What is a Heart Attack?

Heart With Muscle Damage and a Blocked Artery

A heart attack occurs when blood flow to a section of heart muscle becomes blocked. If the flow of blood isn’t restored quickly, the section of heart muscle becomes damaged from lack of oxygen and begins to die.

Fortunately, today there are excellent treatments for heart attack that can save lives and prevent disabilities. Treatment is most effective when started within 1 hour of the beginning of symptoms.

Heart attacks occur most often as a result of a condition called coronary artery disease (CAD). In CAD, a fatty material called plaque builds up over many years on the inside walls of the coronary arteries (the arteries that supply blood and oxygen to your heart). Eventually, an area of plaque can rupture, causing a blood clot to form on the surface of the plaque. If the clot becomes large enough, it can mostly or completely block the flow of oxygen-rich blood to the part of the heart muscle fed by the artery.

Figure A is an overview of a heart and coronary artery showing damage (dead heart muscle) caused by a heart attack. Figure B is a cross-section of the coronary artery with plaque buildup and a blood clot.

During a heart attack, if the blockage in the coronary artery isn’t treated quickly, the heart muscle will begin to die and be replaced by scar tissue. This heart damage may not be obvious, or it may cause severe or long-lasting problems.

Severe problems linked to heart attack can include heart failure and life-threatening arrhythmias (irregular heartbeats). Heart failure is a condition in which the heart can’t pump enough blood throughout the body. Ventricular fibrillation is a serious arrhythmia that can cause death if not treated quickly.

Acting fast at the first sign of heart attack symptoms can save your life and limit damage to your heart. Treatment is most effective when started within 1 hour of the beginning of symptoms.

The most common heart attack signs and symptoms are:

• Chest discomfort or pain—uncomfortable pressure, squeezing, fullness, or pain in the center of the chest that can be mild or strong. This discomfort or pain lasts more than a few minutes or goes away and comes back.
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  Upper body discomfort in one or both arms, the back, neck, jaw, or stomach.
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  Shortness of breath may occur with or before chest discomfort.
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  Other signs include nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat.

WHAT IS AIDS?

WHAT DOES "AIDS" MEAN?

AIDS stands for Acquired Immune Deficiency Syndrome:

Acquired means you can get infected with it;

Immune Deficiency means a weakness in the body's system that fights diseases.

Syndrome means a group of health problems that make up a disease.

AIDS is caused by a virus called HIV, the Human Immunodeficiency Virus. If you get infected with HIV, your body will try to fight the infection. It will make "antibodies," special molecules to fight HIV.

A blood test for HIV looks for these antibodies. If you have them in your blood, it means that you have HIV infection. People who have the HIV antibodies are called "HIV-Positive.

Being HIV-positive, or having HIV disease, is not the same as having AIDS. Many people are HIV-positive but don't get sick for many years. As HIV disease continues, it slowly wears down the immune system. Viruses, parasites, fungi and bacteria that usually don't cause any problems can make you very sick if your immune system is damaged. These are called "opportunistic infections."

HOW DO YOU GET AIDS?

You don't actually "get" AIDS. You might get infected with HIV, and later you might develop AIDS. You can get infected with HIV from anyone who's infected, even if they don't look sick and even if they haven't tested HIV-positive yet. The blood, vaginal fluid, semen, and breast milk of people infected with HIV has enough of the virus in it to infect other people. Most people get the HIV virus by:

* having sex with an infected person

* sharing a needle (shooting drugs) with someone who's infected

* being born when their mother is infected, or drinking the breast milk of an infected woman

Getting a transfusion of infected blood used to be a way people got AIDS, but now the blood supply is screened very carefully and the risk is extremely low.

There are no documented cases of HIV being transmitted by tears or saliva, but it is possible to be infected with HIV through oral sex or in rare cases through deep kissing, especially if you have open sores in your mouth or bleeding gums.

WHAT HAPPENS IF I'M HIV POSITIVE?

You might not know if you get infected by HIV. Some people get fever, headache, sore muscles and joints, stomach ache, swollen lymph glands, or a skin rash for one or two weeks. Most people think it's the flu. Some people have no symptoms.

The virus will multiply in your body for a few weeks or even months before your immune system responds. During this time, you won't test positive for HIV, but you can infect other people.

When your immune system responds, it starts to make antibodies. When this happens, you will test positive for HIV.

After the first flu-like symptoms, some people with HIV stay healthy for ten years or longer. But during this time, HIV is damaging your immune system.

One way to measure the damage to your immune system is to count your CD4 cells you have. These cells, also called "T-helper" cells, are an important part of the immune system. Healthy people have between 500 and 1,500 CD4 cells in a milliliter of blood.

