JMC Human Medicine Exam cheat sheet

Brachial plexus cords are named by relation to the second part of the axillary artery: lateral, medial, posterior; the posterior cord gives axillary and radial nerves.

The femoral triangle borders are the inguinal ligament superiorly, sartorius laterally, and adductor longus medially, with a floor of iliopsoas and pectineus.

The median nerve supplies all forearm flexors except flexor carpi ulnaris and the medial half of flexor digitorum profundus, which are ulnar.

The portal triad in the hepatoduodenal ligament contains the proper hepatic artery, portal vein, and common bile duct; the portal vein lies posterior.

The recurrent laryngeal nerve loops under the subclavian artery on the right and the aortic arch (ligamentum arteriosum) on the left.

The parotid duct crosses the masseter and pierces the buccinator opposite the upper second molar to open in the oral vestibule.

The lateral corticospinal tract decussates in the medullary pyramids and synapses in the ventral horn; lesions cause ipsilateral spastic weakness below the level.

The coronary circulation: the right coronary artery supplies the SA node in about 60% of people and the AV node in about 80%.

Cardiac output = heart rate × stroke volume; mean arterial pressure ≈ diastolic pressure + one-third of pulse pressure.

Renal clearance C = (U × V) / P; inulin clearance estimates GFR and PAH clearance estimates effective renal plasma flow.

Oxygen delivery = cardiac output × arterial oxygen content, where content = 1.34 × Hb × SaO2 + 0.003 × PaO2.

The alveolar gas equation: PAO2 = FiO2 × (Patm − 47) − PaCO2 / 0.8.

In the Starling equation, net filtration = Kf × [(Pc − Pi) − σ(πc − πi)]; albumin is the main determinant of plasma oncotic pressure.

Insulin lowers blood glucose by promoting GLUT4 translocation in muscle and adipose; glucagon raises it via hepatic glycogenolysis and gluconeogenesis.

The Frank-Starling relationship states that stroke volume rises with end-diastolic volume, up to the point of sarcomere overstretch.

Countercurrent multiplication in the loop of Henle builds a medullary osmotic gradient; ADH increases collecting duct water permeability via aquaporin-2.

Glycolysis yields a net 2 ATP and 2 NADH per glucose; the committed step is phosphofructokinase-1, activated by AMP and fructose-2,6-bisphosphate.

Pyruvate dehydrogenase requires thiamine (TPP), lipoic acid, CoA, FAD, and NAD; deficiency causes lactate accumulation.

The urea cycle's rate-limiting enzyme is carbamoyl phosphate synthetase I, activated by N-acetylglutamate.

Heme synthesis: the rate-limiting step is ALA synthase; lead inhibits ALA dehydratase and ferrochelatase, causing microcytic anemia with basophilic stippling.

The pentose phosphate pathway generates NADPH and ribose-5-phosphate; glucose-6-phosphate dehydrogenase deficiency impairs glutathione regeneration.

Ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) are produced in hepatic mitochondria during prolonged fasting and used by extrahepatic tissues.

Vitamin C is required for prolyl and lysyl hydroxylation in collagen; deficiency causes scurvy with poor wound healing and perifollicular hemorrhage.

Phenylketonuria results from phenylalanine hydroxylase or tetrahydrobiopterin deficiency; untreated disease causes intellectual disability and musty urine odor.

Reversible cell injury shows cellular swelling and fatty change; irreversible injury shows membrane rupture, mitochondrial permeability transition, and nuclear pyknosis, karyorrhexis, or karyolysis.

Coagulative necrosis is typical of ischemic injury in heart, kidney, and spleen; liquefactive necrosis occurs in brain infarcts and abscesses.

Malignant tumors show invasion and metastasis; carcinoma arises from epithelium and sarcoma from mesenchyme.

Tumor suppressor genes such as TP53 and RB require loss of both alleles (two-hit hypothesis) for functional inactivation.

Acute inflammation is mediated by histamine, bradykinin, and leukotriene B4; chronic inflammation features macrophages, lymphocytes, and fibrosis.

Nephrotic syndrome shows proteinuria >3.5 g/day, hypoalbuminemia, edema, and hyperlipidemia; nephritic syndrome shows hematuria and hypertension.

Atherosclerosis begins with endothelial injury, LDL accumulation, foam cell formation, and smooth muscle migration into the intima.

The Apgar score assesses heart rate, respiratory effort, muscle tone, reflex irritability, and color at 1 and 5 minutes.

First-order kinetics eliminates a constant fraction per unit time; zero-order eliminates a constant amount, as with phenytoin and ethanol at high doses.

Volume of distribution Vd = dose / plasma concentration; a large Vd indicates extensive tissue distribution.

Half-life t½ = 0.693 × Vd / clearance; steady state is reached after about 4–5 half-lives.

Competitive antagonists shift the dose-response curve right without lowering maximal efficacy; noncompetitive antagonists reduce maximal efficacy.

ACE inhibitors cause cough via bradykinin accumulation and are contraindicated in pregnancy and bilateral renal artery stenosis.

Aminoglycosides bind the bacterial 30S subunit, are nephrotoxic and ototoxic, and require renal dose adjustment.

Warfarin inhibits vitamin K epoxide reductase; heparin potentiates antithrombin III and is monitored by aPTT.

Organophosphate poisoning causes a cholinergic crisis treated with atropine plus pralidoxime before enzyme aging occurs.

Gram-positive bacteria have thick peptidoglycan and retain crystal violet; gram-negative bacteria have an outer membrane with lipopolysaccharide.

Staphylococcus aureus is catalase and coagulase positive and forms clusters; Streptococcus pyogenes is bacitracin sensitive and causes post-streptococcal glomerulonephritis.

