[L. complexus, woven together]

1. Intricate; complicated.
2. A group of related biological entities.
3. An atrial or ventricular systole as it appears on an electrocardiographic tracing.
4. All the ideas, feelings, and sensations connected with a subject.
5. In the psychoanalytic theories of Freud and Jung, a grouping of ideas with an emotional background. These may be harmless, and the individual may be fully aware of them, e.g., an artist sees every object with a view to a possible picture and is said to have established a complex for art. Often, however, the complex is aroused by some painful emotional reaction such as fright or grief that, instead of being allowed a natural outlet, becomes unconsciously repressed and later manifests itself in some abnormality of mind or behavior. According to Freud, the best method of determining the complex is through psychoanalysis.
SEE: Electra complex; SEE: Jocasta complex; SEE: Oedipus complex
6. An anatomical or intracellular structure.
7. In a mass casualty, two or more disasters of similar type, located within reach of a single response team.

AIDS-dementia complex

ABBR: ADC SEE: HIV-associated neurocognitive disorder.

AIDS-related complex

ABBR: ARC The symptomatic stage of infection with HIV before the onset of AIDS. Clinical signs include fatigue, intermittent fevers, weight loss greater than 10%, chronic or persistent intermittent diarrhea, night sweats, diminished delayed hypersensitivity (skin test) response to common allergens, presence of HIV antibodies in blood, and decreased CD4+ T-lymphocyte count.

amygdaloid complex

SEE: Amygdala.

anti-inhibitor coagulant complex

A blood product derived from human plasma, used to augment the effects of clotting factors given to patients with hemophilia. Hemophiliacs who have received repeated injections of clotting factors may develop antibodies to those factors, which decreases the effectiveness of hemophilia treatments. Anti-inhibitors are used to counteract the effect of the unwanted antibodies

castration complex

A morbid fear of being castrated.

Eisenmenger complex

SEE: Eisenmenger syndrome

Ghon complex

SEE: Ghon complex

HAND complex

SEE: AIDS-dementia complex

HLA complex

SEE: Major histocompatibility complex.

immune complex

A substance formed when antibodies and serum complement attach to antigens to destroy them. These complexes circulate in the blood and may eventually attach to the walls of blood vessels, producing a local inflammatory response. Immune complexes form in type III hypersensitivity reactions and are involved in the development of glomerulonephritis, serum sickness, arthritis, and vasculitis.

inferiority complex

The condition of having low self-esteem.

inferior olivary complex

SEE: Inferior olive.

K complex

A complex of slow waves on an electroencephalogram related to arousal from sleep by a sound, the consolidation of sleep-based memory, and characteristic of sleep stage 2.
SEE: non-rapid eye movement sleep

Leishmania mexicana complex

SEE: Leishmania mexicana

major histocompatibility complex

ABBR: MHC A complex of genes on chromosome 6 that code for the antigens that determine tissue and blood compatibility. In humans, histocompatibility antigens are called human leukocyte antigens (HLA) because they were originally discovered in large numbers on lymphocytes. There are thousands of combinations of HLA antigens. Class I MHC antigens (HLA-A, HLA-B, and HLA-C) are found on all nucleated cells and platelets. Class II antigens (HLA-DR, HLA-DQ, and HLA-DP) are found on lymphocytes and antigen processing cells and are important in the specific immune response. In tissue and organ transplantation, the extent to which the HLA or “tissue type” of the donor and recipient match is a major determinant of the success of the transplant.
SYN: SEE: HLA complex
SEE: histocompatibility locus antigen

membrane attack complex

ABBR: C5b-C9 A complex of complement factors C5 through C9 (C5b-9n) that directly attack and kill the cell membranes of microorganisms during the terminal attack phase of the complement cascade.
SEE: complement; SEE: inflammation

migrating motor complex

The electromechanical driver of the gastrointestinal tract motility that occurs between meals. It consists of alternating rest periods and peristaltic contractions.
SYN: SEE: interdigestive migrating contractions

Mycobacterium abscessus complex

A complex of rapidly growing and frequently drug-resistant mycobacterial species. It is often identified in cystic fibrosis patients.

Mycobacterium avium complex

ABBR: MAC, MAI An atypical mycobacterium that causes systemic bacterial infection in patients with advanced immunosuppression, esp. those with AIDS. It occasionally causes lung infections in patients with chronic obstructive lung disease.
SYN: SEE: Mycobacterium avium-intracellulare complex

MAC infection in AIDS patients can cause fatigue, fever, weight loss, cachexia, pancytopenia, and death.

Multiple antimicrobial agents, given at the same time and for long courses, are required to treat MAC. Combination therapy may include macrolide antibiotics such as azithromycin and clarithromycin with drugs such as rifabutin, ethambutol, ciprofloxacin, amikacin, and/or clofazimine.

Mycobacterium avium-intracellulare complex

SEE: Mycobacterium avium complex.

nuclear pore complex

A complex of membrane-associated proteins that regulate the passage of large molecules between the cytoplasm and the cell nucleus.

oculomotor complex

A complex of interrelated nuclei found near the midline in the rostral midbrain. They include the oculomotor nucleus (somatic) and the Edinger-Westphal nucleus. They innervate somatic muscles, e.g., the inferior rectus and levator palpebrae, and visceral muscles, e.g., the ciliaris and sphincter pupillae.

olivary complex

SEE: Olive (2).

osteomeatal complex

The middle turbinate and the middle meatus of the nose.

QRS complex

The pattern traced on the surface electrocardiogram by depolarization of the ventricles. In the anterior chest leads, e.g., V1 to V3, the complex normally consists of a small initial downward deflection (Q wave), a large upward deflection (R wave), and a second downward deflection (S wave). The normal duration of the complex is 0.06 to 0.11 sec. Longer QRS complexes are seen in premature ventricular beats and ventricular arrhythmias.

QRST complex

SEE: Q-T interval.

superiority complex

An exaggerated conviction that one is better than others, a pretense used to compensate for a real or imagined inferiority.

superior olivary complex

SEE: Superior olive.

symptom complex

SEE: Syndrome.

triangular fibrocartilage complex

ABBR: TFCC In the wrist, the ligamentous and cartilaginous complex that suspends the distal radius and ulnar carpus from the distal ulna.

tuberous sclerosis complex

SEE: Tuberous sclerosis.