Deck 7: Muscle Physiology

Question 1

Which of these statements describes troponin

A)It binds with calcium during contraction of skeletal muscle.
B)It breaks down actin.
C)It breaks down myosin.
D)It forms the boundaries of a sarcomere.

Answer 1

A

Question 2

Which of these statements describes the sliding filament mechanism of muscle contraction

A)A bands slide in closer between the I bands.
B)Thin filaments slide inward toward the centre of the A band.
C)Z lines slide between the T tubules.
D)Contractile proteins contract, thus shortening sarcomeres.

Answer 2

B

Question 3

Which of the following describes how sarcomeres are arranged end to end

A)as fascicles
B)as myofibrils
C)as bands
D)as perimysia

Answer 3

B

Question 4

Muscle fibres are some of the longest cells in the body.How long can they be

A)1-2 ìm
B)2-4 ìm
C)10-100 ìm
D)500-1000 ìm

Question 5

Which of these statements describes Z lines

A)They are formed by T tubules.
B)They extend down the middle of the I band.
C)They are formed by cross bridges.
D)They are filaments.

Question 6

Which of these statements describes actin

A)It is spherical.
B)It contains a globular head that forms the cross bridges between the thick and thin filaments.
C)It is referred to as a regulatory protein.
D)It is inhibited by Ca²⁺.

Question 7

Which one of the following is the function of tropomyosin

A)to bind Ca²⁺
B)to form attachments with myosin cross bridges
C)to serve as an ATPase
D)to prevent myosin cross bridges from attaching to thin filaments

Question 8

Which of the following are in the I band of the sarcomere

A)overlapping thin and thick filaments
B)thick filaments only
C)thin filaments only
D)two Z lines

Question 9

Which of these actions happens during contraction of skeletal muscle fibres

A)Contractile proteins contract.
B)Thin filaments slide inward toward A bands' centres as a result of cycles of cross-bridge binding and bending.
C)Thick and thin filaments become tightly coiled, thus shortening the sarcomere.
D)I bands slide between A bands.

Question 10

Which of these statements describes myosin

A)It is found in the A band.
B)It is found in the I band.
C)It is the primary protein found in the thin filaments.
D)It contracts during muscle contraction because it is one of the contractile proteins.

Question 11

Which of these statements describes myosin

A)It is spherical in shape.
B)It is the main structural component of the thin filaments.
C)It is referred to as a contractile protein.
D)It consists of four identical protein subunits.

Question 12

Which of these statements does NOT describe cross bridges

A)They bind to actin during muscle contraction.
B)They are formed by the globular heads of the myosin molecules.
C)They consist of troponin and tropomyosin protruding from the actin helix.
D)They bend during muscle contraction.

Question 13

Which of these statements describes actin

A)It has ATPase activity.
B)It is shaped like a golf club.
C)It is a regulatory protein.
D)It forms a helical chain that forms the main structural component of the thin filaments.

Question 14

Which of these structures is the smallest unit of contraction within a skeletal muscle

A)a myofibril
B)a muscle fibre
C)a thin filament
D)a sarcomere

Question 15

What causes the striated appearance of skeletal muscle

A)regular arrangement of the T tubules running transversely through the muscle fibre
B)presence of the Z lines extending down the middle of the I bands
C)presence of gap junctions
D)regular arrangement of highly organized thick and thin filaments

Question 16

Which of these actions is involved in developing tension in muscle fibres

A)contraction of sarcomeres
B)lengthening of sarcomeres
C)pushing of myosin by actin
D)elongation of myosin fibres

Question 17

What is the functional unit of skeletal muscle

A)the largest contractile component of a muscle fibre
B)the area between two Z lines
C)sarcoplasmic reticulum
D)the area between two I bands

Question 18

Which of the following composes thick filaments in skeletal muscle

A)actin only
B)troponin and tropomyosin only
C)myosin only
D)actin, troponin, and tropomyosin

