ch.9 test 3

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

FALSE

The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment.
True or False

True

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

TRUE

Eccentric contractions are more forceful than concentric contractions.
True or False

TRUE

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

FALSE

Peristalsis is characteristic of smooth muscle.
True or False

TRUE

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

TRUE

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

TRUE

During isometric contraction, the energy used appears as movement.
True or False

FALSE

One of the functions of skeletal muscle contraction is production of heat.
True or False

TRUE

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.
True or False

TRUE

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

FALSE

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

TRUE

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

TRUE

Cells of unitary smooth muscle are found in the longitudinal and circular muscle layers of the intestine.
True or False

TRUE

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

TRUE

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

TRUE

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands do not diminish in length.
True or False

TRUE

Cardiac muscle has a limited regenerative capacity.
True or False

TRUE

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

TRUE

What is the role of tropomyosin in skeletal muscles?
A) Tropomyosin is the chemical that activates the myosin heads.
B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
C) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.
D) Tropomyosin is the receptor for the motor neuron neurotransmitter.

B) 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?
A) skeletal
B) cardiac
C) smooth
D) no muscle can regenerate

C) smooth

Most skeletal muscles contain ________.
A) muscle fibers of the same type
B) a mixture of fiber types
C) a predominance of slow oxidative fibers
D) a predominance of fast oxidative fibers

B) a mixture of fiber types

Fatigued muscle cells that recover rapidly are the products of ________.
A) intense exercise of long duration
B) intense exercise of short duration
C) slow exercise of long duration
D) slow exercise of short duration

B) intense exercise of short duration

The strongest muscle contractions are normally achieved by ________.
A) increasing stimulus above the threshold
B) increasing stimulus above the treppe stimulus
C) increasing the stimulation up to the maximal stimulus
D) recruiting small and medium muscle fibers

C) increasing the stimulation up to the maximal stimulus

Which of the following would be recruited later in muscle stimulation when contractile strength increases?
A) motor units with the longest muscle fibers
B) many small motor units with the ability to stimulate other motor units
C) large motor units with small, highly excitable neurons
D) motor units with larger, less excitable neurons

D) motor units with larger, less excitable neurons

Excitation-contraction coupling requires which of the following substances?
A) Ca2+ and ATP
B) Ca2+ only
C) ATP only
D) ATP and glucose

A) Ca2+ and ATP

Which of the following is a factor that affects the velocity and duration of muscle
contraction?
A) number of muscle fibers stimulated
B) size of the muscle fibers stimulated
C) load on the fiber
D) muscle length

C) load on the fiber

Myoglobin ________.
A) breaks down glycogen
B) is a protein involved in the direct phosphorylation of ADP
C) stores oxygen in muscle cells
D) produces the end plate potential

C) stores oxygen in muscle cells

What structure in skeletal muscle cells functions in calcium storage?
A) sarcoplasmic reticulum
B) mitochondria
C) intermediate filament network
D) myofibrillar network

A) sarcoplasmic reticulum

What does excess postexercise oxygen consumption represent?
A) amount of oxygen needed for aerobic activity to accomplish the same amount of work
B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
C) the amount of oxygen equal to the oxygen already used
D) the amount of oxygen taken into the body immediately after the exertion

B) 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.
A) contraction
B) relaxation
C) latent
D) refractory

C) latent

Creatine phosphate functions in the muscle cell by ________.
A) forming a temporary chemical compound with myosin
B) forming a chemical compound with actin
C) inducing a conformational change in the myofilaments
D) storing energy that will be transferred to ADP to resynthesize ATP

D) storing energy that will be transferred to ADP to resynthesize ATP

What is the primary function of wave summation?
A) produce smooth, continuous muscle contraction
B) increase muscle tension
C) prevent muscle relaxation
D) prevent muscle fatigue

A) produce smooth, continuous muscle contraction

The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
A) make and store phosphocreatine
B) synthesize actin and myosin myofilaments
C) provide a source of myosin for the contraction process
D) regulate intracellular calcium concentration

