Week 11 A&P Lab & Inquiry: Name the Muscle, Name the Action

Human Anatomy and Physiology I Free sample edition

Part 1 — The Big Picture

This week you learned that a muscle pulls its insertion toward its origin, that muscles work in teams whose roles swap when a movement reverses, and that a limb works as a lever whose class is named by what sits in the middle. In this lab you use that knowledge the way an anatomist does. You open a free virtual atlas, find six major muscles in three opposing pairs, and record each one's region, main action, and the muscle that pulls the joint back. Then you work the forearm lever step by step and check a chatbot's account of the same muscles, catching where it mislabels an attachment, pairs the wrong action, miscomputes the effort, scrambles an order, confuses a direction, or invents a number.

Time budget: Plan for about 120 minutes.

Part 2 — The Task

Guiding question: Can you find six major muscles on a virtual atlas and, for each one, name its region, its main action, and the muscle that pulls the same joint back the other way?

Before you begin — hypothesis: Before you identify anything, write your hypothesis in the if… then… because… form: if you find each muscle's main action, then you will or will not find a second muscle that pulls the same joint the opposite way, because of a reason you can state about how muscles work.

Workshop data: Your own identifications of six muscles on a free virtual atlas, or the printed fallback captions, plus the forearm lever worked on the course's illustrative numbers

Source: Six identifications you make yourself on a free virtual anatomy atlas with the procedure in Part 3; if you cannot open an atlas, use the six printed captions in the fallback, which were written for this lab as a stand-in for an atlas view. The lever numbers are the course's illustrative forearm lever, engineered to land on clean values rather than measured.

Rows: 6 muscle identifications in the identification table and 5 steps in the lever table; the planning table has 3 rows that set up the hypothesis rather than data
Columns: muscle, region, main action, and antagonist for the identifications; step and your work with units for the lever

Part 3 — Materials & Procedure

Tools and materials

A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet)

Ways of working

structure-identification-on-a-virtual-atlas
histology-on-a-virtual-microscope
at-home-physiology-measurement-and-data-table

Procedure

Open a free virtual anatomy atlas or 3D anatomy viewer that needs no login, in any web browser, and choose the muscular system view of the whole body in the anatomical position. If your instructor names a particular atlas, use that one. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: The whole body's muscles fill the screen, seen from the front.
Before you identify anything, write your guiding question, your hypothesis, and the six muscles you plan to find in the first table in Part 4. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: The first table has its three cells filled.
Find the biceps brachii and the triceps brachii in the arm. Rotate the model if you need to see the back of the arm. Record each muscle's region, its main action, and the muscle that pulls the elbow the other way. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: Two rows of the identification table are filled.
Find the quadriceps femoris and the hamstrings in the thigh, then the gastrocnemius and the tibialis anterior in the leg. Record each one's region, main action, and antagonist. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: All six rows of the identification table are filled.
Work the forearm lever in the lever table: a 60 N load sits 36 cm from the elbow and the biceps brachii inserts 4 cm from the elbow. Name the four lever parts and the class, then multiply the load by its arm and divide by the effort arm, writing every unit. To check your arithmetic, you may type the multiplication and the division into spreadsheet cells. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: All five rows of the lever table are filled, each with a unit.
Answer the analysis questions in Part 5, then complete the critique in Part 6. Tool: A free virtual anatomy atlas or 3D anatomy viewer (Innerbody, GetBodySmart), a virtual microscope for histology (Histology Guide), free physiology simulations (PhET pH Scale, Membrane Channels, Neuron, Gene Expression Essentials), and a spreadsheet (Google Sheets or any free spreadsheet). Check: Every analysis question has a written answer.

Fallback route

When to use it: Use this route if you cannot open a free virtual anatomy atlas, if the atlas will not load on your device, or if it has no muscular system view.

Use the six printed captions below, written for this lab as a stand-in for an atlas view, to fill every cell of the identification table, then work the lever table, complete every analysis question and the critique, and submit the same items for equal credit.

This route earns the same credit as the primary route.

Six printed captions of labeled muscles, written for this lab as a stand-in for an atlas animation.

