Chapter 9 - Muscles and muscle tissues

Fascicles

"Bundles" Groups of muscle fibers within each skeletal muscle.

Rigor Mortis

"Death rigor", This is the process of muscles stiffening 3-4 hours after death and rigidity peaks at 12 hours. It gradually dissipates over the next 48-60 hrs. Process: 1. Dying cells are unable to exclude calcium and calcium influx into muscle cells promotes formation of myosin cross bridges. 2.After breathing stops, ATP synthesis ceases, but ATP continues to be consumed and cross bridge detachment is impossible. 3. Actin and myosin become irreversibly cross-linked, producing the stiffness. 4. It gradually disappears as muscle proteins break down after death.

Epimysium

"Outside the muscle" This type of muscle connective tissue is an overcoat of dnese irregular connective tissue that surrounds the whole muscle. It sometimes blends with the deep fascia that lies b/w neighboring muscles or the superficial fascia deep to the skin.

Perimysium

"around the muscle", This type of muscle connective tissue surrounds fascicles together and resemble bundles of sticks. It is made up of dense irregular connective tissue.

Terminal cisterns

"end sacs" This structure form larger, perpendicular cross channels at the A band-I band junctions and always occur in pairs.

Sarcomeres

"muscle segment" This region can be found in a myofibril b/w 2 successive Z discs.

Endomysium

"within the muscle" This type of muscle connective tissue is a wispy sheath that surrounds ea individual muscle fiber. Consists of an areolar connective tissue.

Nebulin

(3%) This structural protein is an actin-biding protein which is localized to the I band.

Titin

(9%) This structural protein connects the Z disc to the thick filament to attach to the M line. Maintains the organizations of the A band. Helps muscle resist excessive stretching. Forms elastic filament.

Excess postexercise oxygen consumption

(EPOC) This refers to the extra amount of oxygen the body must take in for the restorative process. It represents the diff. b/w the amount of oxygen needed for totally aerobic muscle activity and the amount actually used.

Isometric contractions

(measure) In this type of muscle contractions tension may build to the muscle's peak tension-producing capacity, but the muscle neither shortens nor lengthens. Muscles act this way to maintain upright posture or to hold joints staionary while movements occur at the other joints.Ex. the muscle attempts to move a load that is greater than the force (tension) the muscle is able to develop. trying to lift a piano.

Isotonic contraction

(same;tension) In this type of muscle contraction muscle length changes and moves load. Two different kinds: 1. Concentric contractions 2. Eccentric contractions

Muscle development and facts

1. All come from myoblasts. Several fuse together. Myotube matures into skeletal muscle fiber. 2. skeletal muscles stop dividing early on but satelliete cells help repair injured fibers and allow limited regeneration of dead skeletal muscle. capability declines w age 3. Cardiac muscle have a modest regeneration rate. Injured heart muscle is repaired by scar tissue. 4. Smooth muscles have a good regenerative capacity. 5. As we age, connective tissue increases, muscle fibers decrease. 6. By 30, sarcopenia (loss of muscle mass), may be reversed w exercise 7. By 80. muscle strength decreases by 50%

Smooth muscle E-C coupling

1. Ca enterthe cytosol from the ECF via voltage gater or non-voltage-gated Ca channels, or from the scant SR 2. Ca binds to and activates calmodulin 3. Activated calmodulin activates myosin light chain kinase 4. The activatedkinaze enzymes catalize transfer of phosphate to myosin, activating the myosin ATPases 5. Activated myosin forms cross bridges with actin of the thin filaments. shortening begins.

Cross bridge cycle

1. Cross bridge formation. (ATP->ADP, P, myosin attaches) 2. The power stroke ( -ADP,P, myosin pivots+bends, pulls actin) 3. Cross bridge detachment (+ATP, myosin detaches) (No ATP = rigor mortis 4. Cocking of the myosin head (ATP->ADP,P, myosin returns to prestroke high-energy position)

4 Structural proteins

1. Titin (9%) Connects the Z line to the M line 2. Nebulin (3%) Actin-binding protein, in the I band 3. Myomeisn forms M line/stabilizes thick filament 4. Dystrophin anchors proteins to outside of cell

Duration of muscle contraction energy production

6 seconds - ATP stored in muscle 10 seconds- ATP formed from creatine phosphate and ADP 30-40 - end of exercise, sec - Glycogen stored in muscles is broken down to glucose which is oxidize to generate ATP (anaerobic_ Hours - ATP is generated by breakdown of several nutrient energy fuel aerobic pathway.