Without treatment, your CD4 cell count will most likely go down. You might start having signs of HIV disease like fevers, night sweats, diarrhea, or swollen lymph nodes. If you have HIV disease, these problems will last more than a few days, and probably continue for several weeks.

HOW DO I KNOW IF I HAVE AIDS?

HIV disease becomes AIDS when your immune system is seriously damaged. If you have less than 200 CD4 cells or if your CD4 percentage is less than 14%, you have AIDS. See Fact Sheet 124 for more information on CD4 cells. If you get an opportunistic infection, you have AIDS. There is an "official" list of these opportunistic infections put out by the Centers for Disease Control (CDC). The most common ones are:

* PCP (Pneumocystis pneumonia), a lung infection;

* KS (Karposi's sarcoma), a skin cancer;

* CMV (Cytomegalovirus), an infection that usually affects the eyes

* Candida, a fungal infection that can cause thrush (a white film in your mouth) or infections in your throat or vagina

AIDS-related diseases also includes serious weight loss, brain tumors, and other health problems. Without treatment, these opportunistic infections can kill you.

AIDS is different in every infected person. Some people die a few months after getting infected, while others live fairly normal lives for many years, even after they "officially" have AIDS. A few HIV-positive people stay healthy for many years even without taking antiretroviral medications (ARVs).

IS THERE A CURE FOR AIDS?

There is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to your immune system. There is no way to "clear" the HIV out of your body.

Other drugs can prevent or treat opportunistic infections (OIs). In most cases, these drugs work very well. The newer, stronger ARVs have also helped reduce the rates of most OIs. A few OIs, however, are still very difficult to treat. See Fact Sheet 500 for more information on opportunistic infections.

Transpiration

Transpiration is the evaporation of water from plants. It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis.

But air that is not fully saturated with water vapour (100% relative humidity) will dry the surfaces of cells with which it comes in contact. So the photosynthesizing leaf loses substantial amount of water by evaporation. This transpired water must be replaced by the transport of more water from the soil to the leaves through the xylem of the roots and stem.

Importance

Transpiration is not simply a hazard of plant life. It is the "engine" that pulls water up from the roots to:

- supply photosynthesis (1%-2% of the total)

- bring minerals from the roots for biosynthesis within the leaf

- cool the leaf

 

Environmental factors that affect the rate of transpiration

1. Light

Plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of the stomata (mechanism). Light also speeds up transpiration by warming the leaf.

2. Temperature

Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises. At 30°C, a leaf may transpire three times as fast as it does at 20°C.

3. Humidity

The rate of diffusion of any substance increases as the difference in concentration of the substances in the two regions increases.When the surrounding air is dry, diffusion of water out of the leaf goes on more rapidly.

4. Wind

When there is no breeze, the air surrounding a leaf becomes increasingly humid thus reducing the rate of transpiration. When a breeze is present, the humid air is carried away and replaced by drier air.

5. Soil water

A plant cannot continue to transpire rapidly if its water loss is not made up by replacement from the soil. When absorption of water by the roots fails to keep up with the rate of transpiration, loss of turgor occurs, and the stomata close. This immediately reduces the rate of transpiration (as well as of photosynthesis). If the loss of turgor extends to the rest of the leaf and stem, the plant wilts.

The volume of water lost in transpiration can be very high. It has been estimated that over the growing season, one acre of corn plants may transpire 400,000 gallons of water. As liquid water, this would cover the field with a lake 15 inches deep. An acre of forest probably does even better.

Plant Tissue Systems

The tissues of a plant are organized into three tissue systems: the dermal tissue system, the ground tissue system, and the vascular tissue system.

Dermal Tissue System - Epidermis, Periderm (in older stems and roots)

• protection
• prevention of water loss

Ground Tissue System - Parenchyma tissue, Collenchyma tissue, Sclerenchyma tissue
• photosynthesis
• food storage
• regeneration
• support
• protection

Vascular Tissue System - Xylem, Phloem
• transport of water and minerals
• transport of food

Homeostasis

Homeostasis is the maintenance of a relatively stable internal condition . The liver, the kidneys, and the brain (hypothalamus, the autonomic nervous system and the endocrine system) help maintain homeostasis. The liver is responsible for metabolising toxic substances and maintaining carbohydrate metabolism. The kidneys are responsible for regulating blood water levels, re-absorption of substances into the blood, maintenance of salt and ion levels in the blood, regulation of blood pH, and excretion of urea and other wastes.

An inability to maintain homeostasis may lead to death or a disease, a condition known as homeostatic imbalance. For instance, heart failure may occur when negative feedback mechanisms become overwhelmed and destructive positive feedback mechanisms take over. Other diseases which result from a homeostatic imbalance include diabetes, dehydration, hypoglycemia, hyperglycemia, gout and any disease caused by the presence of a toxin in the bloodstream.

