeds in a garden, doesn't it? The picture actually shows a child's neocortex - a part of the brain. You can guess what happens — more 'weeds" grow as the child gets older. Scientists call these neuronal networks. The networks grow around our neurons, or nerve cells. What makes them grow? Learning! Learning is brain change, says Professor James Zull from Case Western University in Cleveland, Ohio, USA. "Without learning, nothing changes in the brain. For every new word you learn in your English lesson, every puzzle you solve in maths, every new song you learn to sing, a neuronal network grows in your brain and the brain changes. (3) The more neuronal networks we grow, the better we can think and the better we remember. You may wonder if there is anything you can do to make the networks in your brain grow better. Professor Zull says yes, there is. He says that brain change is strongest when a) you are interested in and like what you are learning, b) you are in control of what you learn and c) you get challenging tasks that make you think hard and concentrate. Understanding a challenging task makes you feel good and develops your brain!

Hi, I'm John Green, this is Crash Course U.S. History, and today, we're going to talk about slavery, which is not funny. 0:06 Yeah, so we put a lei on the eagle to try and cheer you up, but let's face it, this is going to be depressing. 0:10 With slavery, every time you think, like, "Aw, it couldn't have been that bad," it turns out to have been much worse. 0:14 Mr. Green, Mr. Green! But what about – 0:15 Yeah, Me from the Past, I'm going to stop you right there, because you're going to embarrass yourself. Slavery was hugely important to America. 0:20 I mean, it led to a civil war and it also lasted what, at least in U.S. history, counts as a long-ass time, from 1619 to 1865. 0:29 And yes, I know there's a 1200-year-old church in your neighborhood in Denmark, but we're not talking about Denmark! 0:35 But slavery is most important because we still struggle with its legacy. 0:38 So, yes, today's episode will probably not be funny, but it will be important. 0:42 [Theme Music] North & South economic ties 0:51 So the slave-based economy in the South is sometimes characterized as having been separate from the Market Revolution, but that's not really the case. 0:57 Without southern cotton, the North wouldn't have been able to industrialize, at least not as quickly, because cotton textiles were one of the first industrially products. 1:04 And the most important commodity in world trade by the nineteenth century, and 3/4 of the world's cotton came from the American South. 1:11 And speaking of cotton, why has no one mentioned to me that my collar has been half popped this entire episode, like I'm trying to recreate the Flying Nun's hat. 1:18 And although there were increasingly fewer slaves in the North as northern states outlawed slavery, cotton shipments overseas made northern merchants rich. 1:26 Northern bankers financed the purchase of land for plantations. 1:29 Northern insurance companies insured slaves who were, after all, considered property, and very valuable property. 1:35 And in addition to turning cotton into cloth for sale overseas, northern manufacturers sold cloth back to the South, where it was used to clothe the very slaves who had cultivated it. 1:45 But certainly the most prominent effects of the slave-based economy were seen in the South. Slave-based agriculture in the South 1:49 The profitability of slaved-based agriculture, especially King Cotton, meant that the South would remain largely agricultural and rural. 1:56 Slave states were home to a few cities, like St. Louis and Baltimore, but with the exception of New Orleans, 2:00 almost all southern urbanization took place in the upper South, further away from the large cotton plantations. 2:06 And slave-based agriculture was so profitable that it siphoned money away from other economic endeavors. 2:11 Like, there was very little industry in the South. 2:13 It produced only 10% of the nation's manufactured goods. 2:16 And, as most of the capital was being plowed into the purchase of slaves, there was very little room for technological innovation, like, for instance, railroads. 2:23 This lack of industry and railroads would eventually make the South suck at the Civil War, thankfully. 2:27 In short, slavery dominated the South, shaping it both economically and culturally, and slavery wasn't a minor aspect of American society. Popular attitudes concerning slavery 2:35 By 1860, there were four million slaves in the U.S., and in the South, they made up one third of the total population. 2:42 Although in the popular imagination, most plantations were these sprawling affairs with hundreds of slaves, 2:47 in reality, the majority of slaveholders owned five or fewer slaves. 