CH10 Flashcards

Question

what are muscle fascicles?

Answer 1

groups of 10-100 or more muscle fibres surrounded by perimysium

Answer 2

a chronic, painful, nonarticular rheumatic disorder that **affects the fibrous connective tissue components of muscles, tendons, and ligaments** - pain that results from gentle pressure at specific “tender points”, severe fatigue, poor sleep, headaches, depression, irritable bowel syndrome, and inability to carry out their daily activities, pain, tenderness, and stiffness of muscles, tendons, and surrounding soft tissues - treatment: stress reduction, regular exercise, application of heat, gentle massage, physical therapy, medication for pain, and a low-dose antidepressant to help improve sleep

Answer 3

Invagination of the perimysium separating each individual muscle fiber, mostly reticular fibres

Answer 4

A white fibrous cord of dense regular connective tissue that attaches muscle to bone

Answer 5

A **sheetlike** tendon joining one muscle with another or with bone, broad flat sheet

Answer 6

neurons that stimulate skeletal muscle to contract

Answer 7

- bring in oxygen and nutrients and remove heat and the waste products of muscle metabolism - muscle fiber synthesizes and uses considerable ATP, which requires oxygen, glucose, fatty acids, and other substances to be delivered to muscle fiber

Answer 8

mesodermal cells that fuse into skeletal muscle fibers during embryonic development

Answer 9

when fusion of the myoblasts occurs

Answer 10

the plasma membrane of a muscle fiber

Answer 11

tiny tube-shaped invaginations of the sarcolemma that tunnel in from the surface toward the center of each muscle fiber

Answer 12

T tubules are open to the outside of the fiber

Answer 13

- muscle action potentials travel along the sarcolemma and through the T tubules, quickly spreading throughout the muscle fiber - ensures that an action potential excites all parts of the muscle fiber at essentially the same instant

Answer 14

the cytoplasm of a muscle fiber - includes substantial amount of glycogen and myoglobin

Answer 15

red-coloured, iron-containing protein found only in sarcoplasm of muscles - binds oxygen molecules that diffuse into muscle fibers from interstitial fluid - releases oxygen when it is needed by the mitochondria for ATP production

Answer 16

mitochondria lie in rows throughout the muscle fiber, **strategically close to the contractile muscle proteins that use ATP during contraction** so that ATP can be produced quickly as needed

Answer 17

enlargement of existing muscle fibers - due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum, and other organelles - results from very forceful, repetitive muscular activity, such as strength training - capable of more forceful contractions - growth hormone, testosterone promotes enlargement of skeletal muscle fibers

Answer 18

myoblasts that persist in mature skeletal cells - retain the capacity to fuse with one another or with damaged muscle fibers to regenerate functional muscle fibers

Answer 19

the replacement of muscle fibers by fibrous scar tissue when the number of new skeletal muscle fibers that can be formed by satellite cells is not enough to compensate for significant skeletal muscle damage or degeneration

Answer 20

a decrease in size of individual muscle fibers because of progressive loss of myofibrils

Answer 21

Atrophy that occurs because muscles are not used

Answer 22

muscle decreases in size as nerve supply is disrupted or cut - Over a period of 6 months to 2 years, the muscle shrinks to about one-fourth its original size, and its fibers are **irreversibly** replaced by **fibrous connective tissue**

Answer 23

the sarcoplasmic reticulum

Answer 24

the contractile organelles of skeletal muscle - their prominent striations make the entire skeletal muscle fiber appear striated - are about 2 µm in diameter and extend the entire length of a muscle fiber

Answer 25

fluid-filled system of membranous sacs that encircles each myofibril

Answer 26

Dilated end sacs of the sarcoplasmic reticulum that butt against a transverse tubule from both sides

Answer 27

terminal cistern | T tubule | terminal cistern

Answer 28

- release of Ca2+ from the terminal cisterns of the sarcoplasmic reticulum triggers muscle contraction - the sarcoplasmic reticulum stores Ca2+ in a relaxed muscle fiber

Answer 29

smaller protein structures within myofibrils

Answer 30

the basic contractile unit in a striated muscle fiber extending from one Z disc to the next Z disc

