an ch 10

Botulinum toxin causes muscle paralysis because calcium is removed from the neuromuscular junction sodium is removed from the synaptic cleft the acetylcholine receptors at the motor end-plate are blocked no acetylcholine enters the synaptic cleft

no acetylcholine enters the synaptic cleft

Myosin heads directly use ______________ to transition to their _____________________ conformation, which enables them ready to bind to actin ATP; energized calcium; energized calcium; non-energized ATP; non-energized

ATP; energized

Place the events involved in muscle contraction in the correct order.

1. A nerve impulse causes acetylcholine (ACh) release at a neuromuscular junction. 2.ACh binds receptors on the motor end plate, initiating a muscle impulse. 3.Calcium ions bind to troponin, causing tropomyosin to move and expose active sites. 4.Myosin heads attach to actin and form crossbridges. 5.A cyclic "attach, pivot, detach, return" event occurs. 6.Calcium ions are moved back into the sarcoplasmic reticulum by ATP-driven pumps. 7. Myofilaments passively return to their original state.

Place the following excitation-contraction coupling events in the order that they occur.

End-plate potential reaches threshold Action potential sent throughout the sarcolemma Voltage-sensitive DPH receptors are activated Conformational change opens RyR1 channels Release of calcium into sarcoplasm

During contraction, the actin myofilaments slide toward the H zone. I band. A band. sarcomere. Z disk.

H zone.

Isometric Contraction -weightlifter attempts to lift a barbell but cannot because it is too heavy -man holds open a door for his date -Tension is building but muscle length does not change

Isotonic Contraction -sprinter leaves the starting block -mother lowers an infant into his crib

Which is a characteristic of skeletal muscle from the selections below? Multinucleated Contains intercalated discs Lack of striations Under autonomic nervous control

Multinucleated

In a 1500-meter run, an event that may take about 5 to 6 minutes, ATP is supplied by which energy sources? Phosphagens and anaerobic sources Phosphagens, anaerobic, and aerobic sources Phosphagens only Aerobic sources only

Phosphagens, anaerobic, and aerobic sources?

Which of the following muscle characteristics characterize an effect of aging? Increase in myoglobin content in muscle Slow, progressive loss of muscle mass Increase capacity to recover from disease Increase in muscle fiber diameter

Slow, progressive loss of muscle mass

Which of the following refers to a sustained muscle contraction? Summation Tetanus Relaxation Fatigue Latency

Summation

Which of the following connects muscle to bone? Tendons Epithelial tissue Cartilage Ligaments Menisci

Tendons

Hundreds of mutations have been identified in RyR1 that contribute to multiple muscular diseases. Assume that a new mutation was discovered that causes this receptor to continually remain open. Based on what you know about the function of this receptor, how would you expect this new mutation to impact contraction This mutation will decrease levels of calcium in the sarcoplasm, which will prevent muscle contraction. This mutation will decrease the sensitivity of the DPH receptor to voltage changes,which will prevent muscle contraction. This mutation will increase the sensitivity of the DPH receptor to voltage changes, which will induce continued muscle contraction. This mutation will increase levels of calcium in the sarcoplasm, which will induce continued muscle contraction

This mutation will increase levels of calcium in the sarcoplasm, which will induce continued muscle contraction

During tetany, a muscle fiber under continuous stimulation and contraction becomes unable to contract at all until it has rested. a second stimulus arrives at the muscle before complete relaxation of the first contraction, causing the second contraction to have greater tension than the first one. the stimuli arrive at the muscle fiber so rapidly that there is no muscle relaxation between stimuli, but rather, a continuous contraction of the muscle fiber. stimuli arrive at the muscle fiber at a rate that allows it to contract and then completely relax between each stimulus.

a muscle fiber under continuous stimulation and contraction becomes unable to contract at all until it has rested???

If there was a high concentration of acetylcholine within the synaptic cleft, but little to no response at the motor end-plate, you would expect ________________ to be the responsible neuromuscular-blocking agent botulinum toxin curare

curare

Rigor mortis occurs after death because detachment of crossbridges does not occur due to the lack of ATP the power stroke becomes stronger after death no calcim is present to bind to the regulatory protein tropomyosin actin binding sites become permanently blocked so that crossbridge formation cannot occur

detachment of crossbridges does not occur due to the lack of ATP

The presence of calcium in the sarcoplasm is directly responsible for the movement of actin towards the M line decreasing the length of the myosin myofilament exposing the binding sites on actin energizing the myosin heads

exposing the binding sites on actin

The sequence for skeletal muscle contraction is increased cytosolic calcium, which binds to calmodulin in cytosol, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin head groups, resulting in contraction. increased cytosolic calcium, which binds to calmodulin in cytosol, which binds with myosin head groups, resulting in contraction. increased cytosolic calcium, which binds to troponin, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin head groups, resulting in contraction. increased cytosolic calcium, which binds to troponin, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin head groups, which bind to actin filaments, resulting in contraction. increased cytosolic calcium, which binds to calmodulin in cytosol, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin head groups, which bind to actin filaments, resulting in contraction.

increased cytosolic calcium, which binds to troponin, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin head groups, resulting in contraction.

If it were possible to move the terminal cisternae further away from the T-tubules, it would prevent the voltage signal from entering the T-tubules increase the sensitivity of the sarcoplasmic reticulum, causing it to release large amounts of calcium interfere with the signal required for the release of calcium from the sarcoplasmic reticulum prevent the production of an action potential

interfere with the signal required for the release of calcium from the sarcoplasmic reticulum

The antidote that holds the most promise to counteract the effects of tubocurarine is one that removes acetylcholine receptors from the end-plate modifies acetylocholine so that it is unable to bind to acetylcholine receptors modifies acetylcholine receptors so that they can no longer bind acetylcholine modifies acetylcholine receptors so that they bind acetylcholine stronger than tubocurarine

modifies acetylcholine receptors so that they bind acetylcholine stronger than tubocurarine

At the ends of muscles, the connective tissues merge to form a __________, which attaches the muscle to other structures. ligament tendon superficial fascia sheath

tendon

Acetylcholine causes an end-plate potential by triggering the opening of chloride channels opening of sodium channels closing of sodium channels opening of calcium channels closing of calcium channels closing of chloride channels

opening of sodium channels

The amount of additional oxygen that must be inhaled following exercise to restore pre-exercise conditions is called fatigue. muscle failure. glycolysis. oxygen debt.

oxygen debt.

Facial wrinkles, such as glabellar or "frown" lines, appear with aging as a result of natural, repetitive muscle contractions. Botox® helps alleviate the appearance of these wrinkles by destroying the motor nerves that serve the muscles responsible for forming the wrinkles relaxing the facial muscles that cause the wrinkles overstimulating the facial muscles to tighten their appearance overstimulating the facial nerves to produce a steady contraction of the facial muscles

relaxing the facial muscles that cause the wrinkles

Acetylcholine (ACh) is released from motor neurons and enters the axon terminal transverse tubules synaptic cleft sarcomere

synaptic cleft

Thin filaments connect to and extend from either side of a ___________. These thin filaments are composed largely of the myofilament M line; actin z disc; actin M line; myosin Z disc; myosin

z disc; actin