Mycobacterium tuberculosis is acid-fast due to mycolic acids and is cultured on Lowenstein-Jensen medium.

Hepatitis B is a DNA virus transmitted by blood and sexual contact; hepatitis A and E are transmitted by the fecal-oral route.

HIV infects CD4 T cells via gp120 binding CD4 and CCR5 or CXCR4, with reverse transcriptase converting RNA to DNA.

Malaria is transmitted by female Anopheles mosquitoes; Plasmodium falciparum causes cerebral malaria and is diagnosed by thick and thin blood films.

Clostridioides difficile toxin causes pseudomembranous colitis, typically after broad-spectrum antibiotic use.

Sterilization kills all microorganisms including spores; disinfection reduces pathogens on inanimate surfaces but does not necessarily kill spores.

Incidence measures new cases per population at risk per unit time; prevalence measures all existing cases and equals incidence × mean duration.

Sensitivity = TP / (TP + FN); specificity = TN / (TN + FP); positive predictive value depends on prevalence.

Relative risk is used in cohort studies; odds ratio approximates relative risk in case-control studies when the disease is rare.

The number needed to treat = 1 / absolute risk reduction.

Herd immunity threshold ≈ 1 − 1/R0; it determines the vaccination coverage needed to interrupt transmission.

Infant mortality rate = deaths under age 1 per 1,000 live births in a year; it reflects overall population health.

A randomized controlled trial reduces confounding by randomization and reduces bias with blinding and intention-to-treat analysis.

Screening tests require high sensitivity and a treatable detectable disease with an accepted, safe test.

Acute myocardial infarction is diagnosed by a rising troponin with ischemic symptoms or ECG changes; ST-elevation MI requires urgent reperfusion.

Diabetic ketoacidosis shows hyperglycemia, ketonemia, and anion-gap metabolic acidosis; treatment is isotonic saline, insulin, and potassium replacement.

Hyponatremia is assessed by serum osmolality and volume status; symptomatic severe cases are corrected slowly to avoid osmotic demyelination.

Community-acquired pneumonia is commonly caused by Streptococcus pneumoniae; CURB-65 guides site of care.

Nephrotic syndrome is treated with sodium restriction, diuretics, and ACE inhibitors or ARBs for proteinuria.

Hyperthyroidism shows low TSH with high free T4; Graves disease is treated with antithyroid drugs, radioiodine, or surgery.

Cirrhosis complications include ascites, variceal bleeding, hepatic encephalopathy, and spontaneous bacterial peritonitis.

Anemia is classified by mean corpuscular volume: microcytic (iron deficiency, thalassemia), normocytic, or macrocytic (B12 or folate deficiency).

Acute appendicitis presents with periumbilical pain migrating to the right lower quadrant with rebound tenderness at McBurney point.

Small bowel obstruction shows colicky pain, vomiting, distension, and absent flatus; initial management is IV fluids and nasogastric decompression.

The ATLS approach orders priorities as airway with cervical spine protection, breathing, circulation, disability, and exposure.

Cholecystitis is diagnosed by right upper quadrant pain, Murphy sign, and ultrasound showing wall thickening and pericholecystic fluid.

Shock is classified as hypovolemic, cardiogenic, distributive, or obstructive; initial resuscitation uses isotonic crystalloid.

Breast cancer staging uses tumor size, nodal involvement, and metastasis; sentinel lymph node biopsy assesses axillary spread.

Fracture management follows reduction, immobilization, and rehabilitation; open fractures require antibiotics and urgent debridement.

Peritonitis is diagnosed clinically with rigid abdomen and is treated with IV antibiotics and source control by surgery.

Estimated date of delivery = first day of last menstrual period + 280 days (Naegele rule).

Preeclampsia is defined as blood pressure ≥140/90 mmHg after 20 weeks with proteinuria or end-organ dysfunction; delivery is the definitive treatment.

Antepartum hemorrhage causes include placenta previa and placental abruption; placenta previa presents with painless bleeding.

Gestational diabetes is screened at 24–28 weeks with an oral glucose tolerance test; first-line therapy is lifestyle change, then insulin.

The fetal heart rate baseline is 110–160 beats per minute; late decelerations suggest uteroplacental insufficiency.

Postpartum hemorrhage is most often due to uterine atony and is managed with uterine massage plus oxytocin.

Ectopic pregnancy presents with amenorrhea, abdominal pain, and vaginal bleeding; diagnosis is by beta-hCG and transvaginal ultrasound.

Cervical cancer screening uses cytology, HPV testing, or co-testing, starting at age 21–25 depending on local guidelines.

Neonatal resuscitation begins with warmth, drying, and stimulation; positive pressure ventilation is indicated for apnea or heart rate below 100/min.

Neonatal jaundice appearing in the first 24 hours is always pathologic; phototherapy is used for significant hyperbilirubinemia.

Breastfeeding is recommended exclusively for the first 6 months, with complementary feeding thereafter.

Kawasaki disease shows fever ≥5 days, conjunctivitis, rash, mucosal changes, extremity changes, and cervical lymphadenopathy; treat with IVIG and aspirin.

The leading cause of bacterial meningitis in neonates is group B Streptococcus; in older children it is Streptococcus pneumoniae.

Growth is assessed with weight, length, and head circumference plotted on standardized charts; crossing two major percentiles warrants evaluation.

Croup presents with a barking cough and inspiratory stridor; treatment is dexamethasone with nebulized epinephrine for severe cases.

Vitamin D supplementation of 400 IU/day is recommended for breastfed infants to prevent rickets.