HAPP MIDTERM REVIEWER: MUSCULAR SYSTEM

Muscular Tissue

Makes up 40% - 50% of total adult body weight

Muscular Tissue

-Producing body movements.
-Stabilizing body positions.
-Storing and moving substances within the body.
-Generating heat.

Myology

It is the scientific study of muscles.

myo

muscle

logy

study of

Skeletal Muscle Tissue

• Moves most of the bones of the skeletons.

• Striated: Alternating light and dark protein bands.

• Works mainly in a voluntary manner.

Cardiac Muscle Tissue

• Forms most of the heart wall.

• Striated, but its action is involuntary.

• This built-in rhythm is termed autorhythmicity.

Smooth Muscle Tissue

• Located in the walls of hollow internal structures, such as blood vessels, airways, and most organs in the abdominopelvic cavity.

• It is also found in the skin, attached to hair follicles.

• Lacks the striations with involuntary action.

• Some smooth muscle tissue, such as the muscles that propel food through your gastrointestinal tract, has autorhythmicity.

Electrical Excitability

The ability to respond to certain stimuli by producing electrical signals called action potentials (impulses). Action Potentials in muscles are referred to as muscle action potentials; those in nerve cells are called nerve action potentials.

Autorhythmic Electrical Signals

arising in the muscular tissue itself, as in the heart's pacemaker.

Chemical Stimuli

such as neurotransmitters released by neurons, hormones distributed by blood, or even local changes in pH.

Contractility

The ability of muscular tissue to contract forcefully when stimulated by an action potential.

Extensibility

It is the ability of muscular tissue to stretch, within limits, without being damaged.

Elasticity

The ability of muscular tissue to return to its original length and shape after contraction or extension.

Epimysium

it is a thick connective tissue that surrounds the entire skeletal muscle.

Fascicle

bundle of skeletal muscle that is surrounded by perimysium.

Perimysium

thin but dense connective tissue that wraps fascicles.

Muscle Fiber

elongated, multi-nuclear cells composed of several myofibrils.

Endomysium

delicate connective tissue that surround muscle fiber.

Myofibril

long, cylindrical filament bundles in the sarcoplasm of myocytes.

Sarcolemma

surrounds the muscle fiber because it is a plasma membrane

Fascia

it is a dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body. Fascia allows free movement of muscles; carries nerves, blood vessels, and lymphatic vessels; and fills spaces between muscles.

Three Layers of Connective Tissue extend from the Fascia:

Epimysium, Perimysium, Endomysium

Epimysium

it is the outermost layer of dense, irregular connective tissue, encircling the entire muscle.

Perimysium

surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles. Many fascicles are large enough to be seen with the naked eye. They give a cut of meat its characteristic "grain"; if you tear a piece of meat, it rips apart along the fascicles

Endomysium

penetrates the interior of each fascicle and separates individual muscle fibers from one another.

Somatic Motor Neuron

stimulates skeletal muscle to contract.

Muscle Fiber

-Structural and functional unit of a skeletal muscle.

• Diameter: 10 to 100 micrometer.

• Length: average - 10cm (4in) although some are as long as 30cm (12in).

myoblast

Each skeletal muscle fiber arises during embryonic development from the fusion of a hundred or more small mesodermal cells

Sarcolemma

the plasma membrane of a muscle cell.

Transverse (T) Tubules

tiny invaginations of sarcolemma, tunnel in from the surface toward the center of each muscle fiber.

Sarcoplasm

the cytoplasm of a muscle fiber.

Glycogen

- large molecule composed of many glucose molecule; can be used for ATP synthesis.

Myoglobin

red-colored protein; found only in muscles, binds oxygen molecules that diffuse into muscle fibers from interstitial fluid.

Myofibrils

-appear like little threads inside the sarcoplasm; it is the contractile organelles of skeletal muscle.
-2 micrometer in diameter and extend the entire length of a muscle fiber.
-Their prominent striations make the entire skeletal muscle appear striped (striated).

Sarcoplasmic Reticulum

a fluid-filled system of membranous sacs which encircles the entire myofibrils.

Terminal Cisterns

dilated end sacs of the sarcoplasmic reticulum butt against tubule form.

Myofilaments

small protein structures within myofibrils.

Thin Filaments

are 8nm in diameter and 1-2m long and composed mostly of the protein actin.

Thick Filaments

are 16nm in diameter and 1-2m long and composed mostly of the protein myosin.

