Deck 8: Muscle Physiology

Question 1

What shape are actin molecules?​

A)​elongated
B)spherical
C)bicuspid
D)rectangular
E)​triangular

Answer 1

B

Question 2

What are the two membranous structures within the muscle fiber that play important roles in linking excitation to contraction?​

A)​horizontal tubules and sarcoplasmic reticulum
B)transverse tubules and sarcoplasmic reticulum
C)transverse tubules and endoplasmic reticulum
D)horizontal tubules and endoplasmic reticulum
E)​sarcolemma and plasma end plates

Answer 2

B

Question 3

What two molecules participate in cross-bridge interactions?​

A)tropomyosin and myosin
B)troponin and myosin
C)troponin and tropomyosin
D)actin and myoblasts
E)​actin and myosin

Answer 3

E

Question 4

During the embryonic developmental stage,skeletal muscle fibers are derived from:

A)​fibroblasts
B)lymphoblasts
C)connective tissue
D)myoblasts
E)​microfilaments

Question 5

Muscle tension is produced internally within the ____.​

A)​myosin molecules
B)actin molecules
C)T tubules
D)sarcoplasmic reticulum
E)​sarcomeres

Question 6

Approximately what percentage of body weight does muscle comprise?​

A)​20%
B)35%
C)50%
D)70%
E)​85%

Question 7

How many skeletal muscles are there in the body?​

A)​about 400
B)442
C)about 500
D)535
E)​about 600

Question 8

How many thin filaments are on each end of a sarcomere?

A)​6
B)5
C)4
D)3
E)​2

Question 9

During muscle contraction,what becomes smaller?​

A)​H zone
B)thin filaments
C)the width of the A band
D)thick filaments
E)​myosin molecules

Question 10

What happens to a muscle during an isometric contraction?

A)​It produces more calcium.
B)It lengthens.
C)It shortens.
D)It is prevented from shortening.
E)​Sarcomeres are destroyed.

Question 11

What molecules form the thick filaments within muscle?

A)​microfilaments
B)myosin
C)actin
D)myoblasts
E)​troponin

Question 12

What are the three main muscle types?

A)​skeletal,rough,and smooth
B)flexion,extension,and rotation
C)skeletal,cardiac,and smooth
D)thick,thin,and flat
E)​skeletal,arterial,and venous

Question 13

One motor neuron,plus all the muscle fibers it innervates,is known as a(n):

A)​nerve bundle
B)motor unit
C)activated component
D)cross bridge
E)​functional unit

Question 14

How long does a single action potential in a skeletal muscle fiber last?​

A)​1 to 2 seconds
B)0.5 seconds
C)5 milliseconds
D)1 to 2 milliseconds
E)​0.5 milliseconds

Question 15

What happens when two or more overlapping action potentials are "added" together within a muscle?​

A)​twitch fatigue
B)twitch summation
C)contraction addition
D)contraction paralysis
E)​sarcoplasmic reduction

Question 16

How many "heads" does each myosin molecule have?

A)​5
B)4
C)3
D)2
E)​1

Question 17

The portion of a lever between the fulcrum and the point where a force is applied by the muscle is called the ____.​

A)​fulcrum angle
B)velocity
C)power arm
D)load arm
E)​interactive unit

Question 18

What types of muscles are involuntary in terms of movement?

A)​cardiac and smooth
B)skeletal and cardiac
C)arterial and venous
D)rough and smooth
E)​skeletal and contractile

Question 19

Which molecule binds ATP in order for muscle contraction to occur?

A)​sarcolemma
B)actin
C)myosin
D)calcium
E)​phosphate

Question 20

Because of skeletal constraints,what is the maximum percentage that muscles can stretch or shorten relative to their length?​

A)​30% 
B)35%
C)40%
D)45%
E)​50%

Question 21

How many additional pathways supply ATP as needed during muscle contraction?​

A)​1
B)2
C)3
D)4
E)​5

Question 22

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

A)​oxidative phosphorylation
B)glycolysis
C)lactate 
D)creatine phosphate
E)​chondroitin

Question 23

What are the two main types of fatigue?​

A)​skeletal and cardiac
B)skeletal and smooth
C)muscle and cerebral
D)muscle and psychological
E)​muscle and central

Question 24

What does smooth muscle contain that enables it to stretch much more than skeletal muscle?

