Ovarian and Uterine Cycles

http://www.bioteach.ubc.ca/legal-rights-and-the-maternal-fetal-conflict/

The ovarian cycle lasts approximately 28 days, and begins with menstruation, which takes up the first week of the cycle. During that time, 6-12 follicles begin to develop. The follicle is a primary oocyte surrounded by follicle cells, and as it develops, the follicle cells rapidly divide and feed nutrients into the oocyte through gap junctions. All but one of these oocytes will eventually degenerate, with the remainder completing Meiosis I, in which the diploid oocyte divides into two haploid cells. One half, the polar body, contains little cytoplasm while the other half, the secondary oocyte, enters Meiosis II and prepares for fertilization. Around day 14 of the cycle, the oocyte bursts through the wall of the ovary in a process called ovulation, which ends the follicular phase. Cilia lining the oviduct propel the egg forward in case a sperm cell is ready to fertilize it. Meanwhile, during this luteal phase, the remaining follicle tissue in the uterus forms the corpus luteum, an endocrine structure that secretes the hormones estrogen and progesterone, hormones that stimulate the maintenance and development of the uterine lining. In the event that the woman does not become pregnant, the corpus luteum disintegrates.

The uterine cycle is closely tied to the ovarian cycle. It also begins with menstruation when the previous uterine lining, the endometrium, leaves the vagina. The new lining of the uterus prepares for an embryo to be embedded. The period between menstruation and ovulation (days 7-14) is known as proliferation, in which the uterine lining continues to grow. Capillaries in the lining supply the uterus with plenty of nutrients to prepare for a pregnancy, while estrogen and progesterone keep the lining growing. However, if at the end of the secretory phase of the cycle an oocyte has not been fertilized, then no embryo will be created and nothing will be implanted within the endometrium. The lining dies and menstruation occurs, restarting the cycle. Because the woman was not impregnated, the levels of estrogen and progesterone decline until the uterine lining is removed, but these hormones will continue to be produced if an embryo is implanted.

http://www.tutorvista.com/content/biology/biology-iv

Summary of hormones:


LH (luteinizing hormone) - Produced from the anterior pituitary gland shortly before the cycle begins; stimulates oocytes to develop until they rupture the ovarian wall; maintains corpus luteum, and in doing so increases levels of estrogen and progesterone


FSH (follicle-stimulating hormone) - Produced from the anterior pituitary gland shortly before the cycle begins; stimulates oocytes to develop until they rupture the ovarian wall; stimulates the production of estrogen and progesterone


GnRH (gonadotropin-releasing hormone) - Released from the hypothalamus; triggers the anterior pituitary gland to release LH and FSH


Estrogen - Stimulates development of uterine lining; inhibits LH, FSH and GnRH except for days 12-14, when it suddenly has a positive feedback effect that causes a surge of LH and FSH for ovulation; maintains uterine lining


Progesterone - Stimulates development of uterine lining; inhibits LH, FSH and GnRH except for days 12-14, when it suddenly has a positive feedback effect that causes a surge of LH and FSH for ovulation; maintains uterine lining


hCG (human chorionic gonadotropin) - Secreted by a layer of cells surrounding the blastocyst (the multicellular embryo); can cause surges of LH and FSH, but can also maintain the corpus luteum in the event of fertilization, which inhibits the release of LH, FSH and GnRH


Hormonal changes are important for the body to either prepare for a pregnancy or repeat the ovarian and uterine cycles. The aforementioned hormones do not work independently, however; instead, they use positive and negative feedback loops to either promote or hinder their production, respectively. Positive feedback loops mean that as a substance "A" is created, it encourages the production of another substance "B". In a negative feedback loop, "A"'s production inhibits the synthesis of "B." For example, at the beginning of the cycles, low levels of LH and FSH steadily increase the levels of estrogen and progesterone, which in turn inhibit LH and FSH, but not enough to stop the development of an oocyte. Then, around day 12, estrogen and progesterone suddenly encourage a surge of these hormones so that the oocyte quickly grows and breaks through the wall of the ovary. After day 14, estrogen and progesterone created by the corpus luteum return to inhibiting LH and FSH if fertilization has not occurred so that the corpus luteum dissolves and the endometrium can be shed. During ovluation, many hormones are at their peak levels, which may explain the emotional changes that occur in women to cause PMS (premenstrual syndrome). However, if fertilization has occurred, the embryo will release hCG in order to trigger another surge of LH and FSH to keep the corpus luteum producing estrogen and progesterone to prevent menstruation, which is why pregnant woman don't have periods.

