Biol2420 - Muscle Physiology #2

Front 1

What prevents the binding of the myosin head to actin when a muscle fiber is not contracting?

Back 1

Tropomyosin

Hint 1

Pg. 171

Front 2

What molecule must enter the cytoplasm and bind to troponin for contraction to occur?

Back 2

Calcium

Hint 2

Pg. 171

Front 3

Where is the Calcium ions stored when a muscle fiber is at rest?

Back 3

The Sarcoplasmic Reticulum
and
Very little is in the cytoplasm

Hint 3

Pg. 171

Front 4

When a muscle fiber is stimulated, how are the action potentials conducted and produced and what do they stimulate?

Back 4

Action potentials are produced and conducted along the Transverse Tubules
This stimulates the release of Calcium ions from the Sarcoplasmic Reticulum

Hint 4

Pg. 171

Front 5

What does the binding of Calcium to Troponin cause?

Back 5

It causes the Troponin-Tropomyosin complexes to move and allows the myosin heads to bind.

Hint 5

Pg. 171

Front 6

What is each thin filament formed by?

Back 6

300-400 Globular Actin Subunits, arranged in a double row and twisted into a helix.

Hint 6

Pg. 171

Front 7

What is the name of the filamentous protein that is bound to actin and lies within the groove of the double row of actin subunits?

Back 7

Tropomyosin

Hint 7

Pg. 171

Front 8

Each Tropomyosin spans a distance of about ______________ proteins?

Back 8

7 Globular Actin Proteins

Hint 8

Pg. 171

Front 9

What are the three protein complexes that make up the structure that attaches to tropomyosin?

Back 9

1. Troponin T
2. Troponin C
3. Troponin I

Hint 9

Pg. 171

Front 10

What the function of Troponin T?

Back 10

It binds to Tropomyosin

Hint 10

Pg. 171

Front 11

What is the function of Troponin C?

Back 11

It can bind to Calcium ions

Hint 11

Pg. 171

Front 12

What is the function of Troponin I?

Back 12

It participates with Tropomyosin in the inhibition of cross-bridge formation when a muscle is at rest.

Hint 12

Pg. 171

Front 13

What must move out of the way in order for the myosin head to bind to actin?

Back 13

The Tropomyosin along with its attached Troponin

Hint 13

Pg. 171

Front 14

Why is Calcium ions essentially absent from the cytoplasm in a resting muscle fiber?

Back 14

Because when a muscle fiber isn’t contracting the specialized endoplasmic reticulum of a muscle fiber accumulates the Calcium ions inside its terminal cisternae (enlarged cavities).

Hint 14

Pg. 172

Front 15

What is the name of the Endoplasmic Reticulum of muscle cells?

Back 15

The Sarcoplasmic Reticulum (SR)

Hint 15

Pg. 172

Front 16

What process allows the sarcoplasmic reticulum to accumulate a high concentration of Calcium ions within its terminal cisternae while also producing a very low concentration of Calcium ions in the cytoplasm?

Back 16

Active Transport

Hint 16

Pg. 172

Front 17

What are the names of the inward extensions of the sarcolemma that run deep down into the muscle fiber located very close to the terminal cisternae of the sarcoplasmic reticulum?

Back 17

Transverse Tubules (T tubules)

Hint 17

Pg. 172

Front 18

Why will an action potential produced at the surface be conducted along the sarcolemma and down the transverse tubules so that it is brought next to the terminal cisternae of the Sarcoplasmic Reticulum?

Back 18

Because each Transverse Tubule contains extracellular fluid and brings the sarcolemma to even the deepest part of the muscle fiber.

Hint 18

Pg. 172

Front 19

What substance does somatic motor neurons release which diffuse across the synaptic cleft and binds to its receptor proteins in the sarcolemma?

Back 19

Acetylcholine (ACh)

Hint 19

Pg. 172

Front 20

What does the binding of ACh to its receptor proteins in the sarcolemma cause?

