ITEC Anatomy & Physiology cheat sheet

Plasma membrane is a phospholipid bilayer with embedded proteins; hydrophobic tails face inward, hydrophilic heads face the aqueous intracellular and extracellular fluids.

Passive transport (simple diffusion, osmosis, facilitated diffusion) moves solute down its concentration gradient without ATP; active transport (e.g., Na+/K+ ATPase, 3 Na+ out per 2 K+ in) requires ATP.

Tonicity rules: hypertonic solution causes cell shrinkage (crenation), hypotonic causes swelling and possible lysis, isotonic causes no net water movement.

Organelles and roles: mitochondria = ATP via oxidative phosphorylation; ribosomes = protein synthesis; rough ER = protein processing; smooth ER = lipid synthesis and detoxification; Golgi = modification and packaging; lysosomes = intracellular digestion; proteasomes = protein degradation.

Mitosis stages in order: prophase, metaphase, anaphase, telophase; cytokinesis follows. Meiosis produces four haploid gametes with crossing over in prophase I.

Four primary tissue classes: epithelial (covering/lining, avascular, high regeneration), connective (cells plus abundant extracellular matrix; includes bone, cartilage, blood, adipose), muscle (skeletal, cardiac, smooth), nervous (neurons and glia).

Epithelial naming: number of layers (simple = one, stratified = multiple) plus cell shape (squamous, cuboidal, columnar); pseudostratified appears layered but all cells touch the basement membrane.

Cell junctions: tight junctions seal the intercellular space, desmosomes anchor cells to each other, gap junctions form communicating channels for ions and small molecules.

Skeletal muscle is striated and voluntary with multinucleate fibers; cardiac muscle is striated, involuntary, branched with intercalated discs; smooth muscle is non-striated, involuntary, spindle-shaped.

Sarcomere organization: Z discs bound the sarcomere; A band = thick filaments (myosin) including overlap zones; I band = thin filaments (actin) only; H zone = thick filaments only; M line = center.

Sliding filament theory: myosin heads bind actin, pivot (power stroke), and detach using ATP; Ca2+ binds troponin, moving tropomyosin to expose actin binding sites.

Excitation-contraction coupling: motor neuron releases acetylcholine at the neuromuscular junction, depolarization travels along the sarcolemma and T tubules, sarcoplasmic reticulum releases Ca2+, contraction occurs; relaxation follows Ca2+ reuptake.

Muscle fiber types: slow oxidative (type I, fatigue-resistant, aerobic), fast oxidative-glycolytic (type IIa), fast glycolytic (type IIb/IIx, powerful, fatigues quickly).

ATP sources in order of onset: stored creatine phosphate (seconds), anaerobic glycolysis (short, produces lactate), aerobic respiration (sustained, requires oxygen).

Prime movers (agonists) produce the movement, antagonists oppose it, synergists assist, fixators stabilize the origin; isotonic contraction changes length, isometric does not.

Major muscles and actions: biceps brachii flexes elbow; triceps brachii extends elbow; quadriceps femoris extends knee; hamstrings flex knee; gastrocnemius plantarflexes ankle; diaphragm and external intercostals drive inspiration.

Blood flow pathway: right atrium to right ventricle to pulmonary trunk to lungs (gas exchange) to pulmonary veins to left atrium to left ventricle to aorta to systemic circulation.

Heart valves: tricuspid (right AV), bicuspid/mitral (left AV), pulmonary semilunar, aortic semilunar; AV valves prevent backflow into atria, semilunar valves prevent backflow into ventricles.

Cardiac conduction order: SA node (pacemaker) to AV node (delay) to bundle of His to left and right bundle branches to Purkinje fibers; this sequence ensures atrial contraction precedes ventricular contraction.

Cardiac cycle: systole = ventricular contraction, AV valves closed, semilunar valves open; diastole = ventricular relaxation, semilunar valves closed, AV valves open; S1 is AV valve closure, S2 is semilunar valve closure.

Cardiac output = heart rate x stroke volume; stroke volume depends on preload, contractility, and afterload; normal resting output roughly 5 L/min.

Blood vessel structure: arteries have thick tunica media (elastic and smooth muscle), veins have thin walls and valves, capillaries are one cell thick for exchange; blood pressure falls from aorta to venules.

Formed elements: erythrocytes carry O2 via hemoglobin (no nucleus in mature form), leukocytes defend the body (neutrophils, lymphocytes, monocytes, eosinophils, basophils), platelets are cell fragments for hemostasis.

