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Week 8 · Midterm study guide

Midterm Exam — Study Guide

Human Anatomy and Physiology I Free sample edition

Coverage — what the midterm covers

The midterm is cumulative over Weeks 1–7. It opens in the Week 8 module and closes at the due time your instructor sets. There is no time limit, and you get one attempt. The questions appear one at a time, and you cannot go back once you move on.

Format: 25 questions, and every question counts the same. Twenty-one ask you to pick one option, three ask you to judge a statement as true or false, and one asks you to pick every option that applies. Any figure, slide, or chart a question needs is described in words in the question, and the arithmetic is short enough for scratch paper.

What is in scope, with the number of midterm questions on each course objective:

Midterm coverage by course objective: the weeks the drawn questions come from, the main skills, and the number of questions out of 25
Course objective Weeks the questions come from Main skills Questions
1. The language of the body, its organization, and homeostasis 1, 2, 4, and 6 The anatomical position, the directional pairs, and the planes; the levels of organization; the feedback loop and its three parts, wherever a later week runs it again: in blood chemistry, in a working muscle, and on the skin 8
2. The chemistry of the body and the cell 2, 3, 4, and 5 Atoms, bonds, water, pH, and the organic molecules; the membrane, the organelles, and transport; how the cell makes and spends ATP; how a gene becomes a protein; how connective tissue is built 11
3. The tissues and the integumentary system 5 and 6 The four tissue types and their subtypes; naming an epithelium; glands; the skin's layers, cells, and accessory structures, and what the layers mean for an injury 5
4. Bone tissue 7 Bone as a living tissue; the long bone; compact and spongy bone; the four bone cells; growth, remodeling, and the calcium loop 1

By week, the questions come out as 3 from Week 1, 7 from Week 2, 2 from Week 3, 4 from Week 4, 4 from Week 5, 4 from Week 6, and 1 from Week 7. Week 2 carries the most questions, 7 of the 25, so put the most review time on the chemistry of life. The chemistry of the body and the cell is the largest objective, with 11 questions, and homeostasis comes next with 8. Week 1's feedback loop comes back in Week 2's blood chemistry and in Week 6's thermoregulation, so learn it well. Week 8's three-step read is not scored on its own, and practicing it is still good review, because it pairs each structure with its job.

Topic-by-topic review

Each topic gives the key idea in plain words, the course's own definitions, a course example, and the mistakes students make most often with the cure for each. The deeper review for every topic is that week's chapter, lecture page, slide deck, and readings.

Week 1 — Body organization, homeostasis, and anatomical terminology

  • Key idea: the body is described from one fixed pose, built in levels, and held steady by loops that sense, compare, and correct.
  • Two views of one thing: anatomy is the study of the body's structures: what the parts are, how each one is built, and where it sits. Physiology is the study of how the body's parts work, alone and together, to keep a person alive. Structure determines function, and every structure is read in one order: structure, then function, then the clinical connection.
  • The characteristics of life: the seven properties this course uses: the body is organized, carries out metabolism, responds to change, moves, develops, grows, and reproduces. Conventions differ on the list; this course uses these seven.
  • Levels of structural organization, in order: chemical → cellular → tissue → organ → organ system → organism. A new capability appears at each step: a heart cell twitches, but only the organ pumps. A tissue is a group of similar cells working together on one job. The course names eleven organ systems.
  • Homeostasis: the maintenance of a stable internal environment. A set point is the target value a regulated variable is held near, about 37 °C for body temperature. A normal range is the narrow band of values around a set point in which the body works best.
  • The three parts of every loop: a receptor senses the current value and reports it; a control center compares the report with the set point and its normal range; an effector acts to change the regulated variable and reverse the change.
  • Feedback by direction: negative feedback reverses a change and brings the variable back toward its set point, and it runs most of physiology (body temperature, blood glucose, blood pH). Positive feedback intensifies a change until an end event stops it, as in childbirth or blood clotting. The names mean direction, not good or bad.
  • The anatomical position: standing upright, feet parallel and about shoulder-width apart, upper limbs at the sides, and palms facing forward. Every directional term is read from that pose, so the thumb is lateral.
  • The five directional pairs: superior/inferior (toward the head / toward the feet); anterior/posterior, also ventral/dorsal (toward the front / toward the back); medial/lateral (toward the midline / away from it); proximal/distal (closer to / farther from where a limb attaches to the trunk, limbs only); superficial/deep (toward / away from the surface). A directional statement always names the two structures compared, and left and right are always the body's own.
  • The three planes, each named by the two parts it makes: a sagittal plane makes left and right parts (a midsagittal plane passes through the midline); a frontal plane, also called the coronal plane, makes front and back parts; a transverse plane makes top and bottom parts, a cross-section.
  • The cavities: the dorsal cavity holds the cranial cavity, around the brain, and the vertebral cavity, around the spinal cord. The ventral cavity is split by the diaphragm into the thoracic cavity above (two pleural cavities, the pericardial cavity, and the mediastinum between them) and the abdominopelvic cavity below. A serous membrane has a parietal layer on the cavity wall and a visceral layer on the organ. The abdomen is divided into four quadrants or nine regions, the clinic's address system.
  • Course example (illustrative, not real data): the body-temperature loop on a clinic chart. The set point is 37.0 °C and the model band runs from 36.5 to 37.5 °C. The low reading, 36.0 °C, sits 37.0 − 36.0 = 1.0 °C below the set point and below the band, so the effectors constrict the dermal arterioles, shiver, and raise goosebumps. The middle reading, 37.0 °C, is at the set point, so nothing needs correcting. The high reading, 38.5 °C, sits 38.5 − 37.0 = 1.5 °C above, so the effectors are sweat that evaporates and dermal arterioles that dilate. Every response opposes the change, so the loop is negative feedback.
  • Predictable mistakes → cures: (1) "anatomy and physiology are separate subjects." Cure: they are two views of one thing. (2) "negative feedback is bad." Cure: the names mean direction. (3) the control center read as the part that senses. Cure: the receptor senses, the control center compares, and the effector responds. (4) "the thumb is medial." Cure: from the anatomical position, palms forward, it is lateral. (5) proximal and distal used for the trunk or the head. Cure: they are for the limbs only. (6) "the sagittal plane separates front and back." Cure: sagittal makes left and right; the frontal plane makes front and back. (7) the heart and lungs placed in the abdominal cavity. Cure: they sit in the thoracic cavity, superior to the diaphragm. (8) left and right read as the viewer's. Cure: they are always the body's own.

