Physiology And Pathophysiology For Pts

Front 1

how many muscle fibers are there in a typical muscle?

Back 1

100's to 1000's

Front 2

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 2

10's to 100's\nperimysium

Front 3

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 3

diameter = 100 micrometers or 0.1 mm\nlength = 1 cm to 10's of cm

Front 4

How many myofibrils are there per muscle fiber?

Back 4

~1000

Front 5

What are the 2 contractile structures/units of muscle tissue?

Back 5

myofibril and sarcomere

Front 6

What's the diameter of a typical myofibril?

Back 6

1 micrometer

Front 7

What makes up a myofibril?

Back 7

sarcomeres aligned in series

Front 8

How long is a typical sarcomere?

Back 8

2.5 micrometers

Front 9

"With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?"

Back 9

"10 cm / 2.5 micrometers = \n10 x 10^2- meters / 2.5 x 10^6- meters = \n4.0 x 10^4 = \n40,000 sarcomeres in a 10 cm long fiber"

Front 10

What makes up myofilaments?

Back 10

"Thin filaments made up of actin, troponin, and tropomyosin\nThick filaments made up of myosin only"

Front 11

What components make up a myosin molecule and what chemical is used to determine the components?

Back 11

"Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)\nLight meromyosin (tail of myosin)\nPapain is used to cleave the myosin molecule"

Front 12

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 12

two myosin heavy chains (MHC)\nfour myosin light chains (MLC)\nMHC forms the backbone of the head and tail regions \nMLC are arranged on the head portion only\nThe type of MHC mostly determines shortening velocity

Front 13

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 13

"troponin and tropomyosin\ninitiate and terminate contraction\ntropomyosin physically blocks the interaction between actin and myosin while the muscle is at rest\ntroponin has an affinity for calcium, and when calcium binds to troponin, troponin changes shape, pulls on tropomyosin, and causes the tropomyosin to expose the binding sites on actin"

Front 14

How is muscle functionally organized (2 ways)?

Back 14

Motor unit and sarcomere

Front 15

What does a motor unit consist of?

Back 15

"one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other"

Front 16

What's the range for the number of fibers in a motor unit?

Back 16

10-15 up to the 1000's

Front 17

Describe the parts of the sarcomere

Back 17

extends from one Z-line to the next\nA-bands are the regions that contain thick filaments\nH-zone is the part of the A-band that only contains thick filaments (no thin)\nbisected by the M-line\nI-band contains only thin filaments and is bisected by the Z-lines\n

Front 18

What happens to the bands/lines in a sarcomere during contraction?

Back 18

Z-lines move closer together\nI-band and H-zone start to disappear

Front 19

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 19

"1. ATP binds to myosin, actin-myosin complex dissociates\n2. ATP is hydrolyzed by ATPase, energy released to cock"" the myosin head\n3. In presence of calcium, myosin binds with actin, energy stored in ""cocked"" crossbridge moves the thin filament past the thick filament\n4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)"""

Front 20

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 20

"1. Action potential generated in alpha-motoneuron and travels down axon\n2. When the action potential reaches the axon terminal, vesicles in the axon terminal release Ach into the synaptic cleft\n3. ACh binds to receptors on the sarcolemma (muscle side of neuromuscular junction)\n4. Binding of ACh to the sarcolemma receptors causes sodium channels to open on the sarcolemma\n5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)"

Front 21

List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle.

Back 21

1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels

2. Ca2+ is released from the SR into the cell and binds to troponin, beginning the crossbridge cycle

3. Action potentials from the alpha-motoneuron end and release of Ca2+ from SR stops

4. Ca2+ ATPase pumps move calcium from the cytosol back into the SR

Front 22

What are the 5 factors that affect force production in a muscle?

Back 22

1. physiological cross-sectional area (PCSA)\n2. muscle length\n3. muscle shortening/lengthening velocity\n4. number of motor units recruited\n5. rate coding

Front 23

What is the relationship between PCSA and force production in a muscle?

Back 23

"direct relationship between PCSA and force production\nthe more sarcomeres in parallel, the higher the force produced"

Front 24

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 24

allows packing of a large number of fibers in to a small anatomical CSA\npennated muscles generally produce more force than fusiform

Front 25

"If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?"

Back 25

the one with shorter fibers will produce greater force\nit will have a small range of motion and the fibers will be slower

Front 26

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 26

"PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))\nWe can assume that the cosine of the pennation angle ranges from 0.9-1.0, so we can consider it equal to 1 (drops out)\nMuscle density is the same for all muscles (1.056 g/cm3), so when comparing two muscles, we can drop out the density term, leaving us with the relationship:\nPCSA = (muscle mass in grams)/(muscle fiber length)\n"

Front 27

What happens to force production when the sarcomere length is:\na. < 1.6 micrometers\nb. 1.6 - 2.0 micrometers\nc. 2.0 - 2.5 micrometers\nd. 2.5 - 3.6 micrometers\ne. > 3.6 micrometers?\nWhat is happening to the thick and thin filaments in each case?

Back 27

a. force production greatly decreases; thick filaments bump into Z-lines\nb. decrease in force production; thin filaments attached to opposite Z-lines begin to interfere with each other\nc. no change in force production; no change in overlap of thick and thin filaments\nd. linear increase in force production; thick and thin filament overlap increases\ne. no force production; no overlap of thick and thin filaments\n

Front 28

At what length range do most muscle fibers operate? What is this range called?

Back 28

~2.0 - 2.3 micrometers\nplateau region

Front 29

Describe the muscle-length tension curve.

Back 29

"1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap\ntotal force = active force only\n2. increase muscle length beyond optimal length: the amount of overlap of myofilaments begins to decrease, causing active tension to decrease, but passive tension increases due to force on connective tissues\ntotal force increases, but not greatly\n"

Front 30

What are the two types of forces at work that combine to get the total tension on a muscle? \n

Back 30

"two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap"

Front 31

What happens to the muscle beyond its optimal length? \n

Back 31

"stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production"

Front 32

How would the length-tension curve differ between pennated and fusiform muscles?

Back 32

"pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length."

Front 33

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 33

"at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases"

Front 34

What are the three types of muscle contractions? Describe each.

