❤️ Human Physiology

Homeostasis

Maintenance of a stable internal environment through negative feedback control.

Tissues and Organs

Cells form tissues, tissues form organs and organs work together in systems.

Skeletal System

Bones, cartilage and joints that support the body, protect organs and allow movement.

Muscular System

Skeletal, smooth and cardiac muscle produce movement and move substances inside the body.

Digestive System

The mouth, stomach, intestines and accessory organs that break down food and absorb nutrients.

Respiratory System

Airways and lungs that bring oxygen in and remove carbon dioxide.

Circulatory System

The heart, blood vessels and blood that transport materials around the body.

Heart Structure

A four-chambered muscular pump with atria, ventricles and valves that keep blood flowing one way.

Blood Components

Plasma, red cells, white cells and platelets carry out transport, defence and clotting.

Blood Vessels

Arteries carry blood away from the heart, veins return it and capillaries exchange materials.

Excretory System

Kidneys, ureters, bladder and urethra remove metabolic waste and balance water.

Skin

The largest organ, forming a waterproof barrier that protects, senses and regulates temperature.

Nutrition and Diet

A balanced diet supplies carbohydrates, proteins, fats, vitamins, minerals, fibre and water.

Senses

Sight, hearing, taste, smell and touch detect stimuli and send information to the brain.

Exercise Physiology

Regular activity strengthens muscle, heart and bone and changes metabolism.

Intermediate topics (17)

Digestive Enzymes

Amylase, proteases and lipases break carbohydrates, proteins and fats into absorbable units.

Small Intestine Absorption

Villi and microvilli provide a huge surface area for nutrient absorption into blood and lymph.

Liver Functions

Processes nutrients, detoxifies blood, makes bile and proteins and stores glycogen.

Gas Exchange in Alveoli

Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients.

Breathing Mechanism

Diaphragm and intercostal muscles change thorax volume and pressure to move air in and out.

Haemoglobin and Oxygen Transport

Haemoglobin binds oxygen in the lungs and releases it in tissues, with the curve shifted by CO2 and pH.

Cardiac Cycle

The sequence of atrial and ventricular contraction (systole) and relaxation (diastole) in each heartbeat.

Blood Pressure

The force of blood against vessel walls, recorded as systolic over diastolic pressure.

Blood Clotting

Platelets and fibrin form a clot to seal damaged vessels.

Lymphatic System

Vessels and nodes that return tissue fluid to the blood and house immune cells.

Nephron Function

Filtration, selective reabsorption and secretion in the nephron form urine.

Osmoregulation and ADH

Antidiuretic hormone raises kidney water reabsorption when blood is too concentrated.

Thermoregulation

Sweating, shivering and blood vessel changes keep core temperature near 37 degrees Celsius.

Blood Glucose Regulation

Insulin lowers and glucagon raises blood glucose through negative feedback.

Muscle Contraction

Actin and myosin filaments slide past each other using ATP and calcium, according to the sliding filament theory.

Bone Remodelling

Osteoclasts resorb and osteoblasts build bone continuously, controlled by hormones and stress.

Joints and Movement

Hinge, ball-and-socket and pivot joints with ligaments and tendons allow different ranges of motion.

Advanced topics (19)

Acid-Base Balance

Buffers, lungs and kidneys maintain blood pH between 7.35 and 7.45.

Renin-Angiotensin-Aldosterone System

A hormone cascade that raises blood pressure by vasoconstriction and sodium retention.

Countercurrent Multiplier

The loop of Henle creates a salt gradient in the medulla that allows concentrated urine.

Cardiac Conduction System

The SA node, AV node and Purkinje fibres coordinate heartbeat electrical signals seen on an ECG.

Frank-Starling Law

Greater ventricular filling stretches the heart and increases the force of the next contraction.

Hemostasis Cascade

Intrinsic and extrinsic coagulation pathways converge to convert fibrinogen to fibrin.

Lung Compliance and Surfactant

Surfactant reduces alveolar surface tension, preventing collapse and easing breathing.

Respiratory Control

The medulla adjusts breathing rate in response to blood CO2 and pH detected by chemoreceptors.

Gut Hormones

Gastrin, secretin and cholecystokinin coordinate digestive secretions and motility.

Energy Balance and Metabolism

Body weight reflects the balance of intake and expenditure, with leptin and ghrelin regulating appetite.

Renal Autoregulation

Kidneys adjust arteriole resistance to keep glomerular filtration steady despite blood pressure changes.

Fluid Compartments

Body water is divided into intracellular and extracellular fluid, with distinct ion compositions.

Exercise Adaptations

Training increases stroke volume, capillary density and mitochondrial content in muscle.

Altitude Physiology

Low oxygen triggers erythropoietin, raising red cell count over days and weeks.

Sleep Physiology

Cycles of REM and non-REM sleep regulated by circadian clocks and homeostatic drive.

Ageing Physiology

Declining stem cell function, accumulating damage and reduced repair gradually lower organ capacity.

Cardiovascular Disease Mechanisms

Atherosclerosis builds plaques from cholesterol and inflammation, narrowing arteries and risking clots.

Diabetes Mellitus

Type 1 results from loss of insulin-making cells and type 2 from insulin resistance, both leaving high blood glucose.

Medical Imaging Physiology

MRI, CT, ultrasound and PET visualise anatomy and function using different physical principles.