Fallback model data
Labeled muscle	What the caption shows when the muscle shortens
Biceps brachii, a two-headed muscle of the arm	The forearm rises toward the shoulder as the elbow bends
Triceps brachii, a three-headed muscle of the arm	The forearm swings straight as the elbow opens
Quadriceps femoris, a four-headed group of the thigh	The lower leg swings straight at the knee
Hamstrings, a muscle group of the thigh	The knee bends, and the thigh swings back at the hip
Gastrocnemius, a muscle of the leg	The sole presses down and the toes point away from the shin
Tibialis anterior, a muscle of the leg named for its place by the tibia	The front of the foot lifts toward the shin

Part 4 — The Scaffold

State your question and hypothesis before you look, so the identifications test an idea instead of confirming a guess.

Student scaffold table 1
Part of the plan	Your answer
The guiding question in your own words
Hypothesis (if… then… because…)
The six muscles you plan to find, in three pairs

Record each muscle as you find it, with its region, its main action, and the muscle that pulls the same joint back the other way.

Student scaffold table 2
Muscle	Region	Main action	Antagonist
Biceps brachii
Triceps brachii
Quadriceps femoris
Hamstrings
Gastrocnemius
Tibialis anterior

Work the forearm lever one step at a time with a 60 N load 36 cm from the elbow and a 4 cm effort arm, writing the unit with every number.

Student scaffold table 3
Step	Your work with units
Name the lever, the fulcrum, the effort, and the load
Lever class, and what sits in the middle
Load times load arm
Effort: the load side divided by the effort arm
Effort divided by load, and what the arm gains in return

Part 5 — Analysis Questions

For the two muscles of the arm in your table, which one is the agonist when the forearm rises and which one is the agonist when it straightens? Say what changed between the two movements and what stayed the same.
Using your lever table, how many times the load is the biceps' effort? Show the division with units, and explain in one sentence what the hand gains in return for that force.
In a curl, which bone moves and which stays fixed? Use your answer to name the biceps brachii's origin and insertion, and explain why the biceps cannot straighten the arm by itself.
Name one way an on-screen atlas, or the printed captions, differs from a living limb, and explain how that difference could lead someone to mislabel a muscle's action or to miss which bone moves.
Choose one reflection and answer it in three to five sentences: (a) which of your six identifications would be easiest for a classmate to get wrong, and how would you explain it to them? (b) which muscle's name best predicted its action or place, and why?

Part 6 — AI-Critique Moment

Choose one equal-credit critique route. Route A: ask an approved AI tool to critique your completed work, then check its response against your own evidence. Route B is the no-AI equivalent printed below.

Approved tools: Claude, Gemini, ChatGPT, Grok, Microsoft Copilot.

Prompt to paste:

I've pasted my completed Week 11 muscle and lever tables above. For each of the six muscles, tell me its main action, its region, and the muscle that pulls the joint back the other way. Say which attachment of the biceps brachii moves during a curl, the origin or the insertion, and on which bone each sits. Then classify the forearm as a lever, work out the effort the biceps must pull for a 60 N load held 36 cm from the elbow when the biceps inserts 4 cm from the elbow, and list in order the steps from the nerve signal to the biceps pulling. If you use any measurement, count, or study, give its source.

Test the response for these likely failures:

Chatbots sometimes say the biceps brachii's origin is on the radius and that the origin is the end that moves.
Chatbots often say the biceps brachii extends the forearm, or pair the quadriceps femoris with flexing the knee.
Chatbots sometimes multiply the load by the wrong arm, reporting 60 N × 4 cm ÷ 36 cm, about 6.7 N, for the biceps' effort.
Chatbots sometimes put the calcium release before acetylcholine at the neuromuscular junction when they explain how the biceps starts to pull.
Chatbots sometimes place the tibialis anterior on the back of the leg and say it points the toes down.
Asked about muscles, chatbots often state an exact total number of skeletal muscles or a real person's biceps force that this lab never gave.

In three to five sentences, quote at least two statements from the chatbot that you corrected, give the correction with evidence from your tables or Chapter 11, and name one thing the chatbot got right.