Sarcomeres

The filaments inside a myofibril do not extend the entire length of a muscle fiber. Instead, they are arranged in compartments called

Z discs

narrow, plate-shaped regions of dense protein material separate one sarcomere from the next. Thus, a sarcomere extends from one Z disc to the next Z disc.

I band

it is a lighter, less dense area that contains the rest of the thin filaments but no thick filaments and a Z disc passes through the center of each I band.

A band

the darker middle part of the sarcomere which extends the entire length of the thick filaments. Toward each end of the A band is a zone of overlap, where the thick and thin filaments lie side by side.

H zone

located in the center of each A band contains thick but not thin filaments.

M line

so named because it is at the middle of the sarcomere; at the center of the H zone. It contains proteins that hold thick filaments.

Contractile Proteins

- proteins which generate force during contraction.

Myosin

It is the main component of thick filaments; molecules consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filament during muscle contractions, and functions as a motor protein in all three types of muscle tissue; shaped like two golf clubs twisted together.

Motor proteins

pull various cellular structures to achieve movement by converting the chemical energy in ATP to the mechanical energy of motion.

myosin tail

(twisted golf club handles) points toward the M line in the center of the sarcomere.
- Tails of neighboring myosin molecules lie parallel to one another, forming the shaft of the thick filament.

myosin heads

The two projections of each myosin molecule (golf club heads) are called

Actin

• Contractile protein that is the main component of thin filament.

• Individual actin molecules join to form an actin filament that is twisted into a helix.

• On each actin molecule is a myosin-binding site where myosin head of thick filament binds during muscle contraction.

Regulatory Proteins

proteins that help switch muscle contraction process on and off.

Tropomyosin

It is also part of the thin filament. In relaxed muscle, myosin is blocked from binding to actin because strands of tropomyosin cover the myosin-binding sites on actin.

Troponin

It is also part of the thin filament. When calcium ions bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin.

Structural Proteins

• Proteins which keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix.

• Structural proteins, which contribute to the alignment, stability, elasticity, and extensibility of myofibrils. Several key structural proteins are titin, -actinin, myomesin, nebulin, and dystrophin.

Titin

structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.

a-Actinin

structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules.

Myomesin

structural protein that forms M line of sarcomee; binds to titin molecules and connects adjacent thick filaments to one another.

Nebulin

structural protein that wraps around entire length of each thin filament; helps anchor thin filaments to Z discs and regulates length of thin filaments during development.

Dystrophin

structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; is thought to help reinforce sarcolemme and help transmit tension generated by sarcomeres to tendons.

Sliding Filament Theory of Muscle Contraction

//Kapag nastimulate ang skeletal muscle with the help of action potential, ang tendency ay kailangan magkaroon ng binding ang myosin doon sa myosin-binding site na present sa actin. In order for tropomyosin to expose the myosin-binding site, it needs calcium, so yung calcium na nanggaling sa sarcoplasmic reticulum ay magattach sa troponin. Since may naka attach sa troponin na calcium, that's the time na iikot na yung actin at ieexpose na yung myosin-binding site. Kapag nangyari yon, may presence ng calcium, there's a presence of ATP that allows binding and movement of myosin and actin, magkakaroon ng contraction. But kailangan din ng ATP para mag relax ulit, para humiwalay yung binding sa myosin-binding site.

Cardiac Muscle Tissue

The principal tissue in the heart wall

cardiac muscle fibers

have the same arrangement of actin and myosin and the same bands, zones, and Z discs as skeletal muscle fibers.

Intercalated discs

These are microscopic structures that are irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers to one another.

Skeletal Muscle

· Z-disk
· Enclosed sa bawat isang sarcomere ang actin and myosin
· Dalawang z disk ang matutulak sa m line

Smooth Muscle Tissue

· Dense bodies
· Actin and myosin ay nasa pagitan ng dalawang dense bodies
· Dense bodies ay magtutulakan sa isat-isa

Visceral (single-unit) smooth muscle tissue

- It is found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder.
- Like cardiac muscle, visceral smooth muscle is autorhythmic.

Multi-unit smooth muscle tissue

Consists of individual fibers, each with its own motor neuron terminals and with few gap junctions between neighboring fibers. Stimulation of one visceral muscle fiber causes contraction of many adjacent fibers, but stimulation of one multi-unit fiber causes contraction of that fiber only. Multi-unit smooth muscle tissue is found in the walls of large arteries, in airways to the lungs, in the arrector pili muscles that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye.