Spastic paralysis

ACh esterase inhibitors prevent ACh esterase from breaking down ACh. ACh remains attached to ACh receptor sites. Na continues to flow into muscle and muscle remains contracted.

Fused

AKA Complete tetanus, at this point of muscle response, the stimulation frequency continues to increase, muscle tension increases until it reaches maximal tension. All evidence of muscle relaxation disappears and contractions fuse into a smooth, sustain contraction. This happens infrequently.

Unfused

AKA Incomplete tetanus, at this point of muscle response, the degree of wave summation becomes greater and greater, progressing to a sustained but quivering contraction.

Excitability

AKA Responsiveness. This is the ability of a muscle cell to receive and respond to a stimulus by changing its membrane potential. This kind of stimulus is typ. chemical.

Sarcoplasm

AKA cytoplasms, it is similar to the cytoplasms of other cells, but it contains unusually large amounts of gycosomes and myoglobin.

Aerobic exercise

AKA endurance exersice, (swimming, jogging, biking) Skeletal muscle changes: 1. # of capillaries surrounding the muscle fibers increases 2. # of mitochondria within the muscle fibers increases 3. fibers synthesize more myoglobin slower in oxidative fibers.

Myofilaments

AKA filaments, These smaller structures lie within the sarcomeres. Thick filaments Thin filament - Contain actin (blue) and extend across the I band and parthway into the A band.

Direct attachment

AKA fleshy attachment, is when the epimysioum of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage.

Recruitment

AKA multiple motor unit summation, controls the force of contraction more precisely by delivering shocks of increasing voltage to the muscle, calling more and more muscle fibers into play. It allows increase force during weak contractions and different type of uses (caressing vs. slap).

Sarcolema

AKA plasma membrane, #2

Wave summation

AKA temporal summation, this muscle response occurs when the second contraction occurs before the muscle has completely relaxed. Because more Ca is being added, muscle contractions causes more shortening than the first. Contractions are added together.

Myoblasts

All three types of muscle tissue develop from this type of embryonic mesoderm cells.

Motor end plate or Neuromuscular junction

As a rule, each muscle cell has one of these, located approximately midway along its length.

Period of relaxation

During this final phase of a myogram, lastas 10-100ms, and is initiated by reentry of Ca+ into the SR. Contrctile forces are declining. Muscle tension decreases to zero and the tracting returns to the baseline. If the muscle was shorten during contraction, ti now returns to its initial length. Muscle contracts faster than it relaxes.

Latent period

During this period of a myogram, cross bridges begin to cycle but muscle tension is not yet measurable and the myogram does not show a response. It is the fist few milliseconds following stimulation when E-C is occurring.

Period of contraction

During this perior of a myogram, cross bridges are active, from the onset to the peak of tension development. It lasts 10-100ms. If the tension becomes great enough to overcome the resistance of the load, the muscle shortens.

Myosin

Each molecule of this protein is composed of 2 heavy and 4 polypeptide chains and has a rodlike tail attached by a flexible hinge to 2 globular heads. The tails are attache to the M line. The heads are binding sites for Actin and ATP

Maintain posture and body position

In order to perform these actions, muscles perform almost continuously, making one tiny adjustment after another to counteract the never-ending downward pull of gravity.

Anaerobic pathway

In this process of muscle energy generation the formation of glycolysis and lactic acid is key. ATP is generated by breaking down (catabolizing) glucose obtained from the blood or glycogen stored in the muscle. It happens after the stored ATP and CP are exhausted. 1. Glucose 2. Glycolysis in cytosol =2 ATP 3. Pyruvic acid 4. Lactic acid, relased to blood Duration: 30-40 seconds This process harvest only about 5% as much ATP from ea glucose molecule as aerobic pathway but it produces it about 2 1/2 times faster. Activities: Tennis, soccer, 100 m swim

Direct phosphorylation of ADP

In this processthe muscle's ATP storage are depleted after only few twitches, then Creatine phosphate is tapped to regenerate ATP. Coupling Creatine phosphate and DP transfers energy and phosphate group from CP to ADP to form ATP almost instantly: Creatine phosphate + ADP ->Creatine + ATP The reaction is catalized by Creatine Kinase Activities: weight lifting, diving, and springing.

