|myology||sci study of muscle anatomy and physio|
|voluntary muscle tissue||muscle tissue, usually striated, can be controlled (contracted) consciously by motor commands from cerebral cortex, though some control is maintained by lower centers in CNS|
|involuntary muscle tissue||muscle that contracts w/o conscious control;|
includes smooth muscle found in walls of internal organs such as the stomach, intestines, bladder, blood vessels, & cardiac muscle;
a few skeletal muscles also operate under involuntary control, such as the muscles for breathing & swallowing, however, those skeletal muscles are subject to conscious control as well.
|striated muscle tissue||muscle tissue characterized by transverse stripe, a banding pattern observed observed in microscopy, due to parallel arrangement of contractile proteins, actin and myosin, within the cell's contractile organelles, the myofibrils, which are comprised of repeating functional units, sarcomeres;|
skeletal & cardiac muscles are striated
|nonstriated muscle tissue|
smooth muscle tissue
|characterized by absence of transverse stripes/banding pattern observed in microscopy, due to the diffuse network arrangement of the contractile proteins, actin & myosin, which are not organized into myofibrils;|
cytoplasm also lacks the T tubule system and the C.T. around this muscle never unites to form tendons or apoeuroses;
spindle-shaped, uninucleate, involuntary contractile cells controlled by the autonomic nervous system; may be autorhythmic; is the type of muscle found in walls of tubular internal organs, iris of eye, arrector pili muscles, uterus, etc.
|satellite cell||low frequency (,1%) striated muscle tissue cell (discovered in 1961) which is an undifferentiated stem cell (myoblast) which is dormant in healthy muscle tissue but can help repair damage by dividing and migrating to an injured area of muscle;|
they are decreased in number w/ increased age or certain diseases (Duchenne muscular dystrophy).
There is a different "satellite cell" in peripheral nervous tissue--any of the glial cells that encapsulate and [provide protection & support for the cell bodies of peripheral neurons in the many peripheral ganglia.
|THREE TYPES OF MUSCLE:||skeletal, cardiac, smooth|
|dense body||dark staining cell organelles (peripheral proteins) w/in smooth muscle ccells, attached to sarcolemma, internally to the thin (actin + myosin) intermediate filaments which move these structures during contraction, and, externally to the surr endomysium.|
|intermediate filaments||1 of 3 types of cytoskeletal elements (along with thin (actin) & microtubules);|
freq. the 3 components wk together to enhance structural integrity, cell shape, and cell & organelle motility; stable, durable, intermediate in size compared with thin filaments & microtubules; prominent in cells that withstand mechanical stress.
|cardiac muscle tissue||specialized involuntary, striated, uninucleate, contractile tissue of the heart; |
comprising the myocardium in which the cells are connected by intercalated discs;
|autorhythmicity||property of cardiac muscle cells (&some smooth);|
ability to depolarize & contract at set rate w/o outside stim or regulation
|intercalated disc||specialized intercellular junction btw cardiac muscle cells, appears as dark line in microscopic specimens;|
at molecular level it contains both electrical synapses provided by gap junctions & structural connections (desmosomes and tight junctions)
|gap junction||intercellular junction which consists of a network of integral membrane protein channels called connexons which facilitate the cell to cell passage of small molecules (ions, small second messengers etc) b/c these junctions are relatively non-selective in their permeability, i.e., they provide direct cytoplasmic connections;|
common in cardiac and some smooth muscle tissues
|desmosome||specialized cell junction which links 2 cells by tying their outer cell membranes together with a tuft of intermediate filaments (tonofilaments) embedded in a mass of dense anchoring material;|
desmosomes are particularly prevalent in tissues such as epidermis & myocardium which have to withstand mechanical stress; nicknames the "spot weld" junction.
|thermogenesis||generation or production of heat by physiological processes;|
in humans the main source of heat comes from contractions of skeletal muscles (muscle tone & shivering);
additional modest increases in general metabolism are regulated by the thyroid hormones, T3 & T4.