Pregnancy is an exciting but critical period in a young mother's life. Intercourse has to be performed at the right time during the ovarian and uterine cycles in order for an oocyte to be fertilized. While hundreds of thousands of sperm are released through ejaculation during intercourse, only one sperm cell will be able to survive the acidic and protective environment of the vagina. Once the woman's reproductive system allows for a sperm cell to fuse with the zona (a protein shield around the oocyte), a zygote is formed. The female and male chromosomes are spread out, providing the genetic material that will determine all the characteristic of the child. The zygote undergoes mitotic divisions called cleavage, formign a ball of cells called a blastocyst. Rarely, the dividing cells split into two groups, beginning life for identical twins. During all these divisions, the blastocyst is being pushed along the fallopian tube into the uterus. It breaks out of the zona and implants itself into the uterine lining.

http://doctorstevenpark.com/what-all-pregnant-women-must-know

Two weeks after fertilization, the blastocyst's cells begin to separate into specific layers in a process known as gastrulation, which I discussed in my blog post on Embryology. Immediately, the embryo begins its nine-month-long journey into becoming a functioning infant. It does so by turning certain genes on and off within the specialized cells to form tissues and organs. The nervous system begins to develop during the first few weeks as a primitive brain is trying to make connections with the environment. Blood vessels, the heart, the spinal cord, and the limbs form within four and a half weeks. Human embryos even form a tail, which will disappear within the first trimester. During this time, chemical messages between cells continue to turn certain genes on and off to create the proteins that help a specific type of cell perform its functions.

The chromosomes can identify sex: girls have two X chromosomes, while boys have an X and a Y chromosome. Around the sixth week of development, genitalia is determined by whether certain genes get turned on by a Y chromosome or not. However, it isn't until the eighteenth week when this genitalia will be viewable by an ultrasound so the parents can identify the sex of their baby. When the embryo is two months old, enough cells have been specialized to resemble the shape of a human infant. At this stage, we call the developing child a fetus, rapidly growing within the amniotic sac. Its organs are in place, but not working yet. The fetus continues to grow in size and its heart beats twice as fast as an adult heart. The other organs gain function because of nutrients delivered through the umbilical cord. The umbilical cord connects the fetus to the placenta, an organ which connects the fetus to the uterine lining. Villi, tiny projections on the placenta, take oxygen and nutrients from the mother's blood and send it to the fetus. It is essential for a mother to properly nourish her child by eating the proper foods and avoiding bad habits such as smoking and drinking.

http://www.charlottetufts.com/ultrasound/

During the second trimester, the organs continue to develop. Ears are formed, and eyes begin to sense light. Soft cartilage gives the fetus support, eventually forming bone as early as the fourth month. The fetus gains hearing in the fifth month. The womb is relatively busy during the first few months of pregnancy, and by the end of the second trimester, all the organ systems have been developed. The third trimester gives the fetus time to grow, as well as to form fat deposits around the body and in the brain to enhance brain power. The mother is also undergoing major changes during this time, as her stomach gets bigger to accomodate more blood flow and room for the child. By the ninth month, the baby can realize that the mother is unable to keep up with his or her needs, so the baby is ready to be born. The uterus begins to contract to dilate the cervix, and as these contractions increase in frequency, it is a sign that the birth will happen soon. Water breaking from the rupture of the amniotic sac is another sign. There is a possibility that the proportions of the baby will cause it to be unable to exit the vagina. If this happens, doctors can perform a Cesarian section (C-section) to take out the baby through the mother's abdomen.

http://cjkennedy.wordpress.com/2007/06/27/

Nowadays, science allows us to fertilize eggs outside of the body through IVF (in vitro fertilization). The first "test tube baby," Louise Brown, was born on July 25th, 1978, and the doctor who created IVF treatment, Robert G. Edwards, was awarded the Nobel Prize in 2010. Technology that alters the natural course of human reproduction is highly controversial, but no matter what the method is, there is nothing more beautiful than the miracle of life which keeps the human race going strong for generations to come. Plus, babies are undeniably cute.

http://blog.bioethics.net/2009/03/

Immune System

While superheroes such as Spiderman, Superman and Batman are highly idolized by young children, I believe the great superheroes of all are the cells of the immune system. The immune system saves our lives by defending us against pathogens, those villainous germs which invade the body and cause disease. Leukocytes (commonly called white blood cells) destroy these substances and come in two types: phagocytes and lymphocytes. Phagocytes directly consume other cells while lymphocytes are responsible for recognizing, destroying and remembering pathogens.

There are four types of pathogens: viruses, bacteria, fungi and parasites. Virus is the only nonliving category, and causes infection by attaching to a cell and inserting DNA into the cell so that when the cell divides, it copies the viral DNA and thus creates more of the virus. Viral replication can occur through the lytic cycle or the lysogenic cycle. The lytic cycle involves the virus destroying the host cell's DNA and taking over the cell's metabolic activities. Once the virus directs the cell's ribosomes to create enough viruses, the cell bursts in a process called lysing, and the new viruses are released. In the lysogenic cycle, the virus inserts its DNA directly into the host cell's own DNA without destroying it. As the cell divides and copies its DNA, it also copies the viral DNA, but it does not destroy the cell and there are no viral symptoms. However, the lysogenic cycle can eventually progress into the lytic cycle.

