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