Answer 31

Narrow, plate-shaped regions of dense protein material that separate one sarcomere from the next

Answer 32

- darker middle part of the sarcomere - extends the entire length of the thick filaments

Answer 33

where the thick and thin filaments lie side by side, found towards each end of the A band

Answer 34

a lighter, less dense area that contains the rest of the thin filaments but no thick filaments - a Z disc passes through the center of each I band

Answer 35

The alternating dark A bands and light I bands`

Answer 36

a narrow band in the center of each A band contains thick but not thin filaments

Answer 37

center of H band where supporting proteins that hold the thick filaments together are found

Answer 38

1. contractile proteins 2. regulatory proteins 3. structural proteins

Answer 39

generate force during contraction

Answer 40

help switch the contraction process on and off

Answer 41

- keep the thick and thin filaments in the proper alignment - give the myofibril elasticity and extensibility - link the myofibrils to the sarcolemma and extracellular matrix

Answer 42

a contractile protein, the main component of thick filaments and functions as a motor protein in all three types of muscle tissue

Answer 43

Motor proteins pull various cellular structures to achieve movement by converting the chemical energy in ATP to the mechanical energy of motion, that is, the production of force

Answer 44

1. actin-binding site 2. ATP-binding site

Answer 45

ATPase, hydrolyzes/catabolizes ATP to generate energy for muscle contraction

Answer 46

A contractile protein that is part of thin filaments in muscle fibers

Answer 47

Z disc - Actin and titin A bands - myosin, actin, troponin, tropomyosin, and titin I bands - actin, troponin, tropomyosin, and titin

Answer 48

regulatory protein, covers the myosin-binding sites on actin, blocking myosin from binding to actin in relaxed muscles

Answer 49

holds tropomyosin strands in place - undergoes conformational change when it binds to Ca2+, moving tropomyosin away from the myosin-binding sites on actin

Answer 50

contribute to the alignment, stability, elasticity, and extensibility of myofibrils

Answer 51

- titin - α-actinin - myomesin - nebulin - dystrophin

Answer 52

connects a Z disc to the M line of the sarcomere, thereby helping stabilize the position of the thick filament - accounts for much of the elasticity and extensibility of myofibrils - helps the sarcomere return to its resting length after a muscle has contracted or been stretched - may help prevent overextension of sarcomeres - maintains the central location of the A bands

Answer 53

binds to actin molecules of the thin filament and to titin

Answer 54

forms the M line, binds to titin and connect adjacent thick filaments to one another - myomesin holds the thick filaments in alignment at the M line

Answer 55

long, nonelastic protein wrapped around the entire length of each thin filament - helps anchor the thin filaments to the Z discs and regulates the length of thin filaments during development

Answer 56

- links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached to proteins in the connective tissue extracellular matrix that surrounds muscle fibers - thought to reinforce the sarcolemma and help transmit the tension generated by the sarcomeres to the tendons

Answer 57

skeletal muscle shortens during contraction because the thick and thin filaments **slide** past one another

Answer 58

- myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the M line - the thin filaments slide inward and meet at the center of a sarcomere - As the thin filaments slide inward, the I band and H zone narrow and eventually disappear altogether when the muscle is maximally contracted - the width of the A band and the individual lengths of the thick and thin filaments remain unchanged - Since the thin filaments on each side of the sarcomere are attached to Z discs, when the thin filaments slide inward, the Z discs come closer together, and the sarcomere shortens - Shortening of the sarcomeres causes shortening of the whole muscle fiber, which in turn leads to shortening of the entire muscle

Answer 59

The I bands and H zones disappear during muscle contraction; the lengths of the thin and thick filaments do not change

Answer 60

1. ATP hydrolysis 2. Attachment of myosin to actin 3. Power stroke 4. Detachment of myosin from actin

Answer 61

when troponin, upon Ca2+ binds to it, moves tropomyosin away from the myosin-binding sites on actin and freeing them

Answer 62

- ATP that binds to ATP-binding site of myosin is hydrolyzed into ADP and Pi, energy generated is stoted in the myosin head for later use - the energized myosin head is "cocked" like a stretched spring (perpendicular to the thick and thin filaments, the proper orientation to bind to an actin molecule) - ADP and Pi are still attached to myosin head