http://health.howstuffworks.com/medicine/modern/light-virus.htm

Bacteria, a living pathogen, can often be described just by looking at the classification of the bacteria. The word "bacillus" signifies that the bacteria is rod-shaped; "coccus" means spherical, and "spirillus" means spiral. The sexually transmitted disease syphilis is an example of a spirillus bacteria. Furthermore, the prefix "strepto-" means that the bacteria is organized in chains, such as the bacteria that causes strep throat. The prefix "staphylo-" means that the bacteria is organized in clumps.

http://steveaoki.dimmak.com/blog/2009/11/useless-information-4-bacteria/

Leukocytes are produced in the thymus gland, spleen and bone marrow, collectively called the lymphoid organs. The leukocytes are stored in lymphoid tissue in the form of lymph ducts and bean-shaped lymph nodes, which are part of the lymphatic system. The lymphatic system filters pathogens from the organs in the body using a clear substance known as lymph that circulates around the body. Lymph is able to provide the white blood cells that fight infection and filter out the harmful invaders, dead cells and toxins.

Leukocytes work by first identifying the pathogen. Then, they signal for help and tag the invaders. Next, they destroy the invaders, and lastly, they remember what caused the infection in the first place. There are eight main leukocytes which carry out these functions:

Macrophage - Type of phagocyte that begins the immune system's attack. It devours invaders through phagocytosis, in which it engulfs the invader in a food vacuole, then fuses it with a lysosome to digest it. They also help by cleaning up dead cellular debris.

Antigen - Macrophage displays part of the virus as a flag to help identify other invaders.

Helper T Cells - Type of lymphocyte store in the thymus gland that recruits and activates other immune system cells through chemical messengers. They help B cells produce antibodies to fight illness.

B Cells - Type of lymphocyte stored in bone marrow that tags invaders with antibodies so that they can be easily identified and destroyed. They can become plasma cells that create thousands of antibodies per second.

Antibodies - Proteins created by B cells that tag antigens. They can also neutralize toxins and activate a group of proteins known as a complement, which assists in destroying bacteria, viruses and infected cells.

Killer Cell - Type of lymphocyte that can either devour invaders or release chemicals that destroy them. They work best when they see germs that have been tagged with antibodies.

Cytotoxic T Cell - Type of lymphocyte that destroys cells infected with a virus before the cell copies the viral DNA. It kills the cell by releasing a chemical that infiltrates the plasma membrane and induces cytolysis by making the cell burst.

Memory Cell - Type of lymphocyte that speeds up the immune system if an invader returns.




http://www.mayoclinic.com/health/medical/IM00419


There are three kinds of immunity:

Innate immunity is the kind of protection humans are naturally born with. Certain invaders that could be lethal to another species have no effect on us. Also, we are born with mucous membranes and special immune cells in the integumentary system which are our first lines of defense when an invader tries to infect.  

Adaptive immunity is developed as we are exposed to new pathogens, because memory cells try to prevent us from suffering from that infection again. Immunization vaccines can also help with adaptive immunity by introducing a harmless amount of a pathogen into a person so that they build up enough antibodies to fight if the germ actually infects them in the future.

Passive immunity is a temporary protection. For example, breast milk contains many of the mother's antibodies that can help prepare the baby's undeveloped immune system to fight against pathogens he or she may encounter as an infant.

http://wamfitandwell.wordpress.com/2008/06/24

Immune disorders fall into four categories:

Immunodeficiency disorders are either present at birth or acquired later in life. A part of the immune system is missing or does not function properly.

Autoimmune disorders are when the body attacks its own tissue as if it were a pathogen.

Allergic disorders are when the body overreacts to a harmless invader called an allergen.

Cancer can occur when leukocytes grow out of control. Lymphoma and leukemia are among the most common childhood cancers.

Two examples of immune disorders:

AIDS (acquired immunodeficiency syndrome) is a disease that slowly destroys the immune system altogether. A virus known as HIV (human immunodeficiency virus) destroys Helper T Cells, which are absolutely essential in protecting us from otherwise harmless infectious agents. AIDS is spread either through birth, unprotected sexual intercourse, or sharing contaminated needles.

Asthma is an example of an allergic disorder in which the lungs become oversensitive to common allergens and triggers the narrowing of the bronchioli, which results in reduced airflow and therefore difficulty breathing.

As I head into the holiday season, I know that I am very thankful for my immune system and everything it does to defend me against foreign invaders. However, it is important to remember that the immune system needs our help too. Studies have shown that proper diet, exercise, and sufficient sleep can all help improve immune function. So, while your leukocytes are working hard to fight crime inside your body, make sure you're taking care of them too.

http://wamfitandwell.wordpress.com/2008/06/24

Sleep



"Blessed is the person who is too busy to worry in the daytime and too sleepy to worry at night." -- Anonymous

http://www.dreamstime.com/

Nearly everyone I know carries around a cell phone or an iPod with them all day long. When the battery power on these devices run low, all a person has to do is plug it into a device so that it can charge and prevent the battery from dying. People work in a similar way. Our busy lives constantly wear us down physically, mentally and emotionally, thus depleting our "battery." So, at the end of the day, we climb into bed and let ourselves recharge, in order to feel refreshed for the challenges of tomorrow. But how exactly do our bodies know when to begin recharging without completely turning off?

http://www.watchmojo.com/blog/children/tag/Crying/

Neurotransmitters are chemical messengers that help communicate signals between nerves in the brain. Two neurotransmitters, serotonin and gamma-aminobutyric acid, are responsible for regulating the sleep-wake cycle by altering their concentrations in the body. The circadian clock is the body's internal biological clock. When the retina of the eye perceives prolonged darkness, it sends a message to the circadian clock to produce melatonin, a hormone which also has been shown to trigger sleep.

