Chapter 10 terms

Fibromyalgia

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

Lactic acid

a colorless syrupy organic acid formed in sour milk and produced in the muscle tissues during strenuous exercise.

Oxygen debt

a cumulative deficit of oxygen available for oxidative metabolism that develops during periods of intense bodily activity and must be made good when the body returns to rest.

Transverse tubule

a deep invagination of the sarcolemma, which is the plasma membrane of skeletal muscle and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.

Myosin

a fibrous protein that forms (together with actin) the contractile filaments of muscle cells and is also involved in motion in other types of cells.

Tendon

a flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone.

Myogram

a graphic representation of the phenomena (as velocity and intensity) of muscular contractions.

Muscular dystrophy

a group of inherited muscle-destroying diseases that cause progressive degeneration of skeletal muscle fibers. (Duchenne muscular dystrophy.

Calcium ion channels

a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the calcium ion Ca2+.

Synapse/synaptic cleft

a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Deep fascia

a layer of fibrous connective tissue which can surround individual muscles, and also divide groups of muscles into fascial compartments. This dense fibrous connective tissue interpenetrates and surrounds the muscles, bones, nerves and blood vessels of the body.

Cramp

a painful spasmodic contraction. May be caused by inadequate blood flow to msucles, overuse of a muscle, dehydration...etc.

Creatine phosphate

a phosphate ester of creatine found in vertebrate muscle, where it serves to store phosphates to provide energy for muscular contraction.

Tropomosin-troponin complex

a protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction.

Actin

a protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cells.

White muscle fibers

a rapid or fast-twitch muscle in which pale, large "white" fibers predominate; mitochondria and myoglobin are relatively sparse compared with findings in red muscle; involved in phasic contraction.

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.

Myoglobin

a red protein containing heme that carries and stores oxygen in muscle cells. It is structurally similar to a subunit of hemoglobin.

Tremor

a rhythmic, involuntary, purposeless contraction that produces a quivering or shaking movement.

Epimysium

a sheath of fibrous elastic tissue surrounding a muscle.

Aponeurosis

a sheet of pearly-white fibrous tissue that takes the place of a tendon in sheetlike muscles having a wide area of attachment.

Muscle tone

a small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units.

Tic (mimic spasm)

a spasmodic twitching made involuntarily by muscles that are ordinarily under voluntary control. (twitching of eye).

Thick myofilament

19 nm in diameter and 1-2 um long and composed mostly of the protein myosin.

Thin myofilament

8 mm in diameter and 1-2 um long and composed mostly of the protein actin

Gap junctions

a specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.

Fibrillation

a spontaneous contraction of a single muscle fiber that is not visible under the skin but can be recorded by electromyography. May signal destruction of motor neurons.

Sarcomere

a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band. Defined as the segment between two neighbouring Z-lines (or Z-discs, or Z bodies).

Spasm

a sudden involuntary contraction of a single muscle in a large group of muscles.

Fused (complete) tetanus

a sustained contraction in which individual twitches cannot be detected.

Neuromuscular junction

a synapse between a motor neuron and skeletal muscle. This lesson describes the events of synaptic transmission leading to contraction of skeletal muscle

Electromyogram

a test that measures the electrical activity in resting and contracting muscles.

Anaerobic cell respiration

a type of respiration that does not use oxygen. It is used when there is not enough oxygen for aerobic respiration. It can be summarised by the following equation: glucose → lactic acid (+ energy released)

Cardiac muscle tissue

an extremely specialized form of muscle tissue that has evolved to pump blood throughout the body. In fact, _______ is only found in the heart and makes up the bulk of the heart's mass.

Myofibrils

any of the elongated contractile threads found in striated muscle cells.

Slow oxidative fibers

appear dark red because they contain large amounts of myoglobin and many blood capillaries. Generate ATP mainly by aerobic respiration.

Interval training

application of highly structured exercise with rest intervals using "supermaximum" effort to overload the specific systems of energy transfer, allows performance of inordinately high exercise intensities with minimal fatigue.

Intercalated discs

are microscopic identifying features of cardiac muscle. Cardiac muscle consists of individual heart muscle cells (cardiomyocytes) connected by intercalated discs to work as a single functional organ or syncytium.

Skeletal muscle tissue

connected at either or both extremities with a bone and consists of elongated, multinucleated, transversely striated, ________ fibers, together with connective tissues, blood vessels, and nerves.

Motor unit

consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates.

Sliding filament mechanism

contraction where the thick and thin filaments slide past one another.

A band

dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.

Smooth muscle

muscle tissue in which the contractile fibrils are not highly ordered, occurring in the gut and other internal organs and not under voluntary control.

H zone

narrow region in center of each A band that contains thick filaments but no think filaments.

Z discs

narrow, plate-shaped regions of dense material that separate one sarcomere from the next.

Smooth muslce tissue

one of the types of muscle tissue in the body. ___________ generally forms the supporting tissue of blood vessels and hollow internal organs, such as the stomach, intestine, and bladder.

