General Biology - NCLEX-PN

The muscle body is encased in a fibrous elastic sheath called the epimysium (epi meaning on or above and mys meaning muscle). It is composed of dense irregular connective tissue and is continuous with tendon fibers. The perimysium surrounds muscle fascicles, while the endomysium surrounds muscle fibers.

The only type of muscle that is not striated is smooth muscle. Smooth muscle does not use sarcomeres for contraction - rather, each muscle cell is a spindle that is covered in a mesh of contractile fibrils. These fibrils contract in unison when calcium enters the cell.

Endocrine glands secrete hormones into the blood. The endocrine glands include the ovaries, testes, hypothalamus, thyroid, pituitary, adrenal glands, pancreas, the pineal gland, and others. Salivary glands are considered exocrine glands. Exocrine glands secrete substances through ducts to the body surface or into body cavities, such as the mouth in the case of salivary glands.

The pituitary is located just below the hypothalamus. The pituitary and the hypothalamus are connected by nerves and maintain an important working relationship with one another. Both are located near the base of the brain.

Lysozymes are a group of defense enzymes found in tears, saliva, mucus, and breast milk. It is considered part of our innate immune systems, as its presence in tears prevents infectious conjunctivitis. Cathelicidin, Defensin-5, and DEFA1 are found in the lysosomes of polymorphonuclear leukocytes (PMN's) and macrophages.

The mot common cause of osteomalacia (known as rickets in children) in the United States is vitamin D deficiency. This is due to vitamin D's vital role in calcium absorption, homeostasis, and metabolism. Osteomalacia is categorized by the softening of the bones.

Interleukins (IL) are cytokines that play a role in signaling the immune cells. IL-8 is produced mainly by macrophage and dendritic cells and plays a major role in inflammation as a chemoattractant for neutrophils. IL-1 and IL-6 both induce acute phase proteins. TNF-alpha is involved in the acute phase reaction. It is an endogenous pyrogen (meaning it induces fever) and is also involved in apoptosis and tumor inhibition.

Patients who are taking potassium sparing diuretics must be counseled to eat a diet low in potassium. This is due to the fact that consumption of potassium-rich foods, such as orange juice, can lead to dangerously high potassium levels. Excess potassium levels can cause heart arrhythmia and sudden cardiac death.

The kidney is the main route of potassium excretion in the body. During kidney failure, the kidneys are unable to remove excess potassium from the blood. This can lead to hyperkalemia, which can cause nausea, weakness, numbness, arrhythmia, and cardiac arrest.

Major histocompatibility complex 1 in a membrane protein that binds to peptide fragments from pathogens such as viruses and bacteria and then displays them on the cell surface in order to alert other immune cells of the presence and nature of infection.

All cells with nuclei express MHC-1. Red blood cells do not have nuclei, and do not express MHC-1 on membranes.

Antibodies are only produced by B cells, specifically by a type of specialized B cell called a plasma cell. B cells belong to a broader category of leukocytes known as lymphocytes, which are agranulocytes.

T lymphocytes are so titled because they mature in the thymus, unlike B lymphocytes, which mature in the bone marrow. The thymus is located in the anterior superior mediastinum, ventral to the heart and dorsal to the sternum. It is most active in the neonatal and pre-adolescent periods, afterwards, it degenerates and is replaced with adipose tissue.

Lymphoid progenitor cells are produced in all of the following tissues: the liver, the bone marrow, spleen, and gut associated lymphoid tissue (mainly found in the liver and intestines). However, note that the vast majority of all blood cells are produced in the red bone marrow of long bones by hematopoietic stem cells.

Mast cells are rich in granules that contain high concentrations of heparin, histamine, and trypsin, among other preformed proteases. These granules also contain serotonin and various eicosanoids. The function of mast cells is primarily to regulate immune (inflammatory) responses to allergens.

While all of the cells listed may have some indirect involvement in the overall response to a parasitic infection, eosinophils are the only immune cells that are specialized to respond to multicellular parasites, especially helminths such as hookworms and pinworms.

The brain stem consists of the medulla, the pons, and the midbrain. The cerebellum is an outgrowth posterior to the pons. The corpus callosum is the broad bundle of neural fibers that attaches the left hemisphere of the brain to the right hemisphere.

Olfaction is form of chemoreception, or a translation of a chemical signal into an action potential. Smells are triggered by molecules of volatile chemicals that trigger chemoreceptors in the epithelium of the olfactory cleft.

Mitochondria are often called "the powerhouse of the cell" because they produce ATP, the body's most basic unit of energy. The nucleus houses the cell's DNA, the rough endoplasmic reticulum is the site of cellular protein manufacturing, and the Golgi apparatus packages protein manufactured in the cell for release and transport to the rest of the body.

While the nucleus houses the DNA and plays an integral role in the transcription of genetic code in order to produce specific proteins, actual protein synthesis is carried out by the ribosomes. These organelles consist of two subunits and are either independent in the cytoplasm of the cell or housed in the rough endoplasmic reticulum. Note that ribosomes can be in the cytoplasm or on the endoplasmic reticulum, hence making it rough.