Chapter 9- Muscles and Muscle Tissues

Aponeurosis

A tendon is called this when the CT elements extend as a BROAD, FLAT LAYER.

Elasticity of Muscle

Ability of muscle fibers to recoil and resume their resting length after being stretched.

Contractility of Muscle

Ability to shorten and thicken forcibly. Unique to muscles.

Extensibility of Muscle

Ability to stretch or extend. Muscle fibers shorten when contracting; they can be stretched beyond their resting length when relaxed.

Myofibrils

Each muscle fiber is seen to contain large numbers of these rod like structures that run parallel to its length. Are contractile elements of skeletal muscle.

Action Potential

Electrical signal or current

Unipennate

Fascicles insert into only 1 side of the tendon.

Generate heat

Generate Heat as the muscles contract. VITALLY IMPORTANT in the maintenance of normal body temperature. SKELETAL MUSCLES most responsible.

Fermentation

Glycolysis is the initial pathway of glucose respiration. Glucose is broken down into two pyuvic acid molecules and some of the engr. released is captured to form SMALL amounts of ATP. Does NOT use Oxygen. ANAEROBIC

Bipennate

If Fascicles are inserted into the tendon from opposite sides.

Movement

Just about all movements results from muscle contractions. SKELETAL MUSCLES are responsible for all locomotion and manipulation. Skeletal muscles enable the body to respond quickly to changes in the external environment.jump out of the way of a car,direct your eyes and smile or frown

Origin

Less moveable bone

Nerve supply to Muscles

Muscle Activity is ABSOLUTELY DEPENDENT on this. Contraction uses LARGE amounts of ATP and therefore needs large amounts of nutrients and oxygen.

Sacromeres

Myofilaments are arranged into these compartments.

***Events at the Neuromuscular Junction*** #1

Net entry of Na+ initiates an Action Potential which is propagated along the sarcolemma and down the T tubules

***Events at the Neuromuscular Junction*** PRE STEP

Neurotransmitter realsed diffuses across the synaptic cleft and attaches to ACh receptors on the sarcolemma.

Connective Tissue

Reinforces the muscles as a whole and provides muscle tissues with its natural elasticity.

***Events at the Neuromuscular Junction*** #5

Removal of Ca2+ by active transport into the SR after the Action Potential ends.

Blood Supply to Muscles

Requires large amounts of energy,therefore require a rich blood supply to deliver oxygen and nutrients as well as remove wastes.Waste products from the reactions must be eliminated. Muscle action depends on a rich blood supply to deliver nutrients and oxygen and remove wastes and heat. Each Muscle Fiber (cell) is in close contact with one or more capillaries.

Fascicle

SEVERAL ensheathed muscle fibers(cells) are bound together side by side into larger bundles.

Motor Neurons

Stimulate muscle to contract.

Isometric Contraction

Tension builds to the muscle's peak tension-producing capacity, but the muscle neither shortens nor lengthens because the weight EXCEEDS the muscle's capacity to move it.

Peristalsis of Smooth muscle

The cyclic contraction and relaxation of opposing layers allow the lumen of the organ to alternately constrict and dilate.

Ultrastructure

The two contractile proteins in muscles are 1. Myosin 2. Actin

***Events at the Neuromuscular Junction*** #6

Tropsmyosin blockage restored, blocking myosin binding sites on actin; contraction ends and muscle fiber relaxes.

Tendon

When the muscle coverings(wrappings) extend beyond the muscle fibers.

Actin

a contractile protein

Motor Unit

a motor neuron + all the muscle fibers it stimulates --a single one of these makes contact with an average of 150 muscle fibers.

Myoglobin

a red pigment that stores oxygen

Synaptic cleft

a small gap that separates the neuron and muscle fibers (they do NOT touch)

Fixator

a type of synergist which immobilizes a bone, or a muscle's origin so that the prime mover has a stable base on which to act.

Creatine Phosphate

a unique high energy compound stored in muscles in LARGE amounts. Reserves are quickly exhausted.

Cross Bridge Attachment

activated by myosin heads are strongly attracted to the exposed binding sites on actin.

Muscles Striated Appearance

alternating dark "A" bands and and the light "I" bands give it this appearance.

Thick Filaments

are composed of myosin molecules.

Transverse tubules (T-tubule)

are tunnel-like infoldings of the sarcolemma that protrude deep into the cell interior. The T tubules are open to the outside of the fiber and filled with EXTRACELLULAR fluid. Thousands of these form a T system. CONDUCTS NEREVE stimulus deep into the cell to every sarcomere. Also provide inlets the bring EXTRA-CELLULAR fluid (glucose, O, ions) into close contact with deeper parts of the muscle cell.

