Un circuito es una red eléctrica (interconexión de dos o más componentes, tales como resistencias, inductores, condensadores,fuentes, interruptores y semiconductores) que contiene al menos una trayectoria cerrada. Los circuitos que contienen solo fuentes, componentes lineales (resistores, condensadores, inductores), y elementos de distribución lineales (líneas de transmisión o cables) pueden analizarse por métodos algebraicos para determinar su comportamiento en corriente directa o en corriente alterna. Un circuito que tiene componentes electrónicos es denominado un circuito electrónico. Estas redes son generalmente no lineales y requieren diseños y herramientas de análisis mucho más complejos.

Clasificación

Los circuitos eléctricos se clasifican de la siguiente forma:

1.       Por el tipo de señal

a.       De corriente continua

b.      De corriente alterna

c.       Mixtos

2.       Por el tipo de régimen:

a.       Periódico

b.      Transitorio

c.       Permanente

3.       Por el tipo de componentes:

a.       Eléctricos: Resistivos, inductivos, capacitivos y mixtos

b.      Electrónicos: digitales, analógicos y mixtos

4.       Por su configuración:

a.       Serie

b.      Paralelo

c.       Mixto

Partes del circuito eléctrico

GENERADOR: Transforma cualquier tipo de energía en energía eléctrica.

RECEPTOR: Transforma energía eléctrica en cualquier tipo de energía.

LÍNEA: Transporta la corriente eléctrica.

Circuito en serie y paralelo

Electricidad

Electricidad

El término electricidad estática se refiere a la acumulación de un exceso de carga eléctrica en una zona con poca conductividad eléctrica, un aislante, de manera que la acumulación de carga persiste. Los efectos de la electricidad estática son familiares para la mayoría de las personas porque pueden ver, notar e incluso llegar a sentir las chispas de las descargas que se producen cuando el exceso de carga del objeto cargado se pone cerca de un buen conductor eléctrico (como un conductor conectado a una toma de tierra) u otro objeto con un exceso de carga pero con la polaridad opuesta.

Los materiales con los que tratamos en nuestra vida diaria están formados por átomos y moléculas que son eléctricamente neutros porque tienen el mismo número de cargas positivas (protones en el núcleo) que de cargas negativas (electrones alrededor del núcleo). El fenómeno de la electricidad estática requiere de una separación sostenida entre las cargas positivas y negativas.

Separación de cargas inducida por la presencia de un objeto cargado 

Un objeto cargado, puesto cerca de otro eléctricamente neutro, causará la separación de las cargas del otro, dado que las cargas de la misma polaridad se repelen mientras que las de diferente polaridad se atraen. Como la fuerza debida a la interacción entre las cargas eléctricas disminuye rápidamente con el aumento de la distancia, el efecto será mayor si están muy cerca . Este efecto es mayor cuando el objeto inicialmente neutro es un conductor eléctrico porque las cargas tienen más facilidad para moverse.

Es posible inducir una separación de cargas y si el objeto está convenientemente conectado a tierra dejarlo cargado permanentemente. Este es el sistema que utiliza el Generador de Van de Graaff, un aparato habitualmente utilizado para demostrar los efectos de la electricidad estática.

El generador de Van de Graaff es una máquina electrostática que utiliza una cinta móvil para acumular grandes cantidades de carga eléctrica en el interior de una esfera metálica hueca

Calor

Calor
El calor es el proceso de transferencia de energía entre diferentes cuerpos o diferentes zonas de un mismo cuerpo que se encuentran a distintas temperaturas. Este flujo siempre ocurre desde el cuerpo de mayor temperatura hacia el cuerpo de menor temperatura, ocurriendo la transferencia hasta que ambos cuerpos se encuentren en equilibrio térmico (ejemplo: una bebida fría dejada en una habitación se entibia).

 La energía puede ser transferida por diferentes mecanismos, entre los que cabe reseñar la radiación, la conducción y la convección, aunque en la mayoría de los procesos reales todos se encuentran presentes en mayor o menor grado. La energía que puede intercambiar un cuerpo con su entorno depende del tipo de transformación que se efectúe sobre ese cuerpo y por tanto depende del camino.