2:51 And, of course, most white people in the South owned no slaves at all, though, if they could afford to, they would sometimes rent slaves to help with their work. 2:57 These were the so-called yeoman farmers who lived self-sufficiently, raised their own food, and purchased very little in the Market Economy. 3:04 They worked the poorest land and, as a result, were mostly pretty poor themselves. 3:08 But even they largely supported slavery, partly, perhaps, for aspirational reasons, and partly because the racism inherent to the system gave even the poorest whites legal and social status. 3:18 And southern intellectuals worked hard to encourage these ideas of white solidarity and to make the case for slavery. 3:23 Many of the founders, a bunch of whom you'll remember, held slaves, saw slavery as a necessary evil. 3:29 Jefferson once wrote, quote, "As it is, we have the wolf by the ear, and we can neither hold him, nor safely let him go. 3:37 Justice is on one scale, and self-preservation in the other." 3:41 The belief that justice and self-preservation couldn't sit on the same side of the scale was really opposed to the American idea, 3:47 and, in the end, it would make the Civil War inevitable. 3:50 But as slavery became more entrenched in these ideas of liberty and political equality were embraced by more people, 3:55 some southerners began to make the case that slavery wasn't just a necessary evil. 3:59 They argued, for instance, that slaves benefited from slavery. 4:03 Because, you know, because their masters fed them and clothed them and took care of them in their old age. 4:07 You still hear this argument today, astonishingly. 4:09 In fact, you'll probably see asshats in the comments saying that in the comments. 4:12 I will remind you, it's not cursing if you are referring to an actual ass. 4:15 This paternalism allowed masters to see themselves as benevolent and to contrast their family-oriented slavery with the cold, mercenary Capitalism of the free-labor North. 4:26 So yeah, in the face of rising criticism of slavery, some southerners began to argue that the institution was actually good for the social order. 4:33 One of the best-known proponents of this view was John C. Calhoun, who, in 1837, said this in a speech on the Senate floor: 4:40 "I hold that, in the present state of civilization, 4:43 where two races of different origin and distinguished by color and other physical differences as well as intellectual, are brought together, 4:51 the relation now existing in the slave-holding states between the two is, instead of an evil, a good. A positive good." 4:59 Now, of course, John C. Calhoun was a fringe politician, and nobody took his views particularly seriously. 5:04 Stan: Well, he was Secretary of State from 1844 to 1845. 5:07 John: Well, I mean, who really cares about the Secretary of State, Stan? 5:10 Danica: Eh, he was also Secretary of War from 1817 to 1825. 5:13 John: All right, but we don't even have a Secretary of War anymore, so... 5:16 Meredith: And he was Vice President from 1825 to 1832. 5:19 John: Oh my god, were we insane?! 5:21 We were, of course, but we justified the insanity with Biblical passages and with the examples of the Greeks and Romans, 5:28 and with outright racism, arguing that black people were inherently inferior to whites. 5:33 And that not to keep them in slavery would upset the natural order of things. 5:37 A worldview popularized millennia ago by my nemesis, Aristotle. God, I hate Aristotle. 5:42 You know what defenders of Aristotle always say? 5:44 "He was the first person to identify dolphins." 5:47 Well, ok, dolphin identifier. 5:50 Yes, that is what he should be remembered for, but he's a terrible philosopher! Lives & experiences of enslaved people 5:53 Here's the truth about slavery: 5:55 It was coerced labor that relied upon intimidation and brutality and dehumanization. 6:00 And this wasn't just a cultural system, it was a legal one. 6:03 I mean, Louisiana law proclaimed that a slave "owes his master... a respect without bounds, and an absolute obedience." 6:09 The signal feature of slaves' lives was work. 6:12 I mean, conditions and tasks varied, but all slaves labored, usually from sunup to sundown, and almost always without any pay. 6:20 Most slaves worked in agriculture on plantations, and conditions were different, depending on which crops are grown. 6:25 Like, slaves on the rice plantations of South Carolina had terrible working conditions, 6:29 but they labored under the task system, which meant that once they had completed their allotted daily work, they would have time to do other things. 6:36 But lest you imagine this is like how we have work and leisure time, bear in mind that they were owned and treated as property. 6:42 On cotton plantations, most slaves worked in gangs, usually under the control of an overseer, or another slave who was called a "driver." 