Question 19

What is the term for the region between two Z lines

A)muscle fibre
B)myofibril
C)myofilament
D)sarcomere

Question 20

The striated appearance of skeletal muscle is due to regular orderly arrangement of which of the following

A)T tubules
B)lateral sacs of the sarcoplasmic reticulum
C)motor units
D)thick and thin filaments into A and I bands

Question 21

Which of the following happens during a cross-bridge cycle in skeletal muscle

A)The cross bridge is energized as myosin and ATPase activity hydrolyzes ATP.
B)The myosin cross bridge is able to bind with a troponin molecule when Ca²⁺ pulls the troponin-tropomyosin complex aside.
C)The linkage between actin and the myosin cross bridge is broken at the end of the cross-bridge cycle as Mg2+ binds to the cross bridge.
D)The power strokes of all cross bridges are directed toward the periphery of the thick filament.

Question 22

Which of these actions happens during muscle contraction

A)The contractile proteins contract.
B)The A band becomes shorter.
C)The H zone becomes smaller or disappears.
D)The I band remains unchanged.

Question 23

Which of these statements describes cross bridges

A)They extend between the A and the I bands, and bend to pull the bands together during muscle contraction.
B)They are formed by the spherical actin molecules.
C)They extend from the thick filaments and bind to actin, then bend to pull the thin filaments in closer together during muscle contraction.
D)The A band is shorter than the I band.

Question 24

Which of these components are involved with regulation of cross-bridge attachment activity

A)calcium ions and troponin
B)troponin and titin
C)tropomyosin and calmodulin
D)titin only

Question 25

Which of the following directly blocks cross bridge interaction between actin and myosin in skeletal muscle

A)acetylcholine
B)Z lines
C)calcium
D)tropomyosin

Question 26

Which of these statements does NOT describe cross bridges

A)They are the globular heads of myosin molecules.
B)They have actin binding sites that are normally covered by troponin and tropomyosin, except during excitation-contraction coupling.
C)They bind with actin and then bend to pull the thin filaments inward during contraction according to the sliding filament mechanism.
D)They require Mg2+ to bind ATP to them.

Question 27

Which of these statements applies to T tubules

A)They store Ca²⁺.
B)They run longitudinally between the myofibrils.
C)They store ATP.
D)They provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fibre.

Question 28

How does an action potential spread rapidly to the central portions of a muscle cell

A)by means of the Z lines
B)by means of the sarcoplasmic reticulum
C)by means of the H zone
D)by means of the T tubules

Question 29

Which of these statements is NOT characteristic of cross bridges

A)They are a component of thin filaments.
B)They are composed of myosin.
C)They have an actin binding site.
D)They have an ATPase binding site.

Question 30

Which of these statements describes the H zone

A)It is the area within the middle of the Z lines where the thin filaments do not reach.
B)It shortens or disappears during contraction.
C)It contains only thin filaments.
D)It is the area within the middle of the I band.

Question 31

Which of the following provides the energy for cross-bridge cycling during muscle contraction

A)acetylcholine
B)Ca²⁺
C)ATP
D)myosin

Question 32

Which of the following two molecules participate in cross-bridge interactions

A)tropomyosin and myosin
B)troponin and myosin
C)troponin and tropomyosin
D)actin and myosin

Question 33

Which of these conditions occurs as the result of a lack of acetylcholinesterase in the synaptic cleft

A)decreased acetylcholine production by the motor neuron
B)relaxation of the muscle fibre
C)excessive, continuous stimulation of the muscle fibre
D)inability of the motor neuron to stimulate the muscle fibre

Question 34

Which of these events happens during excitation-contraction coupling

A)The action potential travels down the thin myofilaments.
B)Ca²⁺ is released from the sarcoplasmic reticulum.
C)Ca²⁺ is taken up by the sarcoplasmic reticulum.
D)Calcium blocks the binding sites on the actin molecules.