Many things may throw neurotransmitters or the circadian clock off balance (examples: irregular schedule, a significant time zone change, taking a night shift, illness, trauma, stress, drugs). If any of these things happen for an extended amount of time, a person may develop a sleep disorder, which will be discussed later on.

http://thebrain.mcgill.ca/flash/index_i.html

Neurotransmitters and the circadian clock help communicate to the body that it is time to sleep, but there is still a great deal of activity going on in the brain during the sleep cycle. The cycle usually lasts 90-100 minutes and can be broken down into five stages that repeat between 4 and 6 times per night. The combination of the first four stages is known as nREM (non-rapid eye movement) sleep. As the stages progress, a person will experience deeper sleep, and activities in the nervous system, cardiovascular system and respiratory system will continually slow down. If a person is awoken in the middle of stages three or four, they will feel groggy and disoriented. It is ideal to wake up between cycles in order to feel fully refreshed.

The fifth stage is called REM sleep, and it is characterized by intense brain activity, increased blood pressure, increased heart rate, increased respiration, and paralysis of the limbs. The brain processes information acquried throughout the day and forms memories. The length of REM sleep increases each time that the cycle is repeated. REM sleep is most notable for being the stage in which dreaming occurs. Scientists are still trying to discover the exact function of dreaming in humans. There are many religious and spiritual connections to dreams, particularly among some Native-American tribes. The 2010 movie Inception portrayed dreams as a complex representation of our subconscious desires, and even explored dreams within dreams. While there are certainly many artistic and mysterious things to say about dreaming, a common theory states that dreaming helps us use newly learned techniques to confront a previous stressor if it came up again. This may explain why people sometimes have reoccurring dreams, as their mind figures out how to triumph over the anxiety.

http://health.howstuffworks.com/mental-health/sleep/basics/sleep1.htm

As mentioned earlier, there are a variety of sleep disorders that people have been diagnosed with. They include insomnia, sleep apnea, restless leg syndrome, and narcolepsy.

Insomnia is the most commonly reported sleep disorder. It can be caused by elevated levels of the stress hormone cortisol, which increases activity in the brain and central nervous system. Other contributers include poor sleep hygiene or mental health troubles. Insomniacs have trouble falling asleep, or they may wake up repeatedly through the night. There are medications used to treat insomnia, but they are highly addictive. To combat insomnia, it is preferable to improve sleep hygiene through healthier lifestyle habits, such as relaxing more, not consuming caffeine or alcohol before bed, and abstaining from the usage of television, computers and video games.

Sleep apnea is a rather terrifying disorder typically found in obese individuals with excess body fat around the pharynx. This restricts their air supply, making it dangerous for them to sleep unmonitored because they may stop breathing. Many people don't know they have sleep apnea, but dramatic snoring and/or gasping may be a warning sign. Sleep apnea can be treated by using a CPAP device to keep airways open, or better yet, improving ones health to promote healthy air flow.

http://snoringstopsnow.com/pros-cons-sleep-apnea-machine/

Restless Legs Syndrome is classified by the sudden urge to move ones legs. The legs may twitch on their own, causing difficulty in falling asleep. It can be cured by medication.

Narcolepsy is the sensation of extreme sleepiness during the day which causes people to suddenly fall into REM sleep without progressing through nREM sleep prior to it. While it may seem refreshing to some to be able to spontaneously sleep, it is also highly debilitating as it affects job performance as well as the ability to concentrate while driving. People with narcolepsy may experience hallucinations and paralysis upon waking. It is treated with medication.

Most people need between 7 and 9 hours of sleep per night, and it is recommended that teenagers get 8.5 to 10 hours. Unfortunately, due to excessive work loads and the stress of high school, very few teenagers report getting the recommended amount of sleep. Getting the proper amount of sleep is essential to performing to one's fullest potential. Even losing just one hour of the recommended sleep length can be detrimental to concentration. While daytime drowsiness is certainly an unpleasant consequence of losing sleep, there are many serious risks as well. These risks include: car accidents, relationship troubles, poor job performance, job-related injuries, memory problems, mood disorders, reduced creativity, hindered immune response, and inability to cope with stress. Recent studies also suggest sleep disorders may contribute to heart disease, obesity, and diabetes. To enjoy longer and deeper sleep, stick to a routine time to wake up and go to bed, even on weekends. Try to prepare for bed by doing nighttime rituals that involve relaxing activities, such as drinking warm milk or taking a bath.

