Endocrine and Immune Systems - NCLEX-PN

Leptin is secreted by adipose cells, and acts on the arcuate nucleus of the lateral hypothalamus to promote the synthesis of alpha-MSH (alpha-melanocyte-stimulating hormone), which is a hunger suppressant. It also binds to receptors for neuropeptide Y (NPY), a powerful hunger promoter, in the arcuate nucleus.

None of the other hormones listed, while all involved in nutrient and blood sugar metabolism, directly trigger feeling of satiety.

Leptin, the hormone responsible for feelings of satiety, goes down during times of fasting, with high testosterone, during sleep deprivation, and during periods of prolonged exercise or physical training.

Insulin has many physiological effects on metabolism. It increases uptake of glucose and various ions, especially potassium, from the blood. It promotes glycogen and protein synthesis, and encourages storage of fats. Conversely, insulin inhibits lipolysis, gluconeogenesis, ketogenesis, and proteolysis.

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.

The nutrients specifically required for thyroid hormone production are tyrosine, iodine, and selenium, in addition to zinc and several B vitamins. While magnesium, manganese, and methionine are all essential for metabolism and overall hormone production, they are not direct substrates or cofactors in the production of thyroid hormone.

Tyrosine and iodine are both precursors for synthesis of T4. Selenium is essential for conversion of T4 to T3, and iron is the cofactor for conversion of phenylalanine into tyrosine.

IgA, primarily in its secretory form (sIgA), is the most abundant immunoglobulin in the lining of the gastrointestinal tract and in the mucus membranes of the respiratory tract. It is also present in the urogenital tract, in tears, in saliva, and in breast milk. All of the other immunoglobulins may be present in mucus membranes, depending on the presence of active infection or allergy, but none is as abundant in secretions as IgA. IgE is primarily involved in binding allergens and inducing the allergic response via release of histamine. IgM is expressed on the surface of B cells and is the first immunoglobulin to fight pathogens at the site of infection/injury. IgG are the most abundant antibody throughout the body and play the largest role in fighting pathogens. IgG can cross the placenta and thus confer passive immunity to the fetus.

The presence of CMV IgM would suggest an active cytomegalovirus infection, as IgM is the immunoglobulin released during the initial, active infection with a pathogen. The presence of IgG would suggest a past infection, where IgG specific to the virus would be present as part of adaptive immunity (ready to respond to the virus should the host ever be re-exposed). IgE is not formed when an individual contracts CMV, as IgE is produced in response to allergens rather than pathogens (except parasites). The function of IgD is thought to be related to the allergic response by regulating basophils and mast cells.

The only immunoglobulin that has been shown to be able to cross the placenta is IgG. This is important in that it confers short term immunity to the fetus that continues into the first few months of the infant's life. Note that it is common to give Rh-negative anti-Rh IgG injections at about 28 weeks gestation; a booster may also be given at about 34 weeks gestation.

Insulin is produced by beta cells of the pancreatic islets. Insulin's action is to decrease blood glucose, facilitating its uptake into cells. Alpha cells produce glucagon, which has the opposite effect as insulin. Delta cells produce somatostatin, which inhibits many digestive processes. and gamma cells produce pancreatic polypeptide, which regulate pancreatic secretion.

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.

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.

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.

The correct answer is "CD4 T-cells."

In AIDS, which is the most progressed stage of HIV, the cell type that is most significantly diminished is CD4 T-cells. Often times, the degree of disease progress of HIV and AIDS is established by monitoring the patient's CD4 T-cell count across the course of the illness. The CD4 count guides differential diagnoses when patients with HIV or AIDS present with various complaints, and also guides what prophylactic measures (e.g. antibiotics, antifungals) are administered to these patients.

While CD8 T-cell, monocyte, platelet, and neutrophil counts may each be decreased for various reasons in patients with HIV and AIDS, the most substantial association between diminished cell count and HIV/AIDS is that of CD4 T-cells.

Thyroid-stimulating hormone (TSH) is produced in the anterior pituitary. Somatostatin, dopamine, and gonadotropin releasing hormone are all hypothalamic hormones. Somatostatin is also secreted by the pancreas, and slows down digestive processes. To remember the hormones of the anterior pituitary, use the following mnemonic: FLAT PEG, Follicle-stimulating hormone, Luteinizing hormone, Adrenocorticotropic hormone, Thyroid-stimulating hormone, Prolactin, Endorphins, Growth hormone.

Calcitonin is produced by the thyroid gland. The hormone plays an important role in lowering blood calcium levels. It is also synthesized as a drug and used in the treatment of hypercalcemia. The other three hormones are indeed secreted by the islets of Langerhans in the pancreas. Insulin, secreted by the beta cells lowers blood sugar, glucagon, secreted by the alpha cells, increases blood sugar, and somatostatin, secreted by the gamma cells regulates digestive and metabolic processes. Lipase is not a hormone, but an enzyme that facilitates the breakdown of lipids. The pancreas does indeed secrete lipase.

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.