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