Back 34

1. concentric: muscle shortens while it is activated\n2. isometric: muscle does not change length while activated\n3. eccentric: muscle lengthens while it is activated (pliometric contractions)

Front 35

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 35

"by using involuntary contractions (external electrical stimulation) rather than voluntary\ncompared to isometric and concentric contraction, eccentric contraction produces force with fewer motor units and fewer energetic costs (ATP and oxygen consumption): there is increased force produced per crossbridge and myosin is forcibly detached from actin, reducing the requirement of ATP for detachment"

Front 36

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 36

"in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.\nHenneman principle or Size principle"

Front 37

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 37

Slow (S) units: Type I or slow oxidative (SO) muscle fibers

Fast Fatigue-resistant (FR) units: Type IIa or fast oxidative glycolytic (FOG) fibers

Fast Fatigable (FF) units: Type IIb or fast glycolytic (FG) fibers

Front 38

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 38

"S: small number of fibers, low force producing\nFR: intermediate number of fibers and intermediate strength\nFF: high number of fibers and high force producing"

Front 39

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 39

"During novel, eccentric contractions and during sudden movements\nThe normal recruitment order is followed almost all the time -- a different order of recruitment is rare\nRecruitment is driven by demand for force and not by speed of movement"

Front 40

What is rate coding?

Back 40

discharge frequency for an alpha-motoneuron\nthe rate that action potentials are received at the synaptic terminal of an alpha-motoneuron branch

Front 41

What is the relationship between force production and stimulation frequency?

Back 41

force increases sigmoidally with stimulation frequency\n

Front 42

To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?

Back 42

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active

50-80% MVC: force is increased by increasing rate coding only

Front 43

What factors affect muscle shortening velocity?

Back 43

load imposed on the muscle\nmuscle fiber length (not related to stretching a fiber)\nmotor units recruited

Front 44

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 44

"The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)"

Front 45

"What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?"

Back 45

"the longer the fiber length, the greater the shortening velocity\nthe number of sarcomeres in series is greater"

Front 46

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 46

fast twitch fibers shorten faster (2x-4x) than slow twitch\nthis is due to the increased myosin ATPase activity and thus an increased crossbridge cycling rate in fast twitch fibers

Front 47

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 47

"wide variation in fiber type between individuals, but not between men and women\nfemale fiber size (CSA) is 50-70% less than for males"

Front 48

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 48

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 49

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 49

"genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)\nalso, the types of activities a person does affects the % of fiber types, \n\nthe best correlation between fiber type compositoin and performance is for Type I and endurance time = 0.70\nthe correlation between Type II and torque and Type II and movement speed = 0.50"

Front 50

"What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?"

Back 50

Effect on PSA:\n1. resistance training: mass increases = PSA increases\n2. decreased use: mass decreases = PSA decreases\n3. no use: mass decreases = PSA decreases\n4. endurance training: no significant change

Front 51

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Back 51

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Front 52

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Back 52

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Front 53

how many muscle fibers are there in a typical muscle?

Back 53

100's to 1000's

Front 54

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 54

10's to 100's\nperimysium

Front 55

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 55

diameter = 100 micrometers or 0.1 mm\nlength = 1 cm to 10's of cm

Front 56

How many myofibrils are there per muscle fiber?

Back 56

~1000

Front 57

What are the 2 contractile structures/units of muscle tissue?

Back 57

myofibril and sarcomere

Front 58

What's the diameter of a typical myofibril?

Back 58

1 micrometer

Front 59

What makes up a myofibril?

Back 59

sarcomeres aligned in series

Front 60

How long is a typical sarcomere?

Back 60

2.5 micrometers

Front 61

"With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?"

Back 61

"10 cm / 2.5 micrometers = \n10 x 10^2- meters / 2.5 x 10^6- meters = \n4.0 x 10^4 = \n40,000 sarcomeres in a 10 cm long fiber"

Front 62

What makes up myofilaments?

Back 62

"Thin filaments made up of actin, troponin, and tropomyosin\nThick filaments made up of myosin only"

Front 63

What components make up a myosin molecule and what chemical is used to determine the components?

Back 63

"Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)\nLight meromyosin (tail of myosin)\nPapain is used to cleave the myosin molecule"

Front 64

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 64

two myosin heavy chains (MHC)\nfour myosin light chains (MLC)\nMHC forms the backbone of the head and tail regions \nMLC are arranged on the head portion only\nThe type of MHC mostly determines shortening velocity

Front 65

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 65

"troponin and tropomyosin\ninitiate and terminate contraction\ntropomyosin physically blocks the interaction between actin and myosin while the muscle is at rest\ntroponin has an affinity for calcium, and when calcium binds to troponin, troponin changes shape, pulls on tropomyosin, and causes the tropomyosin to expose the binding sites on actin"

Front 66

How is muscle functionally organized (2 ways)?

Back 66

Motor unit and sarcomere

Front 67

What does a motor unit consist of?

Back 67

"one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other"

Front 68

What's the range for the number of fibers in a motor unit?

Back 68

10-15 up to the 1000's

Front 69

Describe the parts of the sarcomere

Back 69

extends from one Z-line to the next\nA-bands are the regions that contain thick filaments\nH-zone is the part of the A-band that only contains thick filaments (no thin)\nbisected by the M-line\nI-band contains only thin filaments and is bisected by the Z-lines\n

Front 70

What happens to the bands/lines in a sarcomere during contraction?

Back 70

Z-lines move closer together\nI-band and H-zone start to disappear

Front 71

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 71

"1. ATP binds to myosin, actin-myosin complex dissociates\n2. ATP is hydrolyzed by ATPase, energy released to ""cock"" the myosin head\n3. In presence of calcium, myosin binds with actin, energy stored in ""cocked"" crossbridge moves the thin filament past the thick filament\n4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)"

Front 72

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 72

"1. Action potential generated in alpha-motoneuron and travels down axon\n2. When the action potential reaches the axon terminal, vesicles in the axon terminal release Ach into the synaptic cleft\n3. ACh binds to receptors on the sarcolemma (muscle side of neuromuscular junction)\n4. Binding of ACh to the sarcolemma receptors causes sodium channels to open on the sarcolemma\n5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)"

Front 73

"List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle."

