Biol 306 Test 3

Front 1

During contraction, the parallel thick and thin filaments of the myofibrils are connected by __________ that span the space between the parallel thick and thin filaments.

Back 1

crossbridges

Front 2

Caveolae are important because they contain

Back 2

voltage-regulated Ca2+ channels which allow Ca2+ entry into the muscle cell.

Front 3

A contraction that generates force and moves a load is known as __________,

Back 3

isotonic

Front 4

Whereas one that generates force without movement is known as __________.

Back 4

isometric

Front 5

A motor unit consists of

Back 5

one neuron and the muscle fibers it controls

Front 6

After death, when metabolism stops, in which step of the contractile cycle will skeletal muscles remain stuck if they have been contracting, for most of the first day or so?

Back 6

the rigor state

Front 7

An important difference between single-unit and multiunit smooth muscle is

Back 7

numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet.

Front 8

As ATP binds to the myosin head at the beginning of a muscle contraction cycle,

Back 8

the myosin head detaches from actin.

Front 9

At the conclusion of the power stroke,

Back 9

inorganic phosphate has been released from the myosin.

actin has been moved toward the M line.

ADP is released from the myosin head.

the myosin head is tightly bound to actin.

Front 10

Compared to skeletal muscle, smooth muscle in a latch state

Back 10

is slower to contract in response to a stimulus and sustains contractions longer without fatigue

Front 11

For striated muscle, each myosin head (leaflet) has

Back 11

a binding site for an ATP molecule, a binding site for an actin molecule, and the ability to swivel (rachet) when powered by ATP

Front 12

Excitation-contraction coupling refers to

Back 12

the chemical and electrical events form the neuron inwards that trigger the contractile events in a muscle fiber.

Front 13

In smooth muscle, what is the small protein chain that regulates contraction and relaxation?

Back 13

myosin light chain kinase (MLCK)

Front 14

Complete the following sentence to describe the state of relaxed muscle fibers: myosin heads are

Back 14

not bound to actin, and contain ADP and Pi.

Front 15

One of the major differences among skeletal muscle fiber types is in their resistance to fatigue. The fibers with the most endurance rely on __________ for energy.

Back 15

oxidative phosphorylation

Front 16

Regulation of cross-bridge formation in striated muscle is accomplished by

Back 16

tropomyosin, troponin, and calcium ions

Front 17

Smooth muscle cells lack which protein(s)?

Back 17

troponin

Front 18

Striated muscles are so-called because of a repeating pattern of light and dark bands. One repeating unit of the banding pattern is called a

Back 18

sarcomere

Front 19

The H zone contains

Back 19

thick filaments

Front 20

The I band contains

Back 20

thin filaments

Front 21

For both striated and smooth muscle the contraction cycle is triggered by the rise in __________ in intracellular fluid.

Back 21

Ca2+

Front 22

The period of time during which the sarcomeres return to their resting length is referred to as

Back 22

the relaxation phase

Front 23

When the membrane potential of a cell is resting which of the following ions are at equilibrium?

Back 23

Cl-

Front 24

The resting membrane potential of cells appears to have resulted as a solution to what problem?

Back 24

The need to have the same quantity of solute on either side of the membrane.

Front 25

A pharmacomechanical coupling in smooth muscle results in no change in the membrane potential.

Back 25

true