Chapter 10

Question 1

Skeletal muscle

Answer 1

Location: skeletal
Function: move bones
Appearance:multi-nucleated and striated
Control: voluntary

Question 2

Cardiac muscle

Answer 2

Location: heart
Function: pump blood
Appearance: one nucleus, striated, and intercalated discs
Control: involuntary / autorhythmic hormones, neurotransmitters

Question 3

Visceral (smooth muscle)

Answer 3

Location: various organs, ex. GI tract
Function: various functions, ex. Peristalsis
Appearance: one nucleus and no striations
Control: involuntary / autorythmicity

Question 4

General properties of muscle tissue

• Electrical excitability

Answer 4

• ability to respond to certain stimuli by producing electrical signals called action potentials (impulses)

Question 5

2 main types of action potential stimuli

Answer 5

Autorhythmic electrical signals: arises in the muscular tissue itself, as in the heart’s pacemaker
Chemical stimuli: neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH

Question 6

2 main types of action potential stimuli

Answer 6

Autorhythmic electrical signals: arises in the muscular tissue itself, as in the heart’s pacemaker
Chemical stimuli: neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH

Question 7

General properties of muscle tissue

• Contractility

Answer 7

• Ability of muscular tissue to contract forcefully when stimulated by an action potential

• when a skeletal muscle contracts, it generates tension (Force of contraction) while pulling on its attachment points

Question 8

General properties of muscle tissue

• Extensibility

Answer 8

• the ability of muscular tissue to stretch, within limits, without being damaged

Question 9

General properties of muscle tissue

• Elasticity

Answer 9

• the ability of muscular tissue to return to its original length and shape after contraction or extension

Question 10

Functions of muscular tissue

• Producing body movements

Answer 10

• movement of the whole body as well as localized movements

Question 11

Functions of muscular tissue

• Stabilizing body positions

Answer 11

• skeletal muscle contractions stabilize joints and help maintain body positions, such as standing or sitting

Question 12

Functions of muscular tissue

• Storing and mobilizing substances within the body

Answer 12

• storage is accomplished by sustained contractions of ringlike bands of smooth muscle called sphincters, which prevent outflow of the contents of a hollow organ

Question 13

Functions of muscular tissue

• Generating heat

Answer 13

• As muscular tissue contracts, it produces heat, a process known as thermogenesis. Involuntary contractions of skeletal muscles, known as shivering, can increase the rate of heat production

Question 14

Various connective tissue components

• Epimysium

Answer 14

• the outer layer, encircling the entire muscle. It consists of dense irregular connective tissue

Question 15

Various connective tissue components

• Perimysium

Answer 15

• also a layer of dense irregular connective tissue, but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles

Question 16

Various connective tissue components

• Endomysium

Answer 16

• penetrates the interior of each fascicle and separates individual muscle fibers from one another. The endomysium is mostly reticular fibers

Question 17

Various connective tissue components

• Fascia

Answer 17

• is a sheet or band of fibrous connective tissue that is deep to the skin and surrounds muscles and other organs of the body

Question 18

Various connective tissue components

• Aponeurosis

Answer 18

• If, the connective tissue layers extend beyond the muscle to form a rope-like structure it is called a tendon, if they form a flat sheet

Question 19

The microscopic anatomy of the muscle and the types of muscle filaments

• Sarcolemma

Answer 19

• the plasma membrane of a muscle cell

Question 20

The microscopic anatomy of the muscle and the types of muscle filaments

• sacroplasm

Answer 20

• the muscle cell cytoplasm and contains a large amount of glycogen for energy production and myoglobin for oxygen storage

Question 21

The microscopic anatomy of the muscle and the types of muscle filaments

• Transverse tubules (T tubules)

Answer 21

• are tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber

Question 22

The microscopic anatomy of the muscle and the types of muscle filaments

• Myofibrils

Answer 22

• small thread like structures within the sarcolemma that act as the contractile organelles of skeletal muscle

Question 23

The microscopic anatomy of the muscle and the types of muscle filaments

• The sarcoplasmic reticulum

Answer 23

• encircles each myofibril. It is similar to smooth endoplasmic reticulum in non-muscle

Question 24

The microscopic anatomy of the muscle and the types of muscle filaments

• Terminal cisterns

Answer 24

• Dilated sacs of the sarcoplasmic reticulum that butt against the T tubule from both sides