Sleep is one of the most peaceful and essential things we need to sustain life. In fact, the average person will spend one-third of his or her life asleep. It is important to help our bodies be as refreshed as possible so that we can have the energy to make the world a better place tomorrow. And, last but not least...

NEVER WAKE A SLEEPWALKER! EVER!

Good night and sweet dreams!




http://wopico.blogspot.com/2009/02/flying-man.html






Aging

"We as for long life, but 'tis deep life, or noble moments that signify. Let the measure of time be spiritual, not mechanical."

- Ralph Waldo Emerson

http://www.time.com/time/specials/packages/article/0,28804,1963392_1963365_1963378,00.html

It is difficult to pinpoint a direct cause for aging, as many studies have shown that various factors contribute to an organism's lifespan. Therefore, it is safe to say that aging is caused by both genetic and environmental factors. We are not able to control the genes we inherit, but our lifestyle choices can help us amplify beneficial genes and negate the effects of undesirable ones. For instance, if someone has a family history of heart attacks and high cholesterol, choosing to lead a healthy lifestyle can help him or her overcome these predispositions and live to a much higher age than previous generations.

One genetic trait tied to aging is telomere length. Telomeres are stretches of DNA at the end of chromosomes that help protect genes from being harmed by general use. However, as cells divide, telomeres get shorter and shorter. There is a gene that controls the default telomere length, so naturally, having longer telomeres signifies longer lifespan (Moisse, 2010). The shortening of these telomeres correlates directly with age-related diseases, such as heart disease, cancer, diabetes and Alzheimer's, which is why it may seem hopeless for someone with a low expression of the telomere size gene to want to be healthy. However, there are benefits to not smoking, eating unhealthy foods and being inactive: these things all accelerate the rate at which our telomeres are shortened, so in that regard, making good lifestyle choices can help a person overcome genetic deficiencies (Park, 2010).

Shortened telomeres are an example of a gene expression related to early death, but there are also genes that signify longevity. This family of genes known as sirtuins enable a physiological response to stress within a cell, promoting DNA repair and preventing cell death. The power of these genes was highly underestimated until biologist David Sinclair fed one group of yeast cells a normal amount of glucose, and gave the other group a restricted amount (Chaddha, 2007). He found that the yeast cells with the restricted diet lived up to 50% longer because SIR2, yeast's primary sirtuin, activated an emergency response that slowed the formation of waste DNA. Without this waste interfering with the cell's processes, the group with the lower-calorie diet actually seemed to age slower, and thus allowing them to divide more over the course of their lives (Chaddha, 2007). Later research revealed that SIRT1 is the primary sirtuin in mammals, so scientists are now looking at what lifestyle choices we can make to encourage the expression of SIRT1 to promote longevity.

http://www.cakens.com/research/understanding-the-mechanisms-of-ageing-worth-a-nobel-prize/

As shown by Sinclair's experiment, calorie restriction, while unproven, seems like a probable method to increasing lifespan. However, it is an impractical solution, because humans typically like to eat. Luckily, a substance known as resveratrol (commonly found in red wine) has been shown to induce the effects of calorie restriction without the need of going on a strict diet. Some studies have shown that drinking red wine increases lifespan, but the degree to which it helps is currently unknown. In one study, mice who were given resveratrol lived 10-20% longer, but to simulate the same effect in a human, it is predicted that we would have to drink 1000 glasses of red wine a day (Cohen, 2007). Again, not very practical.

http://www.pfiwestern.com/magazine/index.php/2008/09/26/red-wines/

The interplay between genetics and lifestyle is evidence once again when we examine HDL (high density lipoproteins). Blood samples taken from people who have lived past the average life expectancy of 78 years in the United States have shown that the amounts and sizes of HDL within these people are typically larger (Cohen, 2007). HDL, commonly referred to as the "good" cholesterol, cleans out the blood vessels by removing LDL (low density lipoproteins, the "bad" cholesterol) that clog vessels and may lead to atherosclerosis and heart attack. While HDL/LDL levels certainly have a genetic component to them, eating foods low in saturated fat may be incredibly beneficial, as it reduces LDL in the body and leaves blood vessels clean and open. Because of this, it is important to remember just how much control we have over our health. While our family histories may lead us to believe that we are predisposed to certain diseases, scientists are discovering more and more just how important lifestyle is to extending our lifespans as much as possible.

Lastly, I'll emphasize this: it is not the quantity of years that determines a person's value, but rather the quality of those years. There is no point to a long life if you can't enjoy that life. I wish you the best life possible.

http://www.pfiwestern.com/magazine/index.php/2008/09/26/red-wines/

Chaddha, Rima. (2007, January 1). Healthy Old Age. Retrieved November 10, 2010 from http://www.pbs.org/wgbh/nova/body/aging-longevity.html. 

Cohen, Chad (Producer). (2007). Aging [Videoclip]. Boston, MA: PBS Video.