Week 2 — The chemistry of life

  • Key idea: a bond is named by its verb, water's uneven charge explains its jobs, and the pH scale counts tenfold steps, never ruler marks.
  • Atoms and elements: an atom is built from protons, neutrons, and electrons. The number of protons in the nucleus, the atomic number, decides which element an atom is. Oxygen, carbon, hydrogen, and nitrogen make up about 96% of body mass (about 65%, 18%, 10%, and 3%). Calcium, phosphorus, potassium, sodium, chlorine, and magnesium are named because later weeks need them as ions.
  • The three bonds: an ionic bond transfers: one atom transfers an electron to another, and the two oppositely charged ions attract, as sodium and chloride do in table salt. A covalent bond shares one or more pairs of electrons: evenly in a nonpolar covalent bond, unevenly in a polar covalent bond. A hydrogen bond is a weak attraction between a slightly positive hydrogen on one molecule and an electronegative atom on a neighboring molecule, drawn as a dotted line.
  • Water: in one water molecule the oxygen is δ− and each hydrogen is δ+, an uneven spread of charge called polarity. The bonds inside one water molecule are polar covalent; the hydrogen bonds sit between molecules. Polarity gives water four jobs in your body: the solvent in which your reactions happen, a heat sink that absorbs heat with little rise in its own temperature, the lubricant in synovial and pleural fluid, and a reactant consumed in hydrolysis and produced in dehydration synthesis. Water is up to about 60% of an adult's body mass.
  • pH: a measure of hydrogen-ion concentration on an inverse logarithmic scale from 0 to 14, with 7 neutral and each whole unit a tenfold change. Lower pH means more hydrogen ions and more acidic. Count the whole-unit steps first, then raise ten to that power.
  • Acids, bases, and buffers: an acid adds hydrogen ions to a solution; a base adds hydroxide ions or takes up hydrogen ions. A buffer is a weak acid paired with its conjugate base. It soaks up modest amounts of added acid or base, so the pH resists change, but only up to its capacity.
  • The blood's range: your blood is held between 7.35 and 7.45, typically 7.4, with the bicarbonate system as its main buffer. Below 7.35 is acidosis; above 7.45 is alkalosis. Working muscle makes CO₂, CO₂ makes carbonic acid, and buffers and breathing hold the line. That is homeostasis in chemistry.
  • The four classes of organic compounds: carbohydrates are built from monosaccharides; lipids such as a triglyceride (one glycerol joined to fatty acids) have no single repeating building block; proteins are chains of amino acids, of which 20 kinds make up nearly all human proteins; nucleic acids are built from nucleotides. A protein's sequence sets its shape, and its shape sets its job. Denaturation is the unfolding of a protein's shape by heat, a change in pH, or another physical or chemical stress, which can cost the protein its function.
  • ATP: adenosine triphosphate, a molecule of adenine, ribose, and three phosphate groups that releases usable energy when one phosphate group is split off.
  • Course example: pH 4 against pH 7. From 4 up to 7 is 4 to 5, 5 to 6, and 6 to 7, three whole-unit steps, so 10³ = 10 × 10 × 10 = 1,000 times more hydrogen ions at pH 4. The companion, pH 5 against pH 7, is two steps, so 10² = 100 times, never 20. An illustrative chart value of 7.0 sits below 7.35, on the acidosis side; the drop from 7.4 is 7.4 − 7.0 = 0.4 of a unit, described in words as a meaningful rise in hydrogen ions.
  • Predictable mistakes → cures: (1) a hydrogen bond mistaken for the bond inside water. Cure: polar covalent inside the molecule, hydrogen bonds between molecules. (2) "pH 4 is three times more acidic than pH 7." Cure: three steps means 1,000 times. (3) "two units is twentyfold." Cure: two steps is 10 × 10 = 100. (4) "a higher pH means more acidic." Cure: lower pH, more hydrogen ions. (5) "a buffer holds blood at pH 7" or "never lets it change." Cure: it resists change and holds blood near 7.4, and an overwhelmed buffer means acidosis or alkalosis. (6) a lipid given a single monomer. Cure: a triglyceride is glycerol plus fatty acids.