 Los cuerpos no tienen calor, sino energía interna.

 En la naturaleza existen tres estados usuales de la materia: sólido, líquido y gaseoso. Al aplicarle calor a una sustancia, ésta puede cambiar de un estado a otro. A estos procesos se les conoce como cambios de fase. 

Los posibles cambios de fase son:
de estado sólido a líquido, llamado fusión,
de estado líquido a sólido, llamado solidificación,
de estado líquido a gaseoso, llamado evaporación o vaporización,
de estado gaseoso a líquido, llamado condensación,
de estado sólido a gaseoso, llamado sublimación progresiva,
de estado gaseoso a sólido, llamado sublimación regresiva o deposición,
de estado gaseoso a plasma, llamado ionización.

 El calor puede ser transmitido de tres formas distintas: por conducción, por convección o por radiación.


Conducción térmica: es el proceso que se produce por contacto térmico entre dos ó más cuerpos, debido al contacto directo entre las partículas individuales de los cuerpos que están a diferentes temperaturas, lo que produce que las partículas lleguen al equilibrio térmico. Ej: cuchara metálica en la taza de té.


Convección térmica: sólo se produce en fluidos (líquidos o gases), ya que implica movimiento de volúmenes de fluido de regiones que están a una temperatura, a regiones que están a otra temperatura. El transporte de calor está inseparablemente ligado al movimiento del propio medio. Ej.: los calefactores dentro de la casa.

Radiación térmica: es el proceso por el cual se transmite a través de ondas electromagnéticas. Implica doble transformación de la energía para llegar al cuerpo al que se va a propagar: primero de energía térmica a radiante y luego viceversa. Ej.: La energía solar. La conducción pura se presenta sólo en materiales sólidos.

 La convección siempre está acompañada de la conducción, debido al contacto directo entre partículas de distinta temperatura en un líquido o gas en movimiento. En el caso de la conducción, la temperatura de calentamiento depende del tipo de material, de la sección del cuerpo y del largo del cuerpo. Esto explica por qué algunos cuerpos se calientan más rápido que otros a pesar de tener exactamente la misma forma, y que se les entregue la misma cantidad de calor.

La termodinámica se interesa en la cantidad de transferencia de calor a medida que un sistema pasa por un proceso, sin indicar cuánto tiempo transcurrirá. Un estudio termodinámico sencillamente nos dice cuánto calor debe transferirse para que se realice un cambio de estado específico, con de fin de cumplir con el principio de conservación de la energía. En la experiencia nos enfocamos más en la velocidad de la transferencia de calor que en la cantidad transferida.

La termodinámica trata de los estados en equilibrio y de los cambios que ocurren entre un estado de equilibrio y otro. Por otra parte, la transferencia de calor se ocupa de los sistemas en los que se presenta desequilibrio térmico y, por tanto, existe una condición de no equilibrio. En consecuencia, el estudio de la transferencia de calor no puede basarse sólo en los principios de la termodinámica; sin embargo, existen leyes de la termodinámica que constituyen la base científica de la transferencia de calor.

La primera ley de la termodinámica establece que la velocidad de transferencia de energía hacia un sistema es igual a la velocidad de incremento de la energía de dicho sistema. Su segunda ley, establece que el calor se transfiere en dirección de la temperatura decreciente. El requisito básico para la transferencia de calor es la presencia de una diferencia de temperatura. No existe la más mínima posibilidad de que se dé transferencia neta de calor entre dos medios que están a la misma temperatura, esta diferencia de temperaturas constituye la condición básica necesaria para que se dé transferencia de calor.

Anteriormente mencionamos que el análisis termodinámico no se ocupa de la velocidad de la transferencia de calor en cierta dirección pero, ahora, podemos decir que este parámetro depende de la magnitud del gradiente de temperatura (o diferencia de temperatura por unidad de longitud, o la razón o relación de cambio de la temperatura en esa dirección). A mayor gradiente de temperatura, mayor es la velocidad de transferencia de calor.