Perimysium

around the muscle-fibrous connective tissue surrounding the fascicles EACH fascicle is bound by this connective tissue (CT) sheath.

Cross Bridge detachment

as new ATP binds to the myosin head, the myosin cross bridge is released.

Convergent

broad origin , fascicles converge toward a single tendon-essentially triangular. EX pectoralis major.

Neurotransmitter

cells communicate by releasing this chemical messenger.

"M" line

composed of accessory proteins that link thick filaments

"I" band

contains the rest of the thin filaments but NO thick filaments. The" Z "line passes through the center of each of these bands.

Disuse Atrophy

degeneration and loss of mass due to complete immobilization or loss of neural stimulation.

Motor Neuron

delivers the stimulus that causes a muscle fiber to contact

Prolonged and Vigorous Muscle Activity

depletes both oxygen and glucose. Under anaerobic conditions most the pyruvic acid produced is converted to LACTIC ACID, rather than carbon dioxide and water.

Stabilize Joints

even as they pull on bones to cause movement,they strenthen and stabilize the joints of the skeleton.

Prime Mover (Agonist)

has the major responsibility for producing a specific movement.

Insertion

moveable bone

sacroplasma

muscle cell cystoplasm

sacrolemma

muscle cell membrane

Indirect Attachments

muscle fascia extends beyond the muscle as a tendon (rope-like) or a flat broad aponeurosis and anchors the muscle to the bone. MORE COMMON ATTACHMENT

Synergist

muscles that help the prime mover by either adding extra force to the same movement or reducing undesirable or unnecessary movements that might occur as the prime mover contracts.

Power Stroke

myosin head pivots pulling on the thin filament, sliding it toward the center of the sarcomere. ENERGY REQUIRING step.

"Z" " lines

narrow plate -shaped regions that separate one sarcomere from the next. Passes through the center of each "I" band.

Synapses

neurons and muscle fibers make contact and communicate at this specialized region.

Acetylcholine ACh

neurotransmitter molecules

Aerobic Respiration

occurs in the mitochondrion and requires OXYGEN. Involves chemical reactions in which the bonds of fuel molecules are broken and energy is released to make ATP. Glucose is broken down entirely, yielding water, carbon dioxide, and LARGE amounts of ATP.

Antagonist

opposes or reverses a particular movement. When the prime mover is active, these muscles are usually stretched or relaxed.

Epimysium

outside of the muscle-overcoat of dense irregular connective tissue surrounding the whole muscle. Fascicles are bound together by this COARSER wrap of DENSE FIBROUS CT that surrounds the ENTIRE muscle.

Elastic filament

part of the sarcomere, is the filament which ANCHORS thick filaments to the "Z" line and helps stabilize the position of the thick filaments.

Muscle Fatigue

prolonged tetanus leads to a situation in which the muscle is unable to contract.

Myo,Mys.sacro

refer to muscle

A Muscle Fiber

refers to a SINGLE muscle cell. Are soft and fragile,elongated muscle

Tropomyosin and Troponin

regulatory proteins

Circular layer of muscle tissue

runs around the circumference of the organ

Longitudinal layer of smooth muscle

runs with the long axis of the organ

connective tissue

sheaths of connective tissue which allow transfer of contractile forces from muscle fibers to the outside skeleton. Also,contribute to the elasticity of the muscle

Sarcoplasm

similar to cytoplasm of other cells and contains large amounts of stored glycogen and myoglobin.

Muscle fibers of the Motor unit

CONTRACT and RELAX TOGETHER

***Events at the Neuromuscular Junction*** #3

Ca ions bind to troponin; troponin changes shape, removing the blocking action of tropomyosin, leaving actin active sites exposed.

***Events at the Neuromuscular Junction*** #4

Contraction; myosin heads alternately attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process.

Sliding Filament Theory of Contraction

-Contraction involves sliding of thin F past thick ones so that the extent of the myofilament overlap increases. -In a RELAXED muscle fiber, the thick and thin overlap only SLIGHTLY. -During CONTRACTION, the thin F penetrate more and more DEEPLY into the central region of the "A" band. -During CONTRACTION, myosin CROSS bridges PULL on the thin F, causing them to slide INWARD. -The SLIDING of the F and SHORTENING of the sarcomeres causes SHORTENING of the WHOLE muscle fiber. -Muscle contraction requires CALCIUM and energy in the form of ATP. -ATP ATTACHES to binding sites on myosin cross-bridge. a portion of each myosin HEAD acts as an ATP base, splitting ATP into ADP + P. This transfers energy to the myosin HEAD. -Activated myosin HEADS spontaneously BIND to the myosin-binding sites on ACTIN when Ca levels rises and tropomyosin moves away from its blocking position. -The shape change that occurs when myosin binds to actin produces the POWER STROKE of contraction. -Once binding sites on actin are exposed: 1. Cross Bridge Attachment 2. Power Stroke 3. Cross Bridge detachment 4. Cocking of the myosin Head