Week 3 — The cell and membrane transport

  • Key idea: the membrane is a gate, each organelle has one job, and water follows solute.
  • The plasma membrane: the border of every cell, a phospholipid bilayer of two rows of phospholipids with their phosphate heads facing the water on both sides and their nonpolar, hydrophobic tails tucked inward, studded with channel, carrier, and receptor proteins. It is selectively permeable: only certain substances cross it without help from a membrane protein.
  • Organelles and their jobs: the nucleus holds the DNA (46 chromosomes in human body cells), and its nucleolus makes the RNA used to build ribosomes. Ribosomes build proteins. The rough ER makes and modifies proteins headed for the membrane or for export. The smooth ER makes phospholipids and steroid hormones, stores and regulates Ca²⁺, and detoxifies some substances. The Golgi apparatus modifies, sorts, and ships. Lysosomes break down worn-out cell parts. Mitochondria convert the energy in nutrients into ATP. The cytoskeleton holds the cell's shape. Cilia beat, and a flagellum propels.
  • Passive transport (no ATP, downhill): diffusion, the net movement of particles from higher to lower concentration; facilitated diffusion, diffusion through a membrane protein for substances that cannot cross the bilayer because of their size, charge, or polarity; and osmosis, the diffusion of water across a selectively permeable membrane toward the side with more solute. Water follows solute. Osmosis moves water, not salt.
  • Tonicity, read from the cell's side in three moves: compare the bath with the cell, name the bath, then state where the water goes. A hypotonic bath has less solute than the cell, so water moves in and the cell swells and may burst. An isotonic bath matches, so there is no net movement. A hypertonic bath has more, so water moves out and the cell shrinks. An IV fluid is isotonic so the body's cells neither swell nor shrink.
  • Dilution: C₁V₁ = C₂V₂. The starting concentration times the starting volume equals the new concentration times the new volume, so doubling the volume halves the concentration.
  • Active transport: movement against the concentration gradient, paid for with ATP. Active means uphill and paid for, not fast. The sodium-potassium pump moves 3 Na⁺ out and 2 K⁺ in per ATP, in that order.
  • Bulk transport: endocytosis brings material in inside a vesicle (phagocytosis for particles, pinocytosis for fluid); exocytosis releases a vesicle's contents outside.
  • Course example (illustrative): a model cell at 300 mOsm/L in three baths. The 100 mOsm/L bath: 100 < 300, hypotonic, water moves in, and the cell swells. The 300 mOsm/L bath: 300 = 300, isotonic, no net movement. The 500 mOsm/L bath: 500 > 300, hypertonic, water moves out, and the cell shrinks. Diluting the 300 mOsm/L solution into twice the volume gives 300 ÷ 2 = 150 mOsm/L, which is hypotonic to the model cell.
  • Predictable mistakes → cures: (1) the ribosome, the Golgi apparatus, and the mitochondrion swapped. Cure: build, ship, and power, in that order. (2) "osmosis moves the salt." Cure: osmosis moves water. (3) hypotonic and hypertonic flipped. Cure: read the bath from the cell's side. (4) "active transport means fast or through a protein." Cure: it means against the gradient and paid in ATP. (5) the pump stated as 2 Na⁺ out and 3 K⁺ in. Cure: 3 Na⁺ out, 2 K⁺ in, per ATP.