|shivering||irregular involuntary contractions of skeletal muscles which produce vibrations of the muscles rather than coordinated movements of the limbs;|
triggered in response to cold or fear in some inflammatory responses such as fevers;
mechanism for thermogenesis
|property manifested by living organisms, and certain of their tissues (nervous, muscular, glandular) of responding to a stim of some sort, generally a response to some sort of kinetic energy(light, sound, motion)|
|conductivity||ability of a tissue to receive a stim and transmit a wave of excitation (electrochem activity), an impulse, over the rest of the structure, perhaps to adjacent cells in the tissue;|
property of nervous, muscular, and glandular tissues
|contractility||power posessed by the fibers of living (skeletal, cardiac, smooth) muscle of contracting or shortening in length which is achieved by the interaction of cytoplasmic contractile proteins (actin & myosin)|
|extensibility||term used to describe the ability of a muscle to be stretched after a contraction, even to a length greater than the resting length.|
|elasticity||the inherent property in tissues by which they recover their former shape and dimensions, after the removal of external pressure or altering force;|
tendency to rebound
as in the elasticity of muscle tissue
|THREE functions of skeletal muscle tissue||MOTION: external;(walking, running, talking, looking)|
internal (heartbeat, blood pressure, digestion, elimination) body part movements;
STABILIZATION: maintain body posture, stabilize joints--muscles have tone even at rest;
THERMOGENESIS:generating heat by normal contractions or by shivering.
|FIVE Physio characteristics of muscle tissue||excitability/irritability|
|Sketch and Label homeostatic thermogenesis by the shivering mechanism||http://apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%203%20Review/thermogenesis.fig.25.26.jpg|
|subcutaneous||located or placed just beneath the skin, usually w/in dermis|
|fascia||gross anatomical term for the layers of dense fibrous CT which cover & connect skeletal muscles and form boundaries which define specific muscles and groups|
|superficial fascia / hypodermis||thin layer of loose adipose tissue underlying dermis of the skin & binding skin to the parts beneath (muscle or bone)|
|deep fascia||layer of dense fibrous CT (fascia) which wraps and bunds together muscles in muscle groups and also binds together other internal structures.|
|epimysium||protective external sheath of dense irregular fibrous CT surrounding a skeletal muscle;|
is continuous with the fascia external to the muscle and with the perimysium surrounding the fascicles within the muscle.
|perimysium||protective external sheath of dense irregular fibrous CT surrounding each fascicle (bundle) of a skeletal muscle;|
is continuous with the epimysium surrounding the entire muscle and with the endomysium surrounding each muscle fiber/cell within the muscle.
|endomysium||protective external sheath of LOOSE irregular fibrous CT surrounding each skeletal muscle fiber/cell; it is continuous with the perimysium surrounding each fascicle (bundle) of the muscle and contains the main capillary blood supply for each muscle fiber/cell within the muscle.|
|fascicle / fasciculus||bundke of anatomical fibers, as of a muscle or a nerve;|
each fascicle is bounded by a thin wrapping of irregular fibrous CT
|muscle fiber||general name for the individual contractile cells in all types of muscle tissue|
|tendon||band, strap, or cord of tough inelastic dense regular fibrous CT which connects a muscle with its bony attachment or to whatever other structure the muscle moves (portion of skin, eyeball, etc)|
|aponeurosis||visible sheet or membrane of tough inelastic dense regular fibrous CT which may serve as a layer of fascia to bind muscles together or as an indirect attachment connecting muscle to bone, serving as a flattened alternative to a tendon|
|tendon sheath||any tube-like cavity lined wtih a synovial membrane that secretes a viscous lubricationg synovial fluid, covering regions of tendons at points of friction btw moving structures.|
|Describe or Sketch & Label:|
CT Components of a Muscle
|motor neuroon||type of neuron whose cell body is located in the brain or spinal cord, and whose axon runs along a peripheral nerve to synapse with an individual effector cell or group of cells to stim the effector into action(contraction or secretion);|
somatic motor neurons innervate skeletal muscle and activate contraction of a group of skeletal muscle cells, i.e., a motor unit;
visceral or autonomic motor neurons innervate visceral effectors, i.e., smooth muscle, cardiac muscle, endocrine glands, or exocrine glands.