Hemostasis sequence: vascular spasm, platelet plug formation, coagulation cascade converting fibrinogen to fibrin; lymph returns excess interstitial fluid via lymphatic vessels and lymph nodes filter it.

Conducting zone (nose, pharynx, larynx, trachea, bronchi, bronchioles) warms, humidifies, and filters air; respiratory zone (respiratory bronchioles, alveolar ducts, alveoli) performs gas exchange.

Alveolar gas exchange is diffusion driven by partial pressure gradients: alveolar PO2 about 104 mmHg vs deoxygenated blood about 40 mmHg; alveolar PCO2 about 40 mmHg vs blood about 45 mmHg.

Inspiration is active: diaphragm contracts and flattens, external intercostals lift ribs, thoracic volume rises, intrapulmonary pressure drops below atmospheric and air enters.

Quiet expiration is passive elastic recoil; forced expiration uses internal intercostals and abdominal muscles.

Lung volumes: tidal volume ~500 mL; inspiratory reserve volume; expiratory reserve volume; residual volume (cannot be exhaled); vital capacity = TV + IRV + ERV; total lung capacity = vital capacity + residual volume.

Respiratory control: medullary respiratory centers set rhythm; central chemoreceptors respond mainly to rising CO2 (falling pH) in cerebrospinal fluid; peripheral chemoreceptors in carotid and aortic bodies respond to falling O2.

Oxygen transport: about 98% bound to hemoglobin, remainder dissolved in plasma; CO2 travels mainly as bicarbonate (about 70%), some bound to hemoglobin, some dissolved.

Boyle's law (pressure inversely proportional to volume) and Dalton's law (total pressure equals sum of partial pressures) explain ventilation and gas exchange.

Digestive tract order: mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, rectum, anus; accessory organs are salivary glands, liver, gallbladder, pancreas.

Mechanical digestion: chewing, churning in the stomach, segmentation in the small intestine; chemical digestion relies on enzymes; peristalsis propels contents along the tract.

Enzyme actions: salivary amylase digests starch; pepsin (activated from pepsinogen by HCl) digests protein in the stomach; pancreatic amylase, lipase, and proteases act in the duodenum; brush-border enzymes complete digestion.

Bile is produced by the liver, stored in the gallbladder, and emulsifies fats (no enzymes); the pancreas secretes bicarbonate to neutralize chyme plus amylase, lipase, and proteases.

Absorption sites: most nutrient absorption occurs in the jejunum; water and electrolytes mainly in the large intestine; villi and microvilli increase surface area.

Hormones: gastrin stimulates gastric acid secretion; secretin stimulates pancreatic bicarbonate; cholecystokinin (CCK) stimulates gallbladder contraction and pancreatic enzyme release; gastric inhibitory peptide slows gastric emptying.

Stomach cells: parietal cells secrete HCl and intrinsic factor (needed for vitamin B12 absorption); chief cells secrete pepsinogen; G cells secrete gastrin; mucous cells protect the lining.

Liver functions include bile production, nutrient storage (glycogen), plasma protein synthesis, detoxification, and urea formation from ammonia.

Neuron parts: dendrites receive, cell body integrates, axon conducts, axon terminals release neurotransmitter; myelinated axons conduct faster via saltatory conduction at nodes of Ranvier.

Resting membrane potential is about -70 mV maintained by the Na+/K+ pump; depolarization opens Na+ channels, repolarization opens K+ channels; the threshold must be reached to fire an action potential.

Synaptic transmission: action potential reaches the terminal, Ca2+ enters, vesicles release neurotransmitter into the synaptic cleft, it binds receptors on the postsynaptic membrane; transmission is one-way.

CNS = brain and spinal cord; PNS = cranial and spinal nerves, divided into somatic (voluntary) and autonomic (involuntary); autonomic splits into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest).

Brain regions: cerebrum (thought, voluntary movement, sensation), cerebellum (coordination and balance), medulla oblongata (vital centers: breathing, heart rate), hypothalamus (homeostasis, temperature, pituitary control).

Endocrine glands and hormones: pituitary (growth hormone, ADH, oxytocin, tropic hormones), thyroid (thyroxine, calcitonin), parathyroid (PTH), adrenal cortex (cortisol, aldosterone) and medulla (adrenaline), pancreas (insulin, glucagon), gonads (sex hormones).