Answer 63

energized myosin head attaches to the myosin-binding site on actin and releases Pi

Answer 64

only one, each myosin only has one actin-binding site

Answer 65

myosin head is attached to an actin molecule

Answer 66

- myosin head pivots, changing its position from a 90° angle to a 45° angle relative to the thick and thin filaments - power stroke occurs: as the myosin head changes to its new position, it pulls the thin filament past the thick filament toward the center of the sarcomere, generating tension - ADP is released from the myosin head

Answer 67

- cross-bridge remains firmly attached to actin until it binds to another ATP - myosin head detaches from actin as ATP binds

Answer 68

If ATP were not available, the cross-bridges would not be able to detach from actin. The muscles would remain in a state of rigidity, as occurs in rigor mortis.

Answer 69

The sequence of events that links excitation (a muscle action potential) to contraction (sliding of the filaments) that occurs at the triads of the skeletal muscle fiber

Answer 70

on the T tubule membrane, arranged in tetrads

Answer 71

to serve as voltage sensors that trigger the opening of the Ca2+ release channels

Answer 72

on the terminal cisternal membrane of the sarcoplasmic reticulum

Answer 73

the part of the Ca2+ release channel that extends into the sarcoplasm is blocked by a given cluster of voltage-gated Ca2+ channels, preventing Ca2+ from leaving the SR

Answer 74

when an action potential travels along the T tubule, the voltage-gated Ca2+ channels detect the change in voltage and undergo a conformational change that causes the Ca2+ release channels to open - copious amounts of Ca2+ flow out of the SR into the sarcoplasm around the thick and thin filaments - Ca2+ concentration in the sarcoplasm rises tenfold - The released calcium ions combine with troponin and start the contraction cycle

Answer 75

proteins located on the terminal cisternal membrane of the SR that use ATP to constantly transport Ca2+ from the sarcoplasm back into the SR

Answer 76

proteins that bind to Ca2+, allowing even more Ca2+ to be sequestered (stored) within the SR

Answer 77

a branch of medicine concerned with the diagnosis of neuromuscular disorders

Answer 78

the speed of nerve impulses conducted through nerves outside the brain and spinal cord; for example, those of your limbs - involve stimulating a nerve with an electrical impulse applied to the skin and recording the response from a muscle (contraction) or another portion of a nerve through patches placed on the skin - used to diagnose conditions such as carpal tunnel syndrome, herniated discs, and sciatica

Answer 79

- a very thin needle, which serves as a recording device, is placed through the skin into a muscle - The needle is connected by a wire to the screen of a device (an oscilloscope) - Resting muscle produces no electrical activity as there are no muscle action potentials - The more forceful the contraction, the higher the level of electrical activity - the client is asked to contract a muscle and the activity is recorded on the screen and may also be detected audibly with a speaker - used to diagnose disorders such as muscular dystrophy, myasthenia gravis, and amyotrophic lateral sclerosis

Answer 80

the forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins

Answer 81

when zone of overlap in each sarcomere is optimal, close to resting length in most muscles - when the zone of overlap between a thick and thin filament extends from the edge of the H zone to one end of a thick filament

Answer 82

(1) Its hydrolysis by an ATPase activates the myosin head so it can bind to actin and rotate (2) its binding to myosin causes detachment from actin after the power stroke (3) it powers the pumps that transport Ca2+ from the sarcoplasm back into the sarcoplasmic reticulum

Answer 83

State of partial contraction of muscles after death due to lack of ATP; myosin heads (crossbridges) remain attached to actin, thus preventing relaxation - begins 3–4 hours after death and lasts about 24 hours; then it disappears as proteolytic enzymes from lysosomes digest the cross-bridges

Answer 84

the zone of overlap shortens, and fewer myosin heads can make contact with thin filaments. Therefore, the tension the fiber can produce decreases.