|motor unit||the functional unit of a skeletal muscle composed of a voluntary motor neuron and the one or more skeletal muscle fibers which it innervates;|
muscles with large ratio motor units (1 neuron:many muscle fibers) can provide powerful contractions but cannot provide delicate control for precision movements while muscles with small ratio motor units (1 neuron:few muscle fibers) do not typically provide powerful contractions but can provide delicate control for very precise movements.
|momentary change in electrical voltage potential (wave of depolarization) on the surface of a nerve or muscle cell or gland cell which takes place when the cell is stim at or above its threshold level;|
the all-or-none action potential is capable of transmitting information (inhibition or excitation) to the next cell(s) in the communication pathway.
|depolarization||change in membrane voltage potential which triggers the action potential or nerve impulse;|
change is due to the opening of gated Na+ channels which allow Na+ ions to enter the cell cytoplasm causing the resting potential of -70 mV to change to +30 mV in the cell interior
|axon||unusually long process of a nerve fiber that conducts impulses (action potentials) away from the cell body of the nerve cell and to the next cell in the control pathway.|
synaptic end bulb
|swollen or knob-like distal endings to the terminal branches of axons (& axon collaterals) which house the secretory components of the neuron; the site of synthesis, packaging, storage and release of neurotransmitter molecules.|
|synaptic vesicle||small membranous containers for neurotransmitter substances which are formed by a Golgi apperatus and deliver neurotransmitter into the synaptic cleft by exocytosis.|
|neurotransmitter||chem substance (acetylcholine, dopamine, etc) which transmits a nerve impulse across a synapse by exocytosis and diffusion and binding to a receptor site on a gated ion channel;|
the influence on post-synaptic cell may be excitatory or inhibitory.
|the peripheral excitatory neurotransmitter released at the neuromuscular junction and responsible for stimulating skeletal muscle cells to contract;|
ACh also serves as a neurotransmitter in the periphery in the autonomic nervous system and in the central nervous system.
|motor end plate||the area on the sarcolemma within the synapse which contains acetyl choline receptors and various gated ion channels and which contains the enzyme acetylcholinesterase which can catabolize the neurotransmitter acetylcholine;|
the binding of acetylcholine (released from the motor neuron's axon terminal bulb) to the gated Na+ channels initiates depolarization of the sarcolemma at this postsynaptic communication point (the motor end plate).
|acetylcholine receptor||an integral membrane protein which is a gated Na+ channel which opens in response to the reversible binding of the neurotransmitter acetylcholine; this receptor is located in the post synaptic cell membranes of skeletal muscle cells, cardiac muscle cells, some smooth muscle cells, some glandular cells, all autonomic postganglionic cells, and a variety of CNS neurons.|
|acetylcholinesterase||the enzyme located at the motor end plate which breaks down the neurotransmitter acetyl choline in the synapse and which is responsible for stimulating terminating the stimulation of the skeletal muscle cell to make it contract.|
|the junction or connection, the synapse between axon terminals of a nerve fiber and the skeletal muscle cell(s) it stimulates to contract using acetyl choline as the excitatory neurotransmitter;|
the location for the beginning (excitation) of excitation-coupling of muscle contractions.