Thermoregulation

Humans are warm-blooded, maintaining a near-constant body temperature. Thermoregulation is an important aspect of human homeostasis. Heat is mainly produced by the liver and muscle contractions. Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid. High temperatures pose serious stresses for the human body, placing it in great danger of injury or even death. In order to deal with these climatic conditions, humans have developed physiologic and cultural modes of adaptation.

Temperature may enter a circle of positive feedback, when temperature reaches extremes of 45°C (113°F), at which cellular proteins denature, causing the active site in proteins to change, thus causing metabolism stop and ultimately death.

Glucoregulation

Humans regulate their blood glucose with insulin and glucagon. These hormones are released by the pancreas.

When blood sugar levels become too high, insulin is released from the pancreas, lowering the blood sugar levels. On the other hand, when blood sugar levels become too low, glucagon is released, increasing blood sugar levels.

If the pancreas is for any reason unable to produce enough of these two hormones, diabetes results.

Osmoregulation

Osmoregulation is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the body's water content; that is it keeps the body's fluids from becoming too dilute or too concentrated. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution the more water wants to go into the solution.

The kidneys are used to remove excess ions from the blood, thus affecting the osmotic pressure. These are then expelled as urine

Volume

The body's homeostatic control mechanisms, which maintain a constant internal environment, ensure that a balance between fluid gain and fluid loss is maintained. The hormones ADH (Anti-diuretic Hormone, also known as vasopressin) and Aldosterone play a major role in this.

If the body is becoming fluid-deficient, there will be an increase in the secretion of these hormones (ADH), causing fluid to be retained by the kidneys and urine output to be reduced.

Conversely, if fluid levels are excessive, secretion of these hormones (aldosterone) is suppressed, resulting in less retention of fluid by the kidneys and a subsequent increase in the volume of urine produced.

If you have too much Carbon dioxide(CO2) in the blood, it can cause the blood to become acidic. People respirate heavily not due to low oxygen(O2) content in the blood, but because they have too much CO2.

Fluid Exchange Between Capillaries and Tissues

Capillaries are composed of a single layer of squamos epithelium surrounded by a thin basement membrane. Most capillaries (except those servicing the nervous system) have pores (spaces) between the individual cells that make up the capillary wall. Plasma fluid and small nutrient molecules leave the capillary and enter the interstitial fluid through these pores, in a process called bulk flow. Bulk flow facilitates the efficient transfer of nutrient out of the blood and into the tissues. However, blood cells and plasma proteins, which are too large to fit through the pores, do not filter out of the capillaries by bulk flow.

Together, blood plasma and interstitial fluid make up the extracellular fluid (ECF). Plasma constitutes 20%, while interstitial fluid constitutes 80% of the ECF. The distribution of extracellular fluid between these two compartments is determined by the balance between two opposing forces: hydrostatic pressure and osmotic pressure.

The beating of the heart generates hydrostatic pressure, which, in turn, causes bulk flow of fluid from plasma to interstitial fluid through walls of the capillaries. In other words, the pressure in the system forces plasma to filter out into the interstitial compartment. The composition of the interstitial fluid and the plasma is essentially the same except that plasma also contains plasma proteins not found in the interstitial fluid. Because of the presence of plasma proteins, the plasma has a higher solute concentration than does the interstitial fluid. Consequently, osmotic pressure causes interstitial fluid to be absorbed into the plasma compartment. In other words, the plasma proteins drive the reabsorption of water back into the capillaries via osmosis.

 

The magnitudes of filtration and absorption are not equal. The net filtration of fluid out of the capillaries into the interstitial compartment is greater than the net absorption of fluid back into the capillaries. The excess filtered fluid is returned to the blood stream via the lymphatic system. In addition to its roles in digestion and immunity, the lymphatic system functions to return filtered plasma back to the circulatory system. The smallest vessels of the lymphatic system are the lymphatic capillaries (shown in yellow). These porous, blind-ended ducts form a large network of vessels that infiltrate the capillary beds of most organs. Excess interstitial fluid enters the lymphatic capillaries to become lymph fluid.

 

Lymphatic capillaries converge to form lymph vessels that ultimately return lymph fluid back to the circulatory system via the subclavian vein. The presence of one-way valves in the lymph vessels ensures unidirectional flow of lymph fluid toward the subclavian vein.

If excess fluid cannot be returned to the blood stream then interstitial fluid builds up, leading to swelling of the tissues with fluid, this is called oedema.