6:49 This was back-breaking work done in the southern sun and humidity, and so it's not surprising that whippings – or the threat of them – were often necessary to get slaves to work. 6:58 It's easy enough to talk about the brutality of slave discipline, but it can be difficult to internalize it. 7:03 Like, you look at these pictures, but because you've seen them over and over again, they don't have the power they once might have. 7:09 The pictures can tell a story about cruelty, but they don't necessarily communicate how arbitrary it all was. 7:14 As, for example, in this story, told by a woman who was a slave as a young girl: 7:18 "[The] overseer... went to my father one morning and said, "Bob, I'm gonna whip you this morning." 7:22 Daddy said, "I ain't done nothing," and he said, "I know it, I'm going to whip you to keep you from doing nothing," 7:28 and he hit him with that cowhide – you know it would cut the blood out of you with every lick if they hit you hard." 7:33 That brutality – the whippings, the brandings, the rape – was real, and it was intentional, because, in order for slavery to function, slaves had to be dehumanized. 7:43 This enabled slaveholders to rationalize what they were doing, and it was hoped to reduce slaves to the animal property that is implied by the term "chattel slavery." 7:51 So the idea was that slaveholders wouldn't think of their slaves as human, and slaves wouldn't think of themselves as human. 7:57 But it didn't work. Let's go to the Thought Bubble. 7:59 Slaves' resistance to their dehumanization took many forms, but the primary way was by forming families. Family, love, & religion of enslaved people 8:05 Family was a refuge for slaves and a source of dignity that masters recognized and sought to stifle. 8:10 A paternalistic slave owner named Bennet H. Barrow wrote in his rules for the Highland Plantation: 8:15 "No rule that I have stated is of more importance than that relating to Negroes marrying outside of the plantation... It creates a feeling of independence." 8:23 Most slaves did marry, usually for life, and, when possible, slaves grew up in two-parent households. 8:28 Single-parent households were common, though, as a result of one parent being sold. 8:32 In the upper South, where the economy was shifting from tobacco to different, less labor-intensive cash crops, the sale of slaves was common. 8:40 Perhaps one-third of slave marriages in states like Virginia were broken up by sale. 8:45 Religion was also an important part of life in slavery. 8:47 While masters wanted their slaves to learn the parts of the Bible that talked about being happy in bondage, 8:52 slave worship tended to focus on the stories of Exodus, where Moses brought the slaves out of bondage, 8:57 or Biblical heroes, who overcame great odds, like Daniel and David. 9:01 And, although most slaves were forbidden to learn to read and write, many did anyway. And some became preachers. 9:07 Slave preachers were often very charismatic leaders, and they roused the suspicion of slave owners, and not without reason. 9:13 Two of the most important slave uprisings in the South were led by preachers. 9:16 Thanks, Thought Bubble. 9:17 Oh, it's time for the Mystery Document? Mystery Document 9:19 We're doing two set pieces in a row? All right. [buzzing noise] [music] 9:24 The rules here are simple. 9:26 I wanted to re-shoot that, but Stan said no. 9:29 I guess the author of the Mystery Document. 9:30 If I am wrong, I get shocked with the shock pen. 9:33 "Since I have been in the Queen's dominions I have been well contented, yes well contented for sure, man is as God intended he should be. 9:40 That is, all are born free and equal. 9:43 This is a wholesome law, not like the southern laws which puts man made in the image of God on level with brutes. 9:49 O, what will become of the people, and where will they stand in the day of judgment. 9:53 Would that the 5th verse of the 3rd chapter of Malachi were written as with a bar of iron, 9:59 and the point of a diamond upon every oppressor's heart that they might repent of this evil, and let the oppressed go free..." 10:06 All right, it's definitely a preacher, because only preachers have read Malachi. 10:10 Probably African American, probably not someone from the South. 10:13 I'm going to guess that it is Richard Allen, the founder of the African Methodist Episcopal Church? 10:18 [buzzing noise] DAAAH, DANG IT! 10:19 It's Joseph Taper, and Stan just pointed out to me that I should have known it was Joseph Taper because it starts out, 10:24 "Since I have been in the Queen's dominions..." 10:27 He was in Canada. He escaped slavery to Canada. The Queen's dominions! 