Temario semestral test health

1. Embriologia
2. S. Nervioso
3. S. Musculoesqueletico
4. S. ocular
5. S. Cardiovascular
6. S. Pulmonar
7. S. Digestivo
8. Prefijos y sufijos
9. Médicos
10. Incendios y armas de fuego
11.Señales de emergencia
12. Fenómenos naturales

THE GI SYSTEM

The gastro-intestinal system is essentially a long tube running right through the body, with specialised sections that are capable of digesting material put in at the top end and extracting any useful components from it, then expelling the waste products at the bottom end. The whole system is under hormonal control, with the presence of food in the mouth triggering off a cascade of hormonal actions; when there is food in the stomach, different hormones activate acid secretion, increased gut motility, enzyme release etc. etc.

Nutrients from the GI tract are not processed on-site; they are taken to the liver to be broken down further, stored, or distributed.

Once food has been chewed and mixed with saliva in the mouth, it is swallowed and passes down the oesophagus. The oesophagus has a stratified squamous epithelial lining (SE) which protects the oesophagus from trauma; the submucosa (SM) secretes mucus from mucous glands (MG) which aid the passage of food down the oesophagus. The lumen of the oesophagus is surrounded by layers of muscle (M)- voluntary in the top third, progressing to involuntary in the bottom third- and food is propelled into the stomach by waves of peristalisis.

The stomach is a 'j'-shaped organ, with two openings- the oesophageal and the duodenal- and four regions- the cardia, fundus, body and pylorus. Each region performs different functions; the fundus collects digestive gases, the body secretes pepsinogen and hydrochloric acid, and the pylorus is responsible for mucus, gastrin and pepsinogen secretion.

The stomach has five major functions:

Temporary food storage
Control the rate at which food enters the duodenum
Acid secretion and antibacterial action
Fluidisation of stomach contents
Preliminary digestion with pepsin, lipases etc.

mucosa containing glandular tissue; different areas of the stomach contain different types of cells which secrete compounds to aid digestion. The main types involved are:
- parietal cells which secrete hydrochloric acid
- chief cells which secrete pepsin
- enteroendocrine cells which secrete regulatory hormones.

- muscularis mucosae
- submucosa

The stomach contains three layers of involuntary smooth muscle which aid digestion by physically breaking up the food particles:
- inner oblique muscle
- circular muscle
- outer longditudional muscle

The small intestine is the site where most of the chemical and mechanical digestion is carried out, and where virtually all of the absorption of useful materials is carried out. The whole of the small intestine is lined with an absorptive mucosal type, with certain modifications for each section. The intestine also has a smooth muscle wall with two layers of muscle; rhythmical contractions force products of digestion through the intestine (peristalisis). There are three main sections to the small intestine; The duodenum forms a 'C' shape around the head of the pancreas. Its main function is to neutralise the acidic gastric contents (called 'chyme') and to initiate further digestion; Brunner's glands in the submucosa secrete an alkaline mucus which neutralises the chyme and protects the surface of the duodenum.

The jejunum and the ileum are the greatly coiled parts of the small intestine, and together are about 4-6 metres long; the junction between the two sections is not well-defined. The mucosa of these sections is highly folded (the folds are called plicae), increasing the surface area available for absorption dramatically.

The pancreas consists mainly of exocrine glands that secrete enzymes to aid in the digestion of food in the small intestine. the main enzymes produced are lipases, peptidases and amylases for fats, proteins and carbohydrates respectively. These are released into the duodenum via the duodenal ampulla, the same place that bile from the liver drains into.
Pancreatic exocrine secretion is hormonally regulated, and the same hormone that encourages secretion (cholesystokinin) also encourages discharge of the gall bladder's store of bile. As bile is essentially an emulsifying agent, it makes fats water soluble and gives the pancreatic enzymes lots of surface area to work on.
structurally, the pancreas has four sections; head, neck, body and tail; the tail stretches back to just in front of the spleen.

By the time digestive products reach the large intestine, almost all of the nutritionally useful products have been removed. The large intestine removes water from the remainder, passing semi-solid faeces into the rectum to be expelled from the body through the anus. The mucosa (M) is arranged into tightly-packed straight tubular glands (G) which consist of cells specialised for water absorption and mucus-secreting goblet cells to aid the passage of faeces. The large intestine also contains areas of lymphoid tissue (L); these can be found in the ileum too (called Peyer's patches), and they provide local immunological protection of potential weak-spots in the body's defences. As the gut is teeming with bacteria, reinforcement of the standard surface defences seems only sensible...