Moisse, Katie. (2010, February 8). Researchers Identify Genetic Variant Linked to Faster Biological Aging [Electronic version]. Scientific American. Retrieved November 10, 2010.

Park, Alice. (2010, February 11). How to Love 100 Years [Electronic version]. Time.  Retrieved November 10, 2010.

Stress

High school is meant to prepare teenagers for the rigorous course work of college. By learning introductory classes in subjects such as history, trigonometry and biology, we are taught the foundations that are built upon in more advanced classes. Sociologists, however, would argue that high school comes with a hidden curriculum. This means that the actual experience of going to school may be able to teach life skills outside of textbooks and homework. Unfortunately, this can also be problematic. Besides having to deal with demanding coursework in AP and Honors classes, I also have to balance my time between three clubs, a sport, peer tutoring, and theater. As if that weren't enough, I have my obnoxious (but loveable) friends to deal with. And on top of that, there's dealing with siblings, peer pressure, getting ready for college and finding self-esteem. Needless to say, that's a whole lot.

http://www.emiratesosteoporosissociety.com/tag/how-to-reduce-stress/

As people undergo significant life changes, they may experience stress, a physiological and psychological response. Stressors are things in the environment, body, or thoughts that trigger this response, preparing our bodies for fight-or-flight to provide the energy needed to face the stressor. Nowadays, it is rare that we are confronted with the same challenges as an organism that lives in the wild, but stress still exists as an evolutionary adaptation to help us face everyday issues living in society, such as public speaking, a meeting with someone of higher stature, and job interviews.

Stress can be both a positive and negative thing. If we can constructively deal with the challenges before us, it is considered positive, such as when we increase our concentration before a test or presenation. Slight sweating and an increased heart rate are examples of acute stress, a good and short-term type of stress. As the body recovers from this kind of stress, it rewards itself with a sense of emotional achievement. However, if the stress is ongoing and leads to worsening health conditions, it is negative, because the body is not recovering from its altered state. This is chronic stress, caused by intense feelings of being overwhelmed or uncertain.

Like I mentioned earlier, stress has its effects on both the body and the mind. These changes are caused by the release of hormones in the hypothalamus of the brain called corticotropin-releasing hormones to the pituitary gland, which then releases ACTH into the bloodstream to activate the stress response. Adrenaline (a.k.a. epinephrine) is a major stress hormone released by the adrenal glands.

http://www.impactfactory.com/p/stress_management_skills_training_development/

Physical changes include: Muscle tension, headaches, back pains, ulcers, neck pains, upset stomach, diarrhea, constipation, teeth grinding, insomnia, shaky hands, fatigue, heart disease, high blood pressure, heart burn, and a weakened immune system.

Changes in feeling and behavior inlude: Poor decision making, depression, fear, confusion, nerves, hostility, anger, worry, irritation and poor concentration.

The use of drugs and unhealthy foods are short-term relievers of stress which will ultimately accelerate the worsening of health. These agents also carry a risk of dependency, which may be another source of stress for a person. Exercise is a much more practical method used to alleviate stress, which is one reason why I am a strong advocate of physical activity. For a healthier and more long-term solution, it is necessary to identify what the stressors are in your life that are causing such significant changes. Then, you can begin to understand its physical and mental effects.

Stressors come in three forms: accidental hassles, major life changes and ongoing problems. Accidental hassles are temporary but inconvenient events, such as losing something important, having car problems or getting ticketed. Major life events are noteworthy things that occur during a lifetime, and can be positive (graduation, marriage, child bearing) or negative (divorce, unemployment, death). Ongoing problems are stressful situations such as an unhappy marriage, conflict with a relative or coworker, or accumulating debt.

http://www.new-oceans.co.uk/new/business/images/stress16.jpg

For situations that we have some control over, these methods may be useful for preventing stress:

- Avoid controllable stressors
- Plan major lifestyle changes
- Realize your limitation
- Prioritize
- Improve communication
- Share your throughts
- Develop a positive attitude
- Reward yourself
- Exercise
- Eat and sleep well

For inevitable situations, it may be more practical to utilize these methods to manage stress:

- Plan by visualizing expected events
- Think positively
- Imagine potential negative big events
- Relax with deep breathing
- Relax by clearing your mind
- Relax your muscles
- Relax with stretching and exerise
- Relax with massage therapy
- Ask for help
- Find professional help if needed

http://tweakfit.com/health-wellness/simple-deep-breathing-relaxation-exercises/

Exercise Physiology

“Fitness is a journey, not a destination. It must be continued for the rest of your life.” - Dr. Kenneth Cooper, the Father of Aerobics

http://www.bodyfitnt.com.au/exercise-physiology.php

Exercise physiologists are experts who study how the body functions during rigorous activity. They can test how hard an athlete is working, and then can create training programs to enhance his or her performance.