Back 20

It opens chemically gated ion channels that produce an excitatory postsynaptic potential (EPSP).

Hint 20

Pg. 172

Front 21

In a muscle fiber the _________ are immediately adjacent to the ______________, which are located in the middle of the muscle fiber at the synapse.

Back 21

Voltage-Gated Channels
Chemically Gated Channels

Hint 21

Pg. 172

Front 22

True or False. Action potentials are conducted along the sarcolemma in the same way action potentials are conducted by unmyelinated axons?

Back 22

True

Hint 22

Pg. 172

Front 23

What does the membrane of the Sarcolemma and Transverse Tubules contain?

Back 23

Voltage-Gated Calcium ion channels

Hint 23

Pg. 173

Front 24

What are the voltage-gated Calcium ion channels in the transverse tubules mechanically coupled with in skeletal muscles?

Back 24

They are mechanically coupled to the Calcium ion release channels in the Sarcoplasmic Reticulum (SR)

Hint 24

Pg. 173

Front 25

What is a direct result of the mechanical coupling of the voltage-gated calcium ion channels in the T tubules to the Calcium ion release channels in the SR in skeletal muscles?

Back 25

Opening of the voltage-gated calcium ion channels in the T tubules directly causes the opening of the Calcium ion release channels in the SR.

Hint 25

Pg. 173

Front 26

What is the mechanism called in which additional Calcium release channels in the SR are opened indirectly as response to Calcium ions diffusing from the extracellular fluid into the cytoplasm through the voltage-gated Calcium ion channels in the T tubules?

Back 26

Ca 2+induced Ca 2+ Release

Hint 26

Pg. 173

Front 27

What steps are occurring for a muscle to relax?

Back 27

1. Action potentials in the somatic motor neuron must stop, causing action potentials in the muscle fibers to stop.
2. Voltage-Gated Ca 2+ channels in the T tubules close, and the Ca 2+ release channels in the SR close.
3. Active transport by Ca 2+ pumps in the SR accumulate Ca 2 + from the cytoplasm and store it in the terminal cisternae.

Hint 27

Pg. 173

Front 28

True or False. Relaxation of a muscle requires does not require ATP.

Back 28

False. Relaxation of a muscle, like contraction, requires ATP.

Hint 28

Pg. 173

Front 29

How can ATP in a muscle fiber be made quickly?

Back 29

It can be made quickly using the phosphate group of phosphocreatine.

Hint 29

Pg. 173

Front 30

Which type of muscle fibers is adapted for aerobic respiration?

Back 30

Slow-Twitch fibers

Hint 30

Pg. 174

Front 31

Which type of muscle fiber is adapted for lactic acid fermentation?

Back 31

Fast-Twitch fibers

Hint 31

Pg. 174

Front 32

Why does muscle contraction require ATP?

Back 32

It requires ATP to:
1. Activate the myosin head cross bridges prior to contraction.
2. Bind to the myosin heads after the power stroke, so that the cross-bridges can detach from the actin and again become activated for another cycle.

Hint 32

Pg. 174

Front 33

Why does muscle relaxation require ATP?

Back 33

Because ATP is required to power the active transport Ca 2+pumps in the membrane of the sarcoplasmic reticulum.

Hint 33

Pg. 174

Front 34

Why can’t cells build up a large store of extra ATP for later use?

Back 34

Because ATP exerts a negative feedback inhibition on its own production by cell respiration.

Hint 34

Pg. 174

Front 35

What molecule can the ATP in a resting muscle fiber donate its phosphate to and what does this form?

Back 35

A molecule called Creatine
Forming Phosphocreatine

Hint 35

Pg. 174

Front 36

How is the ATP used for muscle contraction and relaxation during intense exercise quickly regenerated using phosphocreatine?

Back 36

Phosphocreatine is enzymatically converted back into creatine and the phosphate group is donated to ADP, forming ATP.