Back 73

"1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels\n3. Ca2+ is released from the SR into the cell and binds to troponin, beginning the crossbridge cycle\n4. Action potentials from the alpha-motoneuron end and release of Ca2+ from SR stops\n5. Ca2+ ATPase pumps move calcium from the cytosol back into the SR\n"

Front 74

What are the 5 factors that affect force production in a muscle?

Back 74

1. physiological cross-sectional area (PCSA)\n2. muscle length\n3. muscle shortening/lengthening velocity\n4. number of motor units recruited\n5. rate coding

Front 75

What is the relationship between PCSA and force production in a muscle?

Back 75

"direct relationship between PCSA and force production\nthe more sarcomeres in parallel, the higher the force produced"

Front 76

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 76

allows packing of a large number of fibers in to a small anatomical CSA\npennated muscles generally produce more force than fusiform

Front 77

"If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?"

Back 77

the one with shorter fibers will produce greater force\nit will have a small range of motion and the fibers will be slower

Front 78

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 78

"PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))\nWe can assume that the cosine of the pennation angle ranges from 0.9-1.0, so we can consider it equal to 1 (drops out)\nMuscle density is the same for all muscles (1.056 g/cm3), so when comparing two muscles, we can drop out the density term, leaving us with the relationship:\nPCSA = (muscle mass in grams)/(muscle fiber length)\n"

Front 79

What happens to force production when the sarcomere length is:\na. < 1.6 micrometers\nb. 1.6 - 2.0 micrometers\nc. 2.0 - 2.5 micrometers\nd. 2.5 - 3.6 micrometers\ne. > 3.6 micrometers?\nWhat is happening to the thick and thin filaments in each case?

Back 79

a. force production greatly decreases; thick filaments bump into Z-lines\nb. decrease in force production; thin filaments attached to opposite Z-lines begin to interfere with each other\nc. no change in force production; no change in overlap of thick and thin filaments\nd. linear increase in force production; thick and thin filament overlap increases\ne. no force production; no overlap of thick and thin filaments\n

Front 80

At what length range do most muscle fibers operate? What is this range called?

Back 80

~2.0 - 2.3 micrometers\nplateau region

Front 81

Describe the muscle-length tension curve.

Back 81

"1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap\ntotal force = active force only\n2. increase muscle length beyond optimal length: the amount of overlap of myofilaments begins to decrease, causing active tension to decrease, but passive tension increases due to force on connective tissues\ntotal force increases, but not greatly\n"

Front 82

What are the two types of forces at work that combine to get the total tension on a muscle? \n

Back 82

"two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap"

Front 83

What happens to the muscle beyond its optimal length? \n

Back 83

"stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production"

Front 84

How would the length-tension curve differ between pennated and fusiform muscles?

Back 84

"pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length."

Front 85

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 85

"at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases"

Front 86

What are the three types of muscle contractions? Describe each.

Back 86

1. concentric: muscle shortens while it is activated\n2. isometric: muscle does not change length while activated\n3. eccentric: muscle lengthens while it is activated (pliometric contractions)

Front 87

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 87

"by using involuntary contractions (external electrical stimulation) rather than voluntary\ncompared to isometric and concentric contraction, eccentric contraction produces force with fewer motor units and fewer energetic costs (ATP and oxygen consumption): there is increased force produced per crossbridge and myosin is forcibly detached from actin, reducing the requirement of ATP for detachment"

Front 88

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 88

"in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.\nHenneman principle or Size principle"

Front 89

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 89

Slow (S) units: Type I or slow oxidative (SO) muscle fibers\nFast Fatigue-resistant (FR) units: Type IIa or fast oxidative glycolytic (FOG) fibers\nFast Fatigable (FF) units: Type IIb or fast glycolytic (FG) fibers

Front 90

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 90

"S: small number of fibers, low force producing\nFR: intermediate number of fibers and intermediate strength\nFF: high number of fibers and high force producing"

Front 91

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 91

"During novel, eccentric contractions and during sudden movements\nThe normal recruitment order is followed almost all the time -- a different order of recruitment is rare\nRecruitment is driven by demand for force and not by speed of movement"

Front 92

What is rate coding?

Back 92

discharge frequency for an alpha-motoneuron\nthe rate that action potentials are received at the synaptic terminal of an alpha-motoneuron branch

Front 93

What is the relationship between force production and stimulation frequency?

Back 93

force increases sigmoidally with stimulation frequency\n

Front 94

"To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?"

Back 94

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active\n50-80% MVC: force is increased by increasing rate coding only

Front 95

What factors affect muscle shortening velocity?

Back 95

load imposed on the muscle\nmuscle fiber length (not related to stretching a fiber)\nmotor units recruited

Front 96

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 96

"The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)"

Front 97

"What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?"

Back 97

"the longer the fiber length, the greater the shortening velocity\nthe number of sarcomeres in series is greater"

Front 98

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 98

fast twitch fibers shorten faster (2x-4x) than slow twitch\nthis is due to the increased myosin ATPase activity and thus an increased crossbridge cycling rate in fast twitch fibers

Front 99

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 99

"wide variation in fiber type between individuals, but not between men and women\nfemale fiber size (CSA) is 50-70% less than for males"

Front 100

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 100

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 101

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 101

"genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)\nalso, the types of activities a person does affects the % of fiber types, \n\nthe best correlation between fiber type compositoin and performance is for Type I and endurance time = 0.70\nthe correlation between Type II and torque and Type II and movement speed = 0.50"

Front 102

"What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?"

Back 102

Effect on PSA:\n1. resistance training: mass increases = PSA increases\n2. decreased use: mass decreases = PSA decreases\n3. no use: mass decreases = PSA decreases\n4. endurance training: no significant change

Front 103

how many muscle fibers are there in a typical muscle?

Back 103

100's to 1000's

Front 104

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 104

10's to 100's&#8perimysium

Front 105

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 105

diameter = 100 micrometers or 0.1 mm&#8length = 1 cm to 10's of cm

Front 106

How many myofibrils are there per muscle fiber?

Back 106

~1000

Front 107

What are the 2 contractile structures/units of muscle tissue?

Back 107

myofibril and sarcomere

Front 108

What's the diameter of a typical myofibril?

Back 108

1 micrometer

Front 109

What makes up a myofibril?

