(Lesson 7) Muscular System Flashcards
Muscle Functions
Movement, Posture, Joint Stabilization, Heat Generation
Movement
Skeletal muscle attaches to the skeleton an moves the body by moving the bones. Muscles in the walls of visceral organs produce movement by squeezing fluids and other substances through these hollow organs.
Maintenance of Posture
Certain skeletal muscles contract continuously to maintain posture, enabling the body to remain in a standing or sitting position.
Joint Stabilization
Supports and strengthens joints.
Heat generation
Muscle contractions produce heat that plays a vital role in maintaining normal body temperature at 98.6 degrees Fahrenheit.
Skeletal Muscles Tissue
Located in the skeletal muscles. Attach and move the skeleton. Makes up 40% of the body’s weight. Contraction is subject to voluntary control. Cells are striated.
Cardiac Muscle Tissue
Occurs only in the wall of the heart. Cells are striated. Contract involuntarily.
Smooth muscle tissue
Mostly found in the walls of hollow internal organs other than the heart. Stomach, urinary bladder, blood vessels, and respiratory passages. Lacks striation and is involuntary.
Also found in:
- Iris of eye
- Reproductive organs
Sarcoplasmic Reticulum
an elaborate smooth endoplasmic reticulum whose interconnecting tubules surround each microfibril like the sleeve of a loosely crocheted sweater around your arm. Stores large quantities of calcium that are released when muscle is stimulated to contract.
T-Tubule
Deep invaginations of of the sarcoma that run between each pair of terminal cisternae. Allow deep microfibrils to contract at the same time as superficial ones.
Myofilaments
Soecific types of of microfilaments that are responsible for shortening of the muscle cells. Two kinds: One containing actin protein and on containing myosin protein.
Sarcomere
Basic unit of contraction in skeletal muscle. Thick (myosin) filaments contain ATPase enzymes that split ATP molecules which release energy required for muscle contraction.
Organizational Levels of skeletal muscle
Muscle, Fascicle (A portion of the muscle), Muscle Fiber (cell), Myofibril (Organelle), Sarcomere, Myofilament or filament.
Concentric Contraction
Muscle shortens and does work-picking up a book or kicking a ball
Eccentric Contraction
a muscle generates force as it lengthens. Essential for controlled movement and resistance to gravity.
Multinucleate (Skeletal Muscle)
Each muscle fiber cell was formed by the fusion of hundreds of embryonic cells. So skeletal Muscle fibers contain many nuclei which lie at the periphery of each fiber just deep to the sarcolemma.
Cylindrical (Skeletal Muscle)
Skeletal Muscle Cells are Cylindrical.
Skeletal Muscles at a microscopic or cellular level reveals
Cylindrical, striated, and multinucleate.
Origin of striation (Skeletal Muscle)
long, rod-shaped organelles called myofibrils. Un branched cylinders that make up more than 80% of the sarcoplasm.
Sarcolemma
The plasma membrane of muscle cells.
Sarcoplasm
Cytoplasm of muscle cells.
Epimysium
Overcoat of dense irregular connective tissue that surrounds the whole skeletal muscle.
Perimysium
Fibrous connective tissue which surrounds each Fascicle.
Fascicle
groups of muscle fibers surrounded by perimysium
Endomysium
Connective tissue surrounding muscle fibers.
Tendon
Connective tissue structure that joins skeletal muscles to bones.
Origin
The attachment of the muscle on the less movable bone is called the orgin.
Insertion
The attachment on the more movable bone.
Characteristics of Skeletal muscle
- Voluntary motion
- do not undergo mitosis but gro by increasing cell size and number of Myofilaments and Myobibrils
- attached to muscle by insertion and origin
- Cells use different amounts of myoglobin in different myofibers (cells) to provide unique functions
- Connective tissue wrappings: Endomysium, fascicles, perimysium, epimyseum, deep fascia, nerve and blood supply
Connective tissue wrappings
Epithelial layers that cover the muscle tissue. Come together at the end of a muscle to make a tendon which attaches muscle to bone.
Smooth Muscle at a microscopic level shows that this muscle is
- Uninucleated
- Not striated
- Spindle-shaped
- Single
General Qualities of Smooth Muscle
- Involuntary movement-contraction without nervous system stimulation
- Found in hollow organs where they are involved in peristalsis (bladder, intestine, esophogus, etc)
- Connective tissue wrappings (Endomysium)
- Gap Junctions
Peristalsis
the involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wavelike movements that push the contents of the canal forward.
Cardiac Muscle at the microscopic level
- Branching chains of cells (bifurcated)
- Striations
- Uni or binucleated
- intercalated discs
- connective tissue wrapping (endomysium)
- Found in the walls of the heart
Cardiac muscle diagram
Intercalated discs
The complex junctions that join cardiac muscle cells.
Neuromuscular Junction
(Motor end plate) The point at which the nerve ending and single muscle fiber meet. Nerves branch to provide each muscle fiber with a nerve ending that can stimulate contraction.
Muscle Lever Systems
Bone-Muscle Relationships
First Class (Muscle Lever Systems)
- Load-Fulcrum-effort
- Can work at mechanical advantage (for strength) or disadvantage (for speed and distance)
Lever
A rigid bar that moves on a fixed point when a force is applied to the lever. Bones of the skeleton act as levers.
Fulcrum
The fixed point on which the lever moves when force is applied. Joints act as fulcrums.
Effort
The applied force which is used to move a resistance or LOAD.
Mechanical advantage
A small effort is exerted to move a large load. Car jack lifts a car slowly but with little effort.