Myalgia

pain in or associated with muscles.

Red muscle fibers

slow-twitch muscle in which small dark "red" muscle fibers predominate; myoglobin is abundant and great numbers of mitochondria occur, characterized by slow, sustained (tonic) contraction. Contrast with white muscle.

Rigor mortis

stiffening of the joints and muscles of a body a few hours after death, usually lasting from one to four days.

Wave summation

stimuli arriving at different times cause larger contractions.

Unfused (incomplete) tetanus

sustained but wavering contraction. (when a skeletial muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli.

Twitch

the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.

Latent period

the brief delay that occurs between application of the stimulus and the beginning of contraction; lasts about 2msec. During this, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the SR.

Sarcoplasm

the cytoplasm of striated muscle cells.

Muscle fatigue

the decline in ability of a muscle to generate force. It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction.

Sarcolemma

the fine transparent tubular sheath that envelops the fibers of skeletal muscles.

Autorhythmicity

the heart beats because it has a natural pacemaker that initiates each contraction. The built in rhythm.

Motor end plate

the large and complex end formation by which the axon of a motor neuron establishes synaptic contact with a skeletal muscle fiber (cell)

Axon

the long threadlike part of a nerve cell along which impulses are conducted from the cell body to other cells.

Motor unit recruitment

the number of active motor units increases.

Treppe

the occurrence of a successive increase in amplitude of the first few contractions of cardiac muscle that has received a number of stimuli of the same intensity following a quiescent period.

Refractory period

the period of lost excitability, is a characteristic of all muscle and nerve cells. The duration of this period varies with the muscle involved.

Cardiac muscle

the principal tissue in the heart wall. Between the layers of _______ fibers, the contractile cells of the heart, are sheets of connective tissue that contain blood vessels, nerves, and the conduction system of the heart.

Thermogenesis

the production of heat, especially in a human or animal body.

Contraction period

the second phase, lasts 10-100 msec. During this time, calcium binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form.

Perimysium

the sheath of connective tissue surrounding a bundle of muscle fibers.

Power stroke

the site on the cross bridge where ADP is still bound opens. As a result, the cross bridge rotates and releases the ADP.

Sarcoplasmic reticulum

the specialized endoplasmic reticulum of cardiac muscle and skeletal striated muscle that functions especially as a storage and release area for calcium.

Myology

the study of the structure, arrangement, and action of muscles.

Isotonic contraction (concentric & eccentric)

the tension (force of contraction) developed in the muscle remains almost constant while the muscle changes its length. *concentric: the tension is great enough to overcome the resistance of the object to be moved, the muscle shortens and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at a joint. *eccentric: when the length of a muscle increases during a contraction. The tension exerted by the myosin cross-bridges resists movement of a load and slow the lengthening process.

Isometric contraction

the tension generated is not enough to exceed the resistance of the object to be moved.

Superficial fascia

the thin layer of loose fatty connective tissue underlying the skin and binding it to the parts beneath—called also hypodermis, tela subcutanea; compare deep fascia.

Relaxation period

the third phase; lasting 10-100 msec, calcium is actively transported back into the sarcoplasmic reticulum, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases.

Anabolic steriods

to build up proteins. Taken to increase muscle size by increasing the synthesis of proteins in muscle and thus increasing strength during athletic contests.

Fast oxidative fibers

typically the largest fibers. They contain large amounts of myoglobin and many blood capillaries. They have a dark red appearance. Can generate ATP by aerobic respiration, which gives them a moderately high resistance to fatigue.

Calcium ion pump

use ATP to move calcium constantly from the sarcoplasm into the SR

Muscular atrophy

when muscles waste away. The main reason for muscle wasting is a lack of physical activity. This can happen when a disease or injury makes it difficult or impossible for you to move an arm or leg. You may have muscle loss if one of your limbs appears smaller (not shorter) than the other.

Cross bridges

when the myosin heads attach to actin during contraction

Myosin-binding site

where a myosin head can bind.

Endomysium

within the muscle, is a wispy layer of areolar connective tissue that ensheaths each individual myocyte (muscle fiber, or muscle cell). It also contains capillaries and nerves. It overlies the muscle fiber's cell membrane: the sarcolemma.

Muscle fascicle

a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue. (There is also a nerve fascicle of axons.)

All-or-none principle

a characteristic of action potential; an action potential either occurs completely or it does not occur at all.

Neurotransmitter

a chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.

Fast glycolytic fibers

have low myoglobin content, relatively few blood capillaries, and few mitochondria, and appear white in color. They contain large amounts of glycogen and generate ATP mainly by glycolysis.

Myofiber/muscle fiber

hundreds to thousands of cells in each skeletal muscle; elongated shape. a skeletal muscle cell that has a rich concentration of myoglobin and oxidative enzymes.

Muscular hypertrophy

increase in muscle mass and cross-sectional area (1). The increase in dimension is due to an increase in the size (not length) of individual muscle fibers.

I band

lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band.