Multi unit smooth muscle

In this type of smooth muscle Gap junctions and spontaneous depolarizations are rare. Muscle fibers are independent of ea other. Rich in nerve endings. responds with graded contractions w recruitment.

Origin

Muscle attachment to the immovable or less movable bone.

Insertion

Muscle attachment to the movable bone.

2 Contractile proteins

Myosin (44%) and Actin (22%). What kind of proteins are these?

Muscle fibers

Skeletal and smooth muscle cells (but not cardiac muscle cells) are elongated and called this.

Flaccid paralysis

THis type of paralysis occurs when there is a blockon ACh receptro sites on skeletal muscle fibers, preventing muscle from contracting.

Resistance exercise

The result of this kind of exercise can be hypertrophy. Activities: weight lifting. Strength, not stamina, is important. A few minutes every other day is sufficient to allow a proverbial weakling to put on 50% more muscle within a year. Muscles fibers will contain more mitochondria, form more myofilaments and myofibrils, store more glycogen, and develop more connective tissue b/w muscle cells.

Phases leading to muscle fiber contraction

These 2 phases precede what? Excitation and excitation-contraction coupling.

Muscle tissue characteristics

These 4 characteristics allow this type of tissue to perform its activities 1. Excitability (Responsiveness) 2. Contractility 3. Extensibility 4. Elasticity

Muscle functions

These are (at least) 4 important functions of what tissue in the body? 1. Movement 2. Maintain posture and body position 3. Stabilize joints 4. Generate heat

muscle attachemnts

These are classified as? 1. Insertion 2. Origin

Filaments regulatory proteins (Myofilament)

These are consider the regulatoryy proteins of Myofilaments 1. Tropomyosin: Rod-shaped, help stiffen and stabilize it. 2. Troponin

Glycosomes

These are granules of stored glycogen that provide glucose during muscle cell activity for ATP production in the sarcoplasm

Dense bodies

These are intermediate filaments that resist tension arranged like a lattice. They attach tat regular intervals to cytoplasmic structures.

Diffuse junctions

These are junctions in which varicosities release neurotransmitter into a wide synaptic cleft in the general area of the smooth muscle cells.

Varicosities

These are part of smooth muscles and release neurotransmitters into a wide synaptic cleft in the general area of the smooth muscle cells. They are bulbous swellings that are part of the innervating nerve fibers that are part of the nervous system.

Caveolae

These are pouchlike infoldings containing large number of Ca channels located in the sarcolemma in replacement of T tubules.

Two types of graded muscle contraction processes

These are what kind of muscle processes? Changes in stimulus frequency Changes in stimulus strength

Muscle fiber type

These can be described by the following functional characteristics: 1. Speed of concentration: slow and fast fibers 2. Major pathways for forming ATP: Oxidative fibers and gycolytic fibers

Factors affecting velocity and duration of contraction

These describe what?: 1. Muscle fiber type 2. load 3. recruitment

Z discs

These discs are proteins that anchors thin (actin) filaments and connects adjacent sarcomeres. These discs are located within the I band as a midline darker interruption.

Force of muscle contraction

These factors affect what? 1. Number of muscle fibers recruited: The more the greater the force. 2. Size of muscle fibers: The bulkier the greater the tension (Hypertrophy, increase in size) 3. Frequency of stimulation: THe higher the freq., the greater the force 4. Degree of muscle stretch: It varies w/ lenght

Thin filament (Myofilaments)

These filaments Contain actin (blue) and extend across the I band and parthway into the A band.

Thick filaments (Myofilaments)

These filaments contain myosin (red, about 300) and extend the entire length of the A band.

Somatic motor neurons

These never cell activate the skeletal muscle fibers. They resided in the brain or spinal cord. Their long thread like axons (bundled with nerves) extend to the muscle cells they serve. One for each cell.

