Muscles And Muscle Tissue

Front 1

___ is the ability to receive and respond to a stimulus, that is, any change in the environment whether inside or outside the body.

Back 1

Excitability, also termed responsiveness or irritability

Front 2

____ is the ability to shorten forcibly when adequately stimulated. This property sets muscle apart from all other tissue types.

Back 2

Contractility

Front 3

_____ is the ability to be stretched or extended.

Back 3

Extensibility

Front 4

_____ is the ability of a muscle fiber to recoil and resume its resting length after being stretched.

Back 4

Elasticity

Front 5

Muscle performs four important functions for the body: what are they?

Back 5

It produces movement, maintains posture, stabilizes joints, and generates heat.

Front 6

skeletal muscle accounts for at least __ of body mass

Back 6

40%

Front 7

a fine sheath of connective tissue consisting of areolar and reticular fibers-surrounds each individual muscle fiber

Back 7

Endomysium

Front 8

, the endomysium-wrapped muscle fibers are grouped into ____

Back 8

fascicles

Front 9

each fascicle is a layer of fibrous connective tissue called

Back 9

perimysium

Front 10

An “overcoat” of dense irregular connective tissue that surrounds the whole muscle.

Back 10

Epimysium

Front 11

) when a muscle contracts, the movable bone, the muscle’s ______, moves toward the immovable or less movable bone, the muscle’s ____

Back 11

insertion,origin

Front 12

In _____ attachments, the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage.

Back 12

direct, or fleshy,

Front 13

In ____ ____, the muscle’s connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheetlike aponeurosis

Back 13

indirect attachments

Front 14

the sracoplasm contains unsusually large amounts of____ (granules of stored glycogen) , and ____, a red pigment that stores oxygen

Back 14

glycosomes, myogobin

Front 15

The _____ contain the contractile elements of skeletal muscle cells, and they account for about 80% of cellular volume.

Back 15

myofibrils

Front 16

A sarcomere (sar′ko-mĕr; literally, “muscle segment”) is the region of a myofibril between two successive __ ___.

Back 16

Z discs

Front 17

The central ___ filaments extend the entire length of the A band while The more lateral ____ filaments extend across the I band and partway into the A band.

Back 17

thick, thin

Front 18

The __ ___, a coin-shaped sheet composed largely of the protein alpha actinin, anchors the thin filaments.

Back 18

Z disc

Front 19

_____ filaments extending from the Z disc connect each myofibril to the next throughout the width of the muscle cell.

Back 19

Intermediate (desmin)

Front 20

The myofilaments are connected to the sarcolemma at the __ __ and the __ ___.

Back 20

Z discs. M lines.

Front 21

Thick filaments (about 16 nm in diameter) are composed primarily of the protein ___.

Back 21

myosin

Front 22

Each __ __ has a rodlike tail terminating via a flexible hinge in two globular heads.

Back 22

myosin molecule

Front 23

Each thick filament contains about __ myosin molecules bundled together

Back 23

300

Front 24

Besides bearing actin binding sites, the heads contain ATPase enzymes that split ___ to generate energy for muscle contraction.

Back 24

ATP

Front 25

The thin filaments (7–8 nm thick) are composed chiefly of the protein ___

Back 25

actin

Front 26

Two strands of ____ ,a rod-shaped protein, spiral about the actin core and help stiffen it

Back 26

tropomyosin (tro″po-mi′o-sin),

Front 27

The other major protein in the thin filament,___, is a three-polypeptide complex

Back 27

troponin (tro′po-nin),

Front 28

Titin has two basic fxns, what are they?

Back 28

(1) holding the thick filaments in place, thus maintaining the organization of the A band, and (2) assisting the muscle cell to spring back into shape after being stretched or shortening.

Front 29

Another important structural protein is ____, which links the thin filaments to the integral proteins of the sarcolemma (which in turn are anchored to the extracellular matrix)

Back 29

dystrophin

Front 30

At each A band–I band junction, the sarcolemma of the muscle cell penetrates into the cell interior, forming an elongated tube called the _ ____

Back 30

T tubule

Front 31

Muscle contraction is ultimately controlled by nerve-initiated electrical impulses that travel along the ______

Back 31

sarcolemma.

