Chapter 6 Muscle Physiology 3

Front 1

1. Skeletal muscle is divided into bundles of muscle fibers by?

2. muscles attached to bones by?

3. tendons formed by?

Back 1

1. connective tissue covering muscle divides it internally into bundles

2. tendons

3. connective tissue extends beyond ends of muscle to form tendons

Front 2

What is a twitch>

Back 2

when a single action potential in muscle fiber produces a brief, weak contraction - too short and too weak to be useful

Front 3

What are 2 factors that can be adjusted to accomplish muscle contraction?

Back 3

1. # of muscle fibers contracting within a muscle

2. tension developed by contracting fiber

Front 4

Characteristics of contraction of whole muscle

Back 4

1. motor unit

2. motor unit recruitment

Front 5

Motor unit

1. what is a motor unit

2. to accomplish greater tension

3. the larger the muscle, more the fibers

Back 5

1. (motor neuron) + (all fibers it innervates)

2. greater number of muscle fibers must contract

3. greater the tension

Front 6

One motor neuron innervates ______________ but each muscle fibers is supplied by __________________

Back 6

a number of muscle fibers, but each muscle fiber is supplied by only one motor neurons

Front 7

1. What is motor unit recruitment?

2. strength of muscle contraction depends on

Back 7

1. for a stronger contraction, more and more motor units are recruited or stimulated to contract

2. depends on recruitment of each additional motor unit

Front 8

1. muscles that produce precise, delicate movements contain ________ fibers per motor unit

2. muscles performing powerful, coarsely controlled movements have ___________ number of fibers per motor unit

Back 8

1. fewer

2. larger

Front 9

Recruitment of motor units in powerful muscle results in

Back 9

large increment in whole muscle tension

Front 10

Factors that affect the extent to which tension develops (4)

Back 10

1. frequency of stimulation

2. length of fiber at onset of contraction

3. extend of fatigue

4. thickness of fiber

Front 11

Length-Tension Relationship

1. maximal tetanic contraction can be achieved when

Back 11

1. a muscle fiber is at its optimal length before the onset of contraction - because this is the point of optimal overlap of thick filament cbs thin filament cb binding sites

Front 12

The percentage of maximal tetanic contraction decreases when

Back 12

the muscle fiber is longer or shorter than optimal length before contraction

- longer: fewer thin filament binding sits are accessible for binding with thick fil. cbs

- shorter: fewer thin filament binding sites are exposed to thick filament cbs because thin filaments overlap - further shortening and tension developement impeded because thick fil forced against zlines

Front 13

in the body, resting muscle length is

Back 13

at optimal length

Front 14

because of restrictions imposted by skeletal attachments, muscles cannot

Back 14

vary beyond 30% of their optimal length in either direction - beyond that can stillachieve about50% of maximal tetanic contraction

Front 15

contractions with longer duration and greater tension can be achieved by

Back 15

repetitive stimulation of the fiber

Front 16

What is twitch summation

Back 16

- when a muscle fiber is restimulated before it has completely relaxed, second twitch is added onto the first twitch

Front 17

1. What is tetanus?

2. occuris if

3. how much stronger than a twitch

Back 17

1. a maximum sustained contraction

2. occurs if a muscle fiber is stimulated so rapidly that it does not have a chance to relax b/w stimuli

3. 3-4x stronger than single twitch

Front 18

1. what is fatigue

2. fatigue occurs

Back 18

1. the inability to maintain muscle tension at a given level

2. when exercising muscle no longer responds to same degree of contractile activity

Front 19

Factors that affect muscle fatigue (3)

Back 19

1. local increase of inorganic phosphate results from the break down of creatine phosphate

2. accumulation of lactic acid (can inhibit key enzymes involved in excitation-contraction coupling)

3. depletion of energy reserve

Front 20

Power stroke

1. when is Pi released?

2. when is ADP released

from myosin cross bridge

Back 20

1. released during power stroke

2. ADP released after power stroke

Front 21

How is the link b/w actin and myosin broken after power stroke?