Ways to provide energy for contraction (3)

These processes can be described as what kind of muscle aid? 1. Direct phosphorylation of ADP by creatine phosphate 2.Anaerobic pathway: Glycolysis and lactid acid formation 3. Aerobic respiration

Muscle cell three special structures

These structures are highly modified: 1. Myofibrils, 2. sarcoplasmic reticulum 3. T tubule

T tubules

These structures are located at each A band - I band junction. "T" = transverse. Tremendously increases the muscle fiber's surface area. It runs b/w the paired terminal cisterns fo the SR forming triads. This structure helps regulate muscle contraction

Connective tissue sheaths (3)

These structures support each cell and reinforce and hold together the muscle, preventing the bulging muscles from bursting during exceptionally strong contractions. 1. Epimysium 2. Perimysium and fascicles 3. Endomysium

Types of muscle contractions

These two can be classified as? Isotonic and Isomeric.

Lactid acid

This acid is the result of the conversion of pyruvic acid. It happens when the muscles contract vigorously and reaches about 70% or max. capacity and the compression of the blood vessels within them impair blood flow and oxygen delivery. Its accumulation is responsible for muscle soreness during exercise.

Myogram

This apparatus produces a recording of muscle contractile activity. The line recording the activity is called tracing. It has 3 phases: 1. Latent period 2. Period of contraction 3. Period of relaxation

Major pathways for forming ATP

This characteristic of muscle fibers can be divided into 1. Oxydative fibers: Cells that rely in mostly Oxygen-using aerobic pathways for ATP generation 2. Glycolytic fibers: Rely more on anaerobic glycolysis and creatine phosplate.

Speed of contraction

This characteristic of muscle fibers can be divided into Slow fibers and fast fibers. The diff. reflects how fast their myosic ATPases split ATP, and the patter of electrical activity of their motor neurons.

Length-tension relationship

This characteristic of muscle stretch happens when the muscle is slightly stretch and the think and thick filaments overlap optimally, bc this permits sliding along nearly the entire length of the tin filaments.

Motor unit

This consist of one motor neuron and all the muscle fibers it innervates, or supplies. When this fires (transmits an action potential), all the muscle fibers it innervates contract. Small muscles have them small (eyes), Large muscles have them large (hip). Its fibers are spread out throughout the muscle.

Muscular distrophy

This disease is a group of 9 inherited muscle-destroying disease. It primarily affects voluntary muscles by enlarging due to fat and connective tissue deposits and causing fibers to atrophy. Most common is Duchenne muscular distrophy (DMD).

ATP-ase

This enzyme can split ATP to provide usable energy for the muscle cell and ADP.

Creatine Kinase

This enzyme is used to catabolyze the reaction b/w Creatine phosphate + ADP to generate ATP + creatine. It is so efficient that the amount of ATP in muscle cells changes very little during the initial period of contraction.

Acetylcholinesterase

This enzyme terminates effects of ACh after they bind to the ACh receptros. This enzyme breaks down ACh to its building blocks, acetic acid and choline. It prevents continued muscle fiber contraction in the absence of additional nervous system stimulation.

Creatine phosphate

This high-energy molecule is stored in muscles and it is used, in combination of ADP, to create ATP fro muscles during vigorous exercise. It is stored 2-3 more than ATP.

Synaptic cleff

This is a gap in b/w the axon terminal and the muscle fiber, only 50-80 nm apart. This gap is filled with a gel-like extracellular substance rich in glycoproteins and collagen fibers.

Myoglobin

This is a red pigment that stores oxygen in the sarcoplasm.

Striations

This is a skeletal muscle characteristic in which a repeating series of dark and light bands, are evident along the length of ea myofibril. They are formed of A bands (dark) I bands (light).

Muscle fatigue

This is a state of physiological inability to contract even though the muscle still may be receiving stimuli. It is a problem in E-C coupling or neuromuscular junction. It is produced, in general, by intense exercise of short duration.

Triads

This is defined as T tubules running b/w the paired terminal cisterns of the SR

Somatic Motor unit

This is defined as a single motor neuron + all of the corresponding muscle fibers it innervates.

Action potential

This is known as generated electrical impulses traveling down a cell.