A)​calcium
B)glucosamine
C)sarcomeres
D)connective tissue
E)microfilaments​

Question 25

What hormone,elevated during exercise,increases oxygen consumption?

A)​dopamine
B)serotonin
C)acetylcholine
D)norepinephrine
E)​epinephrine

Question 26

Contractile activity in both skeletal muscle and multiunit smooth muscle is ____.

A)​myogenic
B)phasic
C)tonic
D)clonic
E)​neurogenic

Question 27

Damage to the cerebellum or basal nuclei results in ____.​

A)​spastic paralysis
B)flaccid paralysis
C)tetanus
D)clumsy movement
E)​cerebral palsy

Question 28

Loss of descending inhibitory inputs on motor neurons may result in ____.​

A)​spastic paralysis
B)flaccid paralysis
C)tetanus 
D)clumsy movement
E)​cerebral palsy

Question 29

What phenomenon enables smooth muscle to maintain tension with comparatively less ATP consumption,as compared to skeletal muscle?

A)​stretch phenomenon
B)jump phenomenon
C)piggy back phenomenon
D)click phenomenon
E)latch phenomenon​

Question 30

What do the basal nuclei coordinate?​

A)​slow twitch muscle fibers
B)spinal reflexes
C)slow,sustained movement
D)fast movement
E)​fast twitch muscle fibers

Question 31

What level of neural input (to motor neurons)involves pyramidal cells?​

A)​input from the brain stem
B)input from the efferent neurons
C)input from afferent neurons
D)input from the sensory cortex
E)​input from the primary motor cortex

Question 32

What kind of smooth muscle contracts in bursts?​

A)​phasic
B)tonic
C)clonic
D)cardiac
E)​vascular

Question 33

What plays a key role in mediating performance of fine,discrete,voluntary movements of the hands and fingers?

A)​premotor area
B)supplementary motor area
C)multineuronal system
D)corticospinal system
E)​the pons

Question 34

How many steps in the muscle excitation,contraction,and relaxation processes require ATP?

A)​3
B)4
C)5
D)6
E)​7

Question 35

What is the least complex type of purposeful motor movement?

A)​somatic reflex responses
B)voluntary movements
C)rhythmic activities
D)tetanus contraction
E)​fine motor movements

Question 36

What are the two major types of spontaneous depolarizations displayed by self-excitable cells?

A)​fast-wave and slow-wave potentials
B)membrane potentials and slow-wave potentials
C)pacemaker potentials and slow-wave potentials
D)smooth potentials and fast-wave potentials
E)cardiac potentials and fast-wave potentials​

Question 37

How many filament types do smooth muscle cells have?

A)​2
B)3
C)4
D)5
E)6​

Question 38

What are the two types of fast-twitch muscle fibers?​

A)​oxidative and phosphoric
B)oxidative and glycolytic
C)pyruvic and glycolytic
D)acetic and glycolytic
E)​fast and slow

Question 39

For effective control of motor output,what two types of muscle proprioceptors are needed by the CNS?​

A)​muscle spindles and Golgi tendon organs
B)muscle spindles and stretch receptors
C)sarcoplasmic reticulum and Golgi tendon organs
D)sarcomeres and Golgi tendon organs
E)​sarcomeres and stretch receptors

Question 40

How developed is the sarcoplasmic reticulum in cardiac muscle?​

A)​non-existent
B)poorly developed
C)moderately developed
D)well developed
E)​heavily developed

Question 41

Ca₂+binding to tropomyosin causes myosin to change shape,physically moving it away from its blocking position.​

Question 42

During the recovery period,fresh supplies of ATP are formed by oxidative phosphorylation using the newly acquired oxygen,which is provided by the sustained increase in breathing after exercise has stopped.

Question 43

Loss of excitatory input from higher centers brings about flaccid paralysis.​

Question 44

Disuse atrophy occurs when a muscle is not used for a long period of time due to reduced or absent nerve supply.