Causes of Oedema

1. Reduced concentration of plasma proteins. When the concentration of plasma proteins drops, the osmotic potential of plasma drops, thus less interstitial fluid is absorbed into the capillaries. The rate of filtration, however, remain unchanged. Therefore, the ratio of filtration to absorption increases, leading to a build up of interstitial fluid. Any condition that would lead to a reduction in plasma proteins could potentially cause edema. Examples of conditions that reduce plasma proteins include:

     a) Kidney disease can result in the loss of plasma proteins in the urine.

     b) Liver disease can decrease the synthesis of plasma proteins.

     c) A protein-deficient diet will decrease plasma proteins.

     d) Severe burns result in a loss of plasma proteins (albumin) at the burn site

2. Increased capillary permeability. During an inflammatory response, tissue damage leads to the release of histamine from immune cells. Histamine causes an increase in the size of capillary pores. As capillaries become more permeable, the rate of filtration increases.

3. Increase in venous pressure. If venous pressure is increased then blood dams up in the upstream capillary bed, resulting in excess filtration. Examples of this condition include:

     a) Left heart failure. The left half of the heart drains blood from the lungs. When the left ventricle fails to adequately pump blood, venous pressure in the lungs increases. This increases in hydrostatic pressure causes an increase in the rate of filtration of fluid out of the capillaries and into the interstitial compartment. As a result, the lungs fill with fluid, a condition called, pulmonary oedema.

     b) Standing still. If one stands still for long period of time, then blood will pool in the veins of the legs. This will increase venous pressure and lead to weeping of fluid into the tissues. You can actually feel your feet swell if you stand motionless for a long time.

4. Blocked Lymphatic Vessels. If lymph vessels become blocked, then lymph fluid will not be drained from the affected area and the area will swell. Any condition that causes blockage or removal of lymph vessels can lead to oedema. Examples of this condition include:

     a) Filaria round worms are transmitted to humans by some species of mosquitoes. The worms migrate to the lymph vessels and block them. This causes dramatic swelling of the affected area, a condition called elephantiasis.

     b) Treatment for breast cancer may include removal of lymph vessels from breast and arms. This is done to limit the metastasis (spread) of cancerous cells to other parts of the body through the lymph. Removal of lymph vessels results in swelling of the affected area.

Time Management

"Perhaps the most valuable result of all education is the ability to make yourself do the things that you have to do, when it ought to be done, whether you like it or not." - Thomas Huxley

How many times have you planned to do something only to procrastinate or fail to carry out the plan? While there are many explanations for your failure to implement your plan, analysis of this failure has to start with the plan itself. Even if you do not want to do the work, to be successful it is necessary to stay motivated and make yourself do what needs to be done. Many students often say they will "try" to do the work, but unfortunately the definition of "try" in daily English means: "Forget it - I really don't want to do this and I won't do it. Further, when asked of my progress, I will employ excuses that relieve me of the responsibility to change the behaviour." All of these problems occur in school life. The good news is that you can employ effective time management strategies to overcome these obstacles and be successful throughout your career. These include planning, implementing the plan, and evaluating the plan.

Life in school has many distractions that can keep students from managing their time and keeping up with their studies. For example a boy named Nicky. Partying Nicky has tendencies to procrastinate and not manage his time wisely. In short, he is going to fail his subject if he does not shape up and plan his work and activities. Nicky needs to understand there are three main objectives that he must stick to or else his planning will fail. The first is to be ready for an exam 2-3 days before the test is administered. Second, use his daytime hours for studying, because he realises he wants to be with his friends in the evening. Lastly, he needs to distribute his studying hours so as not to cram. To plan his time successfully, he should compare his academic studies to a full-time job, thus leaving his night time hours for fun time. This will help him maintain a healthy balance between work and fun.

After Nicky plans his time he must implement the plan. To implement his plan he needs to stick to his daily and weekly schedule. One way to do this is to identify precise products he will produce during specified time periods. When he completes a task, he crosses it off the list. He should plan to study between classes, when the ideas are still fresh from the class. Further, he should visualise completing the task successfully. Visualisation, properly applied, is a powerful strategy. He should also keep in mind - two hours of studying during the day for every one hour of class time is far more beneficial than cramming for six hours the night before the exam.

Lastly, Nicky needs to monitor himself and his work. For example, he could pretend he is the employer at a large manufacturing corporation. According to his plans and how well he implemented them, he must decide if he should receive a reward as a productive employee, or if he would be fired for poor performance. Put another way, Nicky could monitor himself by answering the following questions each night:

"If he worked in a corporation and he was the President, would he hire himself the way he behaved today?"

"Am I proud of my performance today?"

Effective Time Management strategies lead to success; ineffective Time Management strategies lead to failure. It's that simple. Time Management strategies help students to stay motivated and on top of their deadlines for projects, help eliminate procrastination, and help to balance academic and fun time to maintain a healthy lifestyle in school.