10:31 All right, Canadians, I blame you for this, although, thank you for abolishing slavery decades before we did. 10:36 [electric sounds] AHHH! How people resisted & escaped slavery 10:37 So, the Mystery Document shows one of the primary ways that slaves resisted their oppression: by running away. 10:42 Although some slaves like Joseph Taper escaped for good by running away to northern free states, 10:47 or even to Canada, where they wouldn't have to worry about fugitive slave laws, even more slaves ran away temporarily, hiding out in the woods or the swamps, and eventually returning. 10:55 No one knows exactly how many slaves escaped to freedom, but the best estimate is that a thousand or so a year made the journey northward. 11:01 Most fugitive slaves were young men, but the most famous runaway has been hanging out behind me all day long: Harriet Tubman. 11:07 Harriet Tubman escaped to Philadelphia at the age of 29, and over the course of her life, she made about 20 trips back to Maryland to help friends and relatives make the journey north on the Underground Railroad. 11:17 But a more dramatic form of resistance to slavery was actual, armed rebellion, which was attempted. 11:22 Now, individuals sometimes took matters into their own hands and beat or even killed their white overseers or masters. 11:27 Like Bob, the guy who received the arbitrary beating, responded to it by killing his overseer with a hoe. 11:33 But that said, large-scale slave uprisings were relatively rare. 11:36 The four most famous ones all took place in a 35-year period at the beginning of the 19th century. Slave rebellions 11:41 Gabriel's Rebellion in 1800 – which we've talked about before – was discovered before he was able to carry out his plot. 11:45 Then, in 1811, a group of slaves upriver from New Orleans seized cane, knives, and guns, and marched on the city before militia stopped them. 11:52 And in 1822, Denmark Vesey, a former slave who had purchased his freedom, may have organized a plot to destroy Charleston, South Carolina. 11:59 I say "may have" because the evidence against him is disputed and comes from a trial that was not fair. 12:05 But regardless, the end result of that trial was that he was executed, as were 34 slaves. Nat Turner's Rebellion 12:09 But the most successful slave rebellion, at least in the sense that they actually killed some people, was Nat Turner's in August 1831. 12:15 Turner was a preacher, and with a group of about 80 slaves, he marched from farm to farm in South Hampton County, Virginia, 12:21 killing the inhabitants, most of whom were women and children, because the men were attending a religious revival meeting in North Carolina. 12:27 Turner and 17 other rebels were captured and executed, but not before they struck terror into the hearts of whites all across the American South. 12:34 Virginia's response was to make slavery worse, passing even harsher laws that forbade slaves from preaching, and prohibited teaching them to read. 12:42 Other slave states followed Virginia's lead and, by the 1830s, slavery had grown, if anything, more harsh. 12:47 So, this shows that large-scaled armed resistance was – Django Unchained aside – not just suicidal, but also a threat to loved ones and, really, to all slaves. How enslaved people resisted their oppression & why it matters 12:55 But, it is hugely important to emphasize that slaves did resist their oppression. 12:59 Sometimes this meant taking up arms, but usually it meant more subtle forms of resistance, 13:03 like intentional work slowdowns or sabotaging equipment, or pretending not to understand instructions. 13:08 And, most importantly, in the face of systematic legal and cultural degradation, they re-affirmed their humanity through family and through faith. 13:16 Why is this so important? 13:17 Because too often in America, we still talk about slaves as if they failed to rise up, 13:21 when, in fact, rising up would not have made life better for them or for their families. 13:26 The truth is, sometimes carving out an identity as a human being in a social order that is constantly seeking to dehumanize you, is the most powerful form of resistance. 13:34 Refusing to become the chattel that their masters believed them to be is what made slavery untenable and the Civil War inevitable, so make no mistake, slaves fought back. 13:45 And in the end, they won. I'll see you next week. Credits 13:48 Crash Course is produced and directed by Stan Muller. 13:50 The script supervisor is Meredith Danko. 13:52 Our associate producer is Danica Johnson. 13:54 The show is written by my high school history teacher Raoul Meyer and myself. 13:57 And our graphics team is Thought Cafe. 13:58 Every week, there's a new caption to the Libertage, but today's episode was so sad that we couldn't fit a Libertage in... 14:04 UNTIL NOW! [Libertage Rock Music] 14:08 Suggest Libertage caption in comments, where you can also ask questions about today's video that will be answered by our team of historians. 14:13 Thanks for watching Crash Course, and as we say in my home town, don't forget to be abolitionist.