Question 35

Which of these statements describes foot proteins

A)They span the gap between a lateral sac of the sarcoplasmic reticulum and the cell membrane.
B)They are believed to serve as Ca²⁺ channels.
C)They project from the thick filaments, bind to the thin filaments, and subsequently bend to pull the thin filaments inward toward the A band's centre during muscle contraction.
D)Each contains two subunits arranged in a specific pattern.

Question 36

During muscle contraction, which of the following becomes smaller

A)H zone
B)thin filaments
C)the width of the A band
D)thick filaments

Question 37

Which of these statements does NOT describe cross bridges

A)They are formed by the globular heads of the myosin molecules as they protrude from the thick filaments.
B)They bind to actin during muscle contraction.
C)They are not found in the I band.
D)They bind with troponin and tropomyosin during muscle contraction to pull them away from the actin helical chain.

Question 38

During contraction, asynchronous cycling of cross bridges

A)prevents tetany.
B)prevents thick filaments from slipping backward.
C)prevents thin filaments from slipping backward.
D)utilizes less ATP than prior to contraction.

Question 39

Which of these statements applies to T tubules

A)They form the Z lines.
B)They store Ca²⁺.
C)They provide a means of rapidly transmitting the action potential to the central portions of the muscle fibre.
D)They allow for nutrients to be carried into the cell.

Question 40

Which of the following is the first step in excitation-contraction coupling

A)Exposed actin sites bind with myosin cross bridges.
B)Troponin binds calcium.
C)Calcium is released from the sarcoplasmic reticulum.
D)Sodium channels open in the fibre's membrane.

Question 41

Which of these statements describes why you are able to repeatedly contract and relax your muscles of respiration, allowing you to breathe in and breathe out

A)As soon as all the Ca²⁺ stored in the lateral sacs of the sarcoplasmic reticulum is used up, muscle relaxation occurs.
B)After the muscle cells become excited, acetylcholinesterase maintains the action of acetylcholine.
C)When there is no longer a local action potential in the muscle cell, Ca²⁺ is actively transported back into the lateral sacs of the sarcoplasmic reticulum.
D)ATP is not available soon after the contraction.

Question 42

What is the first source for supplying additional ATP when exercise begins

A)oxidative phosphorylation
B)glycolysis
C)lactate
D)creatine phosphate

Question 43

Binding of which substance to myosin permits cross bridge of which action between actin and myosin

A)ATP; binding actin and myosin
B)ATP; detaching actin and myosin
C)calcium; binding actin and myosin
D)calcium; detaching actin and myosin

Question 44

Which of these statements describes the length-tension relationship of skeletal muscle

A)When a muscle is maximally stretched, it can develop the most tension upon contraction because the thin filaments can slide a maximal distance.
B)Maximum tension can be developed if the muscle is at its shortest length at the onset of contraction.
C)In the body, the relaxed length of a muscle occurs at its optimal length.
D)When the initial length of a muscle prior to contraction becomes very short, tension is decreased during contraction.

Question 45

Which of these factors is NOT a determinant of whole muscle tension

A)the number of muscle fibres contracting
B)the tension produced by each contracting fibre
C)the extent of motor unit recruitment
D)the proportion of each motor unit contracting at any given time

Question 46

Which of the following would happen if ATP supplies became very low or were not available in a muscle cell

A)An increase in tension would develop.
B)Cross bridges would detach from actin.
C)Muscles would relax.
D)ATP would not be required for detachment from actin.

Question 47

Which of these statements describes a motor unit

A)a single motor neuron plus all the muscle fibres it innervates
B)a single muscle fibre plus all the motor neurons that innervate it
C)all the motor neurons supplying a single muscle
D)one pair of antagonistic muscles

Question 48

Which of these methods is NOT a method of gradation of skeletal muscle contraction

A)twitch summation
B)motor unit recruitment
C)varying the number of motor units stimulated
D)stimulating variable portions of each motor unit

Question 49

Which of these statements applies when trying to pick up a book

A)Muscle tension must be less than load.
B)The muscle must lengthen during contraction.
C)Muscle tension remains constant as the muscle changes length.
D)Muscle length remains constant as the muscle tension changes.