Hint 36

Pg. 174

Front 37

What type of metabolic pathway is being utilized in the first 45-90 seconds of exercise in moderate to heavy exercise to generate ATP?

Back 37

Anaerobic metabolism
or
Lactic Acid Fermentation

Hint 37

Pg. 174

Front 38

Why must muscles be forced to get their ATP anaerobically at the beginning of strenuous exercise?

Back 38

Because there hasn’t yet been sufficient time to make the physiological adjustments necessary to increase the oxygen delivery to meet the increased metabolic demand.

Hint 38

Pg. 174

Front 39

What is the only molecule that can be used for lactic acid fermentation?

Back 39

Glucose

Hint 39

Pg. 175

Front 40

True or False. Cells can use fatty acids as well as glucose for aerobic respiration.

Back 40

True

Hint 40

Pg. 175

Front 41

What is the term given for the maximum rate of a person’s oxygen consumption during intense exercise?

Back 41

Aerobic Capacity
or
Maximal Oxygen Uptake

Hint 41

Pg. 175

Front 42

What does a person’s aerobic capacity depend on mostly?

Back 42

It depends mostly on genetics, however it can increase by about 20% through aerobic training.

Hint 42

Pg. 175

Front 43

What is most of the muscle’s energy derived from during light exercise performed at about 25% of the aerobic capacity?

Back 43

It is derived from the aerobic respiration of fatty acids.

Hint 43

Pg. 175

Front 44

What is the muscle’s energy derived from during moderate exercise at about 50%-70% of the aerobic capacity?

Back 44

The energy is derived almost equally from fatty acids and glucose.

Hint 44

Pg. 175

Front 45

During moderate exercise at about 50%-70% of the aerobic capacity how may glucose be obtained?

Back 45

The glucose may be obtained from the blood plasma
and
From the hydrolysis of glycogen stored in the muscle fibers

Hint 45

Pg. 175

Front 46

What is the muscle’s energy derived from during heavy exercise performed at above 70% of the aerobic capacity?

Back 46

About two-thirds of the energy is obtained from the anaerobic fermentation of glucose.

Hint 46

Pg. 175

Front 47

What is the term given to define the percentage of the aerobic capacity that results in a rise in blood lactate levels?

Back 47

Lactate Threshold
or
Anaerobic Threshold

Hint 47

Pg. 175

Front 48

What is the extra oxygen consumed following exercise used for?

Back 48

It is used to repay the oxygen debt incurred during exercise.

Hint 48

Pg. 175

Front 49

What is oxygen bound to within the blood?

Back 49

Hemoglobin in red blood cells

Hint 49

Pg. 175

Front 50

What is oxygen bound to within the muscle fiber?

Back 50

Myoglobin

Hint 50

Pg. 175

Front 51

What are several reasons for oxygen debt?

Back 51

1. Oxygen must be repaid that was withdrawn from the blood (where it is bound to hemoglobin in red blood cells) and from the muscle fibers (where it is bound to a molecule related to hemoglobin called myoglobin.
2. The muscles consume extra oxygen after exercise because they are still warm, with a faster metabolic rate than at rest.
3. Extra oxygen is needed to metabolize the lactic acid produced by the exercising skeletal muscles.

Hint 51

pg. 175

Front 52

True or False. Lactic acid cannot be used in aerobic cell respiration.

Back 52

False. Lactic acid can be used in aerobic cell respiration, where it is metabolized to carbon dioxide and water and releases energy for ATP formation.

Hint 52

pg. 175

Front 53

How are skeletal muscles divided and what are the names of these divisions?

Back 53

They are divided on the basis of their contraction speed. These divisions are:

Slow-Twitch = Type I = Slow Oxidative Fibers = Red Fibers
Fast-Twitch = Type II = White Fibers

Hint 53

Pg. 176

Front 54

What type of muscle fibers do the extraocular muscles of that move the eyes have a high proportion of?

