Ch. 9 Muscles and Muscle Tissue Flashcards
Skeletal and smooth muscles cells that are elongated are called…
Muscle fibers
The type of muscle with the longest muscle cells and obvious striations that are activated voluntarily. It is responsible for overall body mobility
Skeletal muscle
The muscle tissue that is found only in the heart, is striated and moves involuntarily. Makes up the bulk of the heart wall to pump blood
Cardiac muscle
The muscle type that is found in the walls of hollow visceral organs and forces fluids and other substances through internal body channels. It is non striated and voluntary
Smooth muscle
The ability of a cell to receive and respond to a stimulus by changing its membrane potential
Excitability or responsiveness
The ability to shorten forcibly when adequately stimulated
Contractility
The ability to extend or stretch
Extensibility
The ability of a muscle cell to recoil and resume its resting length after stretching
Elasticity
An overcoat of dense irregular connective tissue that surrounds the whole muscle
Epimysium
Within each skeletal muscle, the muscle fibers are grouped into bundles called…
Fascicles
A layer of dense irregular connective tissue that surrounds each fascicle
Perimysium
A wispy sheath of connective tissue that surrounds each individual muscle fiber. It consists of fine areolar connective tissue
Endomysium
The part where the muscle attaches on the movable bone
Insertion
The part where the muscle attaches on the immovable or less movable bone
Origin
The epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage in this form of attachment
Direct (fleshy) attachments
The muscle’s connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheetlike aponeurosis in this form of attachment
Indirect attachments
The plasma membrane of a skeletal muscle fiber
Sarcolemma
The cytoplasm of a muscle cell
Sarcoplasm
Granules of stored glycogen that provide glucose during muscle cell activity for ATP production
Glycosomes
A red pigment that stores oxygen
Myoglobin
These account for about 80% of cellular volume and a single muscle fiber contains hundreds to thousands of these that run parallel to its length
Myofibrils
A repeating series of dark and light bands that are evident along the length of each myofibril
Striations
Dark and light bands that are nearly perfectly aligned in a intact muscle fiber, giving the cell its striated appearance
A bands (dark) and I bands (light)
Each dark A band has a lighter region in its midsection called the…
H zone
Each H zone is bisected vertically by a dark line called the… It is formed by molecules of the protein myomesin
M line
Each light I band also has a midline interruption, a darker area called the…
Z disc
The region of myofibril between two successive Z discs. It is the smallest contractile unit of a muscle fiber- the functional unit of skeletal muscle
Sarcomere
The muscle equivalents of the actin or myosin-containing microfilaments. These structures are located within the sarcomere
Myofilaments
Myosin makes up this type of filament and extends the entire length of the A band
Thick filaments
This type of filament contains actin and extends across the I band and partway into the A band
Thin filaments
This protein molecule consists of two heavy and four light polypeptide chains and has a rodlike tail attached by a flexible hinge to two globular heads.
Myosin
The attachment of linking the thick and thin filaments together by the globular heads on the myosin molecule
Cross bridges
Made up of kidney-shaped polypeptide subunits, which bear the active sites to which the myosin heads attach during contraction
Actin
A rod-shaped protein, spirals about the actin core and helps to stiffen and stabilize it. In a relaxed muscle fiber, they block myosin-binding sites on actin so that myosin heads on the thick filaments cannot bind to the thin filaments
Tropomyosin
A globular three-polypeptide complex that is a major protein in thin filaments
Troponin
Composed of the giant protein titin and holds the thick filaments in place while also helping the muscle cell spring back int shape after stretching
Elastic filament
An important structural protein that links the thin filaments to the integral proteins of the sarcolemma
Dystrophin
An elaborate smooth endoplasmic reticulum that surrounds each myofibril
Sarcoplasmic reticulum (SR)
Part of the SR that forms larger, perpendicular cross channels at the A band-I band junction
Terminal cisterns
At each A band-I band junction, the sarcolemma of the muscle cell protrudes deep into the cell interior, forming an elongated tube called the…
T tubule
Successive groupings of the three membranous structures (terminal cistern, T tubule, and terminal cistern)
Triads
Activation of myosin’s cross bridges (“shortening”)
Contraction
States that during contraction, the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree
Sliding filament model of contraction
An electrical current generated by a nervous system stimulation
Action potential
Nerve cells that activate skeletal muscle fibers. They reside in the brain or spinal cord
Somatic motor neurons
Junction formed by several short, curling branches within a single muscle fiber by an axon
Neuromuscular junction or motor end plate
The space that separates the axon terminal and the muscle fiber
Synaptic cleft
Small membranous sacs containing the neurotransmitter ACh. They are located in the axon terminal
Synaptic vesicles
The neurotransmitter that is released and binds to receptors on sarcolemma to ignite action potential
Acetylcholine or ACh