Question 50

If you wanted to pick up something heavier than your pencil, you would need to have a stronger muscle contraction.Which of these actions might accomplish this

A)Stimulate more motor units.
B)Decrease the frequency of stimulation to allow a more prolonged contraction to occur.
C)Decrease the refractory period.
D)Block acetylcholinesterase at the neuromuscular junction to allow acetylcholine to function longer.

Question 51

Which of these statements applies to the length-tension relationship

A)It refers to the relationship between the length of the muscle before the onset of contraction and the tetanic tension that each contracting fibre can subsequently develop at that length.
B)It is based on the amount of overlap of thick and thin filaments.
C)It allows no tension to develop if the whole muscle is stretched to 30 percent longer than its optimal length.
D)Within the body, it is limited to a functional range because of limitations on muscle length imposed by attachment to the skeleton.

Question 52

Which of these statements describes twitch summation

A)It is a means by which weak muscle contraction may be accomplished.
B)It results from increasing the number of motor units that are firing within a muscle.
C)A high level of calcium ion is not required.
D)It results from increasing the frequency at which motor units are firing within a muscle.

Question 53

Which of these activities is involved in the process of muscle relaxation

A)Acetylcholinesterase promotes the concentration of acetylcholine to allow the muscle membrane to return to resting potential.
B)Ca²⁺ is actively taken up by the lateral sacs of the sarcoplasmic reticulum when there is no longer a local action potential.
C)The cross bridges from the thick filaments bind to the thin filaments and bend in such a way as to return the filaments to their original resting position.
D)ATP becomes unavailable.

Question 54

Which of these statements describes summation

A)It results from increases in cytosolic calcium levels.
B)It refers to the pumping of calcium into the sarcoplasmic reticulum.
C)It can be enhanced by allowing a cell to completely relax.
D)It rarely results in tetany.

Question 55

Which molecule binds ATP in order for muscle contraction to occur

A)tropomyosin
B)actin
C)myosin
D)calcium

Question 56

Which of these events is NOT involved in the relaxation of muscle

A)Acetylcholine is destroyed by acetylcholinesterase.
B)There is no longer a local action potential.
C)The T tubules actively take up the Ca²⁺ that was released.
D)The actin and myosin molecules become unbound.

Question 57

Which of these factors causes muscle relaxation

A)addition of magnesium to muscle cells
B)ACh hyperactivity
C)return of calcium to lateral sacs
D)lack of ATP

Question 58

Which of these statements describes twitch summation

A)The muscle fibre is restimulated before the action potential has returned to resting potential.
B)The muscle fibre is restimulated before the filaments have completely returned to their resting position.
C)Stronger muscle contractions occur with stronger action potentials.
D)Weaker muscle contractions occur despite stronger action potentials.

Question 59

The sarcoplasmic reticulum stores which substance when a muscle is relaxed, and releases it for binding to which substance during contraction

A)calcium; troponin
B)calcium; tropomyosin
C)sodium; tropomyosin
D)potassium; tropomyosin

Question 60

Which of these factors is involved in the gradation of muscle contraction

A)greater number of muscle fibres
B)variation in the frequency of action potentials initiated in each muscle fibre
C)variation in the size of the action potentials initiated in each muscle fibre
D)variation in the distance that action potentials can travel

Question 61

Which of the following applies during an isotonic contraction of a muscle in the arm

A)The muscle does not contract.
B)The muscle does not change length.
C)The tension in the muscle does not overcome a load.
D)The tension in the muscle remains constant.