Question 45

Myofibrils are made from thick and round filaments.​

Question 46

Central fatigue occurs when the central nervous system no longer adequately activates the motor neurons supplying the working muscles.

Question 47

Muscles that produce precise,delicate movements have fewer muscle fibers in their motor units compared to muscles made for powerful movements.​

Question 48

The action potential is over before the contractile apparatus even becomes operational.

Question 49

Slow and fast fibers are interconvertible.​

Question 50

In an isokinetic contraction,the load remains constant as the muscle changes length.​

Question 51

Tropomyosin and troponin are often called stimulation proteins because of their role in covering or exposing the binding sites for cross-bridge interaction between actin and myosin.

Question 52

On binding to actin,the myosin head tilts 45 degrees inward.

Question 53

Both the thin and thick filaments change length during muscle fiber shortening.​

Question 54

Viewed with an electron microscope,a myofibril displays alternating dark bands (the A bands)and light bands (the I bands).​

Question 55

At the outer limits of a muscle's length,it still can achieve about 80% of its maximal contraction strength.​

Question 56

Muscles are categorized as striated (skeletal and cardiac muscle)or unstriated (smooth muscle).​

Question 57

Twitch summation results primarily from a sustained elevation in cytosolic Ca₂+.​

Question 58

A connection involving stimulation of the nerve supply to one muscle and simultaneous inhibition of the nerves to its antagonistic muscle is known as reciprocal innervation.​

Question 59

In contrast to muscle spindles,which lie in the tendons of muscle,Golgi tendon organs are in the belly of muscle.​

Question 60

Tropomyosin molecules are threadlike proteins that lie end to end alongside the groove of the actin spiral.

Question 61

A single ____________________ pulls the thin filament inward only a small percentage of the total shortening distance.​

Question 62

The lighter area within the middle of the A band,where the thin filaments do not reach,is the ____________________.

Question 63

The end of the muscle attached to the more stationary part of the skeleton is called the ____________________,and the end attached to the skeletal part that moves is the ____________________.

Question 64

A single skeletal muscle cell is known as a(n)____________________.​

Question 65

ATP splitting is much slower in smooth muscle,so cross-bridge activity and filament sliding occur about ten times more slowly in smooth muscle than in skeletal muscle.

Question 66

With eccentric contractions,the muscle ____________________.​

Question 67

At each junction of an A band and I band,the surface membrane dips into the muscle fiber to form a(n)____________________.​

Question 68

The crossed extensor reflex is a postural reflex that ensures that the opposite limb is in a position to bear the weight of the body as the injured limb is withdrawn from the stimulus.​

Question 69

____________________ is a protein complex made of three polypeptide units: one binds to ____________________,one binds to actin,and a third can bind with Ca₂+.

Question 70

When the end product of glycolysis,pyruvate,cannot be further processed by oxidative phosphorylation,it is converted to ____________________.

Question 71

A skeletal muscle fiber contains numerous ____________________,which are cylindrical intracellular structures.

Question 72

In a(n)____________________ contraction,the muscle is prevented from shortening,so tension develops at constant muscle length.

Question 73

The H zone,in the center of the ____________________ where the thin filaments do not reach,becomes ____________________ as the thin filaments approach each other when they slide more deeply inward.​

Question 74

The lateral sacs (alternatively known as terminal cisternae)store ____________________.​

Question 75

A(n)____________________ is a rigid structure capable of moving around a pivot point known as a(n)____________________.

Question 76

A smooth muscle cell has many T tubules and well developed sarcoplasmic reticulum.​

Question 77

Unlike skeletal muscle cells,a single smooth muscle cell extends the full length of a muscle.

Question 78

Smooth muscle cells are interconnected by gap junctions found in intercalated discs that join cells together.​

Question 79

Oxidative phosphorylation takes place within the muscle ____________________ if sufficient oxygen is present.​

Question 80

If the muscle fiber is stimulated so rapidly that it does not have a chance to relax at all between stimuli,a smooth,sustained contraction of maximal strength known as ____________________ occurs.