QTBL WEEK 2 1.5

Which of the following statements is true regarding skeletal muscle?

• Spindle-shaped cells

• Under involuntary control

• Many peripherally located nuclei per muscle fiber

• Forms the walls of hollow internal organs

• May be autorhythmic

Which of the following is NOT a major property of muscle tissue?

• Contractility

• Elasticity

• Excitability

• Extensibility

• Secretability

Given the following structures: 1. Whole muscle 2. Muscle fiber (cell) 3. Myofilament 4. Myofibril 5. Muscle fasciculus Which arrangement lists the structures in the correct order from largest to smallest?

• 1,2,5,3,4

• 1,2,5,4,3

• 1,5,2,3,4

• 1,5,2,4,3

• 1,5,4,2,3

Each myofibril:

• Is made up of many muscle fibers

• Contains sarcoplasmic reticulum

• Is made up of many sarcomeres

• Contains T tubules

• Is the same thing as a muscle fiber

Myosin myofilaments are:

• Attached to the Z disk

• Found primarily in the I band

• Thinner than actin myofilaments

• Absent from the H zone

• Attached to filaments that form the M line

Which statement about the molecular structure of myofilaments is true?

• Tropomyosin has a Ca2+ binding site

• The head of myosin binds to an active site on G-actin

• ATPase is found on troponin

• Troponin binds to the rod portion of myosin

• Actin molecules bend and straighten during contraction

The part of the sarcolemma that invaginates into the interior of skeletal muscle fibers is the:

• T-tubule system

• Sarcoplasmic reticulum

• Myofibrils

• Terminal cisternae

• Mitochondria

During the depolarization phase of an action potential, plasma membrane permeability to:

• Ca2+ increases

• Na+ increases

• K+ increases

• Ca2+ decreases

• Na+ decreases

During repolarization of the plasma membrane:

• Na+ moves into the cell

• Na+ moves out of the cell

• K+ moves into the cell

• K+ moves out of the cell

Neuromuscular junction events – choose the correct sequence:

1. 1. Acetylcholine is broken down into acetic acid and choline

2. 2. Acetylcholine diffuses across the synaptic cleft

3. 3. Action potential reaches the motor neuron terminal

4. 4. Acetylcholine binds to ligand-gated ion channels

5. 5. Action potential is generated on the muscle fiber membrane

• a. 2,3,4,1,5

• b. 3,2,4,5,1

• c. 3,4,2,1,5

• d. 4,5,2,1,3

• e. 5,1,2,4,3