Answer 85

When a skeletal muscle fiber is stretched to 170% of its optimal length - because none of the myosin heads can bind to thin filaments, the muscle fiber cannot contract, and tension is zero

Answer 86

the tension that can develop again decreases - thick filaments crumple as they are compressed by the Z discs, resulting in fewer myosin heads contacting thin filaments

Answer 87

by firm attachments of skeletal muscles to bones via their tendons and to other inelastic tissues

Answer 88

A sarcomere length of 2.2 µm gives a generous zone of overlap between the parts of the thick filaments that have myosin heads and the thin filaments without the overlap being so extensive that sarcomere shortening is limited.

Answer 89

The synapse between a somatic motor neuron and a skeletal muscle fiber where muscle action potentials arise

Answer 90

a region where communication occurs between two neurons, or between a neuron and a target cell—between a somatic motor neuron and a muscle fiber

Answer 91

The narrow gap at a chemical synapse that separates the axon terminal of one neuron from another neuron or muscle fiber and across which a neurotransmitter diffuses to affect the postsynaptic cell

Answer 92

One of a variety of molecules within axon terminals that are released into the synaptic cleft in response to a nerve impulse and that change the membrane potential of the postsynaptic neuron

Answer 93

A neurotransmitter liberated by many peripheral nervous system neurons and some central nervous system neurons - It is excitatory at neuromuscular junctions but inhibitory at some other synapses

Answer 94

*telodendria* Terminal branch of an axon where synaptic vesicles undergo exocytosis to release neurotransmitter molecules

Answer 95

Expanded distal end of an axon terminal that contains synaptic vesicles

Answer 96

Region of the sarcolemma of a muscle fiber opposite the synaptic end bulbs that includes acetylcholine receptors, which bind ACh released by synaptic end bulbs of somatic motor neurons

Answer 97

abundant in junctional folds, deep grooves in the motor end plate that provide a large surface area for ACh

Answer 98

1. release of ACh 2. activation of ACh receptors 3. production of muscle action potential 4. termination of ACh activity

Answer 99

- arrival of nerve action potential at synaptic end bulbs stimulates voltage-gated channels to open - Ca2+ flows inward through the open channels, Ca2+ are more concentrated in ECF - Ca2+ in turn stimulates the synaptic vesicles to undergo exocytosis - the synaptic vesicles fuse with the motor neuron’s plasma membrane, liberating ACh into the synaptic cleft - ACh then diffuses across the synaptic cleft between the motor neuron and the motor end plate

Answer 100

- Binding of two molecules of ACh to the receptor on the motor end plate opens an ion channel in the ACh receptor - small cations, most importantly Na+, can flow across the membrane once channel is open

Answer 101

- inflow of Na+ (down its electrochemical gradient) makes the inside of the muscle fiber more positively charged - change in the membrane potential triggers a muscle action potential - muscle action potential then propagates along the sarcolemma into the system of T tubules - sarcoplasmic reticulum releasex its stored Ca2+ into the sarcoplasm, and the muscle fiber subsequently contracts

Answer 102

- effect of ACh binding lasts only briefly because ACh is rapidly broken down by **acetylcholinesterase** located on the extracellular side of the motor end plate membrane - AChE breaks down ACh into acetyl and choline

Answer 103

The part of the sarcolemma that contains acetylcholine receptors is the motor end plate.

Answer 104

only one, usually located near the midpoint of the fiber which permits nearly simultaneous activation (and thus contraction) of all parts of the muscle fiber

Answer 105

- blocks exocytosis of synaptic vesicles at the NMJ - ACh is not released, and muscle contraction does not occur

Answer 106

Breathing stops due to paralysis of respiratory muscles, including the diaphragm

Answer 107

- Injections of Botox into the affected muscles can help patients who have crossed eyes, uncontrollable blinking, or spasms of the vocal cords that interfere with speech - It is also used to alleviate chronic back pain due to muscle spasms in the lumbar region and as a cosmetic treatment to relax muscles that cause facial wrinkles

Answer 108

causes muscle paralysis by binding to and blocking ACh receptors

Answer 109

family of chemicals that have the property of slowing the enzymatic activity of acetylcholinesterase, thus slowing removal of ACh from the synaptic cleft, can strengthen weak muscle contractions (ex. Neostigmine)