Mechanical Disadvantage
A large effort is exerted to move a small load. Can be advantageous, allowing the load to be moved rapidly over a large distance. (Wielding a shovel)
Second Class Lever Systems
- Fulcrum-Load-Effort
- All work at a mechanical advantage
- Levers of strength, sacrificing speed and distance
Third Class Lever Systems
- Load-Effort-Fulcrum
- All work at mechanical disadvantage
- Levers of speed and distance–effort is greater than load
- Most skeletal muscles of the body
What kind of lever is a wheel barrow?
Scissors?
Throwing a football?
Are they at a mechanical advantage or disadvantage?
Wheel-barrow: Second-Class, Mechanical Advantage
Scissors: First-Class, Could be either depending on load?
Football: Third-class, mechanical disadvangtage.
Types of Arrangement of Fascicles in Muscle
- Parallel (Two Types)
- Convergent
- Unipennate
- Bipennate
- Multipennate
- Circular
Convergent
(Arrangement of Fascicles in Muscle)
Origin of the muscle is broad and fascicles coverge toward the tendon of insertion. Triangular or fan shaped. Fibers extend the length of muscle from origin to insertion.
Parallel
(Arrangement of Fascicles in Muscle)
Long axes of the fascicles run parallel to the long axis of the muscle and muscle fibers extend from origin to insertion. Either
- Fusiform w/ expanded central belly like biceps
- Straplike, like satorious of lower limb.
Pennate
(Arrangement of Fascicles in Muscle)
Fascicles/fibers are short and attach obliquely to a tendon that runs the whole length of the muscle, attach obliquely. Makes the muscle look like a feather. (Penna=feather)
Multipennate
(Arrangement of Fascicles in Muscle)
Looks like many feathers situated side by side, wit hall their quills inserting into one large tendon. Deltoid muscle.
Bipennate
(Arrangement of Fascicles in Muscle)
Fascicles insert into the tendon from both sides. Rectus demoris muscle of thigh.
Unipennate
(Arrangement of Fascicles in Muscle)
Fascicles insert into only one side of the tendon. Extensor digitorium longus muscle on anterior leg.
Circular
(Arrangement of Fascicles in Muscle)
Surround external body openings which they close by contracting. General name: sphincter. Orbicularis oculi around the eye.
Steroids
A synthetic steroid hormone that resembles testosterone in promoting the growth of muscle. Such hormones are used medicinally to treat some forms of weight loss and (illegally) by some athletes and others to enhance physical performance
Advantages: Increase muscle mass and strength, increase in oxygen-carrying capacity
Disadvantages: Bloated face, atrophied testes, infertility, liver damage, mental problems.
Muscular Dystrophy
- Inherited group of muscle disorders
- Muscles enlarge with fat and connective tissue, though muscle fibers degenerate and atrophy
- Body is lacking the protein DYSTROPHIN
- Most common and serious form is Duchenne muscular dystrophy. It is an X-linked recessive gene disease. One in 3500 births, mostly males, have this.
Sliding Filament mechanism/theory
Explains concentric contraction of skeletal muscle. Contraction results as the myosin heads of thick filaments attach to the thin filaments at both ends of the sarcomere and pull the thin filaments towards the center of the sarcomere by swiveling inward. After a myosin head pivots at its “hinge”, it lets go, returns to its original position, binds to the thin filament farther along its length, and pivots again. This ratchet-like cycle is repeated many times during a single contraction. Thick/thin filaments do not shorten, they just slide past each other.
Z Discs/Lines
Boundaries at two ends of each sarcomere, attach to thin (actic) filaments.
Thin (actin) filaments
Fine myofilaments that attach to Z Discs/Lines and extend toward the center of the sarcomere. Consists primarily of the protein actin, among other proteins.
Thick (myosin) Filaments
In the center of sarcomere and overlapping the ends of thin filaments. Cylindrical Bundle. Consist largely of Myosin molecule. Also contain ATPase enzymes that split ATP(energy-storing molecules) to release the energy required for muscle contraction. Both ends studded with knobs call myosin heads.
A band
The region with the dark bands of each sarcomere which are created by the full length of the thick filaments, along with the inner ends of the thin filaments, which overlap the thick filaments.
H Zone
The central part of an A band where no thin filaments reach.
M Line
The center of H Zone, containing tiny rods that hold the thick filaments together.
I bands
The two regions on either side of A band, containing only thin filaments. Create light portions of light/dark striation, has Z disc running through it, and is part of 2 adjacent sarcomeres.
Microscopic Anatomy of the skeletal muscle fiber (cell)
When striated muscle fiber is extended after contracting, which of its bands or zones become wider?
H and I
Types of Skeletal Muscle Fibers
Oxidative, glycolytic
Slow Oxidative Fibers (Type I)
Muscle fibers that predominantly use ATP aerobically (using oxygen)
Thin red fibers because of high myoglobin content. Obtain energy from metabolic reactions. Contract slowly, are resistant to fatigue as long as oxygen is present, and deliver prolonged contractions but do not generate much power. (Lower back muscles)
Fast Glycoltic Fibers (Type IIx)
Pale fibers containing little myoglobin. Larger, contain more myofilaments amd generate much more power. Depend on anaerobic pathways to make ATP. Contract rapidly and tire quickly. Muscles of upper limbs which often lift heavy objects for brief periods
Fast Oxidated Fibers (Type IIa)
The middle when compared to other two. Contrac quickly like fast glycolytic, oxygen dependent, high myoglobin content, many mitochondria, and capillaries like slow oxidative. Fatigue resistant because they depend on aerobic metabolism, but less so than slow oxidative. Speed is between that of the other two.
