BIO 240 Exam 2

The movement of what ion contributes the most to the depolarization phase of an action potential?

• K-

• Ca++

• Na+

• Cl

The movement of what ion contributes the most to the repolarization/hyperpolarization phase of an action potential?

• K-

• Ca++

• Na+

• Cl

Which of the following statements about the phases of an action potential is/are correct?

• Indepolarization the permeability of membrane to Na is greater than rest

• repolarization, the permeability of the membrane to K is greater than rest

• repolarization, the permeability of the membrane to K is greater than rest

During the repolarization phase of an action potential, sodium leak channels are open.

• TRUE

• FALSE

Number 1 in the figure above indicates which of the following (USE THE PICTURE)

• A sarcomere

• myofilament

• A cross bridge

• A myofibril

Number 2 in the figure above refers to the __________ and its size __________ during muscle contraction

• Z-band  -  remains constant

• A-band  -  remains constant

• H-zone – decreases

• M-line  -  decreases

If someone who possesses a mutated troponin that in unable to bind calcium, which would happen at the skeletal muscle

• Muscles couldn’t relax

• Power strokes couldn’t be initiated

• Dihydropyridine proteins would be able to interact with ryanodine channels

• Cross bridges couldn’t be formed

Which of the following are functions of ATP in skeletal muscle?

• ATP is hydrolyzed in order to actively take up Ca⁺⁺ into SR

• ATP is hydrolyzed by myosin ATPase to energize cross-bridges.

• Binding of ATP to myosin releases cross bridges

The postural muscles that hold your vertebrae together and allow you to hold your upper body up straight are mostly of?

• Fast glycolytic fibers

• Slow oxidative fibers

• Fast oxidative glycolytic fibers

As you contract a skeletal muscle, the first motor units to be recruited are composed mainly of

• Fast glycolytic fibers

• Slow oxidative fibers

• Fast oxidative glycolytic fibers