Origin

l it is the attachment of a muscle's tendon to the stationary bone.

Insertion

it is the attachment of a muscle's other tendon to the movable bone

The belly (body)

l it is the fleshy portion of the muscle between the tendons

Actions of the muscle

are the main movements that occur when the muscle contracts. In our spring example, this would be the closing of the door.

lever

is a rigid structure that can move around a fixed point

effort (E),

A lever is acted on at two different points by two different forces

load or resistance,

opposes movement

First-class Levers

fulcrum is between the effort and the load.

Second-class Levers

the load is between the fulcrum and the effort

Third-class Levers

The effort is between the fulcrum and the load

Parallel

- fascicles parallel to longitudinal axis of muscle; terminate at either end in flat tendon
Ex. Sternohyoid Muscle

Fusiform

- fascicles nearly parallel to longitudinal axis of muscle; terminate in flat tendons; muscle tapers toward tendons, where diameter is less than at belly. Ex. Digastric Muscle

Circular

fascicles in concentric circular arrangements from sphincter muscles that enclose an orifice (opening). Ex. Orbicularis Oculi Muscle

Triangular

fascicles spread over broad area converge at thick central tendon; gives muscle a triangular appearance. Ex. Pectoralis Major Muscle

Pennate

short fascicles in relation to total muscle length; tendon extends nearly entire length of muscle.

Unipennate

fascicles arranged only on one side of tendon. Ex. Extensor Digitorum Longus Muscle

Bipennate

- fascicles arranged on both sides of centrally positioned tendon. Ex. Rectus Femoris Muscle

Multipennate

fascicles attached obliquely from many directions to several tendons. Ex. Deltoid Muscle

Metabolism

Myriad chemical reactions happen in the body, particularly as they relate to generating, storing, and expending energy. All metabolic reactions are either catabolic or anabolic.

Cell Metabolism

The chemical alteration of molecules in the cell is referred to as cellular metabolism. Enzymes can be used as catalysts, accelerating chemical reactions without being changed by the reactions. The molecules that enzymes react with are called substrates.

Cellular Respiration

The oxidation process in which energy is released from molecules, such as glucose, and transferred to other molecules is called cellular respiration

Aerobic Respiration

Aerobic respiration occurs when oxygen is available. Pyruvic acid molecules and NADH enter mitochondria and, through a series of chemical reactions, called the citric acid cycle and the electron- transport chain, are converted to carbon dioxide and water

Aerobic Respiration

- It produces 36-38 ATP per glucose molecule

Anaerobic Respiration

Anaerobic respiration occurs without oxygen and includes the conversion of pyruvic acid to lactic acid. Produces 2 ATP molecules in every 1 molecule of glucose.

Adenosine Triphosphate

a molecule that stores energy in a cell until the cell needs.

Glycolysis

-Occurs in the cytoplasm.

• 1 molecule of glucose is converted to 2 molecules of Pyruvate, 2 ATP molecules, and 2 NADH (Nicotinamide Adenine Diphosphate).

• Anaerobic Respiration. (di need ng oxygen)

• 10 steps process.

ATP Sources:

A. Aerobic Respiration
B. Anaerobic Respiration
C. Creatine Phosphate Metabolism

Kreb's Cycle

• Also known as a tricarboxylic acid cycle or citric acid cycle.

• Pyruvate will decarboxylate and oxidizes to form Acetyl-CoA.

• Occurs in the mitochondrial matrix.

• Aerobic respiration.

• 8 steps process.

• Produced 2 NADH, 2 FADH2, 2 ATP.

ETC & Oxidative Phosphorylation

• Uses NADH and FADH to generate ATP.

• Electrons from NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane by a series of enzymatic reactions.

• The electron transport chain consists of a series of four enzyme complexes (Complex I - Complex IV) and two coenzymes (ubiquinone and Cytochrome c), which act as electron carriers and proton pumps used to transfer H+ ions into the space between the inner and outer mitochondrial membranes.

• 1 molecule of glucose can produce 36 ATP Molecules.

Lactic Acid Production

• Glycolysis continues because it doesn't need oxygen to take place. But glycolysis does need a steady supply of NAD+, which usually comes from the oxygen-dependent electron transport chain converting NADH back into NAD+.

• In its absence, the body begins a process called lactic acid fermentation, in which one molecule of pyruvate combines with one molecule of NADH to produce a molecule of NAD+ plus a molecule of the toxic by product lactic acid.

Creatine Phosphate

- It is a molecule that can store energy in its phosphate bonds.