Question 25

The microscopic anatomy of the muscle and the types of muscle filaments • Triad

Answer 25

• A transverse tubule and the two terminal cisterns on either side of it - In a relaxed muscle fiber, the sarcoplasmic reticulum stores calcium ions (Ca2+). Release of Ca2+ from the terminal cisterns of the sarcoplasmic reticulum triggers muscle contraction

Question 26

Filaments

Answer 26

• within the myofibrils are smaller protein structures

Question 27

Thin filaments

Answer 27

• composed of actin - directly involved in the contractile process -2 thin filaments for every 1 thick filament in the regions of filament overlap

Question 28

Thick filaments

Answer 28

• composed of myosin - directly involved in the contractile process -2 thin filaments for every 1 thick filament in the regions of filament overlap

Question 29

Sacromeres

Answer 29

• The filaments inside myofibrils do not extend the entire length of the muscle fiber, instead they are arranged in compartments - basic functional units of a myofibril

Question 30

Components of sarcomere • Z discs

Answer 30

• narrow, plate-shaped regions of dense material that separate one sarcomere from the next

Question 31

Components of sarcomere • A band

Answer 31

• dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments

Question 32

Components of sarcomere • I band

Answer 32

• lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band

Question 33

Components of sarcomere • H zone

Answer 33

• narrow region in center of each A band that contains thick filaments but no thin filaments

Question 34

Components of sarcomere • M line

Answer 34

• region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere

Question 35

Components of sarcomere • zone overlap

Answer 35

• thick and thin filaments lie side by side

Question 36

Components of sarcomere diagram

Answer 36

Look on doc!

Question 37

Type of muscle protein and specific proteins within • Contractile proteins

Answer 37

• generate force during contraction - myosin - actin

Question 38

Type of muscle protein and specific proteins within • regulatory proteins

Answer 38

• help switch the contraction process on and off - tropomyosin - troponin

Question 39

Type of muscle protein and specific proteins within • structural proteins

Answer 39

• keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix - titin: helps a sarcomere return to its resting length after a muscle has contracted or been stretched - a-Actinin: binds actin molecules of thin filaments and to titin molecules - myomesin: structural protein that forms M line of sarcomere - nebulin: helps maintain alignment of the thin filaments in the sarcomere - dystrophin: reinforces the sarcolemma and helps transmit the tension generated by the sarcomeres to the tendons

Question 40

mechanism by which muscles contract and the various ions involved • sliding filament mechanism

Answer 40

•Muscle contraction occurs because 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 •Myosin pulls on actin, causing the thin filament to slide inward •Consequently, Z discs move toward each other and the sarcomere shortens •Thanks to the structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction •Note the changes in the I band and H zone as the muscle contracts

Question 41

mechanism by which muscles contract and the various ions involved • contraction cycle

Answer 41

•ATP hydrolysis- the myosin head hydrolyzes ATP and becomes energized and oriented to bind to actin •Attachment- the myosin head binds to actin forming a cross-bridge •Power Stroke- the myosin head pivots, pulling the thin filament past the thick filament toward the center of the sarcomere, and the ADP is released from the myosin head •Detachment- as the myosin binds ATP, the cross-bridge detached from the actin

Question 42

Excitation contraction coupling

Answer 42

•During relaxation, the level of Ca2+ in the sarcoplasm is low, only 0.1μ M, because calcium ions are pumped into the sarcoplasmic reticulum by Ca2+ -ATPase pumps. •A muscle action potential propagating along a transverse tubule causes voltage-gated Ca2+ channels to undergo a conformational change that opens Ca2+ release channels in the sarcoplasmic reticulum, calcium ions flow into the sarcoplasm, and contraction begins •This concept connects the events of a muscle action potential with the sliding filament mechanism

Question 43

Components and functions of neuromuscular junction •somatic motor neurons

Answer 43

• neurons that stimulate skeletal muscle fibers to contract - A muscle fiber contracts in response to one or more action potentials propagating along its sarcolemma and through its system of T tubules

Question 44

Components and functions of neuromuscular junction • neuromuscular junction

Answer 44

• muscle action potential arise • synapse between a somatic motor neuron and a skeletal muscle fiber

Question 45

Components and functions of neuromuscular junction • Synapse

Answer 45

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

Question 46

Components and function of neuromuscular junction • synaptic cleft

Answer 46

• small gap in synapses, separating two cells

Question 47

Components and function of neuromuscular junction • neurotransmitters

Answer 47

• in a synapse, the first cell communicates with the second by releasing a chemical messenger