Question 62

Which of the following areas is the origin of a muscle

A)the main, thick part of the structure
B)the middle, thin part of the structure
C)the movable end of attachment
D)the stationary end of attachment

Question 63

In the body's lever systems, what are the fulcrums represented by

A)joints
B)long bones
C)tendons
D)short bones

Question 64

Muscles developing tension while lengthening are performing what type of contractions

A)concentric
B)eccentric
C)isometric
D)fatiguing

Question 65

Which of these statements applies to eccentric muscle contractions

A)The development of tension occurs at constant muscle length.
B)The muscle lengthens while contracting.
C)The muscle shortens while contracting.
D)Muscle length and tension will vary throughout a range of motion.

Question 66

What causes muscular fatigue

A)accumulation of lactic acid
B)depletion of calcium
C)depletion of sodium
D)glycogenesis

Question 67

Which of these characteristics would NOT be exhibited in the muscle cells of a marathon runner's legs

A)high resistance to fatigue
B)low myoglobin content
C)low glycogen content
D)slow speed of contraction

Question 68

Which of the following is a characteristic feature of isometric muscle contractions

A)They occur at constant tension.
B)The muscle shortens.
C)They are used for body movements.
D)They occur at constant length.

Question 69

Submaximal isometric contractions are important for which of these activities

A)moving large objects
B)walking
C)maintaining posture
D)writing

Question 70

Which of these statements describes muscle tension

A)It is created during muscle contraction as the tension generated by the contractile elements is transmitted via the connective tissue and tendons to the bones.
B)It is the force exerted on a muscle by the weight of an object.
C)It is greater than the load tension during an isometric contraction.
D)It is less than the load tension during isometric contraction.

Question 71

Which of the following properties characterizes fast oxidative (type IIa) muscle fibres

A)high myosin-ATPase activity
B)low myosin-ATPase activity
C)low oxidative capacity
D)high oxidative capacity

Question 72

Which of these statements does NOT apply to different types of muscle fibres

A)The higher the ATPase activity, the faster the speed of contraction.
B)Muscles that have high glycolytic capacity and large glycogen stores are more resistant to fatigue.
C)Muscles with high ATP-synthesizing ability are more resistant to fatigue.
D)Oxidative types of muscle fibres contain myoglobin.

Question 73

Fatigue is the failure of a muscle fibre to maintain which of the following as a result of previous contractile activity

A)excitability
B)muscle mass
C)tension
D)sarcomere number

Question 74

What is the first means by which ATP is produced at the onset of contractile activity

A)transfer of energy and phosphate from creatine phosphate to ADP
B)oxidative phosphorylation
C)glycolysis
D)degradation of myoglobin

Question 75

Which of these statements describes myoglobin

A)It can store small amounts of CO₂.
B)It increases the rate of O₂ transfer from blood into muscle fibres.
C)It is abundant in fast glycolytic fibres.
D)It is abundant in slow red fibres.

Question 76

Which of these statements describes fast glycolytic (type IIb) fibres

A)They contain an abundance of mitochondria.
B)The muscle fibre diameter is small.
C)They are most abundant in muscles specialized for maintaining low-intensity contractions for long periods of time without fatigue.
D)They can be converted into fast oxidative fibres by regular endurance activities.

Question 77

Which of these statements describes the summation of simple twitches

A)They can occur from the long duration of the action potential in a muscle fibre.
B)They reduce the tension in a muscle.
C)They result from the slow stimulation of a muscle fibre.
D)If they are from action potentials, they add together.

Question 78

If the load on a muscle is increased, eventually a load will be reached, at which the velocity of shortening becomes zero.What is the term for the muscle contraction at this point

A)concentric
B)eccentric
C)isotonic
D)isometric

Question 79

Which statement is characteristic of most of the body's lever systems

A)They work at mechanical advantage.
B)They work at a mechanical disadvantage.
C)Muscles must exert lesser forces than the load.
D)Muscles must exert greater forces than the load.

Question 80

During aerobic exercise, what is the primary means by which ATP is produced for contractile activity

A)accumulation of creatine phosphate
B)fermentation
C)oxidative phosphorylation
D)glycolysis