Muscle Tissue

* Skeletal Muscle

* Cardiac Muscle

* Smooth Muscle

Skeletal Muscles are organs composed mainly of skeletal muscle tissue, but they also contain connective tissues, nerves, and blood vessels.

Each cell in the skeletal muscle tissue is a single muscle fiber.

1) Produce Skeletal Movement

2) Maintain Posture and Body Position

3) Support Soft Tissues

4) Guard Body Entrances and Exits

5) Maintain Body Temperature

6) Store Nutrients

1) An epimysium

2) A perimysium

3) An endomysium

1) Tendon

2) Aponeurosis

Multinucleate means that each contains hundreds of nuclei just internal to the plasma membrane.

The more copies of these genes, the faster these proteins can be produced.

Myofibrils. The active shortening of myofibrils is responsible for skeletal muscle fiber contraction.

Myofibrils consist of bundles of protein filaments called myofilaments - thin filaments and thick filaments.

The name of the plasma membrane of a muscle fiber is called sarcolemma. The sarcolemma surround the cytoplasm which is called sarcoplasm.

1) Thick filaments

2) Thin filaments

3) Proteins that stabilize the positions of the which and thin filaments

4) Proteins that regulate the interactions between thick and thin filaments.

The dark bands are called A band, derived from anisotropic.

The light bands are called I bands, derived from isotropic.

2) Muscle Fascicle

3) Muscle Fiber

4) Myofibril

5) Sacromere

This is the Skeletal Muscle level

This is the Muscle Fiber level

This is the Myofibril level

This is the Sarcomere level

An influx of sodium ions leads to depolarization. (More positive)

The movement of potassium ions out of a cell leads to hyper polarization. (Less positive)

A return to the resting potential is called repolarization.

This is where communication between a neuron and another cell occurs at a synapse.

When the other cell is a skeletal muscle fiber, the synapse is known as neuromuscular junction. The NMJ is made up of an axon terminal of a neuron, a specialized region of the sarcolemma called the motor end plate, and, in between, a narrow space called the synaptic cleft.

In an isotonic contraction, tension increases and the skeletal muscle's length changes.

* Lifting an object off a desk

* Walking

* Running involve isotonic contractions.

Concentric and eccentric

Aerobic metabolism normally provides 95 percent of the ATP demands of a resting cell. In this process, mitochondria absorb oxygen, ADP, phosphate ions, and organic substrates (such as pyruvate) from the surrounding cytoplasm.

The molecules then enter the citric acid cycle.

Glycolysis is the anaerobic breakdown of glucose to pyruvate in the cytoplasm of a cell. It is an anaerobic process because it does not require oxygen.

Glycolysis provides a net gain of 2 ATP molecules and generates 2 pyruvate molecules from each glucose molecule.

The shuffling of lactate to the liver and glucose back to the muscle cells .

It is the amount of oxygen required to restore normal, pre-exertion condition.

* fast fibers

* slow fibers

* intermediate fibers

Most of the skeletal muscle fibers in the body are called fast fibers, because they can reach peak twitch tension in 0.01 sec or less after stimulation.

One main characteristics of slow muscle fibers is that they are surrounded by a more extensive network of capillaries than is typical of fast muscle tissue. For this reason, they have a dramatically higher oxygen supply to support mitochondrial activity.

Slow fibers also contain the red pigment myoglobin. Myoglobolin reversibly bind oxygen molecules.

Intermediate fibers are intermediate between those of fast fibers and slow fibers. In appearance, intermediate fibers most closely resemble fast fibers, for they contain little myoglobin and are relatively pale.

Hypertrophy is an enlargement of the stimulated muscle. The number of muscle fibers does not change significantly, but the muscle as a whole enlarges because each muscle fiber increased in diameter.

The reduction in muscle size, tone, and power in muscle is called atrophy.

Anaerobic endurance is the length of time muscular contraction can continue to be supported by glycolysis and by the existing energy reserve of ATP and cp.

Aerobic endurance is the length of time a muscle can continue to contract while supported by mitochondrial activities.

