Week 10 — Squeeze, Slide, Tire: A Grip-Fatigue Report — Traditional alternative (no AI)

Human Anatomy and Physiology I Free sample edition

Traditional alternative (no AI), unpublished. In the course this is a separate assignment that ships unpublished beside the adaptive assignment: same objective, no AI. An instructor who prefers it publishes it and unpublishes or deletes the adaptive one, as the note at its top says.

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 9 of the term — add, average, and read a grip-fatigue series, put a squeeze's steps in order, and explain to someone new why a tiring grip slows down.

This week you learned how a skeletal muscle is built from the whole muscle down to the sarcomere, how thin and thick filaments slide past each other, the five ordered steps that turn a nerve signal into a pull, ATP's three jobs, how a fiber relaxes, how motor units and fiber types differ, and what fatigue is. Week 4 showed you that a cell short on oxygen makes lactic acid, and Week 5 introduced skeletal muscle as long, striated, voluntary tissue; this week you open a muscle fiber and watch it work. In this assignment you work four short problems on the grip-fatigue series, interpret each one, and explain a tiring grip to someone who has never studied anatomy and physiology. This week's lecture tutorial, quiz, discussion, and A&P Lab & Inquiry practise the same ideas from other angles.

The task

This week's shared dataset is Dataset G, the grip-fatigue series. It is illustrative: the course built it to land on clean numbers, and it is not one real person's data. Five 10-second all-out squeeze trials with 15-second rests gave 24, 21, 18, 15, and 12 squeezes. Every squeeze in every trial runs the same ordered chain: ACh at the neuromuscular junction → muscle action potential down the T-tubules → Ca²⁺ from the sarcoplasmic reticulum → Ca²⁺ binds troponin and tropomyosin uncovers actin → cross-bridge and power stroke (ATP).

Work these four problems, showing your arithmetic:

In the illustrative grip-fatigue series, five 10-second trials gave 24, 21, 18, 15, and 12 squeezes. How many squeezes is that in all?
The five trials of the grip-fatigue series sum to 90 squeezes. What is the average number of squeezes per trial?
The grip-fatigue series fell from 24 squeezes in trial 1 to 12 squeezes in trial 5. What is the percent decline?
Across the grip-fatigue series, the count fell by 12 squeezes over the 4 gaps between the five trials. By how many squeezes did it fall per gap?

Beside each answer, add one brief interpretation:

Problem 1: list the five steps of a single squeeze in order, and name where each step happens.
Problem 2: name the thin and the thick filament and what each is made of, and explain what slides when the sarcomere shortens.
Problem 3: name the three causes of fatigue this course uses, and explain what the falling count says about the cross-bridges and the filaments.
Problem 4: name ATP's three jobs in a working fiber, and explain why relaxation costs ATP.

Explain it to a non-expert

A friend who uses a hand gripper during long study breaks asks, "Why does my grip get slower after a few rounds? Are my muscles getting shorter or wearing out?" Write a 3–5 sentence message that explains, in everyday words, that the filaments inside a muscle fiber slide rather than shrink, that fewer cross-bridges keep cycling as a muscle tires, and what is behind that slowdown. Name one limit, for example that the course's grip series is illustrative and not anyone's real data, or that this message is about how muscle works and not about anyone's health. Put any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a relative who asks why fingers can thread a needle but also lift a heavy suitcase. Model answer: "Each nerve cell that runs a muscle controls its own team of muscle fibers, and the nerve cell plus its team is called a motor unit. When one nerve cell fires, every fiber on its team contracts together. Small teams give fine control, because switching one on moves only a few fibers at a time, which suits careful work like threading a needle. This is a simplified classroom picture, and it leaves out how the nervous system decides which teams to use."

Use that pattern for the message to your friend, with your own wording and evidence.

Show your arithmetic. A reader should be able to rebuild every result you report from the numbers given, without guessing which numbers you used or which operation you chose.

Deliverables

Submit a single report containing:

the four answers, each with the arithmetic shown and the brief interpretation the task names for that problem;
your message to your friend, explaining that the filaments slide rather than shrink, that fewer cross-bridges keep cycling as a muscle tires, what is behind that slowdown, and one limit; and
a one-line restatement of the counts you used, so your results are reproducible.

Keep it to roughly one page.

Choose how you show it. Present your report as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labeled sketch of one sarcomere before and after a contraction with a short note. Every form is graded by the same scoring criteria. 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.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

This version is designed to be completed without AI: do the arithmetic, the interpretations, and the writing yourself, without a chatbot or other AI tool. You may use a calculator or a spreadsheet for the arithmetic. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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