Week 4 — Cellular energy and protein synthesis

  • Key idea: ATP is spent and remade all the time, respiration runs three stages in three places, and transcription writes before translation reads.
  • ATP as currency, not a battery: cleaving the third phosphate releases energy, so ATP → ADP + phosphate + energy. ADP is the molecule left when ATP gives up its third phosphate; energy from food adds the phosphate back to remake ATP.
  • Cellular respiration in order, with places: glycolysis (cytoplasm) → citric acid cycle, also called the Krebs cycle (mitochondrial matrix) → electron transport chain (inner mitochondrial membrane). Glycolysis splits one glucose into two pyruvate, uses two ATP and makes four for a net gain of two, and needs no oxygen. In the citric acid cycle, the carbons of pyruvate leave as CO₂ and the electron carriers are loaded. At the chain, electrons, oxygen, and hydrogen ions combine to form water: oxygen is the final electron acceptor, and the chain makes the most ATP by far.
  • The total, in words: the older theoretical estimate is about 36 ATP per glucose, and current estimates are nearer 30 to 32. The total is an estimate to learn in words, never one number.
  • Aerobic and anaerobic: when oxygen is short, pyruvate is converted to lactic acid so glycolysis can keep running, the fast, low-yield backup behind the burn you feel in a sprint. A steady jog leans on the oxygen-using stages and the chain's larger yield.
  • From gene to protein: a gene is a functional segment of DNA that carries the information to build a protein. Transcription writes a complementary mRNA in the nucleus, using RNA polymerase; RNA uses uracil in place of thymine, so adenine pairs with uracil and an mRNA never carries a T. Translation reads the mRNA at a ribosome: a codon is three mRNA bases for one amino acid, and each tRNA's anticodon matches its codon. AUG is the start codon for methionine, and UAA, UAG, and UGA are the stops. Every codon is read from the supplied standard table.
  • Why physiology cares: proteins are the enzymes, channels, pumps, contractile fibers, and collagen of every system, so one changed codon can change one amino acid, one shape, and one job.
  • Course example: the gene decoded. The template 3′-TAC CGA GTA TTC CCA ATT-5′ gives the mRNA 5′-AUG GCU CAU AAG GGU UAA-3′, which reads Met–Ala–His–Lys–Gly, then the stop UAA. Six codons × 3 bases = 18 mRNA bases, and 6 codons − 1 stop codon = 5 amino acids. Glycolysis: 4 ATP made − 2 ATP used = a net 2 ATP per glucose.
  • Predictable mistakes → cures: (1) ATP pictured as a battery stored for days. Cure: it is spent and remade all the time. (2) "glycolysis or the citric acid cycle makes the most ATP." Cure: the chain does. (3) the cycle placed in the cytoplasm. Cure: it runs in the mitochondrial matrix. (4) "oxygen is broken down for energy." Cure: it is the final electron acceptor, forming water. (5) "lactic acid builds up when oxygen is plentiful." Cure: it forms when oxygen is short. (6) transcription and translation swapped. Cure: transcription writes in the nucleus; translation reads at the ribosome. (7) one base per amino acid. Cure: three bases make one codon. (8) a T written into an mRNA. Cure: RNA uses U.

Week 5 — Tissues

  • Key idea: every organ is a mix of four tissue types, and each tissue's build explains its job.
  • The four primary tissue types, by their verbs: epithelial tissue covers and lines; connective tissue supports, binds, and protects; muscle tissue contracts to move; nervous tissue communicates by electrochemical signals. An organ is never one tissue; the skin is built from all four. Histology is the study of tissues under the microscope.
  • Epithelium's signatures: packed with cells and little material between them; an apical surface (the free surface) and a basal surface resting on a basement membrane; and avascular, so no blood vessel crosses the basement membrane and nutrients arrive by diffusion.
  • The two-word name, layers first and shape second: simple is one layer and stratified is stacked layers (pseudostratified is also named); squamous is flat, cuboidal is cube-shaped, and columnar is column-shaped. Simple squamous lines the alveoli and the capillaries, the shortest diffusion path. Stratified squamous forms the skin and lines the mouth, where outer layers can be lost to wear. Simple columnar lines most of the digestive tract.
  • Glands: an exocrine gland releases its secretion through a duct onto a surface or into a cavity; an endocrine gland is ductless, so its secretion passes into the tissue fluid around it and on into the blood.
  • Connective tissue: cells scattered in a matrix of ground substance and protein fibers (collagen, elastic, and reticular) that the cells themselves make. This course uses three categories: connective tissue proper, loose or dense, with tendons and ligaments as dense regular connective tissue; supportive connective tissue, cartilage and bone, where cartilage has no blood vessels and is slow to heal; and fluid connective tissue, blood and lymph. Blood is a connective tissue whose cells travel in a liquid matrix, the plasma.
  • The three muscle tissues: skeletal is long, cylindrical, and striated, with many nuclei at the edge of each fiber, and voluntary. Cardiac is short, branched, and striated, usually with one central nucleus, joined by intercalated discs, and found only in the heart wall. Smooth is spindle-shaped, unstriated, with one nucleus, and involuntary, moving the walls of hollow organs.
  • Nervous tissue: large neurons that carry signals, among smaller neuroglia that support them.
  • The four tissue membranes: mucous lines a cavity open to the outside; serous lines a closed cavity and covers its organs; cutaneous is the skin; synovial lines the cavity of a freely movable joint.
  • Course example: the seven slides, each named type, subtype, location, function. One layer of flat cells on a basement membrane is epithelial, simple squamous, in the alveoli and capillary linings, the thinnest barrier. Striated branching cells joined by intercalated discs are cardiac muscle in the heart wall, for pumping. The count is 2 epithelial + 2 connective + 2 muscle + 1 nervous = 7 slides, and 4 tissue types appear.
  • Predictable mistakes → cures: (1) "blood is a muscle" or "only a fluid." Cure: it is a connective tissue, cells in a fluid matrix. (2) "epithelium is full of blood vessels." Cure: it is avascular. (3) squamous, cuboidal, and columnar read as numbers of layers. Cure: they are shapes. (4) cardiac and skeletal confused because both are striated. Cure: look for the intercalated discs. (5) "simple is stratified." Cure: simple is single; stratified is stacked.