Glycolysis

This is known as the initial phase of glucose breakdown by separating it into 2 pyruvic acid molecules, enough to form small amounts of ATP (2 per glucose). It can occur in both the presence and absence of oxygen, but because it does not use oxygen, it is an anaerobic pathway.

Aerobic endurace

This is known as the length in time a muscle can continue to contract using aerobic pathways.

Voluntary muscle

This is known as voluntary conscious control of the muscle.

Extensibility

This is the ability of a muscle to extend or stretch. Muscle cells shorten when contracting, but they can stretch even beyond their resting length, when relaxed.

Contractility

This is the ability of a muscle to shorten forcibly when adequately stimulated. This ability sets muscle apart from all other tissue types.

Muscle tension

This is the force exerted by a contracting muscle on an object. The opposing force is called load

Myosin (Myofilaments)

This is the main composition of thick filaments. It is made of 4 light polypeptide chains.

Load

This is the opposing force exerted on the muscle by the weight of the object to be moved..

Movement production

This is the process in which muscles enable you to respond quickly. Skeletal muscle are responsible for all locomotion and manipulation.

Peristalsis

This is the propulsive action of alternating contraction and relaxation of longitudinal and circular layers mixes substances in the lumen and squeezes them through the organ's internal pathway.

Skeletal muscle

This kind of muscle tissue can be described as organs that attach to and cover the bony skeleton and are made up of several types of tissue.Blood vessels, nerve fibers, and connective tissue are also present. They are the longest muscle cells. They are responsible for overall body mobility and they are very powerful and adaptable. Striated: Yes Movement: Voluntary

Muscle twitch

This muscle action is a motor unit's response to a single action potential of its motor neuron. The muscle fibers contract quickly and then relax. It may result from certain neuromuscular problems and it is not the way muscles typ. work.

Cross bridge cycling

This muscle contraction process is a series of events during which myosin heads pull thin fillaments toward the center of the sarcomere, it requires Ca2+.

Telodendria

This part of the axon is a distal branch of a neuronal axon that can further branch into axon terminals. While each neuron only has one axon, it can branch into several telodendria and form presynaptic vesicles for neurotransmission at each branch

Junctional folds

This part of the neuromuscular junction provides a large surface for the million of ACh receptors.

Axon

This part of the somatic motor neurons are thread like cords and divides profusely as it enters the muscle. Each gives off several short, curling branches that collectively form an elliptical neuromuscular junction or motor end plate, with a single muscle fiber.

Muscle tone

This phenomenon is described as the muscles always being slightly contracted even when relaxed. It does not produce any active movement but keeps muscles firm, healthy. and ready to respond to stimulation. It helps stabilize and maintain posture.

Size principle

This principle indicates the muscle recruitment process: 1. Motor units with the smallest muscle fibers are activated first. They are the most highly excitable motor neurons. 2. larger motor units start to be excited, contractile strength increases. 3. Largest motor units, containing large, coarse muscle fibers, are activated. They are the least excitable (highest threshold) neurons and are activated only when the most powerful contraction is necessary.

Anaerobic glycolysis

This process happens when the muscles contract vigorously and reaches about 70% or max. capacity and the compression of the blood vessels within them impair blood flow and oxygen delivery and pyruvic acid is converted into lactid acid.

Excitation-contraction (E-C) Coupling

This process is thesequence of events in which transmission of an action potential along the sarcolemma causes myofilaments to slide. The action potential is brief and ends well before any signs of contraction are obvious.

Never and blood supply

This process requires one nerve, one artery, and one or more veins to serve each side of the muscle. Nerve endings help control its activity. Contracting muscle fibers use huge amounts of energy and require almost continuous delivery of oxygen and nutrient via arteries.

Actin (Myofilaments)

This protein has a kidney-shaped polypeptide subunits called globular actin or G actin.

Actin

This protein is a twisted double strand and bears active sites for myosin head. It has a kidney-shaped polypeptide subunits (Globular actin or G actin). It contains 2 regulatory proteins: Tropomyosin and Troponin

Dystrophin (Myofilament)

This protein links the thin filaments to the integral proteins of the sarcolemma.

Hypotonia

This refers to a flaccid muscle

Muscle spasm

This refers to the sudden involuntary contractions in a single muscle

Rhabdomyolysis

This refers to the widespread acute muscle damage, life threatening, can cause renal failure.

