Human Physiology & Anatomy for the Biology Olympiad

Explore the four tissue types: epithelial, connective, muscle, and nervous—and their roles in organs; trace germ layers to tissue origins and learn about intracellular and extracellular fluids.

Explore epithelial tissues, their polarity and basement membrane, junctions, and the diverse forms—simple and stratified, squamous, cuboidal, and columnar—plus glandular and sensory roles.

Explore connective tissue as the body’s binding framework, with cells, ground substance, extracellular matrix fibers like collagen and elastic fibers, and three tissue types: proper, fluid, and supporting.

Explore fluid connective tissue, including blood and lymph, their plasma, plasma proteins, and immune defense, and learn bone and cartilage structure, remodeling by osteoblasts and osteoclasts, and cartilage types.

This episode explains muscle tissue, where actin and myosin drive contraction to generate movement; it covers skeletal, cardiac, and smooth muscle types and their key features.

Explore nervous tissue, responsible for action potentials and coordinating body functions, with the CNS and PNS, glial cells and neurons, and myelin insulation along axons.

Examine the microstructure of osseous tissue, detailing compact bone with osteons, lamellae, lacunae, canaliculi, and the periosteum; contrast with spongy bone and the two ossification pathways intramembranous and endochondral.

Explore the nervous system's organization from central and peripheral components to the brain and spinal cord, and examine afferent and efferent pathways, including somatic and autonomic divisions (sympathetic and parasympathetic).

Explore nervous tissue: neurons, gray matter, ganglia, dendrites, axons, graded and action potentials, and the sensory, motor, and interneuron classifications.

Explore axon transport, distinguishing anterograde flow to the axon terminal from retrograde flow to the soma, via microtubules and kinesin and dynein, and examine neurotransmitters at synapses and glial roles.

Explore neurophysiology fundamentals: membrane potentials, voltage, ion flow, leak and gated channels, equilibrium potentials, and the sodium–potassium pump shaping resting potential.

Explore how graded potentials vary with stimulus strength, undergo temporal and spatial summation, and trigger action potentials when reaching threshold at the axon hillock, propagating nondecrementally.

Learn the generation of action potentials, from depolarization to hyperpolarization, driven by voltage-gated sodium and potassium channels, and the absolute and relative refractory periods.

Explore how action potentials propagate along axons, showing that larger axon diameter and myelination speed conduction, with saltatory conduction at nodes, and how demyelinating diseases disrupt this process.

Discover major neurotransmitter classes, including glutamate, GABA, dopamine, and acetylcholine. Examine NMDA/AMPA receptors, magnesium block, LTP, and links to memory formation and Alzheimer's disease.

Explore catecholamines: dopamine, norepinephrine, and epinephrine, their receptors, plus serotonin, nitric oxide, and endogenous opioids shaping mood, reward, learning, sleep, and addiction.

Explore the spinal cord and spinal nerves, detailing white and gray matter, dorsal root ganglion, ventral and dorsal roots, and how afferent and efferent fibers form mixed nerves.

Explore reflexes as rapid, involuntary responses governed by the spinal cord, including mono- and poly-synaptic reflex arcs, autonomic and somatic pathways, and receptors like muscle spindles and Goji tendon organs.

Explore the efferent division of the PNS, including the somatic, autonomic, and enteric systems, and how they coordinate voluntary and involuntary actions.

Explore the sympathetic division's fight-or-flight response, adrenal medulla release of epinephrine and no epinephrine, and rapid postganglionic signaling via acetylcholine and nicotinic receptors.

Explore the brain's development from neural tube formation to key brain structures. Identify the cerebrum, cerebellum, brainstem, thalamus, hypothalamus, and cortex, and their roles in sensation, movement, and homeostasis.

Explore brainstem structures—midbrain, pons, and medulla—linking eye reflexes, motor control via the substantia nigra, autonomic regulation, and sleep‑wake cycles through the reticular activating system.

Explore the vascular system, detailing arteries, capillaries, and veins, their tunica wall structures, and how blood pressure, flow, and capillary types regulate nutrient and gas exchange.

Explore the heart's anatomy and function within the cardiovascular system, detailing the pulmonary and systemic circuits, atria and ventricles, pericardial layers, and the cardiac conduction system.

Explore the heart’s atrioventricular and semilunar valves and how they regulate blood flow. Trace pulmonary and systemic circuits, coronary arteries, and fetal adaptations like foramen ovale and ductus arteriosus.