Negative feedback dominates endocrine control: rising hormone or metabolite level suppresses further secretion (e.g., insulin lowers glucose; thyroid hormones inhibit TSH).

Steroid hormones cross the membrane and act on intracellular receptors altering gene transcription; peptide and amine hormones bind surface receptors and act via second messengers.

Three layers: epidermis (avascular keratinized stratified squamous epithelium), dermis (connective tissue with blood vessels, nerves, glands, hair follicles), hypodermis/subcutaneous layer (adipose and loose connective tissue).

Epidermal strata from deep to superficial: basale, spinosum, granulosum, lucidum (palms and soles only), corneum; keratinocytes form in the basale and are shed from the corneum.

Cells: keratinocytes produce keratin for waterproofing; melanocytes produce melanin (UV protection); Langerhans cells are immune; Merkel cells are touch receptors.

Skin functions: protection, thermoregulation (sweating and dermal blood flow), sensation, vitamin D synthesis, excretion, and a barrier against water loss.

Glands: eccrine sweat glands cool the body and are widespread; apocrine glands occur in axillae and groin; sebaceous glands secrete sebum into hair follicles.

Hair structure: shaft above the skin, root in the follicle, bulb at the base; growth phases are anagen (growth), catagen (transition), telogen (rest); arrector pili muscle causes goosebumps.

Nail parts: nail plate, nail bed, cuticle (eponychium), lunula (pale crescent), matrix (growth site); nails protect fingertips and aid grasping.

Burn depth: first degree affects epidermis only (redness); second degree extends into dermis (blisters); third degree destroys the full thickness including nerve endings, so it may be painless.

Nephron is the functional unit: glomerulus filters blood into Bowman's capsule; proximal tubule reabsorbs most water, glucose, and ions; loop of Henle creates a concentration gradient; distal tubule and collecting duct fine-tune under hormone control.

Urine formation has three processes: filtration (glomerulus), reabsorption (tubules back to blood), and secretion (blood to tubules); most reabsorption occurs in the proximal convoluted tubule.

Hormonal control: ADH increases collecting duct water reabsorption (concentrated urine); aldosterone increases Na+ reabsorption and K+ secretion; atrial natriuretic peptide promotes Na+ and water loss.

Kidney functions: filter waste (urea, creatinine), regulate water and electrolyte balance, regulate acid-base balance, regulate blood pressure (renin), and produce erythropoietin for red cell formation.

Male reproductive tract: testes produce sperm and testosterone; sperm mature in the epididymis, travel through the vas deferens, receive seminal fluid from seminal vesicles, prostate, and bulbourethral glands.

Female reproductive cycle: FSH stimulates follicle development and estrogen; the LH surge triggers ovulation around mid-cycle; the corpus luteum secretes progesterone to maintain the endometrium; falling hormones cause menstruation.

Fertilization typically occurs in the fallopian tube; the zygote implants in the endometrium; the placenta handles exchange of gases, nutrients, and waste between mother and fetus.

Urine pathway: nephron to collecting duct to renal pelvis to ureter to bladder to urethra; the detrusor muscle and internal urethral sphincter control voiding.

Homeostasis is maintenance of a stable internal environment around a set point; it uses a receptor (detects change), control center (integrates), and effector (responds).

Negative feedback reverses a deviation and is the dominant mechanism (thermoregulation, blood glucose, blood pressure, pH); positive feedback amplifies a change until a defined end point (childbirth, blood clotting).

Blood glucose: rising glucose triggers insulin (lowers glucose by promoting cellular uptake and glycogen storage); falling glucose triggers glucagon (raises glucose by glycogen breakdown and gluconeogenesis).

Thermoregulation: hypothalamus detects temperature change; heat loss via sweating and vasodilation, heat conservation via shivering, vasoconstriction, and piloerection.

Respiratory and cardiovascular systems cooperate: lungs oxygenate blood, the heart pumps it, and capillaries deliver O2 and remove CO2 at tissue level.

Digestive and cardiovascular systems cooperate: absorbed nutrients enter blood or lymph and are transported to cells; the liver buffers blood glucose and detoxifies.

Urinary and respiratory systems both regulate acid-base balance: lungs remove CO2 (respiratory component), kidneys excrete or reabsorb H+ and bicarbonate (metabolic component).

Endocrine and nervous systems coordinate responses: the nervous system acts rapidly via electrical signals and neurotransmitters; the endocrine system acts more slowly via hormones carried in blood.