Viral Hepatitis

What is viral hepatitis?
Hepatitis means inflammation of the liver. Many illnesses and conditions can cause inflammation of the liver, for example, drugs, alcohol, chemicals, and autoimmune diseases. Many viruses, for example, the virus of mononucleosis and the cytomegalovirus can inflame the liver. Most viruses, however, do not primarily attack the liver; the liver is just one of several organs that the viruses affect. When doctors speak of viral hepatitis, they usually are referring to hepatitis caused by a few specific viruses that primarily attack the liver. There are several hepatitis viruses; they have been named types A, B, C, D, E, F (not confirmed), and G. As our knowledge of hepatitis viruses grows, it is likely that this alphabetical list will become longer. The most common hepatitis viruses are types A, B, and C.
The liver is located in the upper right hand side of the abdomen, mostly behind the rib cage. The liver of an adult normally weighs close to three pounds. The liver performs the following vital functions:

1. The liver helps purify the blood by changing harmful chemicals into harmless ones. The source of these chemicals can be external, such as medications or alcohol, or internal, such as ammonia or bilirubin. Typically, these harmful chemicals are broken down into smaller chemicals or attached to other chemicals that then are eliminated from the body in the urine or stool.
2. The liver produces many important substances, especially proteins that are necessary for good health. For example, it produces albumin, the protein building block of the body, as well as the proteins that cause blood to clot properly.
3. The liver stores many sugars, fats and vitamins until they are needed elsewhere in the body.
4. The liver builds smaller chemicals into larger, more complicated chemicals that are needed elsewhere in the body. An example of this type of function is the manufacture of cholesterol.

When the liver is inflamed, it does not perform these functions well, which brings about many of the symptoms, signs, and problems associated with hepatitis.

Kidney Failure

What are the kidneys?

The kidneys play key roles in body function, not only by filtering the blood and getting rid of waste products, but also by balancing levels of electrolyte levels in the body, controlling blood pressure, and stimulating the production of red blood cells.
The kidneys are located in the abdomen toward the back, normally one on each side of the spine. They get their blood supply through the renal arteries directly from the aorta and send blood back to the heart via the renal veins to the vena cava. (The term "renal" is derived from the Latin name for kidney.)
The kidneys have the ability to monitor the amount of body fluid, the concentrations of electrolytes like sodium and potassium, and the acid-base balance of the body. They filter waste products of body metabolism, like urea from protein metabolism and uric acid from DNA breakdown. Two waste products in the blood can be measured: blood urea nitrogen (BUN) and creatinine (Cr).
When blood flows to the kidney, sensors within the kidney decide how much water to excrete as urine, along with what concentration of electrolytes. For example, if a person is dehydrated from exercise or from an illness, the kidneys will hold onto as much water as possible and the urine becomes very concentrated. When adequate water is present in the body, the urine is much more dilute, and the urine becomes clear. This system is controlled by renin, a hormone produced in the kidney that is part of the fluid and blood pressure regulation systems of the body.
Kidneys are also the source of erythropoietin in the body, a hormone that stimulates the bone marrow to make red blood cells. Special cells in the kidney monitor the oxygen concentration in blood. If oxygen levels fall, erythropoietin levels rise and the body starts to manufacture more red blood cells.

Muscle Spasms

What is a muscle spasm?

A muscle spasm, or muscle cramp, is an involuntary contraction of a muscle. Muscle spasms occur suddenly, usually resolve quickly, and are often painful.
A muscle spasm is different than a muscle twitch. A muscle twitch, or fasciculation, is an uncontrolled fine movement of a small segment of a larger muscle that can be seen under the skin.
Muscles are complex structures that cause movement in the body. There are three types of muscle in the body:

• Heart muscle pumps blood (cardiac muscle).
• Skeletal muscle moves the external body parts, like the arms and legs, and the neck, back and trunk.
• Smooth muscle moves portions of hollow structures inside the body. Examples include the muscles that line the esophagus, stomach and intestine, muscles that line large arteries and the muscles of the uterus.

Skeletal muscles are anchored to bone, either directly or by a tendon. When the muscle contracts, the associated structure moves. This allows arms to lift, legs to run, and the face to smile. Most of these muscles are under willful or conscious control of the brain. This type of muscle is striated or striped with dark-colored muscles fibers containing large amounts of myoglobin, the protein that helps carry oxygen and light-colored fibers that have lesser amounts of the protein. The contraction of a skeletal muscle requires numerous steps within cells and fibers that need oxygen, electrolytes, and glucose, which are supplied by the bloodstream.
Smooth muscle is located in the walls of hollow internal structures in the body, like the arteries, intestines, bladder, and iris of the eye. They tend to circle the structure and when they contract, the hollow structure is squeezed. These muscles are involuntary and are controlled by the unconscious part of our brain function using the autonomic nervous system. The autonomic nervous system can run in the background, regulating body processes automatically for us. There is a balance between the sympathetic system (adrenergic nerves) that speed things up and the parasympathetic system (cholinergic nerves) that slow things down. These names are based on the type of chemical that is used to transmit signals at the nerve endings. Adrenaline (epinephrine from the sympathetic nervous system) allows the body to respond to stress. Imagine seeing a bear in the woods; your heart beats faster, your palms get sweaty, your eyes dilate, your hair stands on end, and your bowels move. Acetylcholine is the chemical that is the anti-adrenaline and is involved in the parasympathetic nervous system. Smooth muscle has the same basic contraction mechanism as skeletal muscle, though different proteins are involved.