Explore how the heart contracts via the cardiac conduction system, including sinoatrial node and atrioventricular node and Purkinje fibers; interpret ecg waves and factors affecting heart rate and cardiac cycle.

Explore the cardiac cycle with ECG and heart sounds, and learn how heart rate, stroke volume, preload, afterload, and sympathetic and parasympathetic regulation shape cardiac output.

Learn about blood composition and function: plasma, blood cells and platelets, and how hematopoietic stem cells form myeloid and lymphoid lineages to transport oxygen, nutrients, carbon dioxide, and hormones.

Outline erythropoiesis from hematopoietic stem cells to mature red blood cells, detailing hemoglobin structure and oxygen transport, and disorders such as anemia, thalassemia, and sickle cell disease.

Explore leukopoiesis and how hematopoietic stem cells differentiate into myeloid and lymphoid lineages, detailing neutrophils, eosinophils, basophils, monocytes, and lymphocytes, their tissue migration and chemotaxis to defend against pathogens.

Explore leukopoiesis and the differentiation of myeloid and lymphoid lineages into macrophages, dendritic cells, B cells, T cells, and natural killer cells, and their roles in innate and acquired immunity.

Thrombocytopoiesis shows how megakaryocytes in the bone marrow release platelets that form a plug and drive coagulation, highlighting thrombocytopenia, thrombocytosis, embolism, and hemophilia A and B.

Explore the endocrine system, its hormone messengers, and how peptide, amino acid–derived, and lipid-derived hormones travel via blood, regulate growth and metabolism, and act through receptor pathways.

Explore how hormones diffuse into the bloodstream, reach target cells via intracellular and extracellular receptors, and engage antagonistic, synergistic, and permissive interactions to regulate endocrine signaling.

Explain the hypothalamus–pituitary axis, including releasing and inhibiting hormones that regulate the anterior pituitary, and the posterior pituitary's storage of oxytocin and ADH, and pineal melatonin.

Explore the anterior pituitary hormones—growth hormone, TSH, ACTH, FSH, LH, prolactin, and MSH—and how they regulate target organs under hypothalamic control with negative feedback in the hypothalamic-pituitary-adrenal axis.

Learn how the thyroid gland, its follicles and colloid synthesize T3 and T4 from iodine and thyroglobulin, regulated by TRH and TSH, with calcium balanced by calcitonin and PTH.

Explore the adrenal glands, detailing the cortex and medulla, their hormones—corticosteroids, mineralocorticoids, glucocorticoids, and epinephrine and norepinephrine—and how the HP axis regulates cortisol, with notes on Addison's and Cushing's syndromes.

Study the pancreas as a mixed gland with insulin and glucagon regulating blood glucose, plus islets and diabetes symptoms; and intestinal endocrine hormones gastrin, ghrelin, secretin, and cholecystokinin coordinating digestion.

Explore how ovaries and testes regulate reproductive hormones with LH and FSH, detailing estrogen and progesterone roles in the menstrual cycle, ovulation, corpus leftism, and placental hormones.

Examine nontraditional endocrine organs such as the thymus, heart, adipose tissue, skin, and kidneys, detailing hormones like atrial natriuretic peptide, leptin, adiponectin, vitamin d activation, erythropoietin, and renin-angiotensin-aldosterone effects.

Explore how the lymphatic system maintains fluid balance, absorbs fats via lacteals, and defends the body with innate and acquired immune responses, through lymph nodes, vessels, and lymphocytes.

We trace the development of hematopoietic stem cells into lymphocytes and examine lymph nodes, spleen, thymus, and mucosa-associated lymphoid tissue in immune surveillance and memory.

Explore how innate and adaptive immunity defend against pathogens, from skin and mucosa barriers to toll-like receptors and T and B cell-mediated responses, including antibodies to specific antigens.

Explore how the innate immune system defends the body against pathogens through phagocytosis by phagocytes, natural killer cells, cytokine signaling, complement activation, inflammation, cell death types, and fever.

Explore the acquired immune system and how T cells and B cells provide targeted, memory-based defenses. Learn about active and passive immunity, antigen recognition, and immune tolerance.

Explore the acquired immune system's distinctions between B and T cells, their maturation, antigen recognition, memory formation, and the roles of antibodies, cytotoxic and helper T cells, and MHC-mediated presentation.

Describe how cytotoxic T cells use MHC class I to recognize endogenous antigens, proliferate, and kill targets with perforin and granzymes; show helper T cells driving B cell responses.

