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84 Cards in this Set
- Front
- Back
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Describe the appearance/innervation of skeletal muscle
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Skeletal muscle is striated and voluntary,
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Voluntary Muscle
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Muscle that is usually under conscious control, skeletal muscle.
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Striated Muscle
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Type of muscle characterized by stripes; found in cardiac and skeletal muscle.
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Endomysium
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Sparse layer of areolar connective tissue wrapper that surrounds each muscle fiber (muscle cell/myofiber) and allows room for blood capillaries and nerve fibers to reach each muscle fiber.
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Perimysium
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Connective tissue wrapper that bundles muscle fibers (muscle cells/myofibers) together. Service (blood) vessels are found through these.
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Epimysium
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"On top" Connective tissue wrapper that encloses an entire muscle body.
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Parallel Elastic Component of Collagenous Components of Muscle
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Includes the endomysium, perimysium, and epimysium
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Series Elastic Component of Collagenous Components of Muscle
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Jioned end to end with the contractile part of muscle and constitutes tendons/other connections that bind muscles to bones.
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Myoblasts
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Stem cells which fuse to produce each multi-nucleate muscle fiber (muscle cell/myofiber); each squamous-looking nucleus came from a myoblast
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Satellite cells
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Unspecialized cells orbit between a muscle fiber (muscle cell/myofiber) and endomysium; can multiply when called upon to repair injured muscle to a somewhat limited degree (won't grow back a poisoned muscle)
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General Structure and Contents of a Muscle Fiber (Cell)
Sarcolemma |
The plasma membrane of a muscle fiber (myofiber/muscle cell).
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General Structure and Contents of a Muscle Fiber (Cell)
Sarcoplasm |
Cytoplasm of a muscle cell (muscle fiber/myofiber).
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Why are muscle cells given the misnomer of "muscle fiber"?
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Because of their extraordinary length, muscle cells are usually called muscle fibers or myofibers, although they are not actually made of collagen or other fibers.
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Myofibrils
Myofibril |
Long strings/bundles protein microfilaments (myofilaments) that occupy the sarcoplasm.
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General Structure and Contents of a Muscle Fiber (Cell)
Sarcoplasmic Reticulum (SR) |
The smooth ER of a muscle fiber, which forms a network around each myofibril (which are each made up of myofilaments). It is a reservoir of Calcium Ions.
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What is the singular and the plural version of the cisterns that, along with the T Tubles create a triad? How many make a triad?
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1 Cistern = Terminal Cisterna
Multiple Cisterns = Termina Cisternae It takes 1 T Tubule and 2 adjacent (on on each side) Terminal Cisternae to make a triad. |
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General Structure and Contents of a Muscle Fiber (Cell)
Terminal Cisternae |
Think "rain barrels for collection of water" The dilated end-sacs of Sarcoplasmic Reticulum that transverse a Skeletal Muscle Fiber, adjacent to a T Tubule, where Calcium collects for use.
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Triad
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One T Tube (Transverse Tube) and the two terminal cisternae which run along it on each side. Calcium spreads out from the triad through the whole SR.
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T Tubules (Transverse Tubules)
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Tubular in foldings in the sarcolemma which penetrate the interior of the cell and emerge on the other side. The T-tube is what signals the SR when to release bursts of Ca2+.
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Types of Myofilaments
Thick Filaments |
Bundled myosin molecules; shaped like a golf club w/2 intertwined polypeptides; shaftlike tail, double globular heads on a hinge (when resting pointing away from middle), middle bare zone.
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Types of Myofilaments
Thin Filaments |
Fibrous Actin or F Actin = bead necklace of G (globular) actin with active site for binding to head of myosin molecule, plus Tropomysin (Pr-) which blocks active sites when resting, plus Troponin (calcium binding Pr-)
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Types of Myofilaments
Elastic Filaments |
A giant protein, Titin (connectin), flanks each thick filamint (Myosin) and anchors it to structure called Z disc for stabiliation and prevention of overstretching.
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What are the contractile proteins of a muscle?
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Myosin and Actin are the contractile proteins because they do the work of shortening the muscle fiber.
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Components of Myofilaments
Regulatory Proteins |
Tropomyosin and Troponin (found where there's Actin) are proteins that regulate the myosin-actin binding ("act" like a switch)
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Striated Muscle
A Bands |
Think "dArk" bands; Anisotropic bands; dark band formed by parallel thick filaments that partly overlap the thin filaments. Thick filaments are side by side, and are especially dark where thin/thick filaments overlap (Actin and Myosin).
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Striated Muscle
H Band or H Zone |
A lighter region in the middle of an A band (dArk band) that contains thick filaments only (Myosin); thin filaments do not reach this far into the A band in relaxed muscle.