One of the most useful measurements for an exercise physiologist is the VO₂ max of an athlete, usually measured in milliliters per kilogram of body weight per minute. It is defined as the maximum amount of oxygen a person can take in while exercising. As we run, our need for energy increases. Oxygn helps the body react ADP (adenosine diphosphate) with another phosphate in order to make ATP (adenosine triphosphate), the body's main source of energy. Since oxygen is a contributor to energy production, our oxygen uptake must increase to meet the demand. Having a higher VO₂ max signifies better endurance and thus better fitness. Exercise physiologists work to increase the VO₂ max by challenging athletes to perform at or near their recorded oxygen uptake.

There is a small amount of ATP within the myofibrils of muscles, but there's only enough for one explosive reaction. Therefore, it must be replenished by constantly reacting ADP and phosphate. This is done through a number of energy pathways. Sports that require short explosive moments only need the ATP already reserved in muscles, so athletes who participate in power-lifting rely on ATP splitting as their energy pathway.

http://www.emc.maricopa.edu/

At my high school, I'm a sprinter on the track team. Sprinting requires quick repeated muscular contractions, so it uses CP (creatine phosphate) splitting to resynthesize ATP. There is a certain reserve of CP molecules in the muscles that can be used for this process, but there is only enough to last a few seconds. Luckily, that is exactly how long many short sprint races last. However, I have also run the 400 meter dash before, which is the longest sprint at a track meet. For that race, another energy pathway must be utilized, known as anaerobic glycolysis. In glycolysis, a polysaccharide known as glycogen stored in the muscles is used to create more ATP molecules. Turning the glycogen into ATP creates a byproduct known as lactic acid, and when lactic acid builds up, it causes a painful sensation in the muscles. However, athletes can be trained to perform despite this pain. One of my least favorite workouts during Track season is called "Broken Quarters." In this workout, I sprint to build up lactic acid, and then I continue to run as hard as I can so that I can train my body to handle that much lactic acid in the muscles. By doing this, I increase my anaerobic threshold, the point at which the buildup of lactic acid exceeds its removal.

http://www.lollylegs.com/training/SprintTech.aspx

If the body is too fatigued from the lactic acid, then anaerobic respiration is no longer a viable source of energy. Aerobic respiration is used to sustain long-distance running by using the circulatory system to transport the oxygen in the blood to the muscles in order to create ATP in muscles. In team sports, athletes often have to utilize multiple pathways at times to replenish ATP; in other words, these energy pathways are not mutually exclusive. They form an energy continuum, and exercise physiologists will often create workouts that help an athlete's use of the pathways more efficient.

Besides exercise, an athlete's diet is critical to their success. Most exercise physiologists would agree that a typical athlete's diet should be 30% fat, 55% carbohydrates and 15% protein. Both fats and carbs are necessary to replenish ATP and CP reserves in the body. Fat is important to the diet, because there is a high concentration of fat in the body which is used as long-term energy storage. Carbohydrates, however, make up the majority of the diet because they are used for short-term energy storage, which is what athletes rely upon if they are going to be active for more than a couple minutes. Protein is not typically used as an energy source, but it is still important to consume so that the muscles in which all of these energy pathways take place can remain healthy.

http://healthguide.howstuffworks.com/

While conditioning is crucial to a proper training program, more studies are beginning to show that weight training is an effective way to improve athletic performance. Weight lifting is by far my favorite physical activity. Not only does it help me during Track season, but it also releases endorphins in the body that make me feel better. The principles of weight lifting are straightforward: first, there is the overload principle. This means choosing to lift weight that is challenging but not dangerous for the body. By doing this, you successfully tear muscle fibers, so that during the recovery stage when you are not lifting, they can repair themselves bigger than before to accomodate heavier weight. This is known as hypertrophy.

Because muscles will eventually adapt to meet the challenge required by repeated lifting, it is important to fulfill the principle of progression. This means constantly finding new challenges for the body to meet so that it can still tear those strengthened muscle fibers, thus inducing stress. When experiencing muscular fatigue, the body releases many hormones, including testosterone and endorphins. For overall health, it is essential to work out all of the various muscles in our body. The principle of specificity, which states that to increase strength and/or size in a certain muscle, that muscle must be trained, helps meet this need. Because muscles pull, never push, they must work in antagonistic pairs (for example, biceps and triceps). Therefore, in order to allow for the body to function properly, it is important to work both sides of the pair evenly. Lastly, it is essential to give the muscles rest (around 45-60 seconds in between 2-3 sets of an exercise) in order to give them time to repair.