D) regulate intracellular calcium concentration

What produces the striations of a skeletal muscle cell?
A) a difference in the thickness of the sarcolemma
B) the arrangement of myofilaments
C) the sarcoplasmic reticulum
D) the T tubules

B) the arrangement of myofilaments

During muscle contraction, myosin cross bridges attach to which active sites?
A) myosin filaments
B) actin filaments
C) Z discs
D) thick filaments

B) actin filaments

Which of the following surrounds the individual muscle cell?
A) perimysium
B) endomysium
C) epimysium
D) fascicle

B) endomysium

Rigor mortis occurs because ________.
A) the cells are dead
B) sodium ions leak into the muscle causing continued contractions
C) no ATP is available to release attached actin and myosin molecules
D) proteins are beginning to break down, thus preventing a flow of calcium ions

C) 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?
A) converts lactic acid back into glycogen stores in the liver
B) resynthesizes creatine phosphate and ATP in muscle fibers
C) increases the level of lactic acid in the muscle
D) replaces the oxygen removed from myoglobin

C) increases the level of lactic acid in the muscle

The term aponeurosis refers to ________.
A) the bands of myofibrils
B) a sheetlike indirect attachment to a skeletal element
C) the rough endoplasmic reticulum
D) the tropomyosin-troponin complex

B) a sheetlike indirect attachment to a skeletal element

The oxygen-binding protein found in muscle cells is ________.
A) hemoglobin
B) ATP
C) myoglobin
D) immunoglobin

C) myoglobin

The contractile units of skeletal muscles are ________.
A) microtubules
B) mitochondria
C) T tubules
D) myofibrils

D) myofibrils

What is the functional unit of a skeletal muscle called?
A) a sarcomere
B) a myofilament
C) a myofibril
D) the sarcoplasmic reticulum

A) a sarcomere

What is the functional role of the T tubules?
A) stabilize the G and F actin
B) enhance cellular communication during muscle contraction
C) hold cross bridges in place in a resting muscle
D) synthesize ATP to provide energy for muscle contraction

B) enhance cellular communication during muscle contraction

What is the role of calcium ions in muscle contraction?
A) form hydroxyapatite crystals
B) reestablish glycogen stores
C) bind to regulatory sites on troponin to remove contraction inhibition
D) increase levels of myoglobin

C) bind to regulatory sites on troponin to remove contraction inhibition

Which of the following is not a component of the standard treatment for muscle strain?
A) rest of the muscle
B) ice on the muscle
C) elevation of the limb
D) stretching of the muscle

D) stretching of the muscle

Which of the following is not a connective tissue sheath that wraps individual muscle fibers?
A) endomysium
B) perimysium
C) epimysium
D) aponeurosis

D) aponeurosis

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 ________.
A) a strong base
B) stearic acid
C) hydrochloric acid
D) lactic acid

D) lactic acid

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
A) relaxation period
B) refractory period
C) latent period
D) fatigue period

B) refractory period

In an isotonic contraction, the muscle ________.
A) changes in length and moves the "load"
B) does not change in length but increases tension
C) never converts pyruvate to lactate
D) rapidly resynthesizes creatine phosphate and ATP

A) changes in length and moves the "load"

The muscle cell membrane is called the ________.
A) endomysium
B) sarcolemma
C) perimysium
D) epimysium

B) sarcolemma

Which of the following is the correct sequence of events for muscle contractions?
A) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
B) neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke
C) muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments
D) neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke

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

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
A) actin and myosin interact by the sliding filament mechanism
B) the trigger for contraction is a rise in intracellular calcium
C) the site of calcium regulation differs
D) ATP energizes the sliding process

C) the site of calcium regulation differs

Which of the following describes the cells of unitary smooth muscle?
A) They depend upon recruitment using the autonomic nervous system.
B) They are used for vision and hair raising.
C) They exhibit spontaneous action potentials.
D) They consist of muscle fibers that are structurally independent of each other.

