Week 10 — Readings & Resources · Muscle Tissue & the Physiology of Contraction

Course: Anatomy & Physiology I (BIOL 2301 + BIOL 2101) · Silver Oak University (fictional sample) · Prof. Navarro
Objective covered: Objective 5 — Describe skeletal-muscle structure (the sarcomere) and explain the sliding-filament mechanism and the steps of contraction, in order, including the neuromuscular junction.

How to use this page

Everything here is a link to an external resource — open it in your browser, the same way you'd open a YouTube link. Nothing needs to be downloaded.

This week's load is deliberately light: 1 video + 2 short readings + 1 interactive atlas, grouped by the ideas from the lecture. Watch or read one item per group and you're ready for the quiz; do all of them and you'll be very comfortable. Total time is roughly 35–45 minutes if you do everything, far less if you pick one per group.

Order that matches the lecture: ① muscle structure & the sarcomere → ② the steps of contraction in order (the heart of the week) → ③ the neuromuscular junction & putting it together.

A habit to start now: before you trust any A&P claim — in these resources, in a chatbot, or anywhere — ask the questions from class: Is actin the thin filament (and myosin thick)? Do the steps run in the right order (ACh → action potential → calcium → troponin → cross-bridge)? Is the calcium coming from the sarcoplasmic reticulum?

① Muscle Structure & the Sarcomere

Maps to Lecture Segments 2–3. A muscle is built in nested layers down to the sarcomere — the contractile unit, bounded by Z discs, with actin (thin) and myosin (thick) filaments — and it shortens by sliding, not shrinking.

Video — "The Muscular System" (CrashCourse Anatomy & Physiology, on the CrashCourse channel)
🔗 https://www.youtube.com/c/crashcourse
Why it earns the click: CrashCourse's A&P series devotes its muscle episodes to exactly our week — the sarcomere, the sliding-filament model, and how a contraction is triggered. Open the channel (verified live) and search "CrashCourse Anatomy & Physiology muscles" to pull up the muscle episodes; watch one. (We link the channel rather than a single video ID because individual video URLs occasionally change — the channel is the stable entry point.) If you'd like the series opener for orientation first, the verified A&P #1 intro is here: 🔗 https://www.youtube.com/watch?v=uBGl2BujkPQ
⏱ ~10–11 min

Reading — "Anatomy and Physiology 2e," §10.2 Skeletal Muscle (OpenStax)
🔗 https://openstax.org/books/anatomy-and-physiology-2e/pages/10-2-skeletal-muscle
Why it's assigned: the cleanest plain-language statement of the muscle hierarchy (muscle → fascicle → fiber → myofibril → sarcomere), the sarcomere (Z discs; actin = thin filament, myosin = thick filament), the sarcoplasmic reticulum and T-tubules, and the neuromuscular junction — a free online textbook page, no account needed. (Use the "Previous" link for §10.1's three muscle types if you want the Week-5 callback.)
⏱ ~12 min

② The Steps of Contraction — In Order

Maps to Lecture Segments 4 & 6. The single most important idea of the week: the ordered sequence ACh at the NMJ → muscle action potential → Ca²⁺ from the SR → Ca²⁺ binds troponin (tropomyosin uncovers actin) → cross-bridge/power stroke (needs ATP) → the filaments slide.

Reading — "Anatomy and Physiology 2e," §10.3 Muscle Fiber Contraction and Relaxation (OpenStax)
🔗 https://openstax.org/books/anatomy-and-physiology-2e/pages/10-3-muscle-fiber-contraction-and-relaxation
Why it's assigned: walks the sliding-filament model step by step (the filaments slide past each other — they don't shorten), the cross-bridge cycle and the power stroke, why ATP is needed to detach the myosin head (and why rigor mortis happens without it), and the relaxation sequence — exactly the ordered process we built in class. This is the page to keep open while you study the steps.
⏱ ~12 min

③ The Neuromuscular Junction & Putting It Together

Maps to Lecture Segments 5 & 8. Where the nerve hands off to the muscle (the NMJ, using ACh), and a clickable map of the muscular system to anchor the structures.

Reading — "Anatomy and Physiology 2e," §10.1 Overview of Muscle Tissues (OpenStax)
🔗 https://openstax.org/books/anatomy-and-physiology-2e/pages/10-1-overview-of-muscle-tissues
Why it's assigned: the one-paragraph big picture — actin is pulled by myosin once calcium and the troponin–tropomyosin proteins expose the binding sites, ATP is required to keep contracting, and the muscle relaxes when calcium is removed and the sites are re-shielded. A perfect, short orientation to the whole mechanism before the detailed §10.2–10.3.
⏱ ~6 min

Interactive — InnerBody "Muscular System" Explorer (free, no download)
🔗 https://www.innerbody.com/image/musfov.html
Why it earns the click: a free, clickable atlas of the muscular system with a clear write-up of sarcomere structure (thick = myosin, thin = actin/tropomyosin/troponin) and the contraction cycle (NMJ → ACh → calcium from the SR → troponin/tropomyosin shift → cross-bridge pull). You'll use it in Lab 10 as a reference while you reason about your own grip fatigue; spend five minutes now getting comfortable navigating it.
⏱ ~5 min (browse)

Optional one-stop references (free online)

• Khan Academy — Human Anatomy & Physiology. A free unit with short articles and videos covering muscle structure, the sarcomere, and the sliding-filament mechanism. A good place to return to all term.
  🔗 https://www.khanacademy.org/science/health-and-medicine/human-anatomy-and-physiology
• GetBodySmart — interactive A&P tutorials. Clean, labeled, interactive diagrams of skeletal-muscle structure and the contraction cycle; handy when you want to drill the names and the steps.
  🔗 https://www.getbodysmart.com/

Pick-one quick path (≈20 min total)

In a hurry? Do exactly these two and you'll be ready for the quiz:
1. Read OpenStax §10.3 Muscle Fiber Contraction and Relaxation (the steps in order — the heart of the quiz).
2. Skim OpenStax §10.2 Skeletal Muscle (the sarcomere: actin = thin, myosin = thick, Z discs, the NMJ).

Heads-up (links rot): these point to outside sites that occasionally move or rename pages (YouTube video IDs especially). If a link ever fails, tell Prof. Navarro and use the OpenStax §10.1–10.3 or Khan Academy references above in the meantime.