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Striated Muscle
I Band |
Think "lIght"; (Isotropic Band); a light band composed of thin filaments (Actin) only. Each light I band is bisected by a dark, narrow Z disc of Titin.
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Sarcomere
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The segment of myofibril from one Z disc to the next. The functional, contractile unit of the muscle fiber. Individual sarcomeres shorten to pull Z discs closer to each other.
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General Structure and Contents of a Muscle Fiber (Cell)
Glycogen |
An energy-storage polysaccharide abundant in muscle.
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General Structure and Contents of a Muscle Fiber (Cell)
Myoglobin |
An oxygen-storing red pigment of muscle.
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General Structure and Contents of a Muscle Fiber (Cell)
T Tubule |
Think "manhole", openings/tunnel-like extension of the sarcolemma extending from one side of the muscle fiber (cell) to the other; conveys electrical signals from the cell surface to its interior. Extracellular Ca2+ gets into Sarcoplasmic Reticulum through these.
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Myofibrils
Myofilament |
A threadlike complex of several hundred contractile protein molecules.
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Components of Myofilaments
Myosin |
A protein with long shaftlike tail and a globular head. Constitutes the thick myofilament.
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Components of Myofilaments
F Actin |
A fibrous protein made of a long chain of G actin molecules twisted into a helix; main protein of the thin myofilament.
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Components of Myofilaments
G Actin |
A globular submunit of F Actin with an active site for binding a myosin head.
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Components of Myofilaments
Tropomyosin |
A regulatory protein that lies in the groove of F Actin and, in relaxed muscle, blocks the myosin-binding active sites. Associated with Troponin.
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Components of Myofilaments
Troponin |
A regulatory protein (found with Actin) associated with tropomyosin that acts as a calcium receptor.
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Components of Myofilaments
Titin |
A springy protein that forms the elastic filaments and Z discs.
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Components of Myofilaments
Dystrophin |
A large protein that links think filaments and Z discs to extracellular proteins; transfers the force of sarcomere contraction to the parallel elastic component of muscle.
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Striations and Sarcomeres
Striations |
Altering light and dark transverse bands across a myofibril.
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Innervation
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The nerve supply to a muscle.
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Involuntary Muscle
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Not under conscious control, includes smooth muscle and cardiac muscle.
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Describe the appearance/innervation of cardiac muscle
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The muscle of the heart is striated and involuntary.
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Describe the appearance/innervation of smooth muscle
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The type of muscle found in most internal organs is non-striated and involuntary.
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Does the bladder count as involuntary or voluntary muscle?
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It is involuntary, the only voluntary part is the sphincter.
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Sphincter
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A ring of muscle that opens or closes an opening or passageway; found, for example in the eyelids, around the urinary orifice, and at the beginning of a blood capillary. Circular muscle-anus, mouth, end of bladder.
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Hypertrophy
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"over nutrition" - feed muscle, it gets bigger. The growth of a tissue through cellular enlargement, not cellular multiplication; for example, the growth of muscle under the influence of exercise.
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Atrophy
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"without nutrition" starved muscles. Shrinkage of a tissue due to age, disuse, or disease.
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Do mature skeletal muscle cells divide?
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No, but they do grow or shrink.
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What is the longest muscle cell in the body and where is it located?
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Sartor = tailor. The body's longest muscle crosses the quadriceps from the lateral side of the hip to the medial side of the knee; Flexes the hip/knee joints and laterally rotates the thigh. Named for tailor's cross-legged stance supporting sewing on raised knee.
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How does a tendon grow?
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Tendons grow right into the periosteum like roots. They are hard to pull out, like a tree would be hard to pull straight out by its roots.
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Fascicle
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Muscle fibers (cells) are grouped in these bundles, which are visible to the naked eye as parallel strands. They are the "grain" in a cut of meat. Tender meat is easily pulled apart along these. Each is separated from neighboring groups by perimysium.
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What is the progression from muscle fiber to full muscle, and what are the wrappers?
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Muscle cell (fiber) wrapped by endomysium. Bundles of muscle cells (fascicles) wrapped by perimysium. Bundles of fascicles make up muscle as a whole, wrapped by epimysium.
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Tendon (indirect attachment)
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Thin fibers of epimysium continue as a strong, fibrous, ripelike tendon that merges into the periosteum of a nearby bone. Creates a conspicuous gap between muscle and bone. (i.e. connection of biceps brachii to scapula)
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Direct (flesy) attachment
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Collagen fibers of epimysium are continuous with the periosteum of bone. Red muscle tissue appears to emerge directly from bone. (i.e. intercostal muscles between ribs)
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Body of the muscle
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The muscle as a whole, bundles of fascicles wrapped by epimysium.