Week 6 — The integumentary system

  • Key idea: the skin is a whole organ in layers, with its own glands and its own place in the temperature loop.
  • The system: the integumentary system is the skin together with its accessory structures, the hair, nails, and glands, and it is the body's largest organ system. The skin is a true organ, built from all four tissue types.
  • The layers, surface down: the epidermis is the thin outer layer, a keratinized stratified squamous epithelium. It is avascular, so its living cells are fed by diffusion from the dermis below. The dermis is the thick, vascular connective-tissue layer holding the skin's blood vessels, nerves, glands, and hair follicles; its upper papillary layer is loose connective tissue that rises into the dermal papillae, and its deeper reticular layer is dense irregular connective tissue. The hypodermis of loose areolar connective tissue and fat insulates and cushions, and it is usually not counted as part of the skin itself.
  • Two cells, two products: a keratinocyte makes and stores keratin, for toughness and water resistance. A melanocyte, in the deepest epidermal layer, makes melanin, the pigment that colors skin and hair and shields the living epidermal cells from UV damage.
  • The strata, deep to superficial: stratum basale → stratum spinosum → stratum granulosum → stratum lucidum (thick skin only) → stratum corneum. Thin skin has 4 layers; the thick skin of the palms and soles adds the lucidum, so 4 + 1 = 5. Born at the bottom, dead armor at the top.
  • Accessory structures: a hair is a filament of keratin from a follicle, and the arrector pili muscle contracts to stand it up as goosebumps. A nail is a plate of tightly packed dead keratinocytes. A sebaceous gland secretes sebum, an oily lipid mix that lubricates and waterproofs. An eccrine sweat gland releases watery, hypotonic sweat with a little salt that cools the body as it evaporates. An apocrine sweat gland, in the armpits and groin, releases a thicker secretion that skin bacteria break down into odor.
  • The skin's five jobs: protection (against microbes, chemicals, and water loss), sensation (touch, surface temperature, and pain), thermoregulation, vitamin D synthesis under UV light, and excretion of small amounts of waste in sweat.
  • Thermoregulation: the Week 1 negative-feedback loop run on the skin. Against overheating, eccrine sweat evaporates and the dermal arterioles dilate (vasodilation). Against cold, the dermal arterioles constrict (vasoconstriction), sweating stops, the arrector pili raise goosebumps, and skeletal muscles shiver.
  • Course example (illustrative, not real data): the temperature readings again, now with the effectors named by structure: at 36.0 °C, 1.0 °C below the set point, the dermal arterioles constrict, the eccrine glands stop, the arrector pili contract, and skeletal muscles shiver; at 38.5 °C, 1.5 °C above, eccrine sweat evaporates and the dermal arterioles dilate. A scrape that does not bleed reached only the avascular epidermis; bleeding begins when an injury reaches the vascular dermis.
  • Predictable mistakes → cures: (1) "the epidermis is full of blood vessels." Cure: it is avascular. (2) "the hypodermis is the deepest layer of the skin." Cure: it lies below the skin proper. (3) melanin and keratin swapped. Cure: melanin is pigment and a UV shield; keratin is toughness. (4) the strata out of order. Cure: born at the bottom, dead armor at the top. (5) "sweating warms you." Cure: evaporation cools. (6) sebaceous glands said to make sweat. Cure: they make sebum. (7) "the skin digests food or makes ATP." Cure: neither is on the skin's job list.