Calmodulin

This regulatory molecule exists in smooth muscle and activates myosin by interacting with it. During contraction, it interacts with Myosin kinase or myosin light chain kinase which phorylates the myosin, activating it.

Tropomyosin

This regulatory protein helps stiffen and stabilize actin by its spiral shape around it. When relaxed state they block myosin binding sites on actin.

Troponin

This regulatory protein is a major component of thing filaments. It is a globular three-polypeptide complex. One of then is an inhibitory subunit that binds to actin and the other one binds to tropomyosin and helps position it on actin. The third binds calcium ions.

Synaptic vesicles

This small structures can be found within the moundlike axon terminal. They are membranous sacs containing the neurotransmitter acetylcholine or ACh

Myomesin

This structural protein forms the M line and stabilizes thick filament (Myosin)

Dystrophin

This structural protein links the think filament to the integral proteins of the sarcolema which are anchored to the extracellular matrix (outside). This is the longest gene known, covering 2.4 million bases.

Sarcoplasmic reticulum

This structure can be described as an elaborate smooth Endoplasmic reticulum. most run longitudinally along the myofibril. They communicate at the H zone. It regulates intracellular levels of ionic calcium by storing it and releasing it as necessary. This structure helps regulate muscle contraction.

Myofibrils

This structure is contained in the hundred to thousand numbers inside a single muscle fiber. They are rod-like and run parallel to its length. They are densely packed in the fiber that mitochondria and other organelles appear to be squeezed b/w them. About 80% of cellular volume. Two types of proteins Myosin (thick) and Actin (thin).

Aerobic respiration

This type of ATP generation occurs in the mitochondria, requires oxygen, and involves a sequence of chemical reactions that break the bonds of fuel molecules and releases energy to make ATP. It includes glycolysis and the reactions that take lace in the mitochondira, breaks down glucose entirely. Glucose + Oxygen -> carbon dioxide + H2O + ATP 32 ATP per glucose, but it is slow. This process will continue as long as there is enough Oxygen. Activities: Marathon jogs and running. Endurance rather than power.

Indirect attachment

This type of attachment happens when the muscle's connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheetlike aponeurosis. It anchors the muscle to the connective tissue of a skeletal element or to the fascia of other muscles. This type of attachment is much more common because its durability and small size.

Sliding filament model of contraction

This type of contraction states that during contraction, the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree.

Concentric contractions

This type of isotonic contraction happens when the muscle shortens and does work, such as picking up a bood or kicking a ball.

skeletal muscle fibers

This type of muscle fibers can be very long (up to 30 cm) but small in diameter (Typ. 10-100um). They have multiple oval nuclei just beneath its sarcolemma.

Generate heat

This type of muscle function generate heat as they contact, which play a role in maintaining normal body temperature.

Stabilize Joints

This type of muscle function strengthen and stabilize the joints of the skeleton.

Smooth muscle

This type of muscle is found in the walls of hollow visceral organs. Its role is to force fluids and other substances through internal body channels. Striated: No (Nonstriated) Movement: Involuntary 1. Spindle-shaped cells of variable size and 1 centrally located nucleus. 2. 10 times narrower and 1000 times shorter than skeletal muscle. 3. No connective tissue sheaths, small endomysium. 4. Organized into sheets of closely apposed fibers. 2 sheets of smooth muscle with their fibers oriented at right angles to each other

Cardiac muscle

This type of muscle only occurs in the heart as the bulk of the walls. Striated: Yes Movement: Involuntary

changes in stimulus frequency

This type of muscle response happens when two identical stimuli are delivered to a muscle in rapid succession, the second twitch will be stronger than the first. 1. Relaxation b/w twitches becomes shorter and shorter 2. Concentration of Ca in the cytosol rises higher and higher 3. The degree of wave summation becomes greater and greater. Quivering contraction called unfused or incomplete tetanus. 4.As the stimulation of frequency continues to increase, muscle tension increases until it reaches maximal tension. At that point all contraction fuse into a smooth sustained contraction called fuse or complete tetanus.

