Muscle Physiology

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acetylcholine (ACh)

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a compound that occurs throughout the nervous system

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actin

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

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action potential

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the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell

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aerobic

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relating to, involving, or requiring free oxygen

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aerobic respiration

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a type of respiration in which oxygen is taken in and carbon dioxide and water are produced; also, the use of oxygen in the breakdown of foodstuffs to create energy

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all-or-none

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(of a response) having a strength independent of the strength of the stimulus that caused it

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anaerobic glycolysis

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is a metabolic process in which glucose is transformed to lactate

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antagonists

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a substance that interferes with or inhibits the physiological action of another

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aponeuroses

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

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atrophy

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(of body tissue or an organ) waste away, typically due to the degeneration of cells

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axon (nerve fiber)

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

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axon terminals

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is the very end of a branch of a nerve's axon, a long slender nerve fiber that conducts electrical signals to a nerve synapse

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cardiac muscle

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muscle of the heart, consisting of anastomosing transversely striated musclefibers formed of cells united at intercalated disks

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convergent

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in a convergent muscle, the muscle fibers are spread over a broad area, but all the fibers converge at one common attachment site

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creatine phosphate (CP)

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

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dark (A) bands

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The darker of the two alternating stripes seen along muscle fibers (myofibrils) when viewed with a polarization microscope

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endomysium

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The connective tissue sheath that surrounds each skeletal muscle fiber, separating the muscle cells from one another.

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endurance

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the ability of an organism to exert itself and remain active for a long period of time, as well as its ability to resist, withstand, recover from, and have immunity to trauma, wounds, or fatigue. It is usually used in aerobic or anaerobic exercise

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epimysium

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A fibrous outer sheath of connective tissue surrounding a skeletal muscle.

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fascicle

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A small bundle of muscle or nerve fibers

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fixators

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a muscle that stabilizes or fixes a part of the body to which a muscle in the process of moving another part is attached

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flaccid

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not hard or solid

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fusiform

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Spindle-shaped, that is being wide in the middle while narrowing or tapering at both ends

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graded responses

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A muscle, like the biceps, contracts with varying degrees of force depending on the circumstance (this is also referred to as a graded response). Muscles do this by a process called summation, specifically by motor unit summation and wave summation.

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H zone

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The H zone appears as a lighter band in the middle of the dark A band at the centre of a sarcomere

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insertion

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place of attachment, such as the more movable end of a muscle (contrast to origin of muscle)

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involuntary

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done without will or conscious control

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isometric

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of, relating to, or denoting muscular action in which tension is developed without contraction of the muscle

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contractions

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the process in which a muscle becomes or is made shorter and tighter

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isotonic contractions

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tension remains unchanged and the muscle's length changes

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lactic acid

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

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latissimus dorsi

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either of a pair of large, roughly triangular muscles covering the lower part of the back, extending from the sacral, lumbar, and lower thoracic vertebrae to the armpits

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light (I) bands

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a light band on each side of the Z line of striated muscle fibers, comprising a region of the sarcomere where thin (actin) filaments are not overlapped by thick (myosin) filaments

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M line

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a thin dark line across the center of the H zone of a striated muscle fiber

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motor unit

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a motor neuron and the muscle fibers it acts on

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muscle fatigue

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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

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muscle fibers

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a basic contracting unit of striated muscle such as that in arms and legs, formed from several fused elongated cells myofibrils that contract when stimulated

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muscle tone

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is the continuous and passive part contraction of the muscles, or the muscle's resistance to passive stretch during resting state. It helps to maintain posture and declines during REM sleep

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muscle twitches

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a brief, contractile response of a skeletal muscle elicited by a single maximal volley of impulses in the neurons supplying it

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muscular dystrophy

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

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myofibers

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A muscle cell, especially one of the cylindrical, multinucleate cells that make up skeletal muscles and are composed of numerous myofibrils that contract when stimulated

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myofibril

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one of the slender threads of a muscle fiber, composed of numerous myofilaments

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myofilaments

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one of the filaments that make up a myofibril, either the thicker filaments composed of the protein myosin or the thinner filaments composed of the proteins actin or troponin

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myosin

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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

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neuromuscular

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relating to both nerves and muscles

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junctions

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a point where two or more things are joined

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neurotransmitter

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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

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origin

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the place or point where a muscle, nerve, or other body part arises, in particular

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oxygen deficit

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lack of oxygen

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parallel

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(of lines, planes, surfaces, or objects) side by side and having the same distance continuously between them

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pennate

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is a muscle with fascicles that attach obliquely (in a slanting position) to its tendon

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perimysium

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

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platysma

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a broad sheet of muscle fibers extending from the collarbone to the angle of the jaw

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prime mover

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Muscles that have the sole or principal responsibility for a given action or movement

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resistance exericises

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any form of exercise that forces your skeletal muscles (not the involuntary muscles of your heart, lungs, etc.) to contract

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sarcolemma

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

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sarcomeres

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a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band

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skeletal muscle

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a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band

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sliding filament

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mechanism proposed for muscle contraction where myosin head groups of the thick filaments move along the interdigitated actin of the thin filaments, sliding past them and thereby shortening the sarcomere

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smooth muscle

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

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striated muscle

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muscle tissue in which the contractile fibrils in the cells are aligned in parallel bundles, so that their different regions form stripes visible in a microscope. Muscles of this type are attached to the skeleton by tendons and are under voluntary control

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synaptic cleft

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the space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter-called also synaptic gap

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synergists

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something (as a chemical or a muscle) that enhances the effectiveness of an active agent broadly

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tendons

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

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tetanus

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the prolonged contraction of a muscle caused by rapidly repeated stimuli

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fused tetanus

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where a muscle reached maximum tension with frequency of stimulation being increased

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unfused tetanus

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a partial depletion of tension between stimuli

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voluntary muscle

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a muscle, usually made up of striated fibers, that is consciously controlled

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thick (myosin) filaments

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A protein found in muscle tissue as a thick filament made up of an aggregate of similar proteins

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thin (actin) filaments

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