Front 32

Because _ ___ are continuations of the sarcolemma, they can and do conduct impulses to the deepest regions of the muscle cell and to every sarcomere

Back 32

T tubules

Front 33

____ ends when the cross bridges become inactive and the tension generated declines, inducing relaxation of the muscle fiber.

Back 33

Contraction

Front 34

The sliding filament theory of contraction states that during contraction the thin filaments slide past the thick ones so that the ___ and ___ filaments overlap to a greater degree

Back 34

actin myosin

Front 35

For a skeletal muscle fiber to contract, it must be stimulated by a nerve ending and must propagate an electrical current, or ___ ____, along its sarcolemma.

Back 35

action potential

Front 36

Although the axon terminal and the muscle fiber are exceedingly close (1–2 nm apart), they remain separated by a space, the __ ___

Back 36

synaptic cleft

Front 37

. Within the flattened moundlike axon terminal are synaptic vesicles, small membranous sacs containing the neurotransmitter ___ , or ACh.

Back 37

acetylcholine

Front 38

The ___ __ ___, the troughlike part of the muscle fiber’s sarcolemma that helps form the neuromuscular junction, is highly folded. These junctional folds provide a large surface area for the millions of ACh receptors located there.

Back 38

motor end plate

Front 39

When a nerve impulse reaches the end of an axon, voltage-gated calcium channels in its membrane open, allowing ___ to flow in from the extracellular fluid.

Back 39

Ca2+ (propelled by its electrochemical gradient)

Front 40

The presence of calcium inside the axon terminal causes some of the synaptic vesicles to fuse with the axonal membrane and release ___ into the synaptic cleft by exocytosis

Back 40

ACh

Front 41

Like the plasma membranes of all cells, a resting sarcolemma is _____

Back 41

polarized

Front 42

Describe the first step of the action potential.

Back 42

. First the membrane areas adjacent to the depolarized motor end plate are depolarized by local currents that spread to them from the neuromuscular junction. This opens voltage-gated sodium channels there, so Na+ enters, following its electrochemical gradient, and initiates the action potential

Front 43

Describe the second step of the action potential.

Back 43

During step 2, the action potential is propagated (moves along the length of the sarcolemma) as the local depolarization wave spreads to adjacent areas of the sarcolemma and opens voltage-gated sodium channels there (see Figure 9.8c). Again, sodium ions, normally restricted from entering, diffuse into the cell following their electrochemical gradient.

Front 44

Describe the third step of the action potential.

Back 44

Step 3 is repolarization, which restores the sarcolemma to its initial polarized state. The repolarization wave, which quickly follows the depolarization wave, is a consequence of Na+ channels closing and voltage-gated K+ channels opening. Since the potassium ion concentration is substantially higher inside the cell than in the extracellular fluid, K+ diffuses rapidly out of the muscle fiber

Front 45

During repolarization, a muscle fiber is said to be in a ___ ___, because the cell cannot be stimulated again until repolarization is complete.

Back 45

refractory period

Front 46

__ __ __ is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments.

Back 46

Excitation-contraction (E-C) coupling

Front 47

The events of excitation-contraction coupling occur during the __ __, between action potential initiation and the beginning of mechanical activity (shortening).

Back 47

latent period

Front 48

When intracellular calcium levels are low, the muscle cell is relaxed/excited?

Back 48

relaxed

Front 49

Name the 4 steps to muscle fiber contraction.

Back 49

Cross bridge formation, The power (working) stroke, Cross bridge detachment, “Cocking” of the myosin head.

Front 50

The force exerted by a contracting muscle on an object is called __ ___ , and the opposing force exerted on the muscle by the weight of the object to be moved is called the ___

Back 50

muscle tension load

Front 51

A motor neuron and all the muscle fibers it supplies is called a ___ ___

Back 51

motor unit

Front 52

Define Period of relaxation.

Back 52

The period of contraction is followed by the period of relaxation. This final phase, lasting 10–100 ms, is initiated by reentry of Ca2+ into the SR. Because contractile force is no longer being generated, muscle tension decreases to zero and the tracing returns to the baseline. If the muscle shortened during contraction, it now returns to its initial length.