Back 109

sarcomeres aligned in series

Front 110

How long is a typical sarcomere?

Back 110

2.5 micrometers

Front 111

"With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?"

Back 111

"10 cm / 2.5 micrometers = &#810 x 10^2- meters / 2.5 x 10^6- meters = &#84.0 x 10^4 = &#840,000 sarcomeres in a 10 cm long fiber"

Front 112

What makes up myofilaments?

Back 112

"Thin filaments made up of actin, troponin, and tropomyosin&#8Thick filaments made up of myosin only"

Front 113

What components make up a myosin molecule and what chemical is used to determine the components?

Back 113

"Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)&#8Light meromyosin (tail of myosin)&#8Papain is used to cleave the myosin molecule"

Front 114

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 114

two myosin heavy chains (MHC)&#8four myosin light chains (MLC)&#8MHC forms the backbone of the head and tail regions &#8MLC are arranged on the head portion only&#8The type of MHC mostly determines shortening velocity

Front 115

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 115

"troponin and tropomyosin&#8initiate and terminate contraction&#8tropomyosin physically blocks the interaction between actin and myosin while the muscle is at rest&#8troponin has an affinity for calcium, and when calcium binds to troponin, troponin changes shape, pulls on tropomyosin, and causes the tropomyosin to expose the binding sites on actin"

Front 116

How is muscle functionally organized (2 ways)?

Back 116

Motor unit and sarcomere

Front 117

What does a motor unit consist of?

Back 117

"one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other"

Front 118

What's the range for the number of fibers in a motor unit?

Back 118

10-15 up to the 1000's

Front 119

Describe the parts of the sarcomere

Back 119

extends from one Z-line to the next&#8A-bands are the regions that contain thick filaments&#8H-zone is the part of the A-band that only contains thick filaments (no thin)&#8bisected by the M-line&#8I-band contains only thin filaments and is bisected by the Z-lines&#8

Front 120

What happens to the bands/lines in a sarcomere during contraction?

Back 120

Z-lines move closer together&#8I-band and H-zone start to disappear

Front 121

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 121

"1. ATP binds to myosin, actin-myosin complex dissociates&#82. ATP is hydrolyzed by ATPase, energy released to ""cock"" the myosin head&#83. In presence of calcium, myosin binds with actin, energy stored in ""cocked"" crossbridge moves the thin filament past the thick filament&#84. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)"

Front 122

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 122

"1. Action potential generated in alpha-motoneuron and travels down axon&#82. When the action potential reaches the axon terminal, vesicles in the axon terminal release Ach into the synaptic cleft&#83. ACh binds to receptors on the sarcolemma (muscle side of neuromuscular junction)&#84. Binding of ACh to the sarcolemma receptors causes sodium channels to open on the sarcolemma&#85. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)"

Front 123

"List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle."

Back 123

"1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels&#83. Ca2+ is released from the SR into the cell and binds to troponin, beginning the crossbridge cycle&#84. Action potentials from the alpha-motoneuron end and release of Ca2+ from SR stops&#85. Ca2+ ATPase pumps move calcium from the cytosol back into the SR&#8"

Front 124

What are the 5 factors that affect force production in a muscle?

Back 124

1. physiological cross-sectional area (PCSA)&#82. muscle length&#83. muscle shortening/lengthening velocity&#84. number of motor units recruited&#85. rate coding

Front 125

What is the relationship between PCSA and force production in a muscle?

Back 125

"direct relationship between PCSA and force production&#8the more sarcomeres in parallel, the higher the force produced"

Front 126

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 126

allows packing of a large number of fibers in to a small anatomical CSA&#8pennated muscles generally produce more force than fusiform

Front 127

"If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?"

Back 127

the one with shorter fibers will produce greater force&#8it will have a small range of motion and the fibers will be slower

Front 128

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 128

"PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))&#8We can assume that the cosine of the pennation angle ranges from 0.9-1.0, so we can consider it equal to 1 (drops out)&#8Muscle density is the same for all muscles (1.056 g/cm3), so when comparing two muscles, we can drop out the density term, leaving us with the relationship:&#8PCSA = (muscle mass in grams)/(muscle fiber length)&#8"

Front 129

What happens to force production when the sarcomere length is:&#8a. < 1.6 micrometers&#8b. 1.6 - 2.0 micrometers&#8c. 2.0 - 2.5 micrometers&#8d. 2.5 - 3.6 micrometers&#8e. > 3.6 micrometers?&#8What is happening to the thick and thin filaments in each case?

Back 129

a. force production greatly decreases; thick filaments bump into Z-lines&#8b. decrease in force production; thin filaments attached to opposite Z-lines begin to interfere with each other&#8c. no change in force production; no change in overlap of thick and thin filaments&#8d. linear increase in force production; thick and thin filament overlap increases&#8e. no force production; no overlap of thick and thin filaments&#8

Front 130

At what length range do most muscle fibers operate? What is this range called?

Back 130

~2.0 - 2.3 micrometers&#8plateau region

Front 131

Describe the muscle-length tension curve.

Back 131

"1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap&#8total force = active force only&#82. increase muscle length beyond optimal length: the amount of overlap of myofilaments begins to decrease, causing active tension to decrease, but passive tension increases due to force on connective tissues&#8total force increases, but not greatly&#8"

Front 132

What are the two types of forces at work that combine to get the total tension on a muscle? &#8

Back 132

"two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap"

Front 133

What happens to the muscle beyond its optimal length? &#8

Back 133

"stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production"

Front 134

How would the length-tension curve differ between pennated and fusiform muscles?

Back 134

"pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length."

Front 135

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 135

"at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases"

Front 136

What are the three types of muscle contractions? Describe each.