Answer 110

1. Creatine Phosphate 2. Anaerobic Glycolysis 3. Aerobic Respiration

Answer 111

Most of the excess ATP is used to synthesize creatine phosphate

Answer 112

Creatine Kinase

Answer 113

a small, amino acid–like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers

Answer 114

CK catalyzes the transfer of a high-energy phosphate group from creatine phosphate back to ADP (ADP+Pi=ATP)

Answer 115

direct phosphorylation reaction catalyzed by CK quickly generates new ATP molecules, occurs very rapidly

Answer 116

Together, stores of creatine phosphate and ATP provide enough energy for muscles to contract maximally for about **15 seconds**

Answer 117

- ingesting extra creatine decreases the body’s own synthesis of creatine, not known whether natural synthesis recovers after long-term creatine supplementation - creatine supplementation can cause dehydration and may cause kidney dysfunction

Answer 118

in the cytosol of muscle fibers

Answer 119

- not enough oxygen is available to skeletal muscle fibers, anaerobic conditions - pyruvate converted to lactic acid

Answer 120

- 2 lactic acid molecules - 2 ATP

Answer 121

- most diffuse out of skeletal muscle into blood where liver converts them back to glucose, reducing blood acidity

Answer 122

- lactic acid can accumulate in active skeletal muscle fibers and in bloodstream - buildup is thought to be responsible for muscle soreness during exercise

Answer 123

- provides 2 mins maximal muscle activity

Answer 124

1. oxygen that diffuses into muscle fibers from blood 2. oxygen released by myoglobin within muscle fibers

Answer 125

30-32 ATP - several minutes - an hour or more of activity

Answer 126

inability of a muscle to maintain force of contraction after prolonged activity

Answer 127

- feelings of tiredness and the desire to cease activity - caused by changes in CNS - protective mechanism to stop a person from exercising before muscles become damaged

Answer 128

- inadequate release of Ca2+ from SR - insufficient oxygen - depletion of glycogen - buildup of lactic acid and ADP - failure of action potentials in motor neuron to release enough ACh

Answer 129

the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise

Answer 130

oxygen debt, oxygen is added at a higher amount than resting oxygen consumption after prolonged periods of muscle contraction

Answer 131

- to convert lactic acid back into glycogen stores in the liver - to resynthesize creatine phosphate and ATP in muscle fibers - to replace O2 removed from myoglobin

Answer 132

unit that consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates (a single somatic motor neuron makes contact with an average of 150 skeletal muscle fibers, and all of the muscle fibers in one motor unit contract in unison)

Answer 133

Because all of the muscle fibers of a motor unit contract and relax together, the total strength of a contraction depends, in part, on the size of the motor units and the number that are activated at a given time

Answer 134

Because all of the muscle fibers of a motor unit contract and relax together, the total strength of a contraction depends, in part, on the size of the motor units and the number that are activated at a given time

Answer 135

motor units having many muscle fibers are capable of more forceful contractions than those having only a few fibers

Answer 136

the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron

Answer 137

a brief delay occurs between application of the stimulus and the beginning of contraction - muscle action potential sweeps over the sarcolemma and calcium ions are released from the SR

Answer 138

- Ca2+ binds to troponin - myosin-binding sites on actin are exposed, and cross-bridges form - peak tension develops in the muscle fiber

Answer 139

- Ca2+ is actively transported back into the SR - myosin-binding sites are covered by tropomyosin - myosin heads detach from actin - tension in the muscle fiber decreases

Answer 140

- fast-twitch fibers that move the eyes have contraction periods as brief as 10 msec and equally brief relaxation periods - slow-twitch fibers that move the legs have contraction and relaxation periods of about 100 msec each

Answer 141

period of lost excitability when a muscle fiber receives enough stimulation to contract and cannot respond for a time

Answer 142

because of the refractory period

Answer 143

- skeletal muscle has a short refractory period of about 1 msec - cardiac muscle has a longer refractory period of about 250 msec

Answer 144

phenomenon in which a stimulus that occurs after the refractory period of the first stimulus is over but before the skeletal muscle fiber has relaxed causes larger contractions

Answer 145

sustained but wavering contraction that occurs when a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second and can only partially relax between stimuli

