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Human Anatomy & Physiology, 7e (Marieb) Chapter 9 Muscles and Muscle Tissue

Fast (oxidative or glycolytic), fatigable fibers

Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.
Contain abundant amounts of glycogen.

Slow (oxidative), fatigue-resistant fibers

Depends on oxygen delivery and aerobic mechanisms. Red fibers, the smallest of the fiber types.
Abundant in muscles used to maintain posture.
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.

Tetanus

Continued sustained smooth contraction due to rapid stimulation.

Treppe

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

Multiple motor unit summation

How a smooth increase in muscle force is produced.

Wave summation

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

A sarcomere is the distance between two ________.

Z discs

The ________ contains only the actin filaments.

I band

The thicker filaments are the ________ filaments.

Myosin

Both actin and myosin are found in the ________.

A band

The myosin filaments are located in the ________.

A band

Calcium ions

Serves as the actual "trigger" for muscle contraction by removing the inhibition of the troponin molecules.
Normally stored in the terminal cisternae of the sarcoplasmic reticulum.

Acetylcholine

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

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.

Creatine phosphate

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

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

False

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.

True

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

False

Peristalsis is characteristic of smooth muscle.

True

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

True

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

False

During isometric contraction, the energy used appears as movement.

False

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

True

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.

False

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

True

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

False

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.

True

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

False

Contractures are a result of a total lack of ATP.

True

Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.

True

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

False

With muscular dystrophy ________.

muscle fibers degenerate and atrophy

Which muscle cells have the greatest ability to regenerate?

smooth

Most muscles contain ________.

a mixture of fiber types

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

intense exercise of short duration

The strongest muscle contractions are normally achieved by ________.

increasing the stimulation up to the maximal stimulus

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

motor units with larger, less excitable neurons

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

increase in the number of muscle cells

In skeletal muscle contraction, calcium apparently acts to ________.

remove the blocking action of tropomyosin

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

troponin

Myoglobin ________.

stores oxygen in muscle cells

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

sarcoplasmic reticulum

A sarcomere is ________.

the area between two Z discs

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.

latent

Creatine phosphate functions in the muscle cell by ________.

storing energy that will be transferred to ADP to resynthesize ATP

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

level in the cytoplasm drops

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

regulate intracellular calcium concentration

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

the arrangement of myofilaments

Which of the following are composed of myosin?

thick filaments

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

actin filaments

Which of the following surrounds the individual muscle cell?

endomysium

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

multiunit muscles

Rigor mortis occurs because ________.

no ATP is available to release attached actin and myosin molecules

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

a change of temperature

The term aponeurosis refers to ________.

a sheetlike indirect attachment to a skeletal element

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

myoglobin

The contractile units of skeletal muscles are ________.

myofibrils

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

calmodulin

One functional unit of a skeletal muscle is ________.

a sarcomere

The functional role of the T tubules is to ________.

enhance cellular communication during muscle contraction

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

bind to regulatory sites on troponin, changing the configuration

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

treppe

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

enhance the availability of calcium and the efficiency of enzyme systems

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 ________.

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 ________.

sarcolemma

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

Smooth muscle contracts in a twisting way.

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

the site of calcium regulation differs

The cells of single-unit visceral muscle ________.

exhibit spontaneous action potentials

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

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

Which of the following is true about smooth muscle contraction?

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

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

there are more thick filaments than thin filaments

Muscle tissue has all of the following properties except ________.

secretion

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

A band

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.

Answer: C

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

glycolysis

Muscle tone is ________.

a state of sustained partial contraction

The sliding filament model of contraction involves ________.

actin and myosin sliding past each other and partially overlap

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

acetylcholinesterase destroying the ACh

Which of the following is most accurate?

Muscle tension remains relatively constant during isotonic contraction.

The most distinguishing characteristic of muscle tissue is ________.

the ability to transform chemical energy into mechanical energy

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?

a long, relaxing swim

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

multiunit smooth muscle

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

no muscle tension could be generated

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