Back 136

1. concentric: muscle shortens while it is activated&#82. isometric: muscle does not change length while activated&#83. eccentric: muscle lengthens while it is activated (pliometric contractions)

Front 137

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 137

"by using involuntary contractions (external electrical stimulation) rather than voluntary&#8compared to isometric and concentric contraction, eccentric contraction produces force with fewer motor units and fewer energetic costs (ATP and oxygen consumption): there is increased force produced per crossbridge and myosin is forcibly detached from actin, reducing the requirement of ATP for detachment"

Front 138

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 138

"in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.&#8Henneman principle or Size principle"

Front 139

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 139

Slow (S) units: Type I or slow oxidative (SO) muscle fibers&#8Fast Fatigue-resistant (FR) units: Type IIa or fast oxidative glycolytic (FOG) fibers&#8Fast Fatigable (FF) units: Type IIb or fast glycolytic (FG) fibers

Front 140

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 140

"S: small number of fibers, low force producing&#8FR: intermediate number of fibers and intermediate strength&#8FF: high number of fibers and high force producing"

Front 141

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 141

"During novel, eccentric contractions and during sudden movements&#8The normal recruitment order is followed almost all the time -- a different order of recruitment is rare&#8Recruitment is driven by demand for force and not by speed of movement"

Front 142

What is rate coding?

Back 142

discharge frequency for an alpha-motoneuron&#8the rate that action potentials are received at the synaptic terminal of an alpha-motoneuron branch

Front 143

What is the relationship between force production and stimulation frequency?

Back 143

force increases sigmoidally with stimulation frequency&#8

Front 144

"To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?"

Back 144

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active&#850-80% MVC: force is increased by increasing rate coding only

Front 145

What factors affect muscle shortening velocity?

Back 145

load imposed on the muscle&#8muscle fiber length (not related to stretching a fiber)&#8motor units recruited

Front 146

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 146

"The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)"

Front 147

"What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?"

Back 147

"the longer the fiber length, the greater the shortening velocity&#8the number of sarcomeres in series is greater"

Front 148

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 148

fast twitch fibers shorten faster (2x-4x) than slow twitch&#8this is due to the increased myosin ATPase activity and thus an increased crossbridge cycling rate in fast twitch fibers

Front 149

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 149

"wide variation in fiber type between individuals, but not between men and women&#8female fiber size (CSA) is 50-70% less than for males"

Front 150

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 150

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 151

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 151

"genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)&#8also, the types of activities a person does affects the % of fiber types, &#8&#8the best correlation between fiber type compositoin and performance is for Type I and endurance time = 0.70&#8the correlation between Type II and torque and Type II and movement speed = 0.50"

Front 152

"What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?"

Back 152

Effect on PSA:&#81. resistance training: mass increases = PSA increases&#82. decreased use: mass decreases = PSA decreases&#83. no use: mass decreases = PSA decreases&#84. endurance training: no significant change

Front 153

how many muscle fibers are there in a typical muscle?

Back 153

100's to 1000's

Front 154

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 154

10's to 100's

Front 155

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 155

diameter = 100 micrometers or 0.1 mm

Front 156

How many myofibrils are there per muscle fiber?

Back 156

~1000

Front 157

What are the 2 contractile structures/units of muscle tissue?

Back 157

myofibril and sarcomere

Front 158

What's the diameter of a typical myofibril?

Back 158

1 micrometer

Front 159

What makes up a myofibril?

Back 159

sarcomeres aligned in series

Front 160

How long is a typical sarcomere?

Back 160

2.5 micrometers

Front 161

With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?

Back 161

10 cm / 2.5 micrometers =

Front 162

What makes up myofilaments?

Back 162

Thin filaments made up of actin, troponin, and tropomyosin

Front 163

What components make up a myosin molecule and what chemical is used to determine the components?

Back 163

Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)

Front 164

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 164

two myosin heavy chains (MHC)

Front 165

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 165

troponin and tropomyosin

Front 166

How is muscle functionally organized (2 ways)?

Back 166

Motor unit and sarcomere

Front 167

What does a motor unit consist of?

Back 167

one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other

Front 168

What's the range for the number of fibers in a motor unit?

Back 168

10-15 up to the 1000's

Front 169

Describe the parts of the sarcomere

Back 169

extends from one Z-line to the next

Front 170

\u000A

Front 171

What happens to the bands/lines in a sarcomere during contraction?

Back 171

Z-lines move closer together

Front 172

\u000AI-band and H-zone start to disappear

Front 173

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 173

1. ATP binds to myosin, actin-myosin complex dissociates

Front 174

\u000A4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)

Front 175

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 175

1. Action potential generated in alpha-motoneuron and travels down axon

Front 176

\u000A5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)

Front 177

List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle.

Back 177

1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels

Front 178

\u000A

Front 179

What are the 5 factors that affect force production in a muscle?

Back 179

1. physiological cross-sectional area (PCSA)

Front 180

\u000A5. rate coding

Front 181

What is the relationship between PCSA and force production in a muscle?

Back 181

direct relationship between PCSA and force production

Front 182

\u000Athe more sarcomeres in parallel, the higher the force produced

Front 183

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 183

allows packing of a large number of fibers in to a small anatomical CSA

Front 184

\u000Apennated muscles generally produce more force than fusiform

Front 185

If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?

Back 185

the one with shorter fibers will produce greater force

Front 186

\u000Ait will have a small range of motion and the fibers will be slower

Front 187

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 187

PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))

Front 188

\u000A

Front 189

\u000AWhat is happening to the thick and thin filaments in each case?

Back 189

a. force production greatly decreases; thick filaments bump into Z-lines

Front 190

\u000A

Front 191

At what length range do most muscle fibers operate? What is this range called?

Back 191

~2.0 - 2.3 micrometers

Front 192

\u000Aplateau region

Front 193

Describe the muscle-length tension curve.

Back 193

1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap

Front 194

\u000A

Front 195

\u000A

Back 195

two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap

Front 196

\u000A

Back 196

stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production

Front 197

How would the length-tension curve differ between pennated and fusiform muscles?

Back 197

pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length.

Front 198

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 198

at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases

Front 199

What are the three types of muscle contractions? Describe each.

Back 199

1. concentric: muscle shortens while it is activated

Front 200

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 200

by using involuntary contractions (external electrical stimulation) rather than voluntary

Front 201

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 201

in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.

Front 202

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 202

Slow (S) units: Type I or slow oxidative (SO) muscle fibers

Front 203

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 203

S: small number of fibers, low force producing

Front 204

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 204

During novel, eccentric contractions and during sudden movements

Front 205

What is rate coding?

Back 205

discharge frequency for an alpha-motoneuron

Front 206

What is the relationship between force production and stimulation frequency?

Back 206

force increases sigmoidally with stimulation frequency

Front 207

To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?