She went by the name of Belisa Crepusculario, not because she had been baptized with that name or given it by her mother, but because she herself had searched until she found the poetry of "beauty" and "twilight" and cloaked herself in it. She made her living selling words. She journeyed through the country from the high cold mountains to the burning coasts, stopping at fairs and in markets where she set up four poles covered by a canvas awning under which she took refuge from the sun and rain to minister to her customers. She did not have to peddle her merchandise because from having wandered far and near, everyone knew who she was. Some people waited for her from one year to the next, and when she appeared in the village with her bundle beneath her arm, they would form a line in front of her stall. Her prices were fair. For five centavos she delivered verses from memory, for seven she improved the quality of dreams, for nine she wrote love letters, for twelve she invented insults for irreconcilable enemies. She also sold stories, not fantasies but long, true stories she recited at one telling, never skipping a word. This is how she carried news from one town to another. People paid her to add a line or two: our son was born, so-and-so died, our children got married, the crops burned in the field. Wherever she went a small crowd gathered around to listen as she began to speak, and that was how they learned about each others' doings, about distant relatives, about what was going on in the civil war. To anyone who paid her fifty centavos in trade, she gave the gift of a secret word to drive away melancholy. It was not the same word for everyone, naturally, because that would have been collective dece it. Each person received his or her own word, with the assurance that no one else would use it that way in this universe or the Beyond. Belisa Crepusculario had been born into a family so poor they did not even have names to give their children. She came into the world and grew up in an inhospitable land where some years the rains became avalanches of water that bore everything away before them and others when not a drop fell from the sky and the sun swelled to fill the horizon and the world became a desert. Until she was twelve, Belisa had no occupation or virtue other than having withstood hunger and the exhaustion of centuries. During one interminable drought, it fell to her to bury four younger brothers and sisters, when she realized that her turn was next, she decided to set out across the 2 plains in the direction of the sea, in hopes that she might trick death along the way. The land was eroded, split with deep cracks, strewn with rocks, fossils of trees and thorny bushes, and skeletons of animals bleached by the sun. From time to time she ran into families who, like her, were heading south, following the mirage of water. Some had begun the march carrying their belongings on their back or in small carts, but they could barely move their own bones, and after a while they had to abandon their possessions. They dragged themselves along painfully, their skin turned to lizard hide and their eyes burned by the reverberating glare. Belisa greeted them with a wave as she passed, but she did not stop, because she had no strength to waste in acts of compassion. Many people fell by the wayside, but she was so stubborn that she survived to cross through that hell and at long last reach the first trickles of water, fine, almost invisible threads that fed spindly vegetation and farther down widened into small streams and marshes. Belisa Crepusculario saved her life and in the process accidentally discovered writing. In a village near the coast, the wind blew a page of newspaper at her feet. She picked up the brittle yellow paper and stood a long while looking at it, unable to determine its purpose, until curiosity overcame her shyness. She walked over to a man who was washing his horse in the muddy pool where she had quenched her thirst. "What is this?" she asked. "The sports page of the newspaper," the man replied, concealing his surprise at her ignorance. The answer astounded the girl, but she did not want to seem rude, so she merely inquired about the significance of the fly tracks scattered across the page. "Those are words, child. Here it says that Fulgencio Barba knocked out El Negro Tiznao in the third round." That was the day Belisa Crepusculario found out that words make their way in the world without a master, and that anyone with a little cleverness can appropriate them and do business with them. She made a quick assessment of her situation and concluded that aside from becoming a prostitute or working as a servant in the kitchens of the rich there were few occupations she was qualified for. It seemed to her that selling words would be an honorable alternative. From that moment on, she worked at that profession, and was never tempted by any other. At the beginning, she offered her merchandise unaware that words could be written outside of newspapers. When she learned otherwise, she calculated the infinite possibilities of her trade and with her savings paid a priest twenty pesos to