Explore how V(D)J recombination in bone marrow and thymus reshapes B and T lymphocytes to generate diverse antibodies and receptors via heavy and light chains and V,D,J segments.

B cells produce antibodies that use heavy and light chains to form antigen-binding sites that recognize epitopes, classify as IgA, IgM, IgG, IgD, or IgE, and mediate defense.

Antibodies bind surface antigens to form clumps, helping phagocytes clear pathogens. They activate inflammation, complement, and opsonization; review primary and secondary immune responses and related autoimmune, immunodeficiency, and allergy disorders.

Understand how the digestive system ingests, digests, absorbs nutrients, and eliminates waste, guided by neural and hormonal control and local signals.

Discover the anatomy of the upper GI tract, including the mouth, tongue, teeth, and salivary glands, and how saliva with amylase and lingual lipase begins digestion and forms a bolus.

Explore the upper digestive tract from pharynx to stomach, detailing pharyngeal regions, esophageal mucosa and muscular layers, and the stomach’s regions, glands, mucosa folds, and intrinsic factor.

Explore the upper gastrointestinal tract’s gastric glands, including mucus, parietal and chief cells, and gastrin regulation, and how intrinsic factor enables vitamin B12 absorption in the ileum.

Explore the lower gastrointestinal tract, focusing on the small intestine's duodenum, jejunum, and ileum, where chemical digestion finishes and most nutrient absorption occurs through villi and microvilli.

Explore the pancreas as a dual exocrine–endocrine gland, detailing pancreatic juice secretion, digestive enzymes, and islets of Langerhans that regulate blood sugar with insulin and glucagon.

Examine the liver's lobular anatomy, hepatic triad, and bile production, including gallbladder storage, while detailing its metabolic, detoxification, and blood-regulation roles.

The large intestine absorbs water, electrolytes, and vitamins from gut bacteria, forms feces with mucus, and hosts bacterial synthesis of vitamins K and B5, influencing clotting and glucose metabolism.

Explore how carbohydrates, lipids, proteins, and nucleic acids are chemically digested and absorbed, detailing mouth to small intestine processes, key enzymes, digestion sites, and nutrient transport mechanisms.

Explore digestion and absorption of lipids and proteins, including bile emulsification, pancreatic lipase, micelle and chylomicron formation, and key satiety hormones like insulin, PYY, and leptin.

Explore how the urinary system, including kidneys, filters blood, excretes urine, and regulates pH, blood pressure, vitamin D activation, and EPO.

Examine the nephron across cortex and medulla, detailing glomerulus, Bowman's capsule, proximal tubule, loop of Henle, distal tubule, collecting ducts, and cortical vs juxtamedullary differences.

Explore how kidneys form urine by filtration in the glomerulus and Bowman's capsule across filtration membrane. Understand how hydrostatic pressure and afferent arterial and effluent arterial changes set the GFR.

Explore proximal tubule absorption of sodium, water, glucose, amino acids, and nutrients, and how the loop of Henle creates a hypertonic medulla to drive water reabsorption in collecting ducts.

Examine the distal convoluted tubule's role in aldosterone- and ADH-regulated Na+, water, and chloride reabsorption. Explore macula densa signaling, renin–angiotensin system activation, and PTH/calcitriol-driven calcium regulation.

Explore the composition and physiology of muscle tissue, including elongated cells with actin and myosin, excitability, and contraction, and compare skeletal (voluntary), cardiac and smooth (involuntary) muscles.

Explore skeletal muscle anatomy and physiology, including motor units, connective tissue layers, sarcomeres with actin and myosin, calcium signaling, and antagonistic and agonist muscle actions.

Understand how resting membrane potential and action potentials trigger calcium release initiating skeletal muscle contraction via acetylcholine, DHPR, ryanodine receptor, troponin, and the sliding filament mechanism.

Explore how skeletal muscles generate force through fiber types, calcium dynamics, and tetanus, and how ATP, creatine phosphate, glycolysis, and lactate recycling sustain contraction.

Explore how fast glycolytic, slow oxidative, and fast oxidative fibers differ in metabolism, fatigue, and role in posture and movement, and how endurance and resistance training shape their performance.

Explore how cardiac muscle forms the heart's myocardium, with connected cardiomyocytes via intercalated discs, allowing automatic, coordinated contractions regulated by pacemaker cells and autonomic signals.

Explore smooth muscle tissue in hollow organs and skin, their involuntary contraction regulated by calcium via calmodulin and myosin light chain kinase, with gap junctions and multi-unit varieties.