Back 207

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active

Front 208

What factors affect muscle shortening velocity?

Back 208

load imposed on the muscle

Front 209

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 209

The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)

Front 210

What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?

Back 210

the longer the fiber length, the greater the shortening velocity

Front 211

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 211

fast twitch fibers shorten faster (2x-4x) than slow twitch

Front 212

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 212

wide variation in fiber type between individuals, but not between men and women

Front 213

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 213

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 214

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 214

genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)

Front 215

What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?

Back 215

Effect on PSA:

Front 216

how many muscle fibers are there in a typical muscle?

Back 216

100's to 1000's

Front 217

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 217

10's to 100's

Front 218

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 218

diameter = 100 micrometers or 0.1 mm

Front 219

How many myofibrils are there per muscle fiber?

Back 219

~1000

Front 220

What are the 2 contractile structures/units of muscle tissue?

Back 220

myofibril and sarcomere

Front 221

What's the diameter of a typical myofibril?

Back 221

1 micrometer

Front 222

What makes up a myofibril?

Back 222

sarcomeres aligned in series

Front 223

How long is a typical sarcomere?

Back 223

2.5 micrometers

Front 224

With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?

Back 224

10 cm / 2.5 micrometers =\\u000A10 x 10^2- meters / 2.5 x 10^6- meters =\\u000A4.0 x 10^4 =\\u000A40,000 sarcomeres in a 10 cm long fiber

Front 225

What makes up myofilaments?

Back 225

Thin filaments made up of actin, troponin, and tropomyosin

Front 226

What components make up a myosin molecule and what chemical is used to determine the components?

Back 226

Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)

Front 227

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 227

two myosin heavy chains (MHC)

Front 228

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 228

troponin and tropomyosin

Front 229

How is muscle functionally organized (2 ways)?

Back 229

Motor unit and sarcomere

Front 230

What does a motor unit consist of?

Back 230

one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other

Front 231

What's the range for the number of fibers in a motor unit?

Back 231

10-15 up to the 1000's

Front 232

Describe the parts of the sarcomere

Back 232

extends from one Z-line to the next

Front 234

What happens to the bands/lines in a sarcomere during contraction?

Back 234

Z-lines move closer together

Front 235

\\u000AI-band and H-zone start to disappear

Front 236

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 236

1. ATP binds to myosin, actin-myosin complex dissociates

Front 237

\\u000A4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)

Front 238

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 238

1. Action potential generated in alpha-motoneuron and travels down axon

Front 239

\\u000A5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)

Front 240

List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle.

Back 240

1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels

Front 242

What are the 5 factors that affect force production in a muscle?

Back 242

1. physiological cross-sectional area (PCSA)

Front 243

\\u000A5. rate coding

Front 244

What is the relationship between PCSA and force production in a muscle?

Back 244

direct relationship between PCSA and force production

Front 245

\\u000Athe more sarcomeres in parallel, the higher the force produced

Front 246

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 246

allows packing of a large number of fibers in to a small anatomical CSA

Front 247

\\u000Apennated muscles generally produce more force than fusiform

Front 248

If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?

Back 248

the one with shorter fibers will produce greater force

Front 249

\\u000Ait will have a small range of motion and the fibers will be slower

Front 250

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 250

PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))

Front 252

\\u000AWhat is happening to the thick and thin filaments in each case?

Back 252

a. force production greatly decreases; thick filaments bump into Z-lines

Front 253

\\u000A

Front 254

At what length range do most muscle fibers operate? What is this range called?

Back 254

~2.0 - 2.3 micrometers

Front 255

\\u000Aplateau region

Front 256

Describe the muscle-length tension curve.

Back 256

1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap

Front 258

What are the two types of forces at work that combine to get the total tension on a muscle?

Back 258

two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap

Front 259

What happens to the muscle beyond its optimal length?

Back 259

stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production

Front 260

How would the length-tension curve differ between pennated and fusiform muscles?

Back 260

pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length.

Front 261

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 261

at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases

Front 262

What are the three types of muscle contractions? Describe each.

Back 262

1. concentric: muscle shortens while it is activated

Front 263

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 263

by using involuntary contractions (external electrical stimulation) rather than voluntary

Front 264

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 264

in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.

Front 265

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 265

Slow (S) units: Type I or slow oxidative (SO) muscle fibers

Front 266

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 266

S: small number of fibers, low force producing

Front 267

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 267

During novel, eccentric contractions and during sudden movements

Front 268

What is rate coding?

Back 268

discharge frequency for an alpha-motoneuron

Front 269

What is the relationship between force production and stimulation frequency?

Back 269

force increases sigmoidally with stimulation frequency

Front 270

To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?

Back 270

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active

Front 271

What factors affect muscle shortening velocity?

Back 271

load imposed on the muscle

Front 272

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 272

The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)

Front 273

What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?

Back 273

the longer the fiber length, the greater the shortening velocity

Front 274

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 274

fast twitch fibers shorten faster (2x-4x) than slow twitch

Front 275

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 275

wide variation in fiber type between individuals, but not between men and women

Front 276

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 276

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 277

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 277

genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)

Front 278

What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?

Back 278

Effect on PSA:

Front 279

how many muscle fibers are there in a typical muscle?

Back 279

100's to 1000's

Front 280

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 280

10's to 100's

Front 281

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 281

diameter = 100 micrometers or 0.1 mm

Front 282

How many myofibrils are there per muscle fiber?

Back 282

~1000

Front 283

What are the 2 contractile structures/units of muscle tissue?

Back 283

myofibril and sarcomere

Front 284

What's the diameter of a typical myofibril?

Back 284

1 micrometer

Front 285

What makes up a myofibril?

Back 285

sarcomeres aligned in series

Front 286

How long is a typical sarcomere?

Back 286

2.5 micrometers

Front 287

With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?

Back 287

10 cm / 2.5 micrometers =&#x000A;10 x 10^2- meters / 2.5 x 10^6- meters =&#x000A;4.0 x 10^4 =&#x000A;40,000 sarcomeres in a 10 cm long fiber

Front 288

What makes up myofilaments?

Back 288

Thin filaments made up of actin, troponin, and tropomyosin

Front 289

What components make up a myosin molecule and what chemical is used to determine the components?

