Practice Exam on Test 3

The strongest muscle contractions are normally achieved by ________.

• recruiting small and medium muscle fibers

• increasing the stimulation up to the maximal stimulus

• increasing stimulus above the threshold

• increasing stimulus above the treppe stimulus

Which of the following is a factor that affects the velocity and duration of muscle contraction?

• number of muscle fibers stimulated

• size of the muscle fibers stimulated

• load on the fiber

• muscle length

Immediately following the arrival of the stimulus at a skeletal muscle cell, there is a short period called the ________ period, during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.

• latent

• refractory

• contraction

• relaxation

What is the primary function of wave summation?

• produce smooth, continuous muscle contraction

• prevent muscle fatigue

• increase muscle tension

• prevent muscle relaxation

During muscle contraction, myosin cross bridges attach to which active sites?

• thick filaments

• Z discs

• myosin filaments

• actin filaments

Rigor mortis occurs because ________.

• sodium ions leak into the muscle causing continued contractions

• proteins are beginning to break down, thus preventing a flow of calcium ions

• no ATP is available to release attached actin and myosin molecules

• the cells are dead

Sarcomeres are functional units of ________ muscle.

• cardia

• smooth

• B and C only

• skeletal

During vigorous exercise, insufficient oxygen may be available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.

• lactic acid

• hydrochloric acid

• a strong base

• stearic acid

Which of the following is the correct sequence of events for muscle contractions?

• neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke

• motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

• muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments

• neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke

The sliding filament model of contraction involves ________.

• 
  actin and myosin lengthening in order to slide past each other

• the Z discs sliding over the myofilaments

• actin and myosin sliding past each other and partially overlapping

• the shortening of thick filaments so that thin filaments slide past