Back 21

by fresh molecule of ATP binding to myosin cb (cb assumes original conformation)

Front 22

What are the 3 basic methonds of ATP synthesis?

Back 22

1. creatine phosphate

2. oxidative phosphorylation

3. glycolysis

Front 23

One step process and is a fast-ATP forming method for contractile activity of a muscle

Back 23

Creatine phosphate

Front 24

ATP derived from creatine phosphate supports what activities

Back 24

1. short burst of high contractile efforts such as high jumps, sprints or weight lifting

2. first minute or less of exercise (warm up)

Front 25

Oxidative phosphorylation

1. sources of O2 for it

2. is it a slow or fast process

3. it produces how much ATP

4. supports what ativities

Back 25

1. increased breathing and heart rate, increased myoglobin (store O2 in muscle), blood vessel dilation in exercised muscles, increased hb mols carrying more O2 to musles

2. slow, requires # of steps

3. 36 ATP

4. light exercise to moderate exercies (walk -> jogging/swimming)

Front 26

During relaxation ATP is needed to

Back 26

run the Ca pump that transports Ca back into SR lateral sacs

Front 27

1.Main source of ATP when O2 present

2. Main source of ATP when O2 absent

3. Immediate source of ATP

Back 27

1. oxidative phosphorylation

2. glycolysis

3. creatine phosphate

Front 28

During glyolysis glucose mol broken down into

Back 28

pyruvic acid

Front 29

Glycolysis and oxidative phosphorylation

Back 29

1. near max contracting, muscle compress blood vess. severely limiting O2 available for muscle contraction

2. reduced O2 slows down ox phos and therefore ATP needed during intense activity

3. glycolysis yields product for entry into ox phos (pyruvic acid further degraded by ox pho to extract more energy)

4. glycolysis yelds fewer ATP but is faster than ox phos if sufficient glucose mols present

Front 30

Accumulation of lactic acid during exercise causes (3)

Back 30

1. soreness of muscle during exercise

2. lactic acid picked up by blood causes acidosis (increased H+)

3. depletion of energy reserve and fall of muscle pH (sole cause of onset of muscle fatigue)

Front 31

Muscle fatigue is a ________ mechanism

Back 31

defense mechanism that protects muscle from reach point that it can no longer produce ATP

Front 32

Types of Fatigue (3)

Back 32

1. muscle fatigue

2. central fatigue

3. neuromuscular fatigue

Front 33

1. What is central fatigue?

2. it causes

3. is often _________ based

4. what can cause it?

5. in less strenuous activities, central fatigue may reduce physical performance in association with

Back 33

1. failure of CNS to activate motor neuron supplying working muscles

2. person to slow down or stop exercising even though muscles still bale to perform

3. psychologically

4. biochemical insufficiency within brain

5. association with boredom or tiredness

Front 34

1. what causes neuromuscular fatigue?

2. a person with ___________ can experience NM fatigue

Back 34

1. inability of active motor neurons to synthesize ACh rapidly to sustain chemical transmission of action pot from motor neuron to muscle

2. myasthenia gravis

Front 35

1. What is oxygen debt?

2. O2 is needed for ______________ of energy systems

3. during recovery period, fresh supplies of ___________ formed by _________________ using newly acquired ___________

Back 35

1. process of repayment of O2 that is incurred during exercise

2. recovery

3. supplies of ATP formed by ox phos using newly acquired O2

Front 36

Major types of muscle fibers

1. classified based on

2. 3 major types

Back 36

1. differences in ATP hydrolysis

2.

slow oxidative (type I)

fast oxidative (type IIa)

fast glycolytic (type IIb or IIx)

Front 37

Glycolytic white fibers

1. need how much O2

2. contains higher content of

3. contain abundant of stored ___________ to ...

4. why do they appear white/pale?

Back 37

1. relatively low O2

2. glycolytic enzymes

3. glycogen to provide large amound of glucose for glycolysis

4. very little myglobin

Front 38

What 3 levels of input control motor neuron output?

Back 38

1. input from afferent neurons

2. input from primary motor cortex

3. input from brain stem