In the myofibril the protein that possesses the active site for myosin heads to bind is called

1. myosin
2. titin
3. G actin
4. nebulin
5. actin

G actin

The type of contraction where the tension is less than the load is called

1. isotonic concentric contraction
2. isometric concentric contraction
3. isometric eccentric contraction
4. isotonic eccentric contraction
5. isometric contraction

isotonic concentric contraction

During the time when the action potential moves through the sarcolemma a muscle twitch is in _________.

1. stimulus phase
2. contraction phase
3. relaxation phase
4. isotonic period
5. latent period

latent period

Detachment of myosin cross-bridges occurs during the __________.

1. contraction phase
2. latent period
3. relaxation phase
4. stimulus phase
5. isotonic period

relaxation phase

In the sarcomere which elastic protein attaches thick filament to the Z line?

1. titin
2. actin
3. myosin
4. nebulin
5. G actin

titin

Which of the following is not true of acetylcholine?

1. it diffuses across the synaptic cleft
2. it binds to receptor membrane channels
3. it is stored in the neuron in vesicles
4. it is digested by acetylcholinesterase
5. it enters the muscle fiber to release calcium form the sarcoplasmic reticulum

it enters the muscle fiber to release calcium form the sarcoplasmic reticulum

Put the following events of excitation-contraction coupling in the order in which they occur.

1. Excitation

2. Sarcomere shortening

3. Generation of muscle tension

4. Neural control

5. Contraction cycle begins

6. Release of calcium ions

A) 4,1,5,2,6,3
B) 4,1,6,5,2,3
C) 1,2,5,6,3,4
D) 6,1,4,2,5,3
E) 1,4,6,2,5,3

4,1,6,5,2,3

Which of the following statements about excitation-contraction coupling is incorrect?
A) Calcium ions travel through the transverse tubule.
B) Calcium ion is released from the sarcoplasmic reticulum.
C) Tropomyosin moves to expose myosin binding sites on actin.
D) Troponin binds calcium ion and signals tropomyosin to move.
E) Relaxation requires uptake of calcium ion by the sarcoplasmic reticulum.

Calcium ions travel through the transverse tubule.