Honors A&P Checkpoint Questions

Describe the connective tissue layers associated with skeletal muscle tissue.

-Epiphysium: dense layer of collagen fibers that surrounds entire muscle -Permysium: divides skeletal muscle into a series of compartments containing a bundle of muscle fibers called a fasicle -Endomysium: surrounds individual skletal muscle cells(fibers) -All come together to form tendons or aponeuroses (muscle to bone)

Six major functions of skeletal muscle.

1.) Produce skeletal movement 2.) Maintain posture and body position 3.) Support soft tissues 4.) Guard entrances and exits 5.) Maintain body temperature 6.) Store nutrient reserves

Why does a muscle that has been overstretched produce less tension?

A muscle's ability to contract depends on the formation of cross-bridges 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.

Why would a sprinter experience muscle fatigue before a marathon runner would?

A sprinters requires large amounts of energy for a short burst of activity. The muscles switch to anerobic metabolism and also produces acidic waste products; this contributes to muscle fatigue. Marathon runners derive most of their energy from aerobic metabolism, which is more efficient and produces fewer waste products than anaerobic metabolism.

Which activity would be more likely to create an oxygen debt: swimming laps or lifting weights?

Acitvities that require short periods of strenuous activity produce a greater oxygen debt, because such activities rely heavilyon energy production by anaerobic metabolism. Because lifting weights is more strenuous over the short term than swimming laps, which is an aerobic activity, weight lifting would likely produce a greater oxygen debt than would swimming laps.

Describe the neuromuscular junction.

Aka myoneural junction, is the synapse between a motor neurons, muscle cell nervous system and a skeletal muscle fiber.

How would severing the tendon attached to a muscle affect the muscle's ability to move a body part?

Because tendons attach muscles to bones, severing the tendon would disconnect he muscle from the bone, and so the muscle could not move a body part.

What feature of cardiac muscle tissue allows the heart to act as a functional syncytium?

Cardiac muscle cells are joined by gap junctions, which allow ions and small molecules to flow directly between cells. As a result, action potentials generated in one cell spread rapidly to adjacent cells. Thus, all the cells contrast simultaneously, as if they were a single unit (a syncytium).

Compare and contrast skeletal muscle tissue and cardiac muscle tissue.

Compared to skeletal muscle, cardiac muscle: - Has relatively small cells - Has cells with centrally located nucleus (some with two or more) -Has T-tubules that are short and broad and form diads instead of triads -Has and SR that lacks terminal cisternae and has tubules that contact the cell membrane as well as the T tubules -Has cells that are nearly totally dependent on aerobic metabolism as an energy source -Contains intercalated discs that assist in impulse conduction.

Identify the three types of skeletal muscle fibers.

Fast fibers Slow fibers Intermediate fibers

What would happen to a resting skeletal muscle if the sarcolemma suddenly became very permeable to Ca2+?

If the sarcolemma of resting skeletal muscle suddenly became permeable to Ca2+, the intracellular concentration of Ca2+ would increase and the muscle would contract. Because the amount of calcium ions in the sarcoplasm must decline for relaxation to occur, the increased permeability of the sarcolemma to Ca2+ might prevent the muscle from relaxing completely.

Why are cardiac and smooth muscle contractions more affected by changes in extracellular Ca2+ than are skeletal muscle contractions?

In cardiac and smooth muscles, most of the calcium ions that trigger a contraction come from the extracellular fluid. In skeletal muscle, most of the calcium ions come from the sarcoplasmic reticulum.

Which type of muscle fibers would you expect to predominate in the large leg muscles of someone who excels at endurance activities, such as cycling or long distance running?

Individuals who excel at endurance activities have a higher than normal percentage of slow fivers. Slow fibers are physiologically better adapted to this type of activity than are fast fibers, which are less vascular and fatigue faster.

How do muscle cells continuously synthesize ATP?

Muscle cells synthesize ATP continuously by utilizing creatine phosphate (CP) and metabolizing gyclogen and fats. Most cells generate ATP through aerobic metabolism in the mitochondria and through glycolysis in he cytoplasm.

What is muscle fatique?

Muscle fatique is a muscle's reduced ability to contract due to low pH (lactic acid buildup), low ATP levels or other problems.

Define oxygen debt.

Oxygen debt is the amount of oxygen required to restore normal, pre-exertion conditions in muscle tissue.

How would a drug that blocks acetylcholine release affect muscle contraction?

Releasing acetylcholine is necessary for skeletal muscle contraction becuase it is the first step in the process for cross-bridge formation.

Why do skeletal muscles fibers appear striated when viewed through a light microscope?

Skeletal muscle appears striated when viewed through a light microscope because the Z lines and thick filaments of the myofibrils within the muscle fibers.

Can a skeletal muscle contract without shortening?

Skeletal muscle can contract without shortening. It can shorten (isotonic, concentration), elongate (isotonic,eccentric), or remain the same length (isomertric), depending on the relationship between the load (resistance) and the tension produced by actin-myosin interactions.

Three types of muscle tissue.

Skeletal muscle, cardiac muscle and smooth muscle

Identify the structural characteristics of smooth muscle tissue.

Smooth muscle cells lack sarcomeres and thus smooth muscle tissue is nonstriated. Additionally, the thin filaments are anchored to dense bodies.

Why can smooth muscle contract over a wider range of resting lengths than skeletal muscle can?

The looser organization of actin and myosin filaments in smooth muscle allows it to contract over a wider range of resting lengths.

Predict what would happen to a muscle if the motor end plate failed to produce acetylcholinestrase.

The motor end plate would be continuously stimulated by acetylcholine, locking the muscle in a state of contraction.

Describe structural components of sarcomere.

They're the smallest contractile unites of a striated muscle cell and are segments of myofibrils. Each sarcomer has dark A bands and I bands. The A band contains the M line, the H band, and the zone of overlap. Each I band contains thin filaments, but not thick filaments. Z lines mark the boundaries between adjacent sarcomeres.

Where would you expect the greatest concentration of Ca2+ in resting skeletal muscle to be?

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