teach her to read and write, with her three 3 remaining coins she bought a dictionary. She poured over it from A to Z and then threw it into the sea, because it was not her intention to defraud her customers with packaged words. One August morning several years later, Belisa Crepusculario was sitting in her tent in the middle of a plaza, surrounded by the uproar of market day, selling legal arguments to an old man who had been trying for sixteen years to get his pension. Suddenly she heard yelling and thudding hoofbeats. She looked up from her writing and saw, first, a cloud of dust, and then a band of horsemen come galloping into the plaza. They were the Colonel's men, sent under orders of El Mulato, a giant known throughout the land for the speed of his knife and his loyalty to his chief. Both the Colonel and El Mulato had spent their lives fighting in the civil war, and their names were ineradicably linked to devastation and calamity. The rebels swept into town like a stampeding herd, wrapped in noise, bathed in sweat, and leaving a hurricane of fear in their trail. Chickens took wing, dogs ran for their lives, women and children scurried out of sight, until the only living soul left in the market was Belisa Crepusculario. She had never seen El Mulato and was surprised to see him walking toward her. "I'm looking for you," he shouted, pointing his coiled whip at her, even before the words were out, two men rushed her -- knocking over her canopy and shattering her inkwell -- bound her hand and foot, and threw her like a sea bag across the rump of El Mulato's mount. Then they thundered off toward the hills. Hours later, just as Belisa Crepusculario was near death, her heart ground to sand by the pounding of the horse, they stopped, and four strong hands set her down. She tried to stand on her feet and hold her head high, but her strength failed her and she slumped to the ground, sinking into a confused dream. She awakened several hours later to the murmur of night in the camp, but before she had time to sort out the sounds, she opened her eyes and found herself staring into the impatient glare of El Mulato, kneeling beside her. "Well, woman, at last you've come to," he said. To speed her to her senses, he tipped his canteen and offered her a sip of liquor laced with gunpowder. She demanded to know the reason for such rough treatment, and El Mulato explained that the Colonel needed her services. He allowed her to splash water on her face, and then led her to the far end of the camp where the most feared man in all the land was lazing in a hammock strung between two trees. She could not see his face, because he lay in the deceptive shadow of the leaves and the indelible shadow of all his years as a bandit, but she imagined from the way his 4 gigantic aide addressed him with such humility that he must have a very menacing expression. She was surprised by the Colonel's voice, as soft and well-modulated as a professor's. "Are you the woman who sells words?" he asked. "At your service," she stammered, peering into the dark and trying to see him better. The Colonel stood up, and turned straight toward her. She saw dark skin and the eyes of a ferocious puma, and she knew immediately that she was standing before the loneliest man in the world. "I want to be President," he announced. The Colonel was weary of riding across that godforsaken land, waging useless wars and suffering defeats that no subterfuge could transform into victories. For years he had been sleeping in the open air, bitten by mosquitoes, eating iguanas and snake soup, but those minor inconveniences were not why he wanted to change his destiny. What truly troubled him was the terror he saw in people's eyes. He longed to ride into a town beneath a triumphal arch with bright flags and flowers everywhere, he wanted to be cheered, and be given newly laid eggs and freshly baked bread. Men fled at the sight of him, children trembled, and women miscarried from fright, he had had enough, and so he had decided to become President. El Mulato had suggested that they ride to the capital, gallop up to the Palace, and take over the government, the way they had taken so many other things without anyone's permission. The Colonel, however, did not want to be just another tyrant, there had been enough of those before him and, besides, if he did that, he would never win people's hearts. It was his aspiration to win the popular vote in the December elections. "To do that, I have to talk like a candidate. Can you sell me the words for a speech?" the Colonel asked Belisa Crepusculario. She had accepted many assignments, but none like this. She did not dare refuse, fearing that El Mulato would shoot her between the eyes, or worse still, that the Colonel would burst into tears. There was more to it than that, however, she felt the urge to help him because she felt a throbbing warmth beneath her skin, a powerful desire to touch that man, to fondle him, to clasp him in her arms. All night and a good part of the following day, Belisa Crepusculario searched her repertory for words adequate for a presidential speech, closely watched by El Mulato, who could not