UHS DES Entrance Exam key terms

The repeating contractile unit of a skeletal or cardiac muscle fibre, bounded by two Z lines and built from overlapping actin and myosin filaments. Shortening of sarcomeres in series produces muscle contraction.

The functional unit of the kidney. It consists of a glomerulus, where plasma is filtered, and a tubule, where useful solutes and water are reabsorbed and waste is secreted. Each kidney contains about a million.

The area of skin supplied by the sensory fibres of a single spinal nerve root. Maps of dermatomes help clinicians localise a spinal cord or nerve root lesion from the pattern of altered sensation.

The body's tendency to keep internal conditions such as temperature, pH, blood glucose and fluid volume within narrow limits despite external change. Sensors, control centres and effectors act through negative feedback loops.

A brief, self-propagating change in the membrane voltage of a neuron or muscle cell. Sodium channels open, the inside becomes positive, then potassium channels restore the resting potential; this carries signals along axons.

The volume of blood pumped by one ventricle each minute, equal to heart rate multiplied by stroke volume. At rest it is about five litres per minute; it rises with exercise and falls in pump failure.

The volume of plasma filtered by both kidneys per minute, normally around 125 millilitres. It is the best single index of kidney function and falls as nephrons are lost.

The cytoplasmic pathway that splits one glucose molecule into two pyruvate molecules, producing two ATP and two NADH without using oxygen. It is the first stage of glucose metabolism in every cell.

The substrate concentration at which an enzyme works at half its maximum velocity. A low Km means the enzyme binds substrate tightly; Km is used to describe enzyme affinity and predict activity.

The process in the inner mitochondrial membrane in which electrons from NADH and FADH2 travel down the respiratory chain, pumping protons to drive ATP synthase. It produces most of the ATP used by aerobic cells.

An amino acid that the human body cannot make in sufficient amounts and must obtain from dietary protein. Nine are essential for adults; their absence limits protein synthesis and growth.

Programmed cell death, an orderly energy-dependent process in which a cell shrinks, its chromatin condenses and it breaks into bodies removed by phagocytes. Unlike necrosis it does not trigger inflammation.

Cell death caused by injury such as ischaemia, toxins or infection, marked by swelling, membrane rupture and leakage of cell contents. The leaked material provokes inflammation in the surrounding tissue.

Formation of a solid blood clot within a vessel or heart chamber during life. It usually follows endothelial injury, abnormal blood flow or increased clotting tendency, and may block the vessel and cause infarction.

An abnormal mass of tissue whose growth exceeds and is uncoordinated with normal tissue, and which persists after the stimulus is removed. It may be benign or malignant; malignant tumours invade and metastasise.

The dose of a drug that produces a specified effect in 50 percent of the population studied. It measures potency, so a lower ED50 means a smaller dose is needed for the same response.

The ratio of a drug's toxic dose to its effective dose, usually TD50 divided by ED50. A narrow index means small dose changes can cause toxicity, so levels need monitoring, as with digoxin or warfarin.

Loss of an orally administered drug as it passes through the gut wall and liver before reaching the systemic circulation, which lowers bioavailability. Drugs with extensive first-pass metabolism may need higher oral doses or parenteral routes.

The fraction of an administered drug dose that reaches the systemic circulation unchanged. The intravenous route is 100 percent by definition; oral bioavailability is reduced by incomplete absorption and first-pass metabolism.

An enzyme made by some bacteria that hydrolyses the beta-lactam ring of penicillins and cephalosporins, destroying their antibacterial activity. Production of this enzyme is a common cause of antibiotic resistance.

A lipopolysaccharide found in the outer membrane of Gram-negative bacteria, released when the bacteria die. It causes fever and, in large amounts, septic shock by activating Toll-like receptor 4 on immune cells.

Coating of a microbe with antibodies or complement proteins so that phagocytes can recognise and engulf it more efficiently. It links specific immune recognition to the killing action of neutrophils and macrophages.

An infection acquired in hospital or another healthcare facility that was not present or incubating when the patient was admitted. It is often caused by multidrug-resistant organisms and linked to devices and procedures.

The lowest concentration of an antimicrobial that prevents visible growth of a bacterial isolate in laboratory culture. It guides drug choice and dosing and is used to define susceptibility or resistance.

Death of heart muscle caused by prolonged ischaemia, usually from a blocked coronary artery. It presents with chest pain, ECG changes and raised troponin, and requires urgent reperfusion to limit damage.

A group of metabolic disorders marked by chronic hyperglycaemia caused by deficient insulin secretion, insulin action, or both. Long-term complications include retinopathy, nephropathy, neuropathy and premature cardiovascular disease.

End-stage chronic liver disease in which fibrosis and regenerative nodules distort the liver architecture. It causes portal hypertension and impaired synthetic function, and common causes are alcohol, viral hepatitis and fatty liver disease.

The practices that keep microorganisms away from a wound, surgical field or sterile equipment. They include hand hygiene, sterile gowns, drapes and instruments, and a no-touch technique during procedures.

Air in the pleural space that causes the lung to collapse. A tension pneumothorax additionally shifts the mediastinum and obstructs venous return, and is fatal unless decompressed immediately.

Blockage of the intestinal lumen that causes colicky abdominal pain, vomiting, distension and constipation. Mechanical causes include adhesions, hernias and tumours; paralytic ileus is a non-mechanical variant.

A patient's voluntary agreement to an investigation or treatment after receiving adequate information about its purpose, risks, alternatives and consequences. Valid consent requires capacity, disclosure and freedom from coercion.

A severe, immediate generalised hypersensitivity reaction, usually IgE-mediated, causing airway swelling, bronchospasm and low blood pressure. Intramuscular adrenaline is the first-line treatment and must not be delayed.

A life-threatening state in which inadequate tissue perfusion delivers too little oxygen to meet cellular demand, producing lactic acidosis and organ dysfunction. Causes include haemorrhage, sepsis, heart failure and obstruction.

The process of rapidly sorting patients by urgency so that limited resources reach those who will benefit most. It uses physiological and presenting criteria and is repeated as the patient's condition changes.

A score from 3 to 15 that grades eye opening, verbal response and motor response to assess consciousness. It is used after head injury and in critical illness to track deterioration and guide urgency.

Indirect protection of unvaccinated people that occurs when a large enough proportion of the population is immune, so transmission chains break. The threshold rises with how contagious the pathogen is.

The number of new cases of a disease arising in a defined population during a specified period, divided by the number of people at risk. It measures risk and is used to investigate causation.

The proportion of people who truly have a disease and are correctly identified as positive by a test. A highly sensitive test is useful for ruling out disease when the result is negative.

The proportion of people who do not have a disease and are correctly identified as negative by a test. A highly specific test is useful for ruling in disease when the result is positive.

An experiment in which participants are allocated by chance to an intervention or control group, then followed for outcomes. Randomisation balances known and unknown confounders, making it the strongest design for causal questions.