Week 7 — Bone tissue and structure

  • Key idea: bone is a living tissue that is built, kept, and broken down by its own cells for life.
  • Bone is alive: bone tissue is a living supportive connective tissue with blood vessels, nerves, and cells inside a hard, calcified matrix, and it answers to the stress placed on it. Astronauts on long missions can lose roughly 1 to 1.5 percent of their bone density per month, an estimate to learn in words.
  • Six jobs of the skeletal system: support, movement, protection, blood cell production (hematopoiesis, in the red marrow), mineral storage and release (calcium and phosphorus), and fat storage (triglycerides in the yellow marrow).
  • Five shape classes: long (the femur, the humerus, the phalanges), short (the carpals and tarsals), flat (the sternum, ribs, scapulae, and cranial bones), irregular (the vertebrae and facial bones), and sesamoid (the patellae). The class names a shape, not a size.
  • The long bone: the diaphysis is the tubular shaft; each epiphysis is a wider end, filled with spongy bone. The metaphysis between them holds the epiphyseal plate, a layer of hyaline cartilage in a growing bone, which becomes the epiphyseal line in adulthood. Articular cartilage reduces friction and absorbs shock. The periosteum is the fibrous outer membrane, and the endosteum lines the medullary cavity, which holds yellow marrow. Diaphysis = shaft; epiphysis = end.
  • Compact and spongy bone: compact bone's unit is the osteon, or Haversian system: concentric lamellae around a central canal carrying blood vessels, nerves, and lymphatic vessels, with osteocytes in lacunae linked by canaliculi. Spongy bone is a lattice of trabeculae with red marrow in the spaces, and it has no osteons.
  • The four bone cells: osteogenic cells become osteoblasts; osteoblasts build new bone; osteocytes maintain the matrix; osteoclasts resorb bone, breaking it down and releasing calcium. Blast builds; clast resorbs.
  • Formation and growth: in intramembranous ossification, bone forms straight from mesenchyme with no cartilage model first (the clavicles, the flat bones of the face, and most cranial bones). In endochondral ossification, a hyaline-cartilage model comes first and bone replaces it (the long bones and the skull base). A long bone lengthens at its epiphyseal plate until early adulthood and widens by appositional growth under the periosteum.
  • Remodeling: for life, osteoclasts remove bone and osteoblasts build it, in response to mechanical stress. More stress means more deposition; less stress, as in long spaceflight, means bone is lost.
  • The calcium loop: a typical blood calcium level is about 10 mg/dL, learned in words. When blood calcium drops, parathyroid hormone stimulates osteoclasts to resorb bone and release calcium, so blood calcium rises. When it climbs too high, calcitonin inhibits osteoclasts, so blood calcium falls. Both responses oppose the change, so this is negative feedback with the same three loop parts as Week 1.
  • Course example: the bone key counts 6 functions + 5 classes + 4 cells + 2 ossification routes + 3 loop parts = 20 items.
  • Predictable mistakes → cures: (1) "bone is dead mineral." Cure: it is living tissue that remodels for life. (2) "osteoblasts break down bone." Cure: blast builds, clast resorbs. (3) "the epiphysis is the shaft." Cure: the diaphysis is. (4) "spongy bone is made of osteons." Cure: it is trabeculae. (5) "long bones lengthen from the middle." Cure: they lengthen at the growth plates near the ends. (6) "adult bone never changes." Cure: it remodels continuously.

Week 8's new tool (not scored on its own)

The three-step read is a reading discipline for any structure: name the structure and where it sits, state its function and how its shape makes that possible, then name one clinical connection in standard terms and stop. A clinical connection names one condition or clinical situation that illustrates how a structure's form serves its function, with no treatment or advice. An ordered read is a process stated as a chain of steps in the one order in which they happen, with the place of each step named. The course runs the three-step read on structures you already know, and it will carry the skeleton, the muscles, the nervous system, and the senses ahead.

Representative practice

These are fresh variants, not the midterm's questions. Work each worked example yourself first, then compare your steps. Every number below is a value the course pinned or arithmetic on those values, computed and checked in advance, and every model dataset is labelled illustrative.

Worked example — loops, directions, and the chart's band (Week 1)

Sort two loops by direction:

  • After a family dinner, blood glucose rises, and the body brings it back down toward its set point. The response reverses the change, so this is negative feedback.
  • A kitchen knife nicks a finger while chopping vegetables, and each clotting substance that is activated recruits more until a clot forms. The response builds on itself until an end event, so this is positive feedback.

Read three directions and one plane on a virtual atlas:

  • The pelvis is inferior to the abdomen, so it sits toward the feet.
  • The skin is superficial to the bones, and the brain is deep to the skull.
  • A cut down the midline that makes equal left and right halves is a midsagittal plane.
  • The spinal cord sits in the vertebral cavity, part of the dorsal cavity.

Recompute the chart's band (illustrative):

  • The model band's width is 37.5 − 36.5 = 1.0 °C.
  • The high reading sits 38.5 − 37.5 = 1.0 °C above the top of the band.
  • The low reading sits 36.5 − 36.0 = 0.5 °C below the bottom of the band.

Why it matters: the loop name tells you the direction of the response, and every directional statement names two structures read from one fixed pose.

Worked example — steps, shares, and water at work (Week 2)

Count the steps, then raise ten:

  • pH 4 against pH 5 is one whole-unit step, so 10¹ = 10 times more hydrogen ions at pH 4.
  • pH 5 against pH 7 is two steps, so 10² = 100 times more at pH 5.
  • Chain them: 10 × 100 = 1,000, the same as counting the three steps from pH 4 to pH 7 at once. Steps multiply by ten each time; they never add like ruler marks.

Do the element arithmetic: 65 + 18 + 10 + 3 = 96, so oxygen, carbon, hydrogen, and nitrogen make up about 96% of body mass. That leaves 100 − 96 = 4% for every other element, calcium and phosphorus among them.

Match water's job to the scene:

  • Table salt dissolves in the plasma of the blood: water is the solvent.
  • On a bike ride, the fluid inside each knee joint keeps the bone ends gliding: water is the lubricant in synovial fluid.
  • A larger molecule is split into smaller pieces as a water molecule is used up: water is a reactant in hydrolysis.

