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Once a motor neuron has fired, all the muscle fibers in a muscle contract


The thin filaments (actin) contain active sites for myosin attachment.


The force of muscle contraction is controlled by multiple motor unit summation or recruitment.


Eccentric contractions are more forceful than concentric contractions.


A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate


Peristalsis is characteristic of smooth muscle


A contraction in which the muscle does not shorten but its tension increases is called isometric contraction


Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy


During isometric contraction, the energy used appears as movement


One of the functions of skeletal muscle contraction is production of heat


An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops


Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments


Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units


A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.


The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily


When a muscle fiber contracts the A bands do not diminish in length


Cardiac muscle has a limited regenerative capacity


What is the role of tropomyosin in skeletal muscles?

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

Which muscle cells have the greatest ability to regenerate?


Most skeletal muscles contain ________.

a mixture of fiber types

Excitation-contraction coupling requires which of the following substances?

Ca2+ and ATP

Myoglobin ________.

stores oxygen in muscle cells

What structure in skeletal muscle cells functions in calcium storage?

sarcoplasmic reticulum

What does excess postexercise oxygen consumption represent?

the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

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.


Creatine phosphate functions in the muscle cell by ________.

storing energy that will be transferred to ADP to resynthesize ATP

What is the primary function of wave summation?

produce smooth, continuous muscle contraction

The major function of the sarcoplasmic reticulum in muscle contraction is to ________.

regulate intracellular calcium concentration

What produces the striations of a skeletal muscle cell?

the arrangement of myofilaments

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

actin filaments

Which of the following surrounds the individual muscle cell?


Rigor mortis occurs because ________.

no ATP is available to release attached actin and myosin molecules

Which of the choices below does not describe how excess postexercise oxygen consumption (oxygen deficit) restores metabolic conditions?

increases the level of lactic acid in the muscle

The term aponeurosis refers to ________.

a sheetlike indirect attachment to a skeletal element

The oxygen-binding protein found in muscle cells is ________.


The contractile units of skeletal muscles are ________.


What is the functional unit of a skeletal muscle called?

a sarcomere

What is the functional role of the T tubules?

enhance cellular communication during muscle contraction

What is the role of calcium ions in muscle contraction?

bind to regulatory sites on troponin to remove contraction inhibition

Which of the following is not a connective tissue sheath that wraps individual muscle fibers?


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

lactic acid

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?

refractory period

In an isotonic contraction, the muscle ________.

changes in length and moves the "load"

The muscle cell membrane is called the ________.


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

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

Which of the following is not a role of ionic calcium in muscle contraction?

activates epinephrine released from adrenal gland

Muscle tissue has all of the following properties except ________.


Which of the following statements is true?

A) Cardiac muscle cells have many nuclei.
B) Smooth muscle cells have T tubules.
C) Striated muscle cells are long and cylindrical with many nuclei.
D) Cardiac muscle cells are found in the heart and large blood vessels.
B) Smooth muscle cells have T tubules.

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.


The sliding filament model of contraction involves ________.

actin and myosin sliding past each other and partially overlapping

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?

acetylcholinesterase destroying the ACh

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.

no muscle tension could be generated

What part of the sarcolemma contains acetylcholine receptors?

motor end plate

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