Answer 146

a sustained contraction in which individual twitches cannot be detected, occurs when a skeletal muscle fiber is stimulated at a higher rate of 80 to 100 times per second and does not relax at all

Answer 147

additional Ca2+ is released from the sarcoplasmic reticulum by subsequent stimuli while the levels of Ca2+ in the sarcoplasm are still elevated from the first stimulus

Answer 148

- during wave summation, elastic components are not given much time to spring back between contractions and remain taut - elastic components do not require much stretching before the beginning of the next muscular contraction

Answer 149

The process in which the number of active motor units increases

Answer 150

- the different motor units of an entire muscle are not stimulated to contract in unison - while some motor units are contracting, others are relaxed - the weakest motor units are recruited first, with progressively stronger motor units added if the task requires more force

Answer 151

- precise movements are brought about by small changes in muscle contraction - the small muscles that produce precise movements are made up of small motor units - when a motor unit is recruited or turned off, only slight changes occur in muscle tension - in contrast, large motor units are active when a large amount of tension is needed and precision is less important

Answer 152

activities such as weight lifting that rely more on anaerobic production of ATP through glycolysis - stimulate synthesis of muscle proteins and result, over time, in increased muscle size - diet should include an adequate amount of proteins - protein intake will allow the body to synthesize muscle proteins and to increase muscle mass - builds muscle strength for short-term feats

Answer 153

regular, repeated activities such as jogging or aerobic dancing that increase the supply of oxygen-rich blood available to skeletal muscles for aerobic respiration - builds endurance for prolonged activities

Answer 154

workout regimen that incorporates both anaerobic and aerobic training (ex. alternating sprints with jogging)

Answer 155

a small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units that skeletal muscle exhibits even at rest

Answer 156

neurons in the brain and spinal cord that excite the muscle’s motor neurons

Answer 157

when the motor neurons serving a skeletal muscle are damaged or cut

Answer 158

small groups of motor units are alternatively active and inactive in a constantly shifting pattern

Answer 159

- keeps skeletal muscles firm, but it does not result in a force strong enough to produce movement - especially important in smooth muscle tissues

Answer 160

decreased or lost muscle tone - Flaccid muscles are loose and appear flattened rather than rounded

Answer 161

- loss of muscle tone - loss or reduction of tendon reflexes - atrophy and degeneration of muscles

Answer 162

increased muscle tone and is expressed in two ways: spasticity or rigidity

Answer 163

increased muscle tone (stiffness) associated with an increase in tendon reflexes and pathological reflexes

Answer 164

partial paralysis in which the muscles exhibit spasticity

Answer 165

increased muscle tone in which reflexes are not affected, as occurs in tetanus

Answer 166

the tension (force of contraction) developed in the muscle remains almost constant while the muscle changes its length - used for body movements and for moving objects - concentric/eccentric

Answer 167

the length of a muscle decreases during a contraction, tension remains constant - muscle **shortens** and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at a joint

Answer 168

the length of a muscle increases during a contraction, tension remains constant

Answer 169

eccentric isotonic contractions

Answer 170

the muscle does not change length but tension increases greatly - does not result in movement, but energy is still expended - important for maintaining posture and for supporting objects in a fixed position

Answer 171

Holding your head upright without movement involves mainly isometric contractions

Answer 172

- appear **dark red** - HIGH of myoglobin - HIGH of blood capillaries - LARGE mitochondria - generate ATP mainly by **aerobic respiration** - **slow** speed of contraction - resistant to fatigue - capable of prolonged, sustained, contractions for **many hours** - adapted for maintaining posture and for aerobic, endurance-type activities - running, jogging

Answer 173

- largest fibers - appear **dark red** - HIGH myoglobin - HIGH blood capillaries - generate considerable ATP by **aerobic respiration** - moderately high resistance to fatigue - HIGH lvls intracellular glycogen - MED glycogen stores - can generate ATP through anaerobic glycolysis - **fast** speed of contraction - walking, sprinting

Answer 174

- appear **white** - LOW myoglobin - LOW blood capillaries - LOW mitochondria - HIGH glycogen - generate ATP mainly by **glycolysis** - contract **strongly and quickly** - adapted for intense movements of **short** duration - weightlifting - throwing a ball - fatigue quickly

