Chapter 6 Muscles

Overview of muscle contraction

1. Action potential in the motor neuron triggers an action potential in the muscle cell 2. Action potential spreads down tubules in the muscle cell 3. ER releases calcium ions 4. Calcium ions bind to the protein complex on thin (actin) filament, exposing myosin-binding sites 5. Myosin heads bind to actin ans shorten the sarcomere 6. When action potentials stop, calcium ions pumped back into the ER 7. Myosin binding sites are blocked, and the muscle relaxes

As the sarcomere contracts

ADP is released and is replaced by ATP, which is required to release the myosin from the actin

The thin filaments of sarcomeres are composed of

Actin

The myosin head binds to actin

BIND

Calcium ions

Bind to the protein that blocks the myosin-binding sites on actin

The release of ___ ions form the sarcoplasmic reticulum is required for skeletal muscle contraction

Calcium

Which is the function of calcium ions in the contraction of muscle

Calcium binds to the troponin-tropomyosin complex so that the actin and myosin can interact and the sarcomere can contract

ATP binds to a myosin head. The myosin head is released from the actin filament

DETACH

The breakdown of ATP causes the myosin head to extend

EXTEND

Resistance to which of the following causes loss of muscle mass and strength

Insulin

Which of the following would be best to regularly do to maintain muscle mass

Lift weights

A single muscle cell is referred to as a

Muscle fiber

A muscle cell contains bundles of long

Myofibrils

The thick filaments of sarcomeres are composed of

Myosin

Which of the following proteins makes up the thick filament of the sarcomeres

Myosin

Sarcopenia has been compared to

Osteoporosis

The myosin head pulls the actin filament. This shortens the arcomere

POWER STROKE

T tubules are an invagination of the

Plasma membrance

Which term describes the subunits of a myofibril

Sacromere

By percent females loose more strength over time than males

TRUE

Muscle fibers are among the largest cells in the body and are actually fusions of hundreds of individual cells

TRUE

Which of the following structures is not contained within a muscle fiber

Tendon

When a sarcomere contracts

The actin and myosin filaments do not change in length

Which statement describes sliding-filament theory

The actin and myosin interact and then actin is pulled over the myosin shortening the sarcomere

Which of the following events is the direct result of an action potential in the membrane of a muscle cell

The muscle cells endoplasmic reticulum (ER) releases calcium ions

During the course of muscle contraction the potential energy stored in ATP is transferred to potential energy stored in

The myosin head

When ATP attaches to a myosin head

The myosin head detaches from actin

Of these events, the first to occur when a motor neuron stops sending an impulse to a muscle is __

The pumping of calcium ions out of the cytoplasm and back into the sarcoplasmic reticulum

Myosin heads bind to ___ which they then pull and cause to slide toward the center of the sarcomere

Thin filaments