Heart Surgeries

Fun Facts about Heart Surgeries:

- The first heart transplant was performed in South Africa in 1967 by Dr. Christiaan Barnard. The patient lived 18 days.
- In 1980, 80% of patients survive a year after a heart transplant.
- Robert Jarvik made the first artificial heart in 1982.
- Barney Clark, a retired dentist, was the first person to receive an artificial heart.
- Today, surgeries used to correct congenital heart disorders have about a 95% success rate.
- To make heart surgery as minimally invasive as possible, we can use surgeon-operated robots to make small incisions

http://www.dreamstime.com/

Heart Patient Case History: Baby Fae

Stephanie Fae Beauclair, more commonly known as Baby Fae, was the first infant to receive a non-human heart transplant procedure. She was born three months prematurely, and was only two weeks when the surgery was performed. Baby Fae was born in 1984 with hypoplastic left-heart syndrome, a fatal condition in which the left side of the heart, the side that pumps oxygenated blood throughout the body, is severely undeveloped. Knowing that this was a life-or-death situation (most children with this disorder die within two weeks), Fae's doctor, Dr. Leonard Bailey, frantically searched for an infant donor heart. However, there was no way he could find one in time to save Fae. In an act of desperation, Bailey examined prior research about cross-species transplants and found that perhaps a baboon heart would be his last hope. Fae would be the perfect opportunity to carry out his experiment on a human. After 20 hours of contemplation, Fae's parents finally agreed to let Dr. Bailey try his procedure.

A considerable amount of tests had to be performed to figure out which baboon heart would be a match for Fae's, and there was no time to waste. Eventually, a donor was chosen. However, a major difference between human and baboon hearts is that human hearts have three major arteries that extend from the aortic arch; baboons only have two. To combat this, Dr. Bailey joined two of Fae's arteries together. Then, he connected her to a heart-lung machine to lower her body temperature, slow her metabolism, and allow her blood to continue pumping. Any transplant procedure is tricky, because the intricate wiring of blood vessels has to be disconnected and then reconnected again. And even if the surgeon is able to reconfigure the vascular pathways, there is still a chance that the patient's immune system will reject the foreign tissue. Dr. Bailey used cyclosporine, a drug that suppresses the immune system without taking away its ability to fight infection, which helped Fae accept the heart. Once the heart began beating on its own, both the medical community and the general public were astonished by the miracle and potentially life-altering decision Dr. Bailey had performed on Baby Fae.

The controversy came quickly. Some experts questioned whether Bailey's intentions were pure, and if he was just using Baby Fae and her family to perform medical experiments. Religious individuals were outraged that a Christian doctor would try to undermine God's creation, and animal lovers wre equally upset at the slaughter of a baboon for her heart. However, as the days passed, slowly more faith was shown towards the work of Dr. Bailey as Fae became independent from oxygen masks and intravenous fluids. Unfortunately, after two weeks, signs of rejection were becoming apparent. The most traumatic incident was when Fae's kidneys started to fail. Fae died three weeks after her surgery, but the impact she has had on heart transplant research was enormous. Perhaps one day a human with a simian heart will be capable of sustaining life.

http://www.viewingspace.com/genetics_culture

Heart Beats and Electrocardiograms (EKG):

When the heart is at rest, blood flows into the atria. The right side collects oxygen-poor blood while the left side collects oxygen-rich blood. Clusters of cells called the sinoatrial node send out electrical impulses to make the atria contract, thus forcing blood into the ventricles. Then, the atrioventricular node is triggered, causing the ventricles to contract. This phase is called systole. This releases blood from the right ventricle to the lungs, and from the left ventricle to the rest of the body. The blood pushes against mitral valve on the left and tricuspid valve on the right, which shuts them closed to prevent blood from flowing backwards. This makes the "lub" sound of a heartbeat. The ventricle relax in diastole, causing the pulmonic and aortic valves to shut. This sound is known as "dub."

http://www.nhlbi.nih.gov/

Every time the heart beats, tiny electrical impulses are discharged. Using a process called electrocardiography, those electrical discharges can be recorded and used to measure the heart's condition. Several thin wires are attached to the body. The wires conduct the electrical charges into a machine that measures them and produces a readout that can be interpreted as a series of waves, defined as follows:

P wave - sinoatrial node fires electrical impulses to make the atria contract
QRS complex - atrioventricular node fires electrical impules to make the ventricles contract
T wave - ventricles relax

Types of Heart Surgeries:

Coronary bypass - A healthy blood vessel is removed from another part of the body, such as the leg or chest wall. Surgeons then build a shortcut around a blocked coronary artery. One end of the vessel is attached below the blocked vessel, while the other end is grafted right above it. If it is successful, then blood flow can continue without interruption. Multiple grafts can be built in one surgery, potentially leading to double, triple and even quadruple bypasses.

Heart transplant - A diseased heart is removed from a patient, and then the healthy donor heart is attached. The operation is complicated because so many blood vessels have to be detached and re-attached. After the operation, there is still a risk that the patient's systems may reject the new heart. Tissue types have to be perfectly matched in order for the transplant to be successful. As a result, the number of transplants performed is quite low.

Angiocardiography - Doctors can find where an artery is blocked through coronary arteriography. This means that the coronary arteries are mapped using a procedure called cardiac catheterization. The doctor uses a catheter (a thin plastic tube) and moves it through an artery in the arm or leg and traces it into the coronary arteries. A liquid dye is poured through the catether, and when exposed in an x-ray, the liquid appears white. If there are dark sections of the x-ray of arteries, then the doctor knows that the dye did not pass through, so something must be blocked. Angiocardiography is especially suited for determining the extent and location of coronary artery disease.