Changes in stimulus strenght

This type of muscle response happens when wave summation contributes to contractile force, but its primary function is to produce smooth, continuous muscle muscle contractions by rapidly stimulating a specific number of muscle cells.

Graded muscle responses

This type of muscle responses, healthy muscle contractions are relatively smooth and vary in strength as different demands are placed on them. They are needed for proper control of skeletal movement.

Threshold stimulus

This type of muscle stimuli is the first observable contraction occurring. Beyond this point, the muscle contracts more vigorously as the stimulus strength increases.

Subthreshhold stimuli

This type of muscle stimuli produces no observable contractions.

Maximal stimulus

This type of muscle stimulus is the strongest stimulus that increases contractile force. It represents a point at which all the muscle's motor units are recruited. Stimulus beyond the maximal stimulus does not produce a stronger contraction.

Smooth muscle contraction

This type of muscles exhibit slow, synchronized contractions, the whole sheet responds to a stimulus in unison. Gap junctions allow smooth muscles to transmit action potentials from fiber to fiber. Actin and myosin interact, the final trigger for contraction is a rise in the intracellular calcium ion level, ATP energizes the sliding process. It takes 30x longer than skeletal muscle but it can maintain the tension longer.

Unitary smooth muscles

This type of smooth muscle is commonly call visceral muscle bc it is in the walls of all hollow organs except the heart. All cells are arranged in opposing sheets, are electrically couple by gap junctions and so contract as a unit, respond to various chemical stimuli.

Anaerobic threshold

This type of threshold is known as the point at which muscle metabolism converts to anaerobic glycolysis.

myopathy

This word describes any disease of the muscles

Myalgia

This word means muscle pain

M Line

This zone is located within an H zone and can be identified as a dark line formed by molecules of the protein myomesin. It hold adjacent thick (myosin) filaments together in H band.

H-band (zone)

This zone is within a dark A band in the midsection and it is lighter. Filaments do not overlap in this region and it contains Myosin only and the M line in the middle.

Eccentric contractions

Thys type of isotonic contraction happens when the muscle generates force as it lengthens. They are very important fro coordination and purposeful movements.

Contraction

To physiologists, this term refers only to the activation of myosin's cross bridges, which are the force-generating sites. They generate enough tension on the thin filaments to exceed the forces that oppose shortening. It ends when the cross bridges become inactive, tension declines, and the muscle fiber relaxes. Neither thick or thin filaments change length during contraction.

Kinase enzymes

What kind of enzymes are these? Myosin Kinase Myosin light chain kinase

Skeletal velocity and duration of contraction classification

What kind of muscle fits into the following classifications? 1. Slow oxidative fibers 2. Fast oxidative fibers 3. fast glycolytic fibers

2 regulatory proteins

What kind of proteins are these? Troponin (5%) and Tropomyosin (5%).

Smooth muscle characteristics

What muscle are the following characteristics describing?: 1. Thick filaments are fewer but have myosin heads along their entire lengths. 2.No troponin complex in thin filaments. Calmodulin acts as Ca binding site instead. 3. Thick and think filaments arranged diagonally. Contractile proteins crisscorss. spiral down like stripes on a barber pole. 4. intermediate filament-dense body network. They resist tension It is like a steady, heavy-duty engine, that lumbers along tirelessly.

Sliding filament model of contraction process

What process is this? 1. Stymulated Myosin heads latch onto myosin-binding sites on actin in the think filaments, and the sliding begins. 2. Cross bridge attachments form and break several times during contraction. They generate tension and propel the think filaments towards the center of the sarcomere 3. Simultaneously it occurs in sarcomeres and the muscle cell shortens. 4. Thin filaments slide centrally, the z discs to which they attach are pulled toward the M line 5. I bands shorten 6. Distance of Z discs shorten 7. The H zones disappear 8. Continuous A bands move closer but their length does not change.

Types of muscle tissue

What type of tissue are these: 1. Skeletal 2. Cardiac 3. Smooth

Aponeurosis

a sheet of pearly-white fibrous tissue that takes the place of a tendon in sheetlike muscles having a wide area of attachment.

A band

this band covers both myosin and actin

I band

this band only covers actin

Types of smooth muscle

what kind of muscles are these? 1. Unitary smooth muscle 2. multi unit smooth muscle