Muscle Anatomy and Physiology - Vocabulary Flashcards (Video Notes)

Three muscle tissue types that keep you alive and moving: smooth, cardiac, and skeletal.
- Smooth muscle: found in walls of hollow visceral organs (stomach, airways, blood vessels); involuntary; contracts/relaxes to push fluids and materials through via peristalsis and other movements.
- Cardiac muscle: heart muscle; striated and involuntary; keeps blood pumping; has its own pace (pacemaker-like) and intercalated discs for rapid, coordinated contraction; limited regenerative capacity.
- Skeletal muscle: the muscles you can see and feel; about 640 different muscles; striated and mostly voluntary; attach to skeleton and move it by pulling on bones.
Key takeaway: muscle tissue types differ in control (voluntary vs involuntary), location, and functional roles in movement and vital processes.

Overall organization resembles a rope made of bundles:
- Muscle contains fascicles (bundles of muscle fibers).
- Each fascicle contains many muscle fibers (muscle cells).
- Each muscle fiber contains many myofibrils.
Cellular components:
- Muscle fiber (cell) has a plasma membrane called the sarcolemma and multiple nuclei; mitochondria power ATP production.
- Inside fibers are myofibrils, which are composed of repeating units called sarcomeres.
Connective tissue layers that surround and protect:
- Endomysium: surrounds each individual muscle fiber.
- Perimysium: surrounds each fascicle.
- Epimysium: surrounds the entire muscle.
Functional integration:
- Tendons connect muscles to bones, transmitting force when muscles contract.
Nerve and blood supply:
- Each muscle is supplied by motor nerves and an arterial/venous network to deliver signals, nutrients, and oxygen.

Sarcomere: the contractile unit of a skeletal muscle; extends from one Z-line to the next.
Two main myofilaments:
- Thin filaments: actin (light, I-band regions).
- Thick filaments: myosin (dark, A-band regions).
Z-lines: borders of a sarcomere; movement during contraction brings Z-lines closer together.
Key patterning:
- I-band: region with only actin (light, exposed when sarcomere shortens).
- A-band: region with thick filaments (myosin) and overlapping thin filaments (dark).
Cross-bridges: myosin heads extend from thick filaments and attach to actin to generate force.
Regulatory proteins:
- Tropomyosin: thread-like protein that blocks myosin-binding sites on actin when the muscle is relaxed.
- Troponin: binds calcium and moves tropomyosin away from binding sites when calcium is present.
Resting state vs contraction: actin and myosin do not interact at rest because tropomyosin covers binding sites; calcium binding to troponin during contraction reveals those sites.