Skeletal Muscle Tissue

-Covers bony skeleton -Fibers longest of all muscle cell types -Straited - VOLUNTARY control -subject to conscious control. -Can contract rapidly and vigorously but tire easily. -Can exert tremendous power. Remarkably adaptable. -Multi-nucleated

Smooth Muscle Tissue

-Found in walls of hollow organs--(digestive,urinary bladder,uterus, respiratory,etc). -NONSTRAITED. INVOLUNTARY control. -Contractions are slow and sustained. -uninucleated -Found in sheets of alternating circular and longitudinal layers; synchronized contraction of the sheets give rise to a wave of contraction along the hollow organ- peristalsis.

Cardiac Muscle Tissue

-Found only in the heart. -STRIATIONS and INVOLUNTARY. -Can contract rapidly -mulit-nucleated - Gap Junctions(intercalated disks) allow rapid communication between cells which synchronizes cell contractions.

Excitability of Muscle

-Responsiveness -Ability to receive and respond to a stimulus--stimulus is usually a chemical neurotransmitter, hormone, or pH change. The response is the generation and transmissions of an electrical current (action potentials) that signals the muscle to contract.

Muscle Relaxation

1. ACh is rapidly broken by acetylcholinesterase, which is present at the synaptic cleft. When Action Potentials cease, no new ACh is realized and acetylcholinesterase breaks down the ACh. This stops the generation of muscle action potentials, and Ca release channels in the SR close. 2. Ca Transport pumps rapidly remove Ca from the sarcoplasm into the SR. As Ca levels drop, the tropomyosin -troponin complex slides back over the myosin binding sites on actin, preventing further cross bridge attachment.

Functional Characteristics of Muscle

1. Excitability 2. Contractility 3. Extensibility 4. Elasticity

Functions of Muscle

1. Movement 2. Maintenance of Posture 3. Joint Stability 4. Heat Generation

Muscle Contraction (dumbed down version)

1. Nerve impulses reaches the axon terminal of motor neuron 2. Acetylcholine (ACh) is realized and travels ACROSS synaptic cleft. 3. Acetylcholine(ACh) binds to receptors on the motor end plate of the muscle cell, initiating an ELECTRICAL signal to contact. 4. T tubules CONDUCT the signal deep into the muscle cell. 5. Sarcoplasmic reticulum (SR) adjacent to the T tubules receive the signal which STIMULATES RELEASE of Ca that has been stored in the SR. 6. Calcium BINDS with troponin which causes the tropomyosin-troponin complex to move away (CHANGES SHAPE) from blocking the myosin binding site on the Actin. 7. Myosin Heads that have been activated by the hydrolysis of ATP binds to the actin and exerts POWER STROKE which pulls the thin filament toward the center of the SARCOMERE. 8.When a new ATP binds, myosin head RELEASES from the Actin. 9. Hydrolysis of the new ATP RE-COCKS the myosin head for another round of attaching and pulling.

cell diameter

10 to 100 micrometers yet the length maybe up to several hundred centimeters

Contracting Muscles shorten

30-35%

***Events at the Neuromuscular Junction*** #2

Action Potential in the Tubule activates voltage-sensitive receptors, which in turn trigger Ca2+ release from terminal cisternae of SR(Sarcoplasmic Reticulum) into cytosol.

Connective Tissue (CT) Sheaths (wrappings)

All these sheaths are continuous with one another as well as with the tendons that joins the muscles to bones or other muscles.

Types of Muscle Tissue

DIFFER in cell structure, body location, function, and the means by which they are activated to contract. SIMILAR in that all are elongated and contraction depends on 2 kinds of myofilaments(contractile elements of the muscles) 1. Skeletal Muscle Tissue 2. Cardiac Muscle Tissue 3. Smooth Muscle Tissue

Maintenance of Posture

Defy gravity.Muscles function almost continuously making small adjustments to maintain an erect or seated posture despite the effects of gravity.

Muscle Attachments

Directs-fleshly-epimysium of the muscle is fused to the periosteum of the bone or the perichondrium of the cartiliage. Indirect-epimysium extends beyond the muscle to a rope like(tendon) or sheet like(aponeurosis) connective tissue structure,which attaches to the bone. Most muscles at the joint are attached to bones in at least 2 places. When a muscle contracts the moveable bone (insertion) moves toward the less moveable bone (origin).

