SG #7

Muscle fiber

A cylindrical, multinucleate cell composed of numerous myofibrils that contracts when stimulated

Myoglobin

A single-chain, iron-containing protein found in muscle fibers; gives it color

Autorhythmicity

heart's ability to control its own contractions

Myogram

instrument used to measure twitch tension

Fast oxidative fiber

intermediate muscle fiber that is between slow oxidative and fast glycolytic fibers

Myofibril

long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres

Sarcomere

longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction

Muscular atrophy

loss of structural proteins from muscle fibers

Muscle tone

low levels of muscle contraction that occur when a muscle is not producing movement

White muscle fiber

mitochondria and myoglobin are relatively sparse in this kind of muscle

Motor unit

motor neuron and the group of muscle fibers it innervates

Sliding filament mechanism

muscle contraction in which the actin and myosin filaments of striated muscle slide over each other to shorten the length of the muscle fibres

Isotonic contraction

muscle contraction that involves changes in muscle length

Eccentric contraction

muscle contraction that lengthens the muscle as the tension is diminished

Concentric contraction

muscle contraction that shortens the muscle to move a load

Slow oxidative fiber

muscle fiber that primarily uses aerobic respiration

Fast glycolytic fiber

muscle fiber that primarily uses anaerobic glycolysis

Unfused tetanus

n which each stimulus causes a contraction to be initiated when the muscle has only partly relaxed from the previous contraction

Acetylcholine

neurotransmitter that binds at a motor end-plate to trigger depolarization

Smooth muscle

nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal passageways

Epimysium

outer layer of connective tissue around a skeletal muscle

Myalgia

pain in one or more muscles

Intercalated disc

part of the sarcolemma that connects cardiac tissue, and contains gap junctions and desmosomes

Relaxation period

period after twitch contraction when tension decreases

Creatine phosphate

phosphagen used to store energy from ATP and transfer it to muscle

Sarcolemma

plasma membrane of a skeletal muscle fiber

Lactic acid

product of anaerobic glycolysis

Transverse tubule

projection of the sarcolemma into the interior of the cell

Myosin

protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber

Actin

protein that makes up most of the thin myofilaments in a sarcomere muscle fiber

Electromyogram

record of electrical activity in muscles; uses electrodes attached to the skin or inserted into muscle.

Red muscle fiber

One of the two main types of skeletal muscle, which contains abundant mitochondria and myoglobin.

Muscle fascicle

a bundle of skeletal muscle fibers surrounded by perimysium

Fibromyalgia

a chronic disorder characterized by widespread musculoskeletal pain, fatigue, and tenderness in localized areas.

Muscular dystrophy

a hereditary condition marked by progressive weakening and wasting of the muscles.

Deep fascia

a layer of dense connective tissue which can surround individual muscles

I band

a light band on each side of the Z line of striated muscle fibers

Gap junction

a narrowed portion of the intercellular space, containing channels linking adjacent cells and through which can pass ions and other substances

Cramp

a painful involuntary spasmodic contraction of a muscle

Myasthenia gravis

a rare chronic autoimmune disease marked by muscular weakness without atrophy, and caused by a defect in the action of acetylcholine at neuromuscular junctions

Tremor

a slight shaking movement that is caused especially by nervousness, weakness, or illness

Tic

a small repeated movement of a muscle especially in the face that cannot be controlled

Spasm

a sudden uncontrolled and often painful tightening of a muscle

Tendon

a tough piece of tissue in your body that connects a muscle to a bone

Muscular hypertrophy

addition of structural proteins to muscle fibers

Wave summation

addition of successive neural stimuli to produce greater contraction

Oxygen debt

amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction

Power stroke

another name for the contraction of myosin pulling actin inward (toward the M line)

Aponeurosis

broad, tendon-like sheet of connective tissue that attaches a skeletal muscle to another skeletal muscle or to a bone

Perimysium

connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle

Neurotransmitter

signaling chemical released by nerve terminals that bind to and activate receptors on target cells

Twitch

single contraction produced by one action potential

Synaptic cleft

space between a nerve (axon) terminal and a motor end-plate

Sarcoplasmic reticulum

specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++

Treppe

stepwise increase in contraction tension

Rigor mortis

stiffening of the joints and muscles of a body

Cardiac muscle tissue

striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the circulatory system. Cardiac muscle is under involuntary control.

Skeletal muscle

striated, multinucleated muscle that requires signaling from the nervous system to trigger contraction; most skeletal muscles are referred to as voluntary muscles that move bones and produce movement

Neuromuscular junction

synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal

Fused tetanus

tetanus in which stimuli to a particular muscle are repeated so rapidly that decrease of tension between stimuli cannot be detected.

Motor unit recruitment

the activation of additional motor units to accomplish an increase in contractile strength in a muscle.

A band

the area between two I bands of a sarcomere, marked by partial overlapping of actin and myosin filaments and appearing dark

Sarcoplasm

the cytoplasm of striated muscle cells.

Latent period

the delay between the receipt of a stimulus by a sensory nerve and the response to it.

Thermogenesis

the production of heat

Myology

the scientific study of muscles

Thin myofilament

the thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all to way to, the Z-discs

Superficial fascia

the thin layer of loose fatty connective tissue underlying the skin and binding it to the parts beneath

Thick myofilament

thin strands of actin and its troponin-tropomyosin complex projecting from the Z-discs toward the center of the sarcomere

Refractory period

time after the initiation of an action potential when another action potential cannot be generated

Fibrillation

very rapid irregular contractions of the muscle fibers of the heart resulting in a lack of synchronism between heartbeat and pulse

Tropomosin troponin complex

"guard" that regulates skeletal muscle contraction

Motor end plate

sarcolemma of muscle fiber at the neuromuscular junction, with receptors for the neurotransmitter acetylcholine