Aerobic activities do not promote muscle hypertrophy.

Cardiac muscle tissue contracts without neural stimulation. This is called automaticity.

A skeletal muscle contains muscle tissue, connective tissues, blood vessels, and nerves.

A skeletal muscle consists of fascicles (bindles of muscle fibers) enclosed by the epimysium. The bundles themselves are separated within the epimysium by perimysium. The fibers within a bundle (fascicle) is surrounded by endomysium.

Each muscle fiber has many superficial nuclei, as well as mitochondria and other organelles.

This is an image of a muscle fiber. Several of these fibers are called fascicle.

What we see are the individual fibers called Myofibril bundled together and are immersed in sarcoplasm. This is all enclosed by endomysium. We see that within the fascicle there are several mitochondria, nucleus, and capillaries. `

Myosatellite cells are stem cells and they are found in the endomysium.

They are considered to be voluntary muscle, because we have voluntary control over their contractions.

These unfused cells remain in adult skeletal muscle tissue as the myosatellite cells. After an injury, myosatellite cells may enlarge, divide, and fuse with damaged muscle fibers, thereby assisting in the repair of the tissue.

Wherever a T tubule encircles a myofibril, the tubule is tightly bound to the membranes of the SR. On either side of a T tubule the tubules of the SR enlarge and form expanded chambers called terminal cisternae.

This combination of a pair of terminal cisternae plus a T tubule is known as a triad.

A muscle contraction begins when stored calcium ions are released into the cytosol. These ions then diffuse into individual contractile until called SARCOMERES .

1) F-actin

2) Nebulin

3) Tropomyosin

4) Troponin

When a skeletal muscle fiber contracts, a sarcomere bands narrow. These observations make sense only if the thin filaments are sliding toward the center of each sarcomere, alongside the thick filaments.

You would expect the greatest concentration of calcium ions in resting skeletal muscle to be in the terminal cisternae of the sarcoplasmic reticulum.

Acetylcholine (ACh) is a neurotransmitter, a chemical released by a neuron to change the permeability or other properties of another cell’s plasma membrane.

Excitation-Contraction Coupling. *this coupling occurs at the triads.

1) ACh is released at the neuromuscular junction and binds to ACh receptors on the sarcolemma.

2) An action potential is generated and spreads across the membrane surface of the muscle fiber and along the T tubules.

3) The sarcoplasmic reticulum releases stored calcium ions.

4) Calcium ions bind to troponin, exposing the active sites on the thin filaments. Cross-bridges from when myosin heads bind to those active sites.

5) The contraction cycle begins as repeated cycles of cross-bridge binding, pivoting, and detachment occur - all powered by ATP.

1) ACh is broken down by acetylcholinesterase (AChE), ending action potential generation.

2) Sarcoplasmic reticulum reabsorbs Ca2+. As the calcium ions are reabsorbed, their concentration in the cytosol decreases.

3) Active sites covered, and cross-bridge formation ends. Without calcium ions, the tropomyosin returns to its normal position and active sites are covered again.

4) Contraction ends. Without cross-bridge formation, contraction ends.

5) Muscle relaxation occurs. The muscle returns passively to its resting length.

Most skeletal muscles do not undergo treppe, however treppe is a phenomenon in cardiac muscle.

In any skeletal muscle, some motor units are always active, even when the entire muscle is not contracting. Their contractions do not produce enough tension to cause movement, but they do tense and firm the muscle. This resting tension in a skeletal muscle is called muscle tone.

Resting muscle tone stabilizes the positions of bones and joints. For example, in muscle involved with balance and posture, enough moto units are stimulated to produce the tension needed to maintain body position.

A muscle's ability to contract depends on the formation of cross-brides between the myosin and actin myofilaments in the muscle. In a muscle that is overstretched, the myofilaments would overlap very little, so very few cross-bridges between myosin and actin could form, and thus the contraction would be weak . If the myofilaments did not overlap at all, then no cross bridges would form and the muscle could not contract.