The liver:
The liver is the largest glandular organ of the body. It weighs about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels called the hepatic artery and the portal vein. The heptic artery carries oxygen-rich blood from the aorta (a major vessel in the heart). The portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in very small capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver.

The Gallbladder:
The gallbladder is a small pear-shaped organ that stores and concentrates bile. The gallbladder is connected to the liver by the hepatic duct. It is approximately 3 to 4 inches (7.6 to 10.2 cm) long and about 1 inch (2.5 cm) wide.

THE ENDOCRINE SYSTEM

Although we rarely think about them, the glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.

In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.

About the Endocrine System

The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Although many different hormones circulate throughout the bloodstream, each one affects only the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood.
A gland is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere in the body. Some types of glands release their secretions in specific areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretions in the skin or inside of the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.

Parts of the Endocrine System




The major glands that make up the human endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes. The pancreas is also part of this hormone-secreting system, even though it is also associated with the digestive system because it also produces and secretes digestive enzymes.
Although the endocrine glands are the body's main hormone producers, some non-endocrine organs — such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta — also produce and release hormones.

The Hypothalamus

The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.
Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands. The production and secretion of pituitary hormones can be influenced by factors such as emotions and seasonal changes. To accomplish this, the hypothalamus relays information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary.

The Pituitary Gland

The tiny pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. Among the hormones it produces are:

·growth hormone, which stimulates the growth of bone and other body tissues and plays a role in the body's handling of nutrients and minerals

·prolactin, which activates milk production in women who are breastfeeding

·thyrotropin, which stimulates the thyroid gland to produce thyroid hormones

·corticotropin, which stimulates the adrenal gland to produce certain hormones

The pituitary also secretes endorphins, chemicals that act on the nervous system to reduce sensitivity to pain. In addition, the pituitary secretes hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women.

The posterior lobe of the pituitary releases antidiuretic hormone, which helps control body water balance through its effect on the kidneys and urine output; and oxytocin, which triggers the contractions of the uterus that occur during labor.

The Thyroid and Parathyroids



The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine and triiodothyronine. These hormones control the rate at which cells burn fuels from food to produce energy. As the level of thyroid hormones increases in the bloodstream, so does the speed at which chemical reactions occur in the body.

Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. The production and release of thyroid hormones is controlled by thyrotropin, which is secreted by the pituitary gland.
Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin, which is produced in the thyroids.

The Adrenal Glands



The body has two triangular adrenal glands, one on top of each kidney. The adrenal glands have two parts, each of which produces a set of hormones and has a different function. The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.

The inner part, the adrenal medulla, produces catecholamines, such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress. (Epinephrine injections are often used to counteract a severe allergic reaction.)

The Pineal Gland and Gonads

The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle.
The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonads, or testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development, including enlargement of the penis, the growth spurt that occurs during puberty, and the appearance of other male secondary sex characteristics such as deepening of the voice, growth of facial and pubic hair, and the increase in muscle growth and strength. Working with hormones from the pituitary gland, testosterone also supports the production of sperm by the testes.

The female gonads, the ovaries, are located in the pelvis. They produce eggs and secrete the female hormones estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in pregnancy and the regulation of the menstrual cycle.

The pancreas produces

(in addition to others) two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.
What the Endocrine System Does Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to target cells designed to receive its message. Along the way to the target cells, special proteins bind to some of the hormones. The special proteins act as carriers that control the amount of hormone that is available to interact with and affect the target cells.

Also, the target cells have receptors that latch onto only specific hormones, and each hormone has its own receptor, so that each hormone will communicate only with specific target cells that possess receptors for that hormone. When the hormone reaches its target cell, it locks onto the cell's specific receptors and these hormone-receptor combinations transmit chemical instructions to the inner workings of the cell.

