Principles of Human Physiology - Chapter 12a

These flashcards cover key vocabulary and concepts related to muscle physiology, focusing on skeletal muscle structure, contraction mechanisms, and excitation-contraction coupling.

Skeletal Muscle

Connected to two or more bones by tendons.

Tendon

A connective tissue that connects muscle to bone.

Epimysium

Connective tissue that surrounds a whole muscle.

Fascicles

Bundles of muscle fibers within a skeletal muscle.

Sarcoplasm

The cytoplasm of a muscle fiber.

Sarcoplasmic Reticulum

A type of smooth endoplasmic reticulum important for regulating calcium ions in muscle cells.

Myofibrils

Cylindrical structures that run the length of the muscle fiber and contain the contractile proteins.

Sarcomere

The functional unit of a muscle, defined from Z line to Z line.

Myosin

A thick filament; contractile protein that generates force during muscle contraction.

Actin

A thin filament; contractile protein that interacts with myosin for muscle contraction.

Crossbridge Cycle

A series of steps that myosin and actin undergo to contract muscles.

Excitation-Contraction Coupling

The process by which an electrical signal (action potential) triggers muscle contraction.

Troponin

A regulatory protein that, when bound to calcium ions, enables muscle contraction.

Tropomyosin

A protein that blocks myosin-binding sites on actin when muscle fibers are relaxed.

End-Plate Potential

A graded potential that occurs at the neuromuscular junction, due to the binding of acetylcholine.

Calcium ions (Ca2+)

Essential for muscle contraction; released from the sarcoplasmic reticulum.

Motor Unit

A motor neuron and all the muscle fibers it innervates.

Sliding-Filament Model

Describes the mechanism of muscle contraction by the sliding action of actin and myosin filaments.

M line

The middle line of a sarcomere, where myosin filaments are anchored.

Rigor State

A state in which myosin is tightly bound to actin without an ATP molecule.