Back 289

Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)

Front 290

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 290

two myosin heavy chains (MHC)

Front 291

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 291

troponin and tropomyosin

Front 292

How is muscle functionally organized (2 ways)?

Back 292

Motor unit and sarcomere

Front 293

What does a motor unit consist of?

Back 293

one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other

Front 294

What's the range for the number of fibers in a motor unit?

Back 294

10-15 up to the 1000's

Front 295

Describe the parts of the sarcomere

Back 295

extends from one Z-line to the next

Front 297

What happens to the bands/lines in a sarcomere during contraction?

Back 297

Z-lines move closer together

Front 298

&#x000A;I-band and H-zone start to disappear

Front 299

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 299

1. ATP binds to myosin, actin-myosin complex dissociates

Front 300

&#x000A;4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)

Front 301

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 301

1. Action potential generated in alpha-motoneuron and travels down axon

Front 302

&#x000A;5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)

Front 303

List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle.

Back 303

1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels

Front 305

What are the 5 factors that affect force production in a muscle?

Back 305

1. physiological cross-sectional area (PCSA)

Front 306

&#x000A;5. rate coding

Front 307

What is the relationship between PCSA and force production in a muscle?

Back 307

direct relationship between PCSA and force production

Front 308

&#x000A;the more sarcomeres in parallel, the higher the force produced

Front 309

What does muscle pennation angle do? Do pennated muscles produce less/more force than fusiform?

Back 309

allows packing of a large number of fibers in to a small anatomical CSA

Front 310

&#x000A;pennated muscles generally produce more force than fusiform

Front 311

If two muscles have an equal mass, but one has longer fibers than the other, which muscle will produce greater force? What are the tradeoffs for this muscle?

Back 311

the one with shorter fibers will produce greater force

Front 312

&#x000A;it will have a small range of motion and the fibers will be slower

Front 313

What is the formula for PCSA? What assumptions can we make when calculating PCSA? How can we reduce the formula to one that makes it easy to quickly compare the PCSA's of two different muscles? What is the reduced relationship?

Back 313

PCSA = ((muscle mass in grams) x cos (angle of pennation))/((muscle density in grams per cubic centimeters) x (muscle fiber length))

Front 315

&#x000A;What is happening to the thick and thin filaments in each case?

Back 315

a. force production greatly decreases; thick filaments bump into Z-lines

Front 316

&#x000A;

Front 317

At what length range do most muscle fibers operate? What is this range called?

Back 317

~2.0 - 2.3 micrometers

Front 318

&#x000A;plateau region

Front 319

Describe the muscle-length tension curve.

Back 319

1. start with short sarcomere length and increase muscle length up to the muscle's optimal length: the tension developed is entirely active tension produced within the sarcomere by the degree of myofilament overlap

Front 321

What are the two types of forces at work that combine to get the total tension on a muscle?

Back 321

two forces: 1. passive, due to connective tissue architecture; 2. active/developed, due to amount of myofilament overlap

Front 322

What happens to the muscle beyond its optimal length?

Back 322

stretch sarcomeres to a point where myofilament overlap decreases, decreasing force production

Front 323

How would the length-tension curve differ between pennated and fusiform muscles?

Back 323

pennated muscles have more muscle fibers packed into a particular CSA while fusiform muscles have fewer muscle fibers and more connective tissue; therefore, the passive tension curve would be less steep than that for the pennated muscle, causing the total length-tension curve to plummit beyond the muscle's optimal length and climb sharply as tension on the connective tissue continues to increase with muscle length.

Front 324

Why does muscle force production decrease with greater shortening/lengthening velocity?

Back 324

at a given time, the number of myosin crossbridges in contact with actin decreases as shortening/lengthening velocity increases

Front 325

What are the three types of muscle contractions? Describe each.

Back 325

1. concentric: muscle shortens while it is activated

Front 326

How would you get the greatest production of force during eccentric contractions? What is special about the state the muscle is in during eccentric contraction? What is the effect of velocity on force production during eccentric contractions?

Back 326

by using involuntary contractions (external electrical stimulation) rather than voluntary

Front 327

In what order are alpha-motoneurons recruited to produce increasing force? What is the name of this rule of order?

Back 327

in increasing axon diameter; for low force contractions, motor units with small alpha-motoneurons are recruited, and for increasing force production, larger alpha-motoneurons are recruited.

Front 328

What are the three types of motor units based on alpha-motoneuron size? What kind of muscle fibers does each unit type contain?

Back 328

Slow (S) units: Type I or slow oxidative (SO) muscle fibers

Front 329

Contrast the number of muscle fibers and strength of each type of motor unit.

Back 329

S: small number of fibers, low force producing

Front 330

Under what circumstances would the normal recruitment order of motor units not be followed? Is this a common circumstance? What drives motor unit recruitment?

Back 330

During novel, eccentric contractions and during sudden movements

Front 331

What is rate coding?

Back 331

discharge frequency for an alpha-motoneuron

Front 332

What is the relationship between force production and stimulation frequency?

Back 332

force increases sigmoidally with stimulation frequency

Front 333

To increase force production, but still remaining below 50% MVC, what does the body do? When increasing to a higher force level (> 50-80% MVC)?

Back 333

< 50% MVC: increases motor unit recruitment and increases rate coding of motor units already active

Front 334

What factors affect muscle shortening velocity?

Back 334

load imposed on the muscle

Front 335

What is the relationship between load imposed on a muscle and its shortening velocity? What happens to the shortening velocity when no load is applied and when the load is at its maximum for a particular muscle?

Back 335

The greater the load, the lower the shortening velocity. When load is zero, the muscle can shorten at its maximal shortening velocity (Vmax). When load is so great that the muscle cannot shorten the contraction becomes isometric; the load at this point is called the maximal isometric force (Po)

Front 336

What is the relationship between a muscle's fiber length (normal length, not stretching length) and its shortening velocity? What explains this relationship?

Back 336

the longer the fiber length, the greater the shortening velocity

Front 337

What is the relationship between the type of motor unit recruited and muscle shortening velocity? Why is this the case?

Back 337

fast twitch fibers shorten faster (2x-4x) than slow twitch

Front 338

Is there a great variation in fiber type composition between individuals? Between men and women? How does female fiber size compare to male fiber size?

