Chapter 10 Muscle Tissue Anatomy & Physiology

A comprehensive set of vocabulary flashcards covering skeletal, cardiac, and smooth muscle anatomy, physiology, and contraction mechanisms.

Excitability

Ability to respond to a stimulus by changing electrical membrane potential.

Conductivity

Involves sending an electrical change down the length of the cell membrane.

Contractility

Exhibited when filaments slide past each other, enabling the muscle to cause movement.

Extensibility

The ability of a muscle to be stretched.

Elasticity

The ability of a muscle to return to its original length following a lengthening or shortening.

Epimysium

Dense irregular connective tissue wrapping the whole muscle.

Perimysium

Dense irregular connective tissue wrapping a fascicle; houses many blood vessels and nerves.

Endomysium

Areolar connective tissue wrapping an individual muscle fiber for electrical insulation and capillary support.

Tendon

A cordlike structure of dense regular connective tissue that attaches muscle to bone, skin, or another muscle.

Aponeurosis

A thin, flattened sheet of dense irregular tissue used as a muscle attachment.

Deep fascia

Dense irregular connective tissue superficial to the epimysium that separates individual muscles and binds those with similar functions.

Sarcolemma

The plasma membrane of a muscle cell (muscle fiber) containing voltage-gated ion channels.

Sarcoplasmic reticulum

An internal membrane complex serving as a reservoir for calcium ions ($Ca^{2+}$).

Triad

A structural unit consisting of two terminal cisternae of the sarcoplasmic reticulum with a T-tubule in between.

Sarcomere

The repeating unit of myofilaments in a myofibril, delineated at both ends by Z discs.

Z discs

Specialized proteins perpendicular to myofilaments that serve as anchors for thin filaments.

A band

The dark-appearing region in the center of a sarcomere containing thick filaments and overlapping thin filaments.

H zone

The central portion of the A band where only thick filaments are present; it disappears with maximal muscle contraction.

Connectin

A protein extending from the Z disc to the M line that stabilizes thick filaments and provides passive tension.

Dystrophin

A protein that anchors myofibrils to sarcolemma proteins; deficiencies cause muscular dystrophy.

Motor unit

A single motor neuron and all the muscle fibers it controls.

Synaptic knob

The expanded tip of a motor neuron axon that houses synaptic vesicles filled with acetylcholine ($ACh$).

Motor end plate

The specialized region of the sarcolemma with numerous folds and $ACh$ receptors.

Acetylcholinesterase

The enzyme residing in the synaptic cleft that breaks down $ACh$ molecules.

Resting membrane potential (RMP)

The electrical charge across the sarcolemma when the muscle is at rest, approximately $-90\,mV$. stage.

End-plate potential (EPP)

A local change in membrane potential at the motor end plate caused by the binding of $ACh$ to chemically gated channels.

Refractory period

The time during depolarization and repolarization when a muscle cell is unable to respond to another stimulation.

Crossbridge formation

The step in crossbridge cycling where the myosin head attaches to an exposed binding site on actin.

Power stroke

The step in crossbridge cycling where the myosin head swivels toward the center of the sarcomere, pulling the thin filament.

Sliding filament theory

A description of muscle contraction where thick and thin filaments slide past each other without changing length.

Creatine phosphate

A high-energy molecule that can transfer a phosphate to $ADP$ to form $ATP$, providing energy for $10$-$15$ seconds.

Oxygen debt

The amount of additional oxygen needed after exercise to restore pre-exercise conditions, such as replenishing $ATP$ and glycogen.

Muscle twitch

A brief contraction of a muscle in response to a single stimulus of at least threshold voltage.

Recruitment

The process of increasing the number of active motor units to increase the force of muscle contraction.

Wave summation

An increase in muscle tension occurring when stimuli are delivered in rapid succession, preventing complete relaxation.

Tetany

A smooth, continuous muscle contraction without any relaxation, resulting from high-frequency stimulation.

Muscle tone

The resting tension in a muscle generated by involuntary nervous stimulation.

Isometric contraction

A contraction where muscle tension is generated but the muscle length stays the same.

Isotonic contraction

A contraction where muscle tension overcomes resistance, resulting in a change in muscle length.

Hypertrophy

An increase in muscle size due to the increased synthesis of contractile proteins, mitochondria, and glycogen reserves.

Atrophy

A decrease in muscle size due to lack of use.

Intercalated discs

Specialized junctions between cardiac muscle cells containing desmosomes and gap junctions.

Dense bodies

Anchoring points in smooth muscle where intermediate filaments interact within the sarcoplasm.

Calmodulin

A protein in smooth muscle that binds to $Ca^{2+}$ to trigger the contraction process.

Myosin light-chain kinase (MLCK)

An enzyme in smooth muscle that phosphorylates myosin heads when activated by the calcium-calmodulin complex.

Latchbridge mechanism

A characteristic of smooth muscle where myosin remains attached to actin for an extended time without using additional $ATP$.