Chapter 10 Muscle Tissue Vocabulary Review

Vocabulary and key concepts from Chapter 10 regarding the anatomy, physiology, and organizational levels of muscle tissue.

Muscle tissue

A primary tissue responsible for contraction and movement, categorized into skeletal, cardiac, and smooth types.

Skeletal muscle

A type of muscle responsible for moving the body by pulling on bones.

Cardiac muscle

Specialized muscle responsible for pumping blood through the cardiovascular system.

Smooth muscle

Muscle tissue that pushes fluids and solids through internal passageways and organs.

Excitability

The ability of muscle tissue to receive and respond to stimuli; also known as responsiveness.

Contractility

The ability of muscle cells to shorten.

Extensibility

The ability of a muscle to stretch.

Elasticity

The ability of a muscle to recoil to its original resting length.

Epimysium

A layer of collagen fibers connected to deep fascia that surrounds the entire muscle and separates it from other tissues.

Perimysium

Connective tissue that surrounds individual fascicles (muscle fiber bundles) and contains blood vessels and nerves.

Endomysium

Connective tissue surrounding individual muscle cells that contains capillary networks, nerve fibers, and myosatellite stem cells.

Tendons

Connective tissue bundles that attach skeletal muscles to bones.

Aponeuroses

Broad sheets of connective tissue that attach skeletal muscles to bones.

Myoblasts

Embryonic cells that fuse together to form large, multinucleate skeletal muscle fibers.

Sarcolemma

The plasma membrane of a muscle fiber, which maintains a resting membrane potential of $-85\,mV$.

Sarcoplasm

The cytoplasm of a muscle fiber.

Transverse tubules (T tubules)

Narrow tubes continuous with the sarcolemma that transmit action potentials deep into the sarcoplasm.

Sarcoplasmic reticulum (S R)

A tubular network similar to smooth endoplasmic reticulum specialized for the storage and release of calcium ions.

Terminal cisternae

Chambers of the sarcoplasmic reticulum that attach to T tubules.

Triad

A functional unit consisting of a T tubule and two terminal cisternae.

Myofibrils

Organized collections of myofilaments responsible for muscle contraction running the length of the muscle fiber.

Thin filaments

Myofilaments composed primarily of the protein actin.

Thick filaments

Myofilaments composed primarily of the protein myosin.

Sarcomeres

The repeating structural and functional unit of a myofibril, representing the smallest contractile unit of a muscle fiber.

A bands

Dark bands in a sarcomere containing the full length of the thick filaments.

M line

A vertical line in the center of the A band containing proteins that stabilize thick filaments.

H band

The region on either side of the M line containing only thick filaments.

Zone of overlap

The region of the sarcomere where thick and thin filaments occupy the same area.

I bands

Light bands in the sarcomere containing only thin filaments.

Z lines

The boundaries between adjacent sarcomeres that bisect the I bands.

Titin

An elastic protein extending from the thick filaments to the Z line that aids in restoring resting sarcomere length.

Tropomyosin

A protein that covers active sites on G-actin to prevent actin-myosin interaction in a resting muscle.

Troponin

A globular protein that binds to calcium ions and moves tropomyosin off the actin active sites.

Neuromuscular junction (N M J)

The synapse between a motor neuron and a skeletal muscle fiber.

Acetylcholine (A C h)

The neurotransmitter released at the N M J that binds to chemically gated channels to generate an action potential.

Acetylcholinesterase (A C h E)

An enzyme in the synaptic cleft and motor end plate that breaks down A C h.

Excitation–contraction coupling

The link between the generation of an action potential in the sarcolemma and the start of a muscle contraction.

Cross-bridges

Structural connections formed when myosin heads bind to active sites on actin.

Power stroke

The step where the myosin head uses energy to pivot and pull thin filaments toward the M line.

Rigor mortis

A state of muscle stiffness after death caused by the depletion of A T P and sustained calcium levels in the cytosol.

Twitch

A single stimulus-contraction-relaxation sequence in a muscle fiber lasting from $7-100\,msec$.

Latent period

The time between stimulation and the release of calcium ions where no tension is yet produced.

Treppe

An increase in peak tension from repeated stimuli occuring after the end of each relaxation phase, typically seen in cardiac muscle.

Wave summation

The increase in tension resulting from successive stimuli that arrive before the relaxation phase has completed.

Complete tetanus

A state of continuous contraction with no relaxation phase due to high stimulation frequency.

Motor unit

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

Recruitment

The smooth, steady increase in muscle tension produced by increasing the number of active motor units.

Isotonic concentric contraction

A contraction where muscle tension exceeds the load and the muscle shortens.

Isotonic eccentric contraction

A contraction where peak muscle tension is less than the load, causing the muscle to elongate.

Isometric contraction

A contraction where the muscle develops tension but does not change length.

Creatine phosphate (C P)

An energy reserve in muscles that can convert A D P back to A T P, providing enough energy for about $15\,seconds$ of contraction.

Glycolysis

Anaerobic metabolism in the cytosol providing a net gain of $2$ A T P and $2$ pyruvate molecules per glucose.

Cori cycle

The process where lactate is transferred to the liver and converted back into glucose.

Oxygen debt (E P O C)

The amount of oxygen required to restore pre-exertion conditions after exercise.

Fast fibers

Large-diameter muscle fibers that contract quickly, have large glycogen reserves, and fatigue rapidly.

Slow fibers

Small-diameter muscle fibers containing myoglobin and numerous mitochondria specialized for endurance.

Hypertrophy

Muscle growth resulting from heavy training, characterized by increased fiber diameter and myofibril count.

Atrophy

The reduction of muscle size, tone, and power due to lack of activity.

Intercalated discs

Specialized connections in cardiac muscle that join cells via gap junctions and desmosomes.

Automaticity

The ability of cardiac muscle to contract without neural stimulation via pacemaker cells.

Plasticity

The ability of smooth muscle to function over a wide range of lengths.