Back 338

wide variation in fiber type between individuals, but not between men and women

Front 339

What is the difference in CSA between Type I and Type II fibers? The difference in force produced per CSA?

Back 339

CSA and force per CSA are both the same for Type I and Type II fibers within the same species

Front 340

What determines whether a person has more Type I than Type II muscle fibers? For which fiber type(s) is fiber type composition a decent predictor of performance?

Back 340

genetics, for the most part, and innervation: if you cross-innervate a fast muscle with a nerve from a slow muscle, the fast muscle takes on contractile characteristics of a slow muscle (and vice versa)

Front 341

What are the effects of resistance training, decreased used, no use (as in spinal cord injury) and endurance training on PSA?

Back 341

Effect on PSA:

Front 342

how many muscle fibers are there in a typical muscle?

Back 342

100's to 1000's

Front 343

How many muscle fibers are in a single fascicle and what covers the fascicle?

Back 343

10's to 100's\\u000Aperimysium

Front 344

What's the diameter of a typical muscle fiber? How long are muscle fibers typically?

Back 344

diameter = 100 micrometers or 0.1 mm\\u000Alength = 1 cm to 10's of cm

Front 345

How many myofibrils are there per muscle fiber?

Back 345

~1000

Front 346

What are the 2 contractile structures/units of muscle tissue?

Back 346

myofibril and sarcomere

Front 347

What's the diameter of a typical myofibril?

Back 347

1 micrometer

Front 348

What makes up a myofibril?

Back 348

sarcomeres aligned in series

Front 349

How long is a typical sarcomere?

Back 349

2.5 micrometers

Front 350

With a muscle fiber that is 10 cm long, how many sarcomeres are aligned in series within each of the fiber's myofibrils?

Back 350

10 cm / 2.5 micrometers =\\u000A10 x 10^2- meters / 2.5 x 10^6- meters =\\u000A4.0 x 10^4 =\\u000A40,000 sarcomeres in a 10 cm long fiber

Front 351

What makes up myofilaments?

Back 351

Thin filaments made up of actin, troponin, and tropomyosin\\u000AThick filaments made up of myosin only

Front 352

What components make up a myosin molecule and what chemical is used to determine the components?

Back 352

Heavy meromyosin (site of crossbridge and ATPase activity), subdivided into an S-1 segment (head of myosin) and an S-2 segment (neck of myosin)\\u000ALight meromyosin (tail of myosin)\\u000APapain is used to cleave the myosin molecule

Front 353

How is a single myosin molecule more typically subdivided? What division determines the shortening velocity of a muscle fiber?

Back 353

two myosin heavy chains (MHC)\\u000Afour myosin light chains (MLC)\\u000AMHC forms the backbone of the head and tail regions\\u000AMLC are arranged on the head portion only\\u000AThe type of MHC mostly determines shortening velocity

Front 354

What are the two regulatory proteins involved in crossbridge cycling and what do they generally do? How are these two proteins differ in function during crossbridge cycling?

Back 354

troponin and tropomyosin\\u000Ainitiate and terminate contraction\\u000Atropomyosin physically blocks the interaction between actin and myosin while the muscle is at rest\\u000Atroponin has an affinity for calcium, and when calcium binds to troponin, troponin changes shape, pulls on tropomyosin, and causes the tropomyosin to expose the binding sites on actin

Front 355

How is muscle functionally organized (2 ways)?

Back 355

Motor unit and sarcomere

Front 356

What does a motor unit consist of?

Back 356

one alpha-motoneuron and all the muscle fibers it innervates, which usually all lie within one fascicle, but the fibers do not necessarily lie next to each other

Front 357

What's the range for the number of fibers in a motor unit?

Back 357

10-15 up to the 1000's

Front 358

Describe the parts of the sarcomere

Back 358

extends from one Z-line to the next\\u000AA-bands are the regions that contain thick filaments\\u000AH-zone is the part of the A-band that only contains thick filaments (no thin)\\u000Abisected by the M-line\\u000AI-band contains only thin filaments and is bisected by the Z-lines

Front 360

What happens to the bands/lines in a sarcomere during contraction?

Back 360

Z-lines move closer together\\u000AI-band and H-zone start to disappear

Front 361

What are the four steps of the crossbridge cycle? Start from the beginning of muscle relaxation. Which step is the rate-limiting step?

Back 361

1. ATP binds to myosin, actin-myosin complex dissociates\\u000A2. ATP is hydrolyzed by ATPase, energy released to cock the myosin head\\u000A3. In presence of calcium, myosin binds with actin, energy stored in cocked crossbridge moves the thin filament past the thick filament\\u000A4. Hydrolysis products of the ATPase reaction are released from myosin (rate-limiting step)

Front 362

List the steps of generating an action potential in a muscle cell during excitation-contraction coupling.

Back 362

1. Action potential generated in alpha-motoneuron and travels down axon\\u000A2. When the action potential reaches the axon terminal, vesicles in the axon terminal release Ach into the synaptic cleft\\u000A3. ACh binds to receptors on the sarcolemma (muscle side of neuromuscular junction)\\u000A4. Binding of ACh to the sarcolemma receptors causes sodium channels to open on the sarcolemma\\u000A5. Sodium flows into the muscle cell, causing the depolarization of the muscle cell (from negative to positive)

Front 363

List the steps of excitation-contraction coupling, starting from the moment the muscle cell is depolarized to the removal of calcium from the cytosol of the cell. Do not list the steps of the crossbridge cycle.

Back 363

1. Action potential travels along sarcolemma until enters a T-tubule, is sensed by a T-tubular voltage sensor, and causes a shape change of the sensor, in turn causing a shape change in the sarcoplasmic reticulum's Ca2+ channels\\u000A3. Ca2+ is released from the SR into the cell and binds to troponin, beginning the crossbridge cycle\\u000A4. Action potentials from the alpha-motoneuron end and release of Ca2+ from SR stops\\u000A5. Ca2+ ATPase pumps move calcium from the cytosol back into the SR

Front 365

What are the 5 factors that affect force production in a muscle?

Back 365

1. physiological cross-sectional area (PCSA)\\u000A2. muscle length\\u000A3. muscle shortening/lengthening velocity\\u000A4. number of motor units recruited\\u000A5. rate coding