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What other body system are the naming conventions of the muscle fibers and their bundles analagous to?
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The nervous systems's names are very similar (fascicles, etc.)
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What is a Muscle Fiber and what organelles and other features characterize it?
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A muscle cel. 50+ nuclei, and lots of DNA for protein synthesis. Smooth ER (SR) and mitochondria for ATP. Intracellular Ca2+ concentration huge compared to extracellular, necessary for contractions.
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How many myofibrils does the average muscle cell have?
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The average muscle cell has over 100 of these long strings of protein.
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What was the pencil/plastic wrap analogy Dr. Harvey used in class to describe the composition of a muscle?
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pencil = muscle cell; Yellow paint of pencil = sarcolemma. Plastic wrapper = endomysium. A few wrapped pencils together, wrapped again = perimysium around fascicle. Many fascicles wrapped again, epimycium = muscle body. Twisted ends = tendons into periosteum, very strong.
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Motor Neurons
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Like military units, certain neurons control their own motor units.
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Recruitment of Motor Neurons and Variable Muscle Control
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All "commander" neurons fire at once causing recruitment of all the motor units. This allows variable control of muscles. (i.e. knocking pencil out from between fingers vs. holding pencil tight so it can't be knocked out.)
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Functions of Skeletal Muscle
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MOVEMENT of skeleton; maintain POSTURE, body position; SUPPORT soft tissue; GUARD body openings; maintain body TEMPERATURE.
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If the amount of calcium in a person's body changed by 1/3 either way, what would happen?
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A person would die if there was a 30% increase or decrease of this.
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Actin
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think acTIN = THIN = acTIoN
the thin filaments of protein twisted together. hooks up to Z line, does the action/movement. |
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Myosin
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The thick filament protein, bundled together, found in the zone of overlap and in the area between two Z lines (right in the middle by itself) of a muscle. Each myosin has tail, head, hinge.
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M Line
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Think (M in the Middle of Myosin); The midline of the Myosin part of the muscle, made of a minor protein called Connectin. The Myosin connects up to the M line.
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What causes a muscle contraction?
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When Two Z Lines come in toward the M Line.
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What's are the major proteins that are found in the Zone of Overlap of a muscle?
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Both actin and myosin are found in the zone of overlap.
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What is the name for the area between Z Lines?
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A Sarcomere
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What is the G actin held in place by?
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The Troponin and Tropomyosin Complex holds this globular protein in place.
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What is F Actin comprised of?
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Fibrous Protein made of long chain of globular G Actin molecules twisted into a helix plus Troponin complex (3 with active site for calcium binding) and filamentous Tropomyosin
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Is Tropomyosin found in Actin or Myosin
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It is found in Actin.
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Tropomyosin/Troponin - Which of these covers an active site for calcium binding, and which marks it? What happens when Calcium enters the picture?
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Tropomyosin (strands) actually covers the active site. The troponin marks it. Calcium falls down like snow and the complex rolls out of the way of the active site.
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What direction do the heads of Myosin face when resting? During contraction?
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The heads behave like ratchets. They face away from the M line. When they are working (contraction) they point in toward the M line.
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What are the steps of a muscle contraction?
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1-resting; 2-Ca2+ comes down and Exposes Active Site; 3-myosin heads form Cross Bridge Attachment; 4-Pivoting of Myosin head on hinge; 5-Cross Bridge Detachment (blown free, use ATP); 6-Myosin Reactivation (re-set)
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How many ATP are used in one single muscle contraction?
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3.75 Billion ATP are used
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Myosin ATPase
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The myosin head must have an ATP molecule bound to it it to initiate contraction process. This enzyme in the Myosin head hydrolyzes the ATP, which releases energy and activates the head, which cocks into an extended high-energy position. The head temporarily keeps the ADP and phosphate group bound to it.
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What is the chemical product when an ATP is spent to release energy in a muscle contraction?
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The product is ADP + Phosphate (P1)
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What would be a tug of war or boat rowing analogy for myscle contraction?
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Actin = rope (ACTin does the ACTing). Myosin standing in one spot and pulling rope hand over hand. Or a paddler of a boat putting the oar in and rowing multiple times.
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How is muscle analagous to a slinky?
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A slinky is striped when you hold it on its side, open and loose or compact and tight.
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How much weight can one square inch of muscle handle?
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50 pounds per square inch.
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How much of a muscle's length can it contract by?
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It can contract, or shorten, by 1/3.
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Striated Muscle
Z Lines / Z Disc |
A protein disc to which the thin filaments and elastic filaments are anchored at each end of a sarcomere; appears as a narrow dark line in the middle of the I Band.
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