Equivalent route (no AI required)

No AI account is required for this lab. Instead of the chatbot, critique this flawed analysis, printed here in full: "In my muscle tables, the biceps brachii extends the forearm and the triceps brachii flexes it. During a curl the origin on the radius moves toward the insertion on the scapula. The tibialis anterior sits on the back of the leg and points the toes down. For the forearm lever, the effort is 60 N × 4 cm ÷ 36 cm, about 6.7 N, so the forearm is a strong first-class lever. To make the biceps pull, calcium is released first and acetylcholine arrives at the junction afterward. A fitness site I read says the body has exactly 650 skeletal muscles." Mark it up: quote each flawed sentence, name what is wrong (a mislabeled structure, a wrong structure-to-function pairing, steps out of order, a miscomputed value, a confused directional term or tissue type, or an invented figure), cite the evidence from your tables or Chapter 11, and write a corrected sentence beneath it. This route assesses the same objective (Objective 5 — explain skeletal-muscle structure from the whole muscle to the sarcomere, the sliding-filament model, and the ordered steps of excitation, contraction, and relaxation at the neuromuscular junction and inside the fiber, and describe the organization of the muscular system — origin and insertion, muscle teams, lever classes, and the major muscles by region and action) as the chatbot critique, takes comparable effort (about 30 minutes and 200–300 words), is scored by the same scoring criteria for the same credit, and its own submission artifact is the marked-up flawed analysis, posted in place of the chatbot share link and report.

Part 7 — What to Submit

All three completed scaffold tables, filled from your own atlas work or the printed fallback captions
Written answers to all five analysis questions, including your chosen reflection option
The chatbot critique report with its share link, or the equivalent route's marked-up flawed analysis

Deliverable:

A short A&P Lab & Inquiry report on naming muscles and their actions: three completed tables (the plan with your hypothesis, the six-muscle identification table, and the five-step lever table), written answers to five analysis questions, and a critique of a chatbot's account of your muscles, or, on the equivalent route, a marked-up correction of the printed flawed analysis. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text. Choose a written, recorded, or visual form for your answers; every form is graded by the same scoring criteria.

Rubric

The rubric below shows how each submitted part is evaluated; bands are full, partial, or none.

Workshop evaluation criteria
Criterion	Full	Partial	None
Hypothesis and the planned muscles set before identifying	An if… then… because… hypothesis about opposing muscles appears before the identifications, and the six planned muscles are listed in three pairs.	A hypothesis appears but lacks a because clause or is written after the identifications, or the planned muscles are missing.	No hypothesis and no planned muscles.
Muscle identification table with actions and antagonists	All six rows give a correct region, the correct main action, and an antagonist that pulls the same joint the opposite way.	Four or five rows are fully correct, or an action is swapped within a pair, or an antagonist is mispaired.	Fewer than four rows are correct, or the table is missing.
Forearm lever worked with units	The four lever parts are named, the lever is called third class because the effort sits in the middle, and the load side, the effort, and the ratio are correct with a unit on every number.	The class or a part is wrong, or one calculation step is wrong or missing its unit while the method is visible.	No lever work, or the effort is found with the wrong arms and no method shown.
Analysis in words	Questions 1 to 4 are answered accurately: the agonist swaps when the movement reverses, the ratio is tied to speed at the hand, the origin and insertion are placed with the moving bone, and one concrete limitation is named; the chosen reflection option is answered.	The questions are attempted, but one or two answers have the origin moving, call the lever strong, or give a vague limitation.	The analysis questions are not answered.
Critique of the chatbot or of the printed flawed analysis	On either route, at least two errors are quoted and corrected with evidence from the student's own tables or Chapter 11, and one correct point is acknowledged; both routes earn this band equally.	On either route, errors are named but corrected without evidence, or only one error is caught.	No critique appears on either route, or pasted output is submitted without any checking.

Quality Gate

Every identification comes from your own atlas work or the printed fallback captions, never from memory or a chatbot.
Each muscle's main action matches the chapter's list, and each antagonist pulls the same joint the opposite way.
The origin is placed on the fixed bone and the insertion on the bone that moves.
Every number in the lever table carries its unit, and the effort comes from the lever law with the load side divided by the effort arm.
No measurement, muscle count, study, or source is invented anywhere in the submission.
The critique quotes the chatbot or the flawed analysis and corrects at least two errors with evidence from your tables or Chapter 11.

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