C) They exhibit spontaneous action potentials.

Which of the following is not a role of ionic calcium in muscle contraction?
A) triggers neurotransmitter secretion
B) binds with troponin
C) removes contraction inhibitor
D) activates epinephrine released from adrenal gland

D) activates epinephrine released from adrenal gland

Which of the following is true about smooth muscle?
A) Certain smooth muscle cells can actually divide to increase their numbers.
B) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements.
C) Smooth muscle cannot stretch as much as skeletal muscle.
D) Smooth muscle has well-developed T tubules at the site of invagination.

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

Smooth muscle is characterized by all of the following except ________.
A) it appears to lack troponin
B) there are more thick filaments than thin filaments
C) there are no sarcomeres
D) there are noncontractile intermediate filaments that attach to dense bodies within the cell

B) there are more thick filaments than thin filaments

Muscle tissue has all of the following properties except ________.
A) secretion
B) contractility
C) extensibility
D) excitability

A) secretion

The giant protein titin maintains the organization of the ________ assisting in muscle stretching.
A) A band
B) I band
C) Z disc
D) M line

A) 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.

C) Striated muscle cells are long and cylindrical with many nuclei.

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
A) the citric acid cycle
B) glycolysis
C) hydrolysis
D) the electron transport chain

B) glycolysis

Muscle tone is ________.
A) the ability of a muscle to efficiently cause skeletal movements
B) the feeling of well-being following exercise
C) a state of sustained partial contraction
D) the condition of athletes after intensive training

C) a state of sustained partial contraction

The sliding filament model of contraction involves ________.
A) actin and myosin sliding past each other and partially overlapping
B) the shortening of thick filaments so that thin filaments slide past
C) actin and myosin lengthening in order to slide past each other
D) the Z discs sliding over the myofilaments

A) 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?
A) calcium ions returning to the terminal cisternae
B) the tropomyosin blocking the myosin once full contraction is achieved
C) acetylcholinesterase destroying the ACh
D) the action potential stops going down the overloaded T tubules

C) acetylcholinesterase destroying the ACh

Which of the following statements is most accurate?
A) Muscle tension remains relatively constant during isotonic contraction.
B) T tubules may be sliding during isotonic contraction.
C) The I band lengthens during isotonic contraction.
D) Myofilaments slide during isometric contractions

A) Muscle tension remains relatively constant during isotonic contraction.

What is the most distinguishing characteristic of muscle tissue?
A) the design of the fibers
B) the ability to respond to nervous stimulation
C) the diversity of activity of muscle tissue
D) the ability to transform chemical energy into mechanical energy

D) 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) a sprint by an Olympic runner
B) a long, relaxing swim
C) playing baseball or basketball
D) gym climbing

B) a long, relaxing swim

Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?
A) visceral smooth muscle
B) multiunit smooth muscle
C) cardiac muscle
D) skeletal muscle

B) multiunit smooth muscle

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.
A) cross bridge attachment would be optimum because of all the free binding sites on actin
B) no muscle tension could be generated
C) maximum force production would result because the muscle has a maximum range of travel
D) ATP consumption would increase because the sarcomere is "trying" to contract

B) no muscle tension could be generated

What part of the sarcolemma contains acetylcholine receptors?
A) motor end plate
B) end of the muscle fiber
C) part adjacent to another muscle cell
D) any part of the sarcolemma

A) motor end plate

Which of the following statements is false or incorrect?
A) Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells.
B) Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute.
C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP.
D) Cardiac muscle fibers can use lactic acid to make ATP.

C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP.

Only ________ muscle cells are always multinucleated.

skeletal

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

insertion

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

acetylcholinesterase

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

contraction

Which cells help repair injured skeletal muscle fibers and allow regeneration of dead skeletal muscle?

satellite cells

Only ________ muscle cells commonly branch.

cardiac

A smooth, sustained contraction from rapid stimulation is called ________.

tetanus