Back 54

Fast-Twitch fibers
or
Type II
or
White fibers

Hint 54

Pg. 176

Front 55

What type of muscle fibers does the Soleus muscle in the leg have a high proportion of?

Back 55

Slow-Twitch
or
Type I
or
Slow Oxidative Fibers
or
Red Fibers

Hint 55

Pg. 176

Front 56

True or False. Most muscles of the body do not contain a mixture of fast-and slow-twitch fibers.

Back 56

False. Most muscles of the body contain a mixture of fast- and slow-twitch fibers.

Hint 56

Pg. 176

Front 57

What are Slow-Twitch fibers adapted for and what is another name for them?

Back 57

Aerobic Respiration
Slow Oxidative Fibers

Hint 57

Pg. 176

Front 58

What are the adaptations of Slow-Twitch muscle fibers for aerobic respiration?

Back 58

1. A rich blood supply
2. Numerous mitochondria
3. A high concentration of the enzymes needed for aerobic respiration
4. A large amount of the protein myoglobin

Hint 58

Pg. 176

Front 59

What is Myoglobin?

Back 59

It is an iron-containing red pigment which can bind to oxygen.

Hint 59

Pg. 176

Front 60

Why are slow-twitch muscle fibers also called red fibers?

Back 60

Because they have a high myoglobin content

Hint 60

Pg. 176

Front 61

What are Fast-Twitch fibers adapted for?

Back 61

Anaerobic Metabolism
or
Lactic Acid Production

Hint 61

Pg. 176

Front 62

What are the adaptations of Fast-Twitch muscle fibers?

Back 62

1. Thicker and have a less extensive blood supply
2. Fewer mitochondria
3. They have a large store of glycogen and a high content of the enzymes needed for glycolysis
4. Lower amount of myoglobin than the slow-twitch fibers

Hint 62

Pg. 176

Front 63

What are some fast twitch muscle fibers known as because of their large store of glycogen and high content of the enzymes needed for glycolysis?

Back 63

Fast Glycolytic Fibers

Hint 63

Pg. 176

Front 64

What are the fast twitch fibers that have a greater capacity for aerobic respiration called?

Back 64

Fast Oxidative Fibers

Hint 64

Pg. 176

Front 65

Why are fast-twitch muscle fibers also called White Fibers?

Back 65

Because of their reduced myoglobin content

Hint 65

Pg. 176

Front 66

Why does muscle enlargement occur in weightlifting?

Back 66

Because the increase in the thickness of fast-twitch (type II) because of an increased size and number of myofibrils and their content of sarcomeres and myofibrils.

Hint 66

Pg. 177

Front 67

What is the increased size of individual muscle cells produced in weightlifting called?

Back 67

Hypertrophy

Hint 67

Pg. 177

Front 68

True or False. Weightlifting produces Hyperplasia.

Back 68

False. Weightlifting produces Hypertrophy not Hyperplasia

Hint 68

Pg. 177

Front 69

What is the term used to define an exercise-induced reduction in the ability of a muscle to generate force?

Back 69

Muscle Fatigue

Hint 69

Pg. 177

Front 70

What is fatigue during a sustained maximal contraction as when lifting a very heavy weight appear to be due to?

Back 70

It appears to be due to the accumulation of extracellular K+

Hint 70

Pg. 177

Front 71

What does the extracellular accumulation of K+ result in?

Back 71

It reduces the resting membrane potential and interferes with the ability to produce action potentials.

Hint 71

Pg. 177

Front 72

What is lactic acid production in the muscles and depletion of their glycogen associated with?

Back 72

Muscle Fatigue

Hint 72

Pg. 177

Front 73

What is fatigue produced by changes in the CNS rather than in the muscles called and when does it occur?

Back 73

It is called Central Fatigue
It sets in before the muscles themselves fatigue

Hint 73

Pg. 177