Question 48

Components and function of neuromuscular junction • axon terminal

Answer 48

• At the NMJ, the end of the motor neuron

Question 49

Components and function of neuromuscular junction • synaptic end bulbs

Answer 49

• end of motor neuron divides into cluster, neural part of the NMJ

Question 50

Components and function of neuromuscular junction • synaptic vesicles

Answer 50

•Suspended in the cytosol within each synaptic end bulb are hundreds of membrane enclosed sacs

Question 51

Components and function of neuromuscular junction • acetylcholine (Ach)

Answer 51

• neurotransmitter released at the NMJ

Question 52

Components and function of neuromuscular junction • motor end plate

Answer 52

• region of the sarcolemma opposite of the synaptic end bulbs - muscular part of the NMJ

Question 53

Components and function of neuromuscular junction • acetylcholine receptors

Answer 53

• Within each motor end plate are 30 million to 40 million acetylcholine receptors • integral transmembrane proteins (ligand-gated ion channels) to which ACh specifically binds

Question 54

Components and function of neuromuscular junction • junctional folds

Answer 54

• deep grooves in motor end plate that provide large surface area for Ach • abundant Ach receptors

Question 55

Components and function of neuromuscular junction • NMJ

Answer 55

• includes all of the synaptic end bulbs on one side of the synaptic cleft, the synaptic cleft itself, plus the motor end plate of the muscle fiber on the other side

Question 56

Events at the NMJ produce a muscle action potential • release of acetylcholine

Answer 56

• Voltage-gated calcium channels in a neuron’s synaptic end bulb open, resulting in an influx of calcium. This causes exocytosis of the neurotransmitter, acetylcholine (Ach) into the synaptic cleft

Question 57

Events at the NMJ produce a muscle action potential • activation of Ach receptors

Answer 57

• ACh binds to ligand-gated Na+ channels on the motor endplate, which causes an influx of Na+ into the muscle

Question 58

Events at the NMJ produce a muscle action potential • production of muscle action potential

Answer 58

• This depolarizes the muscle and results in Ca 2+ release from the sarcoplasmic reticulum

Question 59

Events at the NMJ produce a muscle action potential • termination of Ach activity

Answer 59

• ACh gets broken down by acetylcholinesterase (AChE)

Question 60

Muscle metabolism • creatine phosphate (cp)

Answer 60

• only in muscle fibers •The enzyme creatine kinase (CK) catalyzes the transfer of one of the phosphate groups from ATP to creatine, forming creatine phosphate and ADP •When contraction begins and the ADP level starts to rise, CK catalyzes the transfer of a phosphate group from creatine phosphate back to ADP to quickly generates new ATP •Since the formation of ATP from creatine phosphate occurs very rapidly, creatine phosphate is the first source of energy when muscle contraction begins • 15 seconds

Question 61

Muscle metabolism • anaerobic glycolysis

Answer 61

•requires no oxygen •When muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, glucose is catabolized to generate ATP. •Glucose passes easily from the blood into contracting muscle fibers via facilitated diffusion, and it is also produced by the breakdown of glycogen within muscle fibers. •Then, a series of reactions known as glycolysis quickly breaks down each glucose molecule into two molecules of pyruvic acid and two molecules of ATP. •Each molecule of glucose catabolized via anaerobic glycolysis yields 2 molecules of lactic acid and 2 molecules of ATP • 2 minutes

Question 62

Muscle metabolism • cellular respiration

Answer 62

•needs oxygen •pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of ATP •Muscular tissue has two sources of oxygen: -oxygen that diffuses into muscle fibers from the blood -oxygen released by myoglobin within muscle fibers. •Both myoglobin and hemoglobin are oxygen binding proteins. ‐They bind oxygen when it is plentiful and release oxygen when it is scarce. •Aerobic respiration supplies enough ATP for muscles during periods of rest or light to moderate exercise provided sufficient oxygen and nutrients are available. •pyruvic acid obtained from the glycolysis of glucose, •fatty acids from the breakdown of triglycerides, •amino acids from the breakdown of proteins. •In activities that last from several minutes to an hour or more, aerobic respiration provides nearly all of the needed ATP (30-32 molecules of ATP) • several minutes to hours

Question 63

Muscle fatigue

Answer 63

• inability to maintain force of contraction after prolonged activity •The onset of fatigue is due to: -Inadequate release of Ca2+ from SR -Depletion of CP, oxygen, and nutrients -Build up of lactic acid and ADP -Insufficient release of ACh at NMJ

