Chap 10 Muscle Terms

skeletal muscle tissue

A striated, multinucleated muscle tissue under voluntary control, responsible for moving the skeleton and maintaining posture.

smooth muscle tissue

Non-striated, involuntary muscle tissue found in the walls of hollow organs (e.g., intestines, blood vessels), regulating internal movements such as digestion and blood flow

cardiac muscle tissue

Striated, involuntary muscle tissue found in the heart, characterized by intercalated discs that facilitate synchronized contractions for pumping blood

tendon

A fibrous connective tissue that connects muscle to bone, transmitting the force generated by muscle contractions to produce movement.

epimysium

A connective tissue layer that surrounds the entire skeletal muscle, providing support and protection while allowing for flexibility.

fascicle

A bundle of muscle fibers (cells) within a skeletal muscle, encased in perimysium, allowing for organized contraction.

perimysium

A connective tissue sheath that surrounds each fascicle, providing support and facilitating the blood supply and nerve innervation to the muscle fibers.

fiber

A muscle cell; in the context of skeletal muscle, it refers to the long, cylindrical cells that make up muscle tissue.

endomysium

A delicate connective tissue layer that surrounds each individual muscle fiber, providing support and insulating fibers from each other.

sarcolemma

The plasma membrane of a muscle fiber, which surrounds the muscle cell and is involved in the propagation of action potentials.

sarcoplasm

The cytoplasm of a muscle fiber, containing organelles, myofibrils, and various proteins essential for muscle contraction.

myofibril

A long, thread-like structure within a muscle fiber composed of repeating units called sarcomeres, responsible for the contraction of muscle.

sarcoplasmic reticulum

A specialized form of endoplasmic reticulum in muscle fibers, storing calcium ions that are released during muscle contraction.

t-tubules

Transverse tubules that are extensions of the sarcolemma, penetrating into the muscle fiber, allowing for rapid transmission of action potentials.

terminal cisternae

Enlarged regions of the sarcoplasmic reticulum that flank the T-tubules, serving as reservoirs for calcium ions.

myofilament

The filamentous structures within myofibrils, including thick (myosin) and thin (actin) filaments, that are responsible for muscle contraction.

myosin

A thick myofilament protein that interacts with actin to produce muscle contraction through cross-bridge cycling.

actin

A thin myofilament protein that forms the backbone of the sarcomere, interacting with myosin during muscle contraction.

troponin

A regulatory protein complex associated with actin that binds calcium ions, causing a conformational change to facilitate muscle contraction.

tropomyosin

A regulatory protein that wraps around actin filaments, blocking myosin binding sites when the muscle is relaxed.

sarcomere

The basic functional unit of skeletal muscle, defined as the segment between two Z discs, responsible for the contraction and relaxation of muscle fibers.

action potential

A rapid, temporary change in the electrical charge across a cell membrane, leading to the initiation of muscle contraction when propagated along the sarcolemma.

neuromuscular junction

The synapse between a motor neuron and a muscle fiber, where neurotransmitters are released to initiate muscle contraction.

synapse

A junction between two neurons or between a neuron and a muscle cell, facilitating the transmission of signals through neurotransmitter release.

neurotransmitter

Chemical messengers (e.g., acetylcholine) released by neurons that transmit signals across synapses, initiating muscle contractions or other responses.

threshold stimulus

The minimum level of stimulation required to trigger an action potential in a muscle fiber or neuron, leading to contraction.

maximal stimulus

The strongest stimulus that can produce an action potential in a muscle fiber, activating all motor units and resulting in maximal contraction.

aerobic catabolism

The metabolic process that occurs in the presence of oxygen, breaking down glucose and fatty acids to produce ATP for sustained muscle activity.

anaerobic catabolism

The metabolic process that occurs in the absence of oxygen, converting glucose to lactate for short bursts of energy during intense exercise.

creatine phosphate

A high-energy compound stored in muscle cells that donates a phosphate group to ADP to rapidly regenerate ATP during short bursts of activity.

myoglobin

An oxygen-binding protein found in muscle cells that facilitates the storage and transport of oxygen for aerobic respiration.

muscle twitch

A single, brief contraction of a muscle fiber in response to a single stimulus, consisting of a latent period, contraction period, and relaxation period.

latent period

The initial phase of a muscle twitch, where the action potential is generated, but no visible contraction occurs as calcium ions are released.

contraction period

The phase of a muscle twitch where muscle fibers actively shorten and tension increases as myosin and actin interact.

relaxation period

The phase following contraction where muscle tension decreases as calcium ions are reabsorbed and the muscle fiber returns to its resting state.

wave summation

The process by which successive stimuli increase muscle contraction strength by preventing complete relaxation between stimuli.

motor unit

A functional unit consisting of a motor neuron and all the muscle fibers it innervates, responsible for coordinated muscle contractions.

recruitment

The process of activating additional motor units to increase muscle force during contraction, allowing for graded responses to varying demands.

isotonic contraction

A type of muscle contraction where the muscle changes length while maintaining a constant tension, leading to movement (e.g., lifting a weight).

isometric contraction

A type of muscle contraction where the muscle generates tension without changing length, typically occurring against an immovable object.

hypertrophy

An increase in muscle fiber size due to resistance training or increased workload, resulting in greater strength and muscle mass.

atrophy

A decrease in muscle fiber size and strength due to disuse, aging, or disease, resulting in a reduction of muscle mass and function.