Latent period
period of time between stimulation and the onset of muscle contraction
Anaerobic threshold
The point at which muscle metabolism converts to anaerobic glycolysis
Cardiac muscle
specialized muscle of the heart
Sarcoplasmic reticulum (SR)
Specialized endoplasmic reticulum of muscle cells
Motor Unit
A motor neuron and all the muscle cells it stimulates.
Hernia
Abnormal protrusion of an organ or a body part through the containing
wall of its cavity.
Aceteylcholinesterase (AChE)
Enzyme present at the neuromuscular junction and synapses that
degrades acetucholine and terminates its actions.
Resistance exercise
High intensity exercise in which the muscles are pitted against high
resistance or immovable forces and, as a result, muscle cells increase
in size.
Visceral muscle
Type of smooth muscle; its cells contract as a unit and rhythmically,
are electrically coupled by gap junctions, and often exhibit
spontaneous action potentials. Also called unitary smooth muscle.
Creatine phosphate (CP)
Compound that serves as an alternative energy source for muscle tissue.
Lactic acid
product of anaerobic metabolism, especially in muscle.
Neuromuscular junction
Region where a motor neuron comes into close contact with a skeletal
muscle cell.
Peristalsis
Progressive, wavelike contractions that move foodstuffs through the
alimentary tube organs (or that move other substances through other
hollow body organs)
Myofibril
Rod-like bundle of contractile filaments (myofilaments found in
muscle fibers (cells).
T tubule (transverse tubule)
Extension of the muscle cell plasma membrane (sarcolemma) that
protrudes deeply into the muscle cell.
Muscle twitch
The response of a muscle to a single breif threshold stimulus.
Aponeurosis
Fibrous or membranous sheet connecting a muscle and the part it moves.
Varicosities
Knob-like swellings of certain autonomic axons containing
mitochondria and synaptic vesicles.
Excitation-contraction (E-C) coupling
Sequence of events by which transmission of an action potential along
the sarcolemma leads to the sliding of myofilaments.
Myofilament
Filament that constitutes myofibrils. Of teo types: actin and myosin.
Summation
Accumulation of effects especially those of muscular, sensory, or
mental stimuli.
Repolarization
Movement of the membrane potential to the initial resting (polarized) state.
Tetanus
(1) A smooth, sustained muscle contraction resulting from
high-frequency stimulation; (2) an infectious disease caused by an
anaerobic bacterium.
Glycolysis
Glycolysis: breakdown of gluclose to pyruvic acid- an anaerobic process.
Myosin
One of the principal contractile proteins found in muscle.
Atrophy
Reduction in size or wasting away of an organ or cell resulting from
disease or lack of use.
Tendon
Cord of dense fibrous tissue attaching muscle to bone.
Sacroplasm
The nonfibrillar cytoplasm of a muscle fiber.
Contractility
Muscle cell's ability to move by shortening.
Muscle tension
The force exerted by a contracting muscle on some object.
Isotonic contraction
Contraction in which muscle tension remains constant at a given load,
and the muscle shortens.
Action potential
A large transient depolarization event, including polarity reversal,
that is conducted along the membrane of a muscle or a nerve fiber.
Anaerobic
Not requiring oxygen
Epimysium
Sheath of fibrous connective tissue surrounding a muscle.
Anaerobic glycolysis
Energy-yielding conversion of glucose to lactic acid in various
tissues, notably muscle, when sufficient, oxygen is not available.
Aerobic endurance
The length of time a muscle can continue to contract using aerobic pathways.
Excitability (responsiveness)
Ability to respond to stimuli.
Aerobic
Oxygen requiring
Myoblasts
Embryonic mesoderm cells from which all muscle fibers develop.
Insertion
Movable attachment of a muscle.
Creatine kinase
Enzyme that catalyzes the transfer of phosphate from creatine
phosphate to ADP, forming creatine and ATP; important in muscle contraction.
Fascicle
Bundle of nerve or muscle fibers bound together by connective tissue.
Skeletal Muscle
Muscle composed of cylindrical multi-nucleate cells with obvious
striations; the muscles (s) attached to the body's skeleton; voluntary muscle.
Actin
A contractile protein of muscle.
Fascia
Layers of fibrous tissue covering and separating muscle.
Endomysium
Thin connective tissue surrounding each muscle cell.
Smooth muscle
Spindle-shaped cells with one centrally located nucleus and no
externally visible striations (bands). Found mainly in the walls of
hollow organs.
Myoglobin
Oxygen-binding pigment in muscle.
Perimysium
Connective tissue that bundles muscle fibers into fascicles.
Contraction
To shorten or develop tension, an ability highly developed in muscle cells.
Isometric contraction
Contraction in which the muscle does not shorten (the load is too
heavy) but its tension increases.
Threshold stimulus
Weakest stimulus capable of producing a response in an irritable tissue.
Graded muscle responses
Variations in the degree of muscle contraction by changing either the
frequency or strength of the stimulus.
Aerobic respiration
Respiration in which oxygen is consumed and glucose is broken down
entirely; water, carbon dioxide, and large amounts of ATP are the
final products.
Origin
Attachment of a muscle that remains relatively fixed during muscular contraction.
Acetylcholine (ACh)
Chemical transmitter substances released by some nerve endings.
Depolarization
Loss of a state of polarity; loss or reduction of negative membrane potential.
Sarcomere
The smallest contractile unit of muscle; extends from on Z disc to
the next.
Muscle tone
Low levels of contractile activity in relaxed muscle; keeps the
muscle healthy and ready to act.
Myogram
A graphic recording of mechanical contractile activity produced by an
apparatus that measures muscle contraction.
Sarcolemma
The plasma membrane surface of a muscle fiber.
Muscular dystrophy
A group of inherited muscle-destroying diseases.