chpt 10 pt 1: Muscle Basics, Anatomy, and Contraction

Skeletal Muscle

Attaches to and moves bones; striated and voluntary.

Cardiac Muscle

Found only in the heart; striated and involuntary.

Smooth Muscle

Found in walls of hollow organs; non-striated and involuntary.

Excitability

Ability of muscle cells to receive and respond to stimuli

Contractility

Ability of muscle cells to shorten forcibly

Extensibility

Ability of muscle cells to be stretched.

Elasticity

Ability of muscle cells to return to resting length after being stretched.

4 main functions of muscle

Movement, Maintains Posture, Stabilize Joints, Generate Heat

Myo-/Mys-/Sarco-

Prefixes meaning “muscle.”

muscle

bundle of fasicles

Fascicle

bundle of muscle fibers

Muscle Fiber/cell

elongated muscle cell

Epimysium

A dense layer of connective tissue that surrounds the entire skeletal muscle.

Perimysium

A layer of connective tissue that surrounds bundles of muscle fibers, called fascicles.

Endomysium

A thin layer of connective tissue that surrounds each individual muscle fiber (cell).

Origin

Immovable bone attachment point of a muscle.

Insertion

Movable bone attachment point of a muscle.

sarcoplasm

the cytoplasm of a muscle fibre. It is a water solution containing ATP and phosphagens, as well as the enzymes and intermediate and product

multi nuclei

muscles that contain multiple nuclei within each muscle fiber. This is a characteristic feature of skeletal muscles

sarcolemma

the plasma membrane, or outer covering, of a muscle fiber

myofibrils

rod-like structures inside cardiac and skeletal muscle fibers that are responsible for contraction

sarcoplasmic reticulum (sr)

stores, releases, and reabsorbs calcium ions (\(Ca^{2+}\)) to control muscle contraction and relaxation

T-tubules

invaginations of the cell membrane that extend deep into the cytoplasm of muscle cells

Terminal Cisternae

enlarged regions of the sarcoplasmic reticulum in muscle cells that are responsible for storing and releasing calcium ions

A band

a dark-appearing region in the center of a muscle's sarcomere,

I band

a part of the sarcomere, the repeating unit of muscle contraction

H zone

the central region of a sarcomere that contains only thick myosin filaments and lacks thin actin filaments

Z disc

located at the borders of the sarcomere, the functional unit of muscle contraction.

Actin

a protein that plays a crucial role in muscle contraction

Myosin

a protein that plays a crucial role in muscle contraction

Tropomysin

a protein that blocks myosin from binding to actin filaments in muscle fibers when the muscle is relaxed

Troponin

activating myosin ATPase activity and muscle contraction

neuromuscular junction

the synapse where a motor neuron transmits a signal to a muscle fiber, causing it to contract

Acetylcholine (ACh)

a crucial neurotransmitter that plays a vital role in both the central and peripheral nervous systems, enabling communication between nerve cells and other cells like muscles and glands

Action potentiol

a rapid, electrical impulse that travels down a neuron's axon, allowing for communication between cells in the nervous system

latent period

the brief time interval between the arrival of a nerve impulse at the muscle fiber and the onset of visible muscle contraction

crossbridge cycling

the repetitive process of myosin heads binding to and pulling on actin filaments, causing muscle contraction

power stroke

the movement of the myosin head (a protein) along the actin filament (another protein) that generates force and causes the muscle to shorten

Cocking

the process during muscle contraction when the myosin head moves into a high-energy

Triad

a substructure in skeletal muscle formed by a T-tubule flanked by two terminal cisternae of the sarcoplasmic reticulum (SR)

Excitation-Contraction Coupling

the process that links an electrical signal to a mechanical action, converting a neural signal into a muscle contraction

Crossbridge Release

the crucial step in the muscle contraction cycle where the myosin head detaches from the actin filament.

Myosin Reset

the reactivation of the myosin head after a power stroke, returning it to a "cocked" position ready for the next muscle contraction cycle