take his eyes from her firm wanderer's legs and virginal breasts. She discarded harsh, cold words, words 5 that were too flowery, words worn from abuse, words that offered improbable promises, untruthful and confusing words, until all she had left were words sure to touch the minds of men and women's intuition. Calling upon the knowledge she had purchased from the priest for twenty pesos, she wrote the speech on a sheet of paper and then signaled El Mulato to untie the rope that bound her ankles to a tree. He led her once more to the Colonel, and again she felt the throbbing anxiety that had seized her when she first saw him. She handed him the paper and waited while he looked at it, holding it gingerly between thumbs and fingertips. "What the shit does this say," he asked finally. "Don't you know how to read?" "War's what I know," he replied. She read the speech aloud. She read it three times, so her client could engrave it on his memory. When she finished, she saw the emotion in the faces of the soldiers who had gathered round to listen, and saw that the Colonel's eyes glittered with enthusiasm, convinced that with those words the presidential chair would be his. "If after they've heard it three times, the boys are still standing there with their mouths hanging open, it must mean the thing's damn good, Colonel" was El Mulato's approval. "All right, woman. How much do I owe you?" the leader asked. "One peso, Colonel." "That's not much," he said, opening the pouch he wore at his belt, heavy with proceeds from the last foray. "The peso entitles you to a bonus. I'm going to give you two secret words," said Belisa Crepusculario. "What for?" She explained that for every fifty centavos a client paid, she gave him the gift of a word for his exclusive use. The Colonel shrugged. He had no interest at all in her offer, but he did not want to be impolite to someone who had served him so well. She walked slowly to the leather stool where he was sitting, and bent down to give him her gift. The man smelled the scent of a mountain cat issuing from the woman, a fiery heat radiating from her hips, he heard the terrible whisper of her hair, and a breath of sweetmint murmured into his ear the two secret words that were his alone. "They are yours, Colonel," she said as she stepped back. "You may use them as much as you 6 please." El Mulato accompanied Belisa to the roadside, his eyes as entreating as a stray dog's, but when he reached out to touch her, he was stopped by an avalanche of words he had never heard before; believing them to be an irrevocable curse, the flame of his desire was extinguished. During the months of September, October, and November the Colonel delivered his speech so many times that had it not been crafted from glowing and durable words it would have turned to ash as he spoke. He travelled up and down and across the country, riding into cities with a triumphal air, stopping in even the most forgotten villages where only the dump heap betrayed a human presence, to convince his fellow citizens to vote for him. While he spoke from a platform erected in the middle of the plaza, El Mulato and his men handed out sweets and painted his name on all the walls in gold frost. No one paid the least attention to those advertising ploys; they were dazzled by the clarity of the Colonel's proposals and the poetic lucidity of his arguments, infected by his powerful wish to right the wrongs of history, happy for the first time in their lives. When the Candidate had finished his speech, his soldiers would fire their pistols into the air and set off firecrackers, and when finally they rode off, they left behind a wake of hope that lingered for days on the air, like the splendid memory of a comet's tail. Soon the Colonel was the favorite. No one had ever witnessed such a phenomenon: a man who surfaced from the civil war, covered with scars and speaking like a professor, a man whose fame spread to every corner of the land and captured the nation's heart. The press focused their attention on him. Newspapermen came from far away to interview him and repeat his phrases, and the number of his followers and enemies continued to grow. "We're doing great, Colonel," said El Mulato, after twelve successful weeks of campaigning. But the Candidate did not hear. He was repeating his secret words, as he did more and more obsessively. He said them when he was mellow with nostalgia; he murmured them in his sleep; he carried them with him on horseback; he thought them before delivering his famous speech; and he caught himself savoring them in his leisure time. And every time he thought of those two words, he thought of Belisa Crepusculario, and his senses were inflamed with the memory of her feral scent, her fiery heat, the whisper of her hair, and her sweetmint breath in his ear, until he began to go around like a sleepwalker, and his men realized that he might die before he ever sat in the presidential chair. "What's got hold of you, Colonel," El Mulato asked so often that finally one day his chief broke 7 down and told him the source of his befuddlement: those two words that were buried like two daggers in his