Muscle Anatomy
The thick filament protein that forms the cross bridges.
What is myosin?
This ion is released into the sarcoplasm and triggers muscle contraction.
What is calcium (Ca²⁺)?
This is the muscle (or group) that causes the motion.
What is the agonist?
Walking your dog relies mostly on this fiber type, known for high fatigue resistance.
What are Type I fibers?
This muscle is wide in the middle and tapered at the ends where it attaches to tendons
What is a fusiform muscle?
The thin filament protein that myosin heads attach to.
What is actin?
This theory says thin filaments slide past thick filaments, shortening the sarcomere.
What is the Sliding Filament Theory?
This muscle opposes the agonist’s action.
What is the antagonist?
Arm wrestling, a deadlift, and a fastball all rely on this fiber type.
What are Type II fibers?
This long, narrow muscle has fibers running parallel along its whole length.
What is a strap muscle?
This is the smallest contractile unit of a muscle fiber.
What is a sarcomere?
This protein covers the binding sites on actin at rest, blocking myosin.
What is tropomyosin?
In this type of contraction, the muscle produces force but the joint doesn’t move, like holding a plank.
What is isometric?
This consists of a motor neuron and all the muscle fibers it innervates.
What is a motor unit?
This flat, fan-shaped muscle has fibers radiating from a narrow attachment at one end to a broad attachment at the other.
What is a triangular muscle?
These long chains of sarcomeres sit inside a muscle fiber.
What are myofibrils?
In this step, myosin heads pivot and pull the thin filaments toward the center of the sarcomere.
What is the power stroke?
In this type of contraction, the muscle lengthens while producing force, like lowering into a squat.
What is eccentric?
Muscles create more tension by recruiting more of these.
What are motor units?
This fiber arrangement gives a high range of motion but a smaller cross-sectional area and a weaker contraction.
What is a parallel arrangement?
These tunnel-like folds of the muscle fiber membrane carry action potentials deep toward the sarcoplasmic reticulum.
What are transverse tubules (T-tubules)?
Myosin needs this molecule to let go of actin. Without it, muscles stay locked, as in rigor mortis.
What is ATP?
When the agonist and antagonist contract at the same time, it’s called this.
What is co-contraction?
Neural adaptation increases strength in this way, before muscles even get bigger.
What is better recruitment of motor units?
This is the attachment site on the more stable bone, which doesn’t move during a muscle contraction.
What is the origin?