Thin Filaments

extend from anchoring points within the "Z" lines. Each is composed of ACTIN, TROPOMYOSIN, and TROPONIN molecules. Individual actin proteins join to form a actin filament that is TWISTED into a HELIX. On each actin molecule is a myosin binding site, for CROSS BRIDGE attachment. In RELAXED muscle, tropomyosin COVERS the myosin-binding sites on actin, BLOCKING cross-bridge attachment.

Circular

fascicles are arranged in concentric rings. Surround external body openings which they close by contracting sphincters.

Pennate (feather)

fascicles are short and attached obliquely to a central tendon running the length of the muscle.

Synaptic Vesicles

found at the distal end of the axon terminal. Are membrane enclosed sacs which contain Acetylcholine -ACh.

"A" band

found within a sarcomere this darker area extends from one end to the other of the thick filaments and includes portions of the thin filaments where they overlap the thick filaments.

Muscular Dystrophy

group of diseases inherited in a sex-linked recessive mechanism affecting mostly boys: muscles lack dystrophin.

Sarcoplasmic Reticulum (SR)

inside each muscle cell is a fluid filled system that encircles each myofibril. It is a membrane system and is similar to smooth endoplasmic reticulum. In a relaxed muscle fiber, it stores CALCIUM. RELEASE of calcium into the sarcoplasm around the thick and thin filaments triggers MUSCLE CONTRACTION. Major role of this is to REGULATE intercellular levels of CALCIUM.

Anaerobic pathway

is 2 1/2 times FASTER in producing ATP

Aerobic pathway

is 20 times MORE efficient than the anaerobic pathway in ATP production.

Contraction of Smooth Muscle

is SLOW, SUSTAINED, and RESISTANT to FATIGUE.

A Muscle

is a discrete organ composed of hundreds to thousands of fibers,nerves,blood vessels, and connective tissue wrappings.

Sarcolemma

is a muscle fibers plasma membrane and it surrounds the fibers cytoplasm or sarcoplasm.

Skeletal Muscle Composition

is composed of hundreds to thousands of very long, cylindrical cells called muscle fibers. Each fiber has many oval nuclei just under the Sarcolemma, out of the way of the contractile elements.

Myosin molecules

is distinctive in structure. Has a rod-like tail shaft/tail with 2 globular heads (like a GOLF CLUB with 2 heads). They are bundled together so their tails form a central part of the filament and point toward the "M" line. The globular heads of the myosin molecules project OUTWARD and in OPPOSITE directions from all around the shaft in a SPIRALING fashion. Their heads (cross bridges ) extend out toward the thin filaments.

Deep Fascia

is external to the epimysium. Is a STILL COARSER sheet of CT that binds muscles into functional groups and extends the to wrap other structures as well.

When a Muscle Cell Contracts

its individual sarcomeres SHORTEN and the distance between successive "Z" lines in REDUCED. As the length of the sarcomeres DECREASES, the myofibrils SHORTEN resulting in the SHORTENING of muscle fiber.

Mitochondria in muscle fibers

lie in rows through the fiber,close to the muscle proteins that use ATP.

Parallel

long axis of the fascicles run with the longitudinal axis of the muscle- strap like or fusiform - expanded belly- EX biceps

Nerves

skeleton muscle is dependent on nerve stimulation-each muscle fiber is supplied with a nerve ending.Consider the effects on the muscle WITHOUT the nerve stimulations

Tetanus

smooth, sustained contraction. Usual manner of muscle contraction in the body. Results from volleys of motor neuron impulses, rather than a single impulse.

Cocking of the Myosin Head

splitting ATP provides the energy needed to return the head to its high-energy upright or cocked position.

Direct or Fleshy Attachments

the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of cartilage.

Motor end plate

the region of the muscle fiber membrane adjacent to the axon terminal.

Muscle Twitch

the response of a muscle to a SINGLE brief stimulus. May be strong or weak depending on the number of motor units activated.

Myofilaments

the smaller structures within the Myofibrils. 1. Thick 2. Thin 3. Elastic Thick and Thin filaments overlap one another. The pattern of their overlap causes cross-striations seen in muscle fibers. These Filaments do not extend the entire length of a muscle fiber.,make up the contracitile elements(composed of actin and myosin) of the muscle cell

Neuromuscular Junction

the type of synapse formed between a motor unit and a skeletal muscle fiber. Includes both the axon terminals and the motor end plate of the muscle fiber.

Isotonic Contraction

upon stimulation, a muscle develops enough tension (force) to lift the load (weight). Once the resistance is overcome the muscle shortens, and the tension remains constant for the rest of the contraction.

Endomysium

within the muscle-connective tissue=mostly reticular fibers,which surround the individual muscle fibers A fine sheath of connective tissue (CT) that surrounds EACH muscle fiber(cell).