The trough-like part of the muscle fiber’s sarcolemma that helps form the neuromuscular junction. it is highly folded to provide a large surface area for the millions of ACh receptors located there
Junctional folds
Located on the junctional folds of the sarcolemma
ACh receptors
After ACh binds to the ACh receptors, its effects are quickly terminated by this enzyme that is located in the synaptic cleft… It breaks down ACh to its building blocks
Acetylcholinesterase
A disease that involves a shortage of ACh receptors and results in drooping upper eyelids, difficulty swallowing and talking, and generalized muscle weakness
Myasthenia
Depolarization (interior of the sarcolemma becomes less negative)
End plate potential
During repolarization, a muscle fiber is in this period because the cell cannot be stimulated again until repolarization is complete
Refractory period
The sequence of events by which transmission of an action potential along the sarcolemma causes myofilaments to slide
Excitation-contraction (E-C) coupling
When actin and myosin become irreversibly cross-linked this occurs…
Rigor mortis
The force exerted by a contracting muscle on an object
Muscle tension
The opposing force exerted on the muscle by the weight of the object to be moved
The load
When tension builds to the muscle’s peak tension-producing capacity, but the muscle neither shortens nor lengthens
Isometric contraction
When muscle length shortens and moves a load
Isotonic contraction
The nerve-muscle functional unit that consists of one motor neuron and all the muscle fibers it innervates (supplies)
Motor unit
A recording of contractile activity
Myogram
A motor unit’s response to a single action potential of its motor neuron
Muscle twitch
The first few milliseconds following stimulation when excitation-contraction coupling is occuring
Latent period
During this period, the cross bridges are active and the myogram tracing rises to a peak
Period of contraction
During this period, contractile force is declining and the tracing returns to the baseline. It is initiated by reentry of Ca2+ into the SR
Period of relaxation
Variations in strength, needed for proper control of skeletal movement
Graded muscle responses
This occurs when the second contraction occurs before the muscle has completely relaxed. (Contractions are added together on top of one another)
Wave or temporal summation
Sustained but quivering contraction when the degree of wave summation becomes greater and greater but hasn’t reached maximal tension
Unfused or incomplete tetanus
When muscle tension increases until it reaches maximal tension, the contractions fuse into a smooth, sustained contraction plateau called…
Fused or complete tetanus
Controls the force of contraction more precisely
Recruitment (multiple motor unit summation)
Stimuli that produce no observable contractions
Sub-threshold stimuli
The stimulus at which the first observable contraction occurs
Threshold stimulus
The strongest stimulus that increases contractile force. It represents the point at which all the muscle’s motor units are recruited
Maximal stimulus
1) The motor units with the smallest muscle fibers are activated first
2) As motor units with larger muscle fibers begin to be excited, contractile strength increases
3) The largest motor units, are controlled by the largest, least excitable neurons and are activated only when the most powerful contraction is necessary
Size principle of recruitment
The phenomenon that relaxed muscles are almost always slightly contracted and helps stabilize joints and maintain posture
Muscle tone
A type of isotonic contraction in which the muscle shortens and does work
Concentric contractions
A type of isotonic contraction in which the muscle generates force as it lengthens
Eccentric contractions
A unique, high-energy molecule stored in muscles that is tapped to regenerate ATP while the metabolic pathways adjust to the suddenly higher demand for ATP. It is involved in direct phosphorylation
Creatine phosphate
The CP-ADP reaction in direct phosphorylation is catalyzed by this enzyme
Creatine kinase
The initial phase of glucose breakdown that is used to form ATP in the anaerobic pathway
Glycolysis
Overall process of pyruvic acid being converted to lactic acid
Anaerobic glycolysis
A product of anaerobic glycolysis that diffused out of the muscles into the bloodstream and often leads to muscle soreness
Lactic acid
Occurs in the mitochondria, requires oxygen, and involves a sequence of chemical reactions that break the bonds of fuel molecules and release energy to make ATP
Aerobic respiration
The length of time a muscle can continue to contract using aerobic pathways
Aerobic endurance
The point at which muscle metabolism converts to anaerobic glycolysis
Anaerobic threshold
A state of physiological inability to contract even though the muscle still may be receiving stimuli
Muscle fatigue
The extra amount of oxygen that the body must take in for these restorative process
Excess Post-exercise Oxygen Consumption (EPOC)
The situation in which the muscle is slightly stretched and the thin and thick filaments overlap optimally, because this permits sliding along nearly the entire length of the thinfilaments
Ideal Length-tension relationship
Cells that rely mostly on the oxygen-using aerobic pathways for ATP generation
Oxidative fibers
Cells that rely more on anaerobic glycolysis and creatine phosphate
Glycolytic fibers
Exercises such as swimming, jogging, fast walking, and biking are examples of…
Aerobic or endurance exercise
Exercise such as weight lifting, or isometric exercises are examples of…
Resistance exercise
