chapter 9

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Slow (oxidative), fatigue-resistant fibers

Depends on oxygen delivery and aerobic mechanisms

Fast (oxidative or glycolytic), fatigable fibers

Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.

Slow (oxidative), fatigue-resistant fibers

Red fibers, the smallest of the fiber types.

Fast (oxidative or glycolytic), fatigable fibers

Contain abundant amounts of glycogen.

Slow (oxidative), fatigue-resistant fibers

Abundant in muscles used to maintain posture.

Slow (oxidative), fatigue-resistant fibers

A relatively high percentage are found in successful marathon runners.

Maximal stimulus

The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle

Treppe

The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up.

Tetanus

Continued sustained smooth contraction due to rapid stimulation.

Wave summation

The situation in which contractions become stronger due to stimulation before complete relaxation occurs

Multiple motor unit summation

How a smooth increase in muscle force is produced

Z discs

A sarcomere is the distance between two ________.

I band

The ________ contains only the actin filaments.

Myosin

The thicker filaments are the ________ filaments.

A band

Both actin and myosin are found in the ________.

A band

The myosin filaments are located in the ________.

Calcium ions

Serves as the actual "trigger" for muscle contraction by removing the inhibition of the troponin molecules.

Acetylcholine

A neurotransmitter released at motor end plates by the axon terminals.

Aerobic respiration

A metabolic pathway that provides for a large amount of ATP per glucose because oxygen is used. Products are water and carbon dioxide and ATP.

Calcium ions

Normally stored in the terminal cisternae of the sarcoplasmic reticulum

Creatine phosphate

Used to convert ADP to ATP by transfer of a high-energy phosphate group. A reserve high-energy compound.

Acetylcholinesterase

Destroys ACh.

False

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

True

The thin filaments (actin) contain a polypeptide subunit G actin that bear active sites for myosin attachment.

True

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

True

Eccentric contractions are more forceful than concentric contractions

False

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

True

Peristalsis is characteristic of smooth muscle

True

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

False

During isotonic contraction, the heavier the load, the faster the velocity of contraction

False

During isometric contraction, the energy used appears as movement

True

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

False

Oxygen debt refers to the oxygen required to make creatine phosphate.

False

Muscle contraction will always promote movement of body parts regardless of how they are attached.

True

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

False

Whereas skeletal muscle cells are electrically coupled, smooth muscle cells appear to be chemically coupled by gap junctions.

True

Single-unit smooth muscle is found in the intestines.

True

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

True

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

True

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.

False

The more slowly a skeletal muscle is stimulated, the greater its exerted force becomes

True

Contractures are a result of a total lack of ATP.

True

Smooth muscles relax when intracellular levels drop but may not cease contractions.

False

Recruitment is an option in a single-unit smooth muscle cell

muscle fibers degenerate and atrophy

With muscular dystrophy ________.

smooth

Which muscle cells have the greatest ability to regenerate?

a mixture of fiber types

Most muscles contain ________.

intense exercise of short duration

Fatigued muscle cells that recover rapidly are the products of ________.

increasing the stimulation up to the maximal stimulus

The strongest muscle contractions are normally achieved by ________.

motor units with larger, less excitable neurons

Which of the following would be recruited later in muscle stimulation when contractile strength increases?

increase in the number of muscle cells

Which of the following is not a usual result of resistance exercise?

remove the blocking action of tropomyosin

In skeletal muscle contraction, calcium apparently acts to ________.

troponin

Calcium ions bind to the ________ molecule in skeletal muscle cells.

stores oxygen in muscle cells

Myoglobin ________.

sarcoplasmic reticulum

An elaborate network of membranes in skeletal muscle cells that functions in calcium storage is the ________.

the area between two Z discs

A sarcomere is ________.

latent

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.

storing energy that will be transferred to ADP to resynthesize ATP

Creatine phosphate functions in the muscle cell by ________.

level in the cytoplasm drops

After nervous stimulation of the muscle cell has ceased, the calcium ________.

regulate intracellular calcium concentration

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

the arrangement of myofilaments

The striations of a skeletal muscle cell are produced, for the most part, by ________.

thick filaments

Which of the following are composed of myosin?

actin filaments

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

endomysium

Which of the following surrounds the individual muscle cell?

multiunit muscles

Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________.

no ATP is available to release attached actin and myosin molecules

Rigor mortis occurs because ________.

a change of temperature

Which of the following does not act as a stimulus to initiate a muscle contraction?

a sheetlike indirect attachment to a skeletal element

The term aponeurosis refers to ________.

myoglobin

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

myofibrils

The contractile units of skeletal muscles are ________.

calmodulin

The site of calcium regulation in the smooth muscle cell is ________.

a sarcomere

One functional unit of a skeletal muscle is ________.

enhance cellular communication during muscle contraction

The functional role of the T tubules is to ________.

bind to regulatory sites on troponin, changing the configuration

The role of calcium ions in muscle contraction is to ________.

treppe

The warm-up period required of athletes in order to bring their muscles to peak performance is called ________.

enhance the availability of calcium and the efficiency of enzyme systems

The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________.

lactic acid

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

refractory period

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

changes in length and moves the "load"

In an isotonic contraction, the muscle ________.

sarcolemma

The muscle cell membrane is called the ________.

Smooth muscle contracts in a twisting way.

Smooth muscle is significantly different from striated muscle in several ways. Which of the following is true?

the site of calcium regulation differs

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.

exhibit spontaneous action potentials

The cells of single-unit visceral muscle ________.

There is no biological basis for the difference in strength between women and men.

Which of the following statements is not true concerning developmental aspects of muscle?

Certain smooth muscle cells can actually divide to increase their numbers.

Which of the following is true about smooth muscle contraction?

there are more thick filaments than thin filaments

Smooth muscle is characterized by all of the following except ________.

secretion

Muscle tissue has all of the following properties except ________.

A band

The giant protein titin maintains the organization of the ________ assisting in muscle stretching.

Striated muscle cells are long and cylindrical with many nuclei.

Which of the following statements is true?

glycolysis

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

a state of sustained partial contraction

Muscle tone is ________.

actin and myosin sliding past each other and partially overlap

The sliding filament model of contraction involves ________.

acetylcholinesterase destroying the ACh

After nervous stimulation stops, ACh in the synaptic cleft is prevented from continuing stimulation of contraction by ________.

Muscle tension remains relatively constant during isotonic contraction.

Which of the following is most accurate?

the ability to transform chemical energy into mechanical energy

The most distinguishing characteristic of muscle tissue is ________.

a long, relaxing swim

Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers?

multiunit smooth muscle

Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?

no muscle tension could be generated

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

no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode

An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________.

skeletal

Only ________ muscle cells are alwyas multinucleated.

limping

Claudication might more simply be called ________.

insertion

The end of the muscle that typically moves when a muscle contracts is called the ________.

acetylcholinesterase

In the synaptic cleft of a neuromuscular junction, an enzyme called ________ is always present.

contraction

The time in which cross bridges are active is called the period of ________.

Red

________ (color) fibers are slow (oxidative) fibers.

cardiac

Only ________ muscle cells commonly branch.

tetanus

A smooth, sustained contraction is called ________.

Fatigue occurs when ATP production fails to keep pace with ATP use even though the muscle still receives stimuli.

Define physiologic muscle fatigue.

Red muscles tend to have a slow (oxidative) rate and fatigue resistance, whereas white muscle cells have a fast (oxidative) rate and fatigue easily.

Compare red and white muscles relative to their speed of action and endurance.

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