Answer 175

- When a relaxed muscle is physically stretched, its ability to lengthen is limited by connective tissue structures, such as fasciae - To see an improvement in flexibility, stretching exercises must be performed regularly—daily, if possible—for many weeks. - regular stretching gradually lengthens these structures but occurs slowly

Answer 176

synthetic variations of testosterone, the sex hormone responsible for the development of male sexual characteristics - increases muscle size by increasing protein synthesis in muscles, which increases strength - irreversible effects to body - can cause liver cancer - can couse body not to make any more testosterone

Answer 177

- Tissues stretch best when slow, gentle force is applied at elevated tissue temperatures - Exercise heats muscle more deeply and thoroughly than external measures

Answer 178

the process of exercising with progressively heavier resistance for the purpose of strengthening the musculoskeletal system

Answer 179

- stronger muscles - increases bone strength by increasing the deposition of bone minerals - raises resting metabolic rate - helps prevent back injury - reduces stress and fatigue - builds exercise tolerance, takes longer before lactic acid builds up in muscles

Answer 180

- connect the ends of cardiac muscle fibers to one another - desmosomes hold the fibers together - gap junctions allow muscle action potentials to spread from one cardiac muscle fiber to another

Answer 181

- due to prolonged delivery of Ca2+ into the sarcoplasm - Ca2+ enters the sarcoplasm both from the sarcoplasmic reticulum and from the interstitial fluid that bathes the fibers. - the channels that allow inflow of Ca2+ from interstitial fluid stay open for a relatively long time

Answer 182

No, cardiac muscle tissue contracts when stimulated by its own **autorhythmic muscle fibers**

Answer 183

*physiological enlarged heart* cardiac muscle fibers can undergo hypertrophy in response to an increased workload

Answer 184

- through aerobic respiration - mitochondria in cardiac muscle fibers are larger and more numerous than in skeletal muscle fibers - requires a constant supply of oxygen - can also use lactic acid from skeletal fibres to make ATP (during exercise)

Answer 185

autorhythmic smooth muscle, most common type of smooth muscle tisue - found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder - fibers connect to one another by gap junctions, forming a network through which muscle action potentials can spread - one fiber and its neighbours contract in unison, as a single unit

Answer 186

- consists of individual fibers, each with its own motor neuron terminals and with few gap junctions between neighboring fibers - stimulation of one multi-unit fiber causes contraction of that fibre only - found in the walls of large arteries, in airways to the lungs, in the arrector muscles of the hair that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye

Answer 187

- the various filaments have no regular pattern of overlap - lack T tubules - only have small amount of SR for storage of Ca2+ - **caveolae** contain extracellular Ca2+

Answer 188

structures that thin filaments attach to and function similarly to Z discs

Answer 189

Visceral smooth muscle is more like cardiac muscle; both contain gap junctions, which allow action potentials to spread from each cell to its neighbors.

Answer 190

- contraction starts more slowly and lasts much longer - can both shorten and stretch to a greater extent

Answer 191

- no T tubules in smooth muscle - takes longer for Ca2+ to reach the filaments in center of fiber and trigger contraction - calmodulin and myosin light chain kinase work slowly

Answer 192

regulatory protein that binds to Ca2+ in sarcoplasm (like troponin) - activates myosin light chain kinase that allows for contraction to occur in smooth muscle

Answer 193

enzyme that is activated by calmodulin and uses ATP to add a Pi to myosin heads, allowing for contraction to occur - works slowly

Answer 194

continued partial contraction in smooth muscle tissue due to prolonged presence of Ca2+ in the cytosol - important for maintaining steady pressure in vessels and canals that smooth muscle tissue line

Answer 195

mainly due to hypertrophy, enlargement of existing muscle cells

Answer 196

smooth muscle tissue - pericytes/stem cells allow for hyperplasia of smooth muscle

Answer 197

the mesoderm

Answer 198

Block of mesodermal cells in a developing embryo that is distinguished into a **myotome** (which forms most of the skeletal muscles), **dermomyotome** (which forms the subcutaneous tissue, dermis, and all skeletal muscles of the trunk and limbs), and **sclerotome** (which forms the vertebrae and ribs).