Yes, a skeletal muscle can contract without shortening. The muscle can shorten (isotonic, concentric contraction), elongate (isotonic, eccentric contraction), or remain the same length (isometric contraction), depending on the relationship between the load (resistance) and tension produced by actin-myosin interactions.

True.

Under these conditions, ATP transfers energy to creatine.

Creatine is a small molecule that muscle cells assemble from fragments of amino acids.

Creatine Phosphate (CP)

ATP + CREATINE -> ADP + CREATINE PHOSPHATE

It is the enzyme that catalyzes the reaction to convert ADP back to ATP.

ADP + CREATINE PHOSPHATE -> ATP + CREATINE

17 ATP molecules

1) The underutilized pyruvate molecules produced through glycolysis are converted to lactic acid. Because it releases hydrogen ions, production of lactic acid can lower the intracellular pH.

2) Glycolysis is a relatively inefficient way to generate ATP. Under anaerobic conditions, each glucose molecule generates 2 pyruvate molecules, which are converted to lactic acid. In cell gains 2 ATP molecules through glycolysis. Had those pyruvate molecules been catabolized aerobically in a mitochondrion, the cell would have produced 34 additional ATP.

Muscle fatigue is when a skeletal muscle can no longer perform at the required level of activity.

Muscle fatigue has been correlated with

1) depletion of metabolic reserves within the muscle fibers

2) Damage to the sarcolemma and sarcoplasmic reticulum

3) A decline in pH within the muscle fibers and the muscle as a whole, which decreases calcium ion binding to troponin and alters enzyme activities

4) A sense of weariness and a reduction in the desire to continue the activity , due to the effects of low blood pH and sensations of pain.

A twitch is a single stimulus-contraction-relaxation sequence in a muscle fiber.

The three phases are the latent period, the contraction phase, and the relaxation phase.

In the latent period, stimulation being and lasts about 2msec.

In the contraction phase, tension increases to a peak. As the tension increases, calcium ions are binding to troponin, active sites on thin filaments are being exposed, and cross bridge interactions are occurring.

In the relaxation phase, the Ca2+ levels are decreasing, active sites are being covered by tropomyosin, and the number of active cross bridges is declining as they detach.

All the muscle fibers controlled by a single motor neuron constitute a motor unit.

Intercalated Discs

The ability to function over a wide range of lengths.

Actin.

Myosin.

False.

While skeletal and smooth muscle have thick and thin filaments that are arranged similarly, smooth muscle filaments have a more scattered arrangement that affects the shape and the muscle cell when it contracts.

All three layers. Epimysium, perimysium, and endomysium.

A pair of F-Actin molecules twisted together.

About 300 myosin molecules twisted around one another.

Many muscle fibers are controlled by a SINGLE motor neuron.

Number of pivoting cross-bridges.

Cross bridges must produce ENOUGH tension to EXCEED the load to be moved.

Holding a heavy stack of books above the ground.

*no skeletal structures are moved.

Smooth

Smooth muscle cells lack myofibrils and sacomeres.

Calcium ions must interact with calmodulin to trigger muscle contraction.

*This involves a protein not found in skeletal muscle.

Cardiac and smooth

Electrical activity in the sarcolemma and the initiation of a contraction.

* Aerobic respiration

* Glycolysis

Lactic Acid

Isometric

No. Each cell is spindle shaped and has a single, centrally located nucleus.

A smooth muscle fiber has no T tubules, and the sarcoplasmic reticulum forms a loose network throughout the sarcoplasm.

They are nonstriated because they lack myofibrils and sarcomeres.

Smooth muscle cells have more myosin heads per thick filament.

The trigger for smoother muscle contraction is the appearance of free calcium ions in the cytoplasm. On stimulation, a surge of calcium ions enters the cell from the extracellular fluid, and the sarcoplasmic reticulum release additional calcium ions.

One in the sarcoplasm, the calcium ions interact with calmodulin, a calcium-binding protein. Calmodulin then activates the enzyme myosin light chain kinase, which in turn enables myosin heads to attach to actin. ƒa band