Front 53

Define Period of contraction.

Back 53

The period of contraction is when cross bridges are active, from the onset to the peak of tension development, and the myogram tracing rises to a peak. This period lasts 10–100 ms. If the tension (pull) becomes great enough to overcome the resistance of a load, the muscle shortens.

Front 54

Define Latent period.

Back 54

The latent period is the first few milliseconds following stimulation when excitation-contraction coupling is occurring. During this period, muscle tension is beginning to increase but no response is seen on the myogram.

Front 55

In general, muscle contraction can be graded in two ways. Name them.

Back 55

(1) by changing the frequency of stimulation and (2) by changing the strength of the stimulus.

Front 56

if two identical stimuli (electrical shocks or nerve impulses) are delivered to a muscle in rapid succession, the second twitch will be stronger than the first. What is this called?

Back 56

wave summation

Front 57

______ contractions are about 50% more forceful than concentric ones at the same load and more often cause delayed-onset muscle soreness

Back 57

Eccentric

Front 58

Name the two types of isotonic contractions.

Back 58

Eccentric, Concentric

Front 59

The force of contraction is controlled more precisely by _____, also called multiple motor unit summation

Back 59

recruitment

Front 60

delivering shocks of increasing voltage to the muscle, calling more and more muscle fibers into play. The stimulus at which the first observable contraction occurs is called the ____ _____.

Back 60

threshold stimulus.

Front 61

The ____ _____ is the strongest stimulus that produces increased contractile force.

Back 61

maximal stimulus

Front 62

The recruitment process is not random; instead it is dictated by the ___ principle.

Back 62

size

Front 63

Fortunately, after ATP is hydrolyzed to ADP and inorganic phosphate, it is regenerated within a fraction of a second by three pathways

Back 63

1) by interaction of ADP with creatine phosphate, (2) from stored glycogen via the anaerobic pathway called glycolysis, and (3) by aerobic respiration.

Front 64

The initial phase of glucose respiration is ____

Back 64

glycolysis

Front 65

Under these anaerobic conditions, most of the pyruvic acid produced during glycolysis is converted into ___ ____, and the overall process is referred to as ____ _____.

Back 65

lactic acid anaerobic glycolysis

Front 66

During glycolysis, glucose is broken down to two pyruvic acid molecules, releasing enough energy to form small amounts of ATP. How much ATP is produced?

Back 66

(2 ATPs per glucose).

Front 67

The anaerobic pathway harvests only about __& as much ATP from each glucose molecule as the aerobic pathway; however, it produces ATP about__ times faster.

Back 67

5%, 2 1∕2

Front 68

___ ___ is a state of physiological inability to contract even though the muscle still may be receiving stimuli.

Back 68

Muscle fatigue

Front 69

Availability of ATP declines during contraction and a total lack of ATP results in ______, states of continuous contraction because the cross bridges are unable to detach

Back 69

contractures

Front 70

Oxygen debt is defined as what?

Back 70

Oxygen debt is defined as the extra amount of oxygen that the body must take in for these restorative processes.

Front 71

Only about __% of the energy released during muscle contraction is converted to useful work

Back 71

40%

Front 72

What 4 factors affect the force of muscle contraction?

Back 72

(1) the number of muscle fibers stimulated, (2) the relative size of the fibers, (3) frequency of stimulation, and (4) the degree of muscle stretch

Front 73

The more rapidly a muscle is stimulated, the ____ the force it exerts.

Back 73

greater

Front 74

The cells that rely mostly on the oxygen-using aerobic pathways for ATP generation are ____ fibers; those that rely more on anaerobic glycolysis are ____ fibers.

Back 74

oxidative, glycolytic

Front 75

The innervating nerve fibers of smooth muscle tissue, which are part of the autonomic nervous system, have numerous bulbous swellings, called _____

Back 75

varicosities

Front 76

The varicosities release neurotransmitter into a wide synaptic cleft in the general area of the smooth muscle cells. Such junctions are called ____ ____.

Back 76

diffuse junctions.