Answer 199

between 30 and 50

Answer 200

- decrease in maximal strength - slowing of muscle reflexes - loss of flexibility - SO fibers increase

Answer 201

a disease or disorder of the skeletal muscle tissue itself.

Answer 202

- disease - damage to components of motor unit - somatic motor neurons - neuromuscular junctions - muscle fibers

Answer 203

- an autoimmune disease that causes chronic, progressive damage of the neuromuscular junction - immune system inappropriately produces antibodies that bind to and block some ACh receptors, thereby decreasing the number of functional ACh receptors at the motor end plates of skeletal muscles - muscles become increasingly weaker, fatigue more easily, may eventually cease to function

Answer 204

- a group of inherited muscle-destroying diseases that cause progressive degeneration of skeletal muscle fibers

Answer 205

a sudden involuntary contraction of a single muscle in a large group of muscles - if painful, it becomes a cramp

Answer 206

inadequate blood flow to muscles, overuse of a muscle, dehydration, injury, holding a position for prolonged periods, and low blood levels of electrolytes, such as potassium

Answer 207

a spasmodic twitching made involuntarily by muscles that are ordinarily under voluntary control. Twitching of the eyelid and facial muscles are examples of tics.

Answer 208

a rhythmic, involuntary, purposeless contraction that produces a quivering or shaking movement

Answer 209

an involuntary, brief twitch of an entire motor unit that is visible under the skin; it occurs irregularly and is not associated with movement of the affected muscle.

Answer 210

a spontaneous contraction of a single muscle fiber that is not visible under the skin but can be recorded by electromyography. Fibrillations may signal destruction of motor neurons.

Answer 211

Muscle cells lose their ability to undergo cell division after birth. Therefore, the increase in size is not due to an increase in the number of muscle cells but rather is due to enlargement of the existing muscle fibers (hypertrophy). This enlargement can occur from forceful, repetitive muscular activity. It will cause the muscle fibers to increase their production of internal structures such as mitochondria and myofibrils and produce an increase in the muscle fiber diameter.

Answer 212

The “dark meat” of both chickens and ducks is composed primarily of slow oxidative (SO) muscle fibers. These fibers contain large amounts of myoglobin and capillaries, which accounts for their dark color. In addition, these fibers contain large numbers of mitochondria and generate ATP by aerobic respiration. SO fibers are resistant to fatigue and can produce sustained contractions for many hours. The legs of chickens and ducks are used for support, walking, and swimming (in ducks), all activities in which endurance is needed. In addition, migrating ducks require SO fibers in their breasts to enable them to have enough energy to fly for extremely long distances while migrating. There may be some fast oxidative–glycolytic (FOG) fibers in the dark meat. FOG fibers also contain large amounts of myoglobin and capillaries, contributing to the dark color. They can use aerobic or anaerobic cellular respiration to generate ATP and have high-to-moderate resistance to fatigue. These fibers would be good for the occasional “sprint” that ducks and chickens undergo to escape dangerous situations. In contrast, the white meat of a chicken breast is composed primarily of fast glycolytic (FG) fibers. FG fibers have lower amounts of myoglobin and capillaries that give the meat its white color. There are also few mitochondria in FG fibers, so these fibers generate ATP mainly by glycolysis. These fibers contract strongly and quickly and are adapted for intense anaerobic movements of short duration. Chickens occasionally use their breasts for flying extremely short distances, usually to escape prey or perceived danger, so FG fibers are appropriate for their breast muscle.

Answer 213

Destruction of the somatic motor neurons to skeletal muscle fibers will result in a loss of stimulation to the skeletal muscles. When not stimulated on a regular basis, a muscle begins to lose its muscle tone. Through lack of use, the muscle fibers will weaken, begin to decrease in size, and can be replaced by fibrous connective tissue, resulting in a type of denervation atrophy. A lack of stimulation of the breathing muscles (especially the diaphragm) from motor neurons can result in inability of the breathing muscles to contract, thus causing respiratory paralysis and possibly death of the individual from respiratory failure.