When hormone levels reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms to maintain that level of hormone in the blood. This regulation of hormone secretion may involve the hormone itself or another substance in the blood related to the hormone.
For example, if the thyroid gland has secreted adequate amounts of thyroid hormones into the blood, the pituitary gland senses the normal levels of thyroid hormone in the bloodstream and adjusts its release of thyrotropin, the pituitary hormone that stimulates the thyroid gland to produce thyroid hormones.

Finding Your Way In God's World. Science #1

SCIENCE AS A MAP:

Science can tell us many important things that we need to know to live our lives.


10 Reasons to Learn About Science and Technology

1. Because it has the potential to save millions of lives.
2. Because so many popular beliefs are empirically unsound.
3. Because it's the only way to significantly move our entire civilization forward.
4. Because science just means "stuff we know" and technology just means "stuff we can do".
5. Because it's the foundation and context of all other human affairs.
6. Because it makes the main difference between cavemen and modern man.
7. Because ignorance is nothing to be proud of.
8. Because it's challenging and useful.
9. Because progress in science and technology is exponentially accelerating.
10. Because our future depends on it.

The word science comes from the Latin "scientia," meaning knowledge.

How do we define science? According to Webster's New Collegiate Dictionary, the definition of science is "knowledge attained through study or practice," or "knowledge covering general truths of the operation of general laws, esp. as obtained and tested through scientific method [and] concerned with the physical world."

What does that really mean? Science refers to a system of acquiring knowledge. This system uses observation and experimentation to describe and explain natural phenomena. The term science also refers to the organized body of knowledge people have gained using that system. Less formally, the word science often describes any systematic field of study or the knowledge gained from it.

What is the purpose of science? Perhaps the most general description is that the purpose of science is to produce useful models of reality.

We need God to speak to us and tell us how we fit into His World. The Bible tell us that it is the Word of God:"Every scripture is inspired by God and useful for teaching, for reproof, for correction, and for training in righteousness, that the person dedicated to God may be capable and equipped for every good work."
(2Tim. 3:16-17)

As God's infallible word, the Bible confronts us whith a series of authoritative presuppositions.

A Presupposition is an implicit assumption about the world or background belief relating.

the only way to live free of presupposition is to know everything.

The most basic presupposition of Christianity is that God has spoken to the human race in the Bible. And within the Bible we Find many presuppositions that work together to form a worldview.

The essential presuppositions in a Christian worldview are that:

1. God made the world and placed humans at the center of that world.
2. The world has fallen into a broken condition because of human sin; and
3. God is working to redeem this world to himself.

Whit this worldview we are able to make proper use the map of science.

The Bible's teachings about creation tell us where come from. Gen 1-11, Gen 1:26-27.
We were created to exercise a mandate: The Creation Mandate Gen 1: 26,28.
The Bible tells us about the fall of the world because of sin Gen 3: 17-19.
God gives us hope, a promise of salvation through Jesus Gen 3:15, Heb 1: 1-3,
Matt. 28:19.

When we study science, learn from observations and Conclusion made in previous studies, which plays an important role in how we can help the world today.

Secularism is the concept that the entities should exist separately from religion and/or religious beliefs.

Secular is a term which has come into use in the last thirty years to describe a world view with the following elements and principles:

A conviction that dogmas, ideologies and traditions, whether religious, political or social, must be weighed and tested by each individual and not simply accepted on faith.
Commitment to the use of critical reason, factual evidence, and scientific methods of inquiry, rather than faith and mysticism, in seeking solutions to human problems and answers to important human questions.
A primary concern with fulfillment, growth, and creativity for both the individual and humankind in general.
A constant search for objective truth, with the understanding that new knowledge and experience constantly alter our imperfect perception of it.
A concern for this life and a commitment to making it meaningful through better understanding of ourselves, our history, our intellectual and artistic achievements, and the outlooks of those who differ from us.
A search for viable individual, social and political principles of ethical conduct, judging them on their ability to enhance human well-being and individual responsibility.
A conviction that with reason, an open marketplace of ideas, good will, and tolerance, progress can be made in building a better world for ourselves and our children.

Secular humanism does not believe that God is the creator of the universe and that this was done for his glory.