Question

1) Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin in skeletal muscle cells.
A) ATP; detachment B actin; detachment C)calcium; attachment D)ATP; attachment E)calcium; detachment

2) What is the definition of a "motor unit"?

A) a pair of antagonistic muscles

B) all of the muscles that affect the movement of any given joint

C) a single motor neuron plus all the muscle fibers it innervates

D) a single muscle fiber plus all of the motor neurons that innervate it

E) all of the motor neurons supplying a single muscle

3) An action potential in the motor end plate rapidly spreads to the interior regions of a muscle cell by means of the: A) Z lines. B) sarcoplasmic reticulum. C) transverse tubules. D) pores in the plasma membrane. E) H zone.

4) Myasthenia gravis is an autoimmune disease in which the immune system gradually destroys the receptors for acetylcholine at the neuromuscular junction. Which of the following drugs might initially be useful in treating the symptoms of this disease?

A)atropine (a muscarinic acetylcholine receptor antagonist)

B)a nicotinic acetylcholine receptor antagonist

C)a drug that inhibits release of acetylcholine

D) curare

E) a drug that inhibits acetylcholinesterase

5) During an isometric twitch in a skeletal muscle:
A)H zones shorten.
B) sarcomeres do not significantly shorten.
C) tension generated by the muscle always exceeds the load on the muscle.
D) the whole muscle shortens.
E)tetanus occurs

These questions were pulled from a Biology/Physiology exam. PLEASE PLEASE PLEASE, Include an explanation of why the correct answer is a specefic one, I really appreciate that.
thanks