gut. "Tell me what they are and maybe they'll lose their magic," his faithful aide suggested. "I can't tell them, they're for me alone," the Colonel replied. Saddened by watching his chief decline like a man with a death sentence on his head, El Mulato slung his rifle over his shoulder and set out to find Belisa Crepusculario. He followed her trail through all that vast country, until he found her in a village in the far south, sitting under her tent reciting her rosary of news. He planted himself, spraddle-legged, before her, weapon in hand. "You! You're coming with me," he ordered. She had been waiting. She picked up her inkwell, folded the canvas of her small stall, arranged her shawl around her shoulders, and without a word took her place behind El Mulato's saddle. They did not exchange so much as a word in all the trip; El Mulato's desire for her had turned into rage, and only his fear of her tongue prevented his cutting her to shreds with his whip. Nor was he inclined to tell her that the Colonel was in a fog, and that a spell whispered into his ear had done what years of battle had not been able to do. Three days later they arrived at the encampment, and immediately, in view of all the troops, El Mulato led his prisoner before the Candidate. "I brought this witch here so you can give her back her words, Colonel," El Mulato said, pointing the barrel of his rifle at the woman's head. "And then she can give you back your manhood." The Colonel and Belisa Crepusculario stared at each other, measuring one another from a distance. The men knew then that their leader would never undo the witchcraft of those accursed words, because the whole world could see the voracious-puma eyes soften as the woman walked to him and took his hand in hers. Copyright © 1989 by Isabel Allende From The Stories of Eva Luna, Translated by Margaret Sayers Peden

Science Exam Parts of the Atom: The atom consists of a nucleus at its center, containing protons (positively charged) and neutrons (neutral), while electrons (negatively charged) orbit in electron shells around the nucleus. Atomic Number: The atomic number of an element is the number of protons in its nucleus. It defines the element and determines its place on the periodic table. Properties of Metals: Metals have properties like conductivity, malleability (can be flattened into sheets), and ductility (can be drawn into wires). Elements, Compounds, and Mixtures: Elements consist of only one type of atom. Compounds are made of two or more different elements chemically bonded. Mixtures are combinations of substances that are physically mixed but not chemically bonded. Homogeneous and Heterogeneous Mixtures: Homogeneous mixtures have a uniform composition (e.g., saltwater), while heterogeneous mixtures have different phases (e.g., oil and water). Changes of State: Changes like melting, evaporation, and condensation are examples of physical changes of state. Chemical and Physical Properties: Chemical properties describe how a substance can change to form a new substance, while physical properties are characteristics like color, texture, and state (solid, liquid, gas). Physical and Chemical Change: A physical change involves the appearance or state of matter, but the substance remains the same. A chemical change involves the formation of new substances. Chemical Equations: Chemical reactions can be represented with chemical equations that show reactants (what you start with) and products (what is formed). Chemical Formulas: Chemical formulas represent the composition of compounds. For example, NaHCO3 is sodium bicarbonate, consisting of one sodium (Na), one hydrogen (H), one carbon (C), and three oxygen (O) atoms. Energy: Types of Energy: Energy can be kinetic (related to motion), potential (stored energy), thermal (heat energy), electrical, chemical, and more. Units of Energy: Common units of energy include joules (J) and calories (cal). Law of Conservation of Energy: Energy cannot be created or destroyed, only transferred or transformed from one form to another. Energy Transfer and Transformation: Energy moves from one object to another, changing forms along the way. Useful and Waste Energy: Useful energy is what can be harnessed and used for a specific purpose. Waste energy is energy that is not used and is often lost. Energy Flow Diagrams: These diagrams show how energy is transferred or transformed within a system. Energy Efficiency: Efficiency is a measure of how much useful energy is obtained from a system. It can be calculated using the equation: Efficiency = (Useful Energy Output / Total Energy Input) x 100%. Fossil Fuels and Renewable Energy: Fossil fuels, like coal, oil, and natural gas, are non-renewable sources of energy. Renewable energy sources include solar, wind, and hydroelectric power. Variables: Independent Variable: The variable that is manipulated or changed in an experiment. Dependent Variable: The variable that is measured or observed and is affected by changes in the independent variable. Controlled Variables: Factors that are kept constant to ensure a fair and accurate experiment.

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