Question 64

Oxygen consumption

Answer 64

•Why do you continue to breathe heavily for a period of time after stopping exercise? -To “pay back” your oxygen debt! (recovery oxygen uptake) •The extra oxygen goes toward: -Replenishing CP stores -Converting lactate into pyruvate -Reloading O2 onto myoglobin

Question 65

Twitch contraction

Answer 65

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

Question 66

Force of contraction • latent period

Answer 66

• brief delay occurs between application of the stimulus (time zero on the graph) and the beginning of contraction (~2msec)

Question 67

Force of contraction • contraction period

Answer 67

• during this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross bridges form. Peak tension develops in the muscle fiber. (10-100 msec)

Question 68

Force of contraction • contraction period

Answer 68

• during this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross bridges form. Peak tension develops in the muscle fiber. (10-100 msec)

Question 69

Force of contraction • relaxation period

Answer 69

• Ca2+ is actively transported back into the sarcoplasmic reticulum, myosin binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases. (10-100 msec)

Question 70

Force of contraction • refractory period

Answer 70

• when a muscle fiber receives enough stimulation to contract, it temporarily loses its excitability and cannot respond for a time. -If two stimuli are applied, one immediately after the other, the muscle will respond to the first stimulus but not to the second

Question 71

Frequency of stimulation • Wave summation

Answer 71

• occurs when a second action potential triggers muscle contraction before the first contraction has finished -Results in a stronger contraction

Question 72

Frequency of stimulation • Unfused tetanus

Answer 72

• when a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli. The result is a sustained but wavering contraction

Question 73

Frequency of stimulation • Fused tetanus

Answer 73

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

Question 74

Isotonic

Answer 74

• the tension developed in the muscle remains almost constant while the muscle changes its length. -used for body movements and for moving objects. -concentric: the tension generated is great enough to overcome the resistance of the object to be moved, the muscle shortens and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at a joint. -eccentric- when the length of a muscle increases during a contraction

Question 75

Isometric

Answer 75

• muscle contracts but does not change length

Question 76

Skeletal muscle fibers • Slow oxidative fibers (SO)

Answer 76

Location: most commonly attached by tendons to bones • appear dark bc contains large amount of myoglobin and many blood capillaries; have many large mitochondria so fibers generate ATP mainly by aerobic respiration; slow bc the ATPase in the myosin heads hydrolyzes ATP relatively slow and the contraction cycle proceeds at a slower pace than in fast fiber; resistant to fatigue and are capable of prolonged, sustained contractions for many hours; maintains posture and for aerobic, endurance-type activities

Question 77

Skeletal muscle fibers • Fast oxidative-glycolytic fibers (FOG)

Answer 77

• the largest fibers; contain large amount of myoglobin and many blood capillaries so will be dark; can generate considerable ATP by aerobic respiration so moderately high resistance to fatigue; also generate ATP by anaerobic glycolysis; fast bc myosin head hydrolyzes ATP three to five timers faster than the myosin ATPase in SO fiber; for walking

Question 78

Skeletal muscle fibers • Fast glycolytic fibers (FG)

Answer 78

• low myoglobin content, few blood capillaries, few mitochondria, and appear white in color; contain large amounts of glycogen and generate ATP mainly by glycolysis; due to their ability to hydrolyze ATP rapidly, FG fibers contract strongly and quickly; for intense anaerobic movements of short duration (weight lifting or throwing a ball, but they fatigue quickly/strength training programs that engage a person in activities requiring great strength for short times increase the size, strength, and glycogen content of fast glycolytic fibers) •contracts only when stimulated by acetylcholine released by a nerve impulse in a motor neuron.

Question 79

Cardiac muscle fibers

Answer 79

Location: heart •intercalated disc contain desmosomes and gap junctions that allow muscle action potentials to spread from one muscle fiber to another •contracts when stimulated by its own autorhythmic muscle fibers •depends largely on aerobic respiration to generate ATP, and thus requires a constant supply of oxygen

Question 80

Smooth muscle fibers

Answer 80

Location: Walls of hollow viscera, airways, blood vessels, iris and ciliary body of eye, arrector muscles of the hair •It is thick in the middle, tapered on the ends, and is not striated •It can be arranged as either single-unit or multi-unit fibers •contractions start more slowly and last longer than skeletal and cardiac muscle contractions •can shorten and stretch to a greater extent than skeletal and cardiac muscle •shorten in response to stretch!