Name the bond by its verb:

  • Two atoms share a pair of electrons evenly: a nonpolar covalent bond.
  • One atom transfers an electron to another, and the two charged ions attract: an ionic bond.

Why it matters: the pH scale counts tenfold steps, and each of water's jobs traces back to its polarity.

Worked example — a diluted bath, a salad, and the pump (Week 3)

Dilute a hypertonic bath (illustrative): take the 500 mOsm/L bath and double its volume.

  • C₁V₁ = C₂V₂ becomes 500 mOsm/L × 1 volume = C₂ × 2 volumes.
  • C₂ = 500 ÷ 2 = 250 mOsm/L.
  • Compare with the model cell: 250 < 300, so the diluted bath is hypotonic. Water moves in, and the cell swells.

A wilted salad in a kitchen: a salty dressing sits on lettuce leaves. The dressing has more solute than the leaf cells, so it is hypertonic to them. Water moves out of the cells, and the leaves go limp. The water moves, not the salt.

Count the pump for 4 ATP:

  • Sodium out: 3 × 4 = 12 Na⁺.
  • Potassium in: 2 × 4 = 8 K⁺.
  • In all, 12 + 8 = 20 ions moved, and 12 − 8 = 4 more ions leave than enter. Each one moves against its gradient, so this is active transport.

Why it matters: a bath's name depends only on how it compares with the cell, so a dilution can flip a bath from shrinking the cell to swelling it.

Worked example — a codon check and the energy chain (Week 4)

Check a protein's length with a codon chart: a protein of 5 amino acids needs 5 codons plus 1 stop codon, so 5 + 1 = 6 codons, and 6 × 3 = 18 mRNA bases. That is the pinned gene: Met–Ala–His–Lys–Gly, then UAA.

Read the first three codons alone: AUG GCU CAU is 3 codons × 3 bases = 9 bases, and the table reads them as Met–Ala–His. With no stop codon yet, translation would keep going.

Catch the stray T: a classmate writes the second codon of that mRNA as GCT. An mRNA never carries a T, so the codon is GCU, which the table reads as Ala.

Recompute the glycolysis line of the course example: 4 ATP made − 2 ATP used = a net 2 ATP per glucose, and 1 glucose → 2 pyruvate. The chain, not glycolysis, makes the most ATP.

Say the order and the places: glycolysis (cytoplasm) → citric acid cycle (mitochondrial matrix) → electron transport chain (inner mitochondrial membrane).

Spend and recharge: ATP → ADP + phosphate + energy, and the energy in food adds the phosphate back. ATP is spent and remade all the time, never stored for days like a battery.

Why it matters: a protein's length is the codon count minus the stop, and each stage of respiration has one fixed place.

Worked example — name the tissue from its job (Week 5)

Predict the epithelium from the job, at a microscope:

  • The stomach lining: simple columnar epithelium, the epithelium that lines most of the digestive tract.
  • A capillary wall: simple squamous epithelium, because one flat layer is the shortest path for diffusion.

Sort a described tissue into its family:

  • A tendon packed with fibers that run in one line: connective, dense regular connective tissue, which resists pull along that line.
  • Cells that travel in a liquid matrix inside the vessels: connective, blood, with plasma as its matrix.
  • Short, branched, striated cells joined end to end by intercalated discs: muscle, cardiac, the heart wall.

Count the course's lists: 3 muscle tissues, 4 tissue membranes, and 4 primary tissue types.

Why it matters: the amount of matrix sorts epithelial from connective tissue, and the two-word name predicts the job.

Worked example — a tan, an oily scalp, and two dermal layers (Week 6)

Trace a summer tan through structure: after an afternoon outdoors, melanocytes in the stratum basale make more melanin. Melanin colors the skin and absorbs UV light, shielding the living cells beneath. This is not keratin, which gives toughness and water resistance.

Trace an oily scalp in a morning routine: the oil is sebum, made by sebaceous glands in the dermis. Sebum lubricates and waterproofs skin and hair. Sebaceous glands make sebum, not sweat.

Trace a fingernail: a nail is a plate of tightly packed dead keratinocytes, so it shares its toughness with the epidermis.

Read the dermis in two layers: the upper papillary layer is loose connective tissue with dermal papillae; the deeper reticular layer is dense irregular connective tissue.

Why it matters: every skin phenomenon traces to one named structure and its job.

Worked example — sort, slice, and spaceflight (Week 7)

Sort five bones on a virtual skeleton, one per class:

  • Humerus: long.
  • A tarsal: short.
  • A scapula: flat.
  • A facial bone: irregular.
  • A patella: sesamoid.
  • Count the classes: 1 + 1 + 1 + 1 + 1 = 5.

Read a diaphysis in cross-section, outside in: periosteum → compact bone → endosteum → medullary cavity with yellow marrow.