|junction, space, cleft, or gap across which a nerve impulse passes through the action of a neurotransmitter released from an axon terminal to the next cell in the pathway, either another neuron, or a muscle cell or a gland cell.|
|Sketch & Label|
a Motor Unit
|Sketch & Label|
A neuromuscular junction
|myofiber||an alt term for a muscle cell/fiber;|
these cells are specialized for contraction using the sliding filament mechanism
|myofibril||the non-membrane bound cell organelle of skeletal and cardiac (striated) muscle cells which is a long cylindrical mass of contractile protein fibers (actin + myosin), organized as a series of repeating sarcomeres, these contractile organelles are triggered to contract in an all-or-none fashion during excitation-contraction coupling when Ca2+ ions diffuse into the general sarcoplasm where they serve as the second messenger, triggering the sliding filament mechanism of contraction.|
|cross-striations||the series of parallel lines or light and dark bands observed in the cytoplasm of striated muscle cells, the bands are perpendicular to the long axis of the muscle cell;|
the banding pattern is due to the orderly arrangement of contractile myofilaments organized into repeating sarcomeres within each myofibril.
|myofilament||any of the ultremicroscopic protein filaments, comprised of actin and myosin molecules, which are the structural components of a myofibril;|
they form the physical elements acting during the sliding filament mechanism of contraction.
|sarcolemma||the outer lipid bilayer cell membrane or plasmalemma of a skeletal muscle cell;|
muscle contraction is initiated when the sarcolemma is depolarized in response to a nerve impulse from a motor neuron at the motor end plate.
|the general cytoplasm of a striated or skeletal muscle fiber containing all of the organelles and resources required for the sliding filament mechanism of contraction.|
|sarcoplasmic reticulum||the smooth ER found in striated muscle fibers which stores calcium phosphate salts in a gelatinous state until the muscle is stimulated, at which point the Ca2+ release channels open, permitting Ca2+ ions to diffuse into the general sarcoplasm where they serve as second messengers, triggering the sliding filament mechanism of contraction.|
|Ca2+ release channels||the integral membrane proteins which have the abilty, when regulated to be open, to permit calcium ions to diffuse fromone side of the membrane to the other; e.g., the calcium release channels in the sarcoplasmic reticulum membranes of skeletal muscle sells which release Ca ions into the sarcoplasm when muscle contraction is to be initiated (nicknamed: foot proteins)|
|Ca++ ATPase||An integral membrane protein which has the ability to use direct ATP hydrolysis to transport Ca ions from one side of the membrane to the other; e.g., the Ca pumps in the sarcoplasmic reticulum membranes of skeletal muscle which transport Ca ions back into the interior of the cisternae when muscle contraction is ending.|
|calmodulin||a calcium binding second messenger regulatory protein found in all nucleated cells which affects the activity of many Ca-sensitive enzymes, including those involved in muscular contraction; structurally similar to troponin C component.|
|calsequestrin||a Ca-binding storage protein found within the cisternae of the sarcoplasmic reticulum of striated muscle cells.|
|the irregular network of tiny tunnel-like extensions of the sarcolemma which penetrate into the interior of striated muscle cells and make intimate contact with the membranes of the terminal cisternae of the sarcoplasmic reticulum;|
when the striated muscle cell is stimulated by neurotransmitter and depolarization occurs, the wave of depolarization is propagated along these membrane passageways and and the depolarization is transferred to the membrane of the sarcoplasmic reticulum causing its depolarization and the opening of Ca2+ release channels.
|terminal cisterns||the slightly expanded edges of the carcoplasmic reticulum which are found adjacent to the T-tubules in the interior of striated muscle cells.|
|triad||the group of three membranous structures seen in the interior of striated muscle cells, consisting of one T-tubule and the two adjacent terminal cisterns in electron microscopy.|
|sarcomere||one of the segments into which a myofibril of striated muscle is divided;|
"unit of contraction"
the sarcomere has a dArk central A-Band, split in the middle by the lighter H-Zone which contains the M-line, and at each end has one half of a lIghter I-Band which is split by the Z-line;
the borders of the sarcomere are the Z-lines.