Bone in spaceflight: with little load on the skeleton, less bone is deposited and bone is lost, roughly 1 to 1.5 percent of density per month on long missions, an estimate in words. The cell that removes bone is the osteoclast, so remodeling shows bone answering to stress.

Name a route: most cranial bones form by intramembranous ossification, straight from mesenchyme with no cartilage model first.

Why it matters: bone is living tissue, so its cells keep building and removing it in response to load.

Worked example — the three-step read (Week 8)

Run the read on two structures you already know.

  • The plasma membrane: a phospholipid bilayer at the border of every cell → selectively permeable, so water follows solute across it → an IV fluid is mixed to be isotonic so the body's cells neither swell nor shrink; stop.
  • The epiphyseal plate: a layer of hyaline cartilage in the metaphysis of a growing long bone → the zone where the bone lengthens until early adulthood → a fracture through a child's growth plate reaches that lengthening zone; stop.

Why it matters: the read keeps each structure tied to its job and stops at the illustration, with no treatment and no advice.

Self-check questions

Try each one, then read the check and the one-line why.

  1. Which body cavity holds the spinal cord? Check: the vertebral cavity, part of the dorsal cavity. Why: the dorsal cavity holds the cranial cavity and the vertebral cavity.
  2. A loop's response makes a change bigger until an end event stops it. Negative or positive feedback? Check: positive. Why: positive feedback intensifies a change; negative feedback reverses one.
  3. Which particle count decides which element an atom is? Check: the number of protons, the atomic number. Why: the proton count identifies the element.
  4. Which organelle breaks down worn-out cell parts? Check: the lysosome. Why: it is a membrane sac of enzymes that digests worn-out parts.
  5. Which base does an mRNA use in place of thymine? Check: uracil. Why: RNA uses U, so adenine in the template pairs with uracil.
  6. A tissue membrane lines a cavity that opens to the outside of the body. Which one is it? Check: a mucous membrane. Why: serous membranes line closed cavities.
  7. In which epidermal layer are new keratinocytes born? Check: the stratum basale. Why: it is the deepest layer, the stem-cell layer, where melanocytes also sit.
  8. Which bone cell sits in a lacuna and maintains the matrix? Check: the osteocyte. Why: osteoblasts build, osteoclasts resorb, and osteocytes maintain.

Check yourself — choose one. Write two or three sentences to a friend.

  • (a) Explain why diluting the 500 mOsm/L bath to twice its volume turns a bath that shrinks the model cell into one that swells it.
  • (b) Explain why the pinned gene needs six codons to build a protein of only five amino acids.

Either one rehearses an explain-why skill the midterm checks.

Watch before the exam

These videos come from the course's Readings & Resources pages for Weeks 1 to 8, and every one has captions. Use them to review and to connect weeks, not to learn anything new.

Study plan

A short countdown. Count back from the day you plan to sit the midterm.

  • Two weeks out: as you finish Week 6, start a one-page list of the course's swapped pairs: medial and lateral, sagittal and frontal, covalent and ionic, hypotonic and hypertonic, transcription and translation, epithelial and connective, epidermis and dermis. Add osteoblast and osteoclast when Week 7 arrives.
  • One week out: as you finish Week 7, reread the topic reviews above for Weeks 1 and 2, the weeks furthest back and the heaviest on the midterm.
  • At the start of Week 8: take the practice exam once, cold and closed-note. Note which objectives cost you the most. Its mix leans away from Week 2, so check the chemistry of life on your own as well.
  • Three or four days before you sit it: reread the topic reviews for your two weakest objectives, and redo the matching worked examples from scratch without looking.
  • Two days before: run the paired exam-prep tutorial (the copy-and-paste chatbot tutor, or its no-AI route) for active recall. Tell it which areas the practice exam exposed.
  • The day before: retake the practice exam, explain every miss out loud, and work the self-check questions above.
  • Right before: say the three chains aloud, the levels of organization, the stages of respiration with their places, and the strata deep to superficial. Skim the "predictable mistakes → cures" lines for all seven weeks, and then stop studying.

This guide is for review. The exam-prep tutorial and the practice exam are where you rehearse. Pulling ideas back out of memory, not rereading, is what makes them stick.

Exam format

Every one of the 25 questions counts the same, and the midterm checks your own understanding without AI. The questions come one at a time, and there is no going back, so settle each one before you move on.

Test-taking strategies for this material:

  • Name the pair before you choose. Most questions turn on two neighboring ideas, such as covalent and ionic, hypotonic and hypertonic, or epidermis and dermis. Say which pair is in play first.
  • Count pH steps, then raise ten. Never subtract and stop there.
  • Stand the body in the anatomical position first. Then read the directional term, and name both structures it compares.
  • Run a reading through the loop. Subtract it from the set point, place it against the band, then name the effectors that oppose the change.
  • Say the order and the place. For any process, name the stages in order and where each one runs before you read the options.
  • For a "pick every option that applies" question, judge each statement on its own, as if it were a true-or-false question.

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