|the lateral boundaries of a sarcomere;|
a dark line splitting the I-Band which appears dark because it contains a meshwork of fibrous proteins which serve as the anchoring points for actin (thin filaments)
|A Band||the repeating dark (note the "A " in both "A band" and in the word "dark") area in the banding pattern observed in striated muscle when examined my a microscope;|
the A band is darker because within the A band both myosin and actin fibers are present and block the passage of much light;
the center of each A band is marked by a much lighter H zone.
|I Band||The repeating lighter (Note the "I: in both "I band" and in the word "light") area in the center of each A band observed in striated muscle when examined by a microscope;|
the H zone is lighter because within the H zone, only mysosin and no actin fibers are present to block the passage of light;
the center of each H zone is marked by the darker M line.
|M line||the center of the sarcomere;|
a dark line splitting the H zone within the A band which appears dark because it contains a meshwork of fibrous proteins which serve as anchoring points for myosin (thick filaments)
|Sketch & Label|
|Sketch & Label |
an actin fiber
|Sketch & Label|
a myosin fiber
|an enormous elastic protein (2500-3500 KD) found in the sarcomere of striated muscle cells;|
these proteins form a scaffolding important for the correct assembly of the sarcomere;
each titin molecule spans the distance from M line to Z disc and contributes to the passive tension in muscle cells as well as keeping the thick myosin filaments centered.
|the 7-9 nm diameter contractile proteins attached to the Z discs of striated muscle sarcomeres, arranged with opposite polarity in each half sarcomere;|
composed of the protein subunits F-actin, troponin, and tropomyosin;
these contractile proteins are found in the cytoskeleton of smooth muscle and some other tissues as well.
|actin||a contractile protein which is the main constituent of the thin filaments;|
it is involved in muscle contraction and an important cytoskeletal element in many other cell types;
consists of globular = G-actin subunits which combine to the form filamentous = F-actin strands which then will further combine with troponin and tropomysin proteins, to form the fully functional thin filament;
thin filaments are anchored together at the Z line (aka Z disc) of the sarcomere.
|troponin||a protein monomer associated with the thin actin filaments involved in striated muscle contraction;|
this protein complex consists of three functional subunits, one portion which has receptors for Ca ions and two portions which bind the protein to the other two protein components, actin and tropomyosin, of the thin filament;
there is one troponin associated with each tropomyosin protein.
nickname: "the switch molecule"
|tropomyosin||a fibrous protein monomer associated with actin filaments in the sarcomere of striated muscle cells and in the cytoskeleton of most cells;|
composed of two helical chains that span the length of the 6 or 7 G-actin molecules;
there is one tropomyosin associated with each troponin protein;
tropomyosin helos stabilize the actin fiber and participates in the binding of actin to myosin.
|myosin-binding site||specific location on each G-actin molecule where a myosin head can covalently bond to the actin filament during muscle contraction;|
at rest the myosin-binding site is covered by the tropomyosin molecule, but during contraction, the presence of Ca ions causes a conformational change in the tropomyosin molecule so that it shifts position and exposes the myosin-binding site.
|the larger diameter contractile proteins anchored to the M lines of striated muscle sarcomeres, arranged with opposite polarity in each half sarcomere; composed of the protein subunit myosin;|
these contractile proteins are found in the cytoskeleton of smooth muscle and some other tissues as well.
|myosin||the contractile protein monomer comprising myosin fibers which consists of a pair of intertwined strands forming the "tail" and active "head" of each strand which is the specific site for both attachment of myosin to actin and for the repeated power stokes, due to its ATPase activity, which acheive the sliding of actin fibers over the myosin fibers during muscle contraction;|
other related myosin-family proteins are associated with the cytoskeleton and with internal cytoplasmic transport processes.
|myosin heads||the pair of active subregions of each myosin protein monomer which have the capacity to bind and to hydrolyze ATP, to form covalent cross-links with actin filaments, and to perform the power strokes which produce the sliding of filaments that achieves contraction of the sarcomere.|
|myosin tails||the pair of subregions of each myosin protein monomer which align with other myosin monomers' tail regions to produce the huge polymer which is the myosin fiber or thick filament.|
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