Muscle physiology week 2

Question 1

Excitation-Contraction Coupling

Answer 1

the series of events linking muscle excitation to muscle contraction .

Question 2

the link between excitation and contraction.

Answer 2

Calcium

Question 3

Question 4

Calcium release

Question 5

Relaxation

Answer 5

occurs when Calcium is returned to the lateral sacs when local electrical activity stops

Question 6

Sarcoplasmic/endoplasmic reticulum Calcium–ATPase (SERCA) pump

Answer 6

The sarcoendoplasmic reticulum (SR) calcium transport ATPase (SERCA) is a pump that transports calcium ions from the cytoplasm into the SR.

Question 7

No Calcium

Answer 7

– Actin and Myosin can’t bind

Question 8

https://www.youtube.com/watch?v=BVcgO4p88AA

Question 9

A single action potential in a skeletal muscle fiber lasts only

Answer 9

1 to 2 msec.

Question 10

latent period.

Answer 10

The time delay between stimulation and onset of

contraction

Question 11

Whole muscles are groups of muscle fibers bundled together and attached to bones.

Answer 11

Can range from only a few hundred fibers to several hundred thousand fibers.

Question 12

attach muscle to bones

Answer 12

attach muscle to bones

Question 13

How is muscle tension is transmitted

Answer 13

Muscle tension is transmitted to bone as the contractile component (sarcomere) tightens the series-elastic component.

Question 14

A muscle is typically attached to

Answer 14

at least two bones across a joint by means of tendons that extend from each end of the muscle.

Question 15

T/F

all muscle contractions shorten muscles and move bones

Answer 15

False

Not all muscle contractions shorten muscles and move bones

Question 16

Three primary types of contraction:

Answer 16

Isotonic contraction
Isokinetic contraction
Isometric contraction

Question 17

Isotonic contraction

Answer 17

• the load remains constant as the muscle changes length

Question 18

Isokinetic contraction

Answer 18

• the velocity of shortening remains constant as the muscle changes length.

Question 19

Isometric contraction

Answer 19

• the muscle is prevented from shortening, so tension develops at constant muscle length.

Question 20

T/F

The same internal events occur in isotonic, isokinetic, and isometric contractions

Answer 20

True

Question 21

T/F

Muscle contractions often are not of one pure primary type

Answer 21

True

Question 22

https://www.youtube.com/watch?v=T00U5lMWAWQ

Question 23

Muscle tension, length, and velocity of shortening may

Answer 23

vary throughout a range of motion

Question 24

There are also two other descriptors of muscle contraction:

Answer 24

Concentric contraction

Eccentric contraction

Question 25

Velocity of shortening is related to

Answer 25

The load

It is an important determinant of the velocity with which a muscle changes length.

Question 26

Load – Velocity relationship

Answer 26

Question 27

Contractions of a whole muscle can be of varying strength

Answer 27

A single action potential in a muscle fiber produces a brief, weak contraction called a twitch.

Question 28

You can vary the force you exert by the same muscle.

Two primary factors can be adjusted

Answer 28

(1) Number of muscle fibers contracting within a muscle

(2) Tension developed by each contracting fiber

Question 29

What leads to greater muscle tension

Answer 29

The greater the number of fibers contracting, the greater the total muscle tension

Question 30

Each whole muscle is innervated by a number of :

Answer 30

different motor neurons - Motor Unit –>Motor Unit Recruitment

Question 31

Contraction strength depends on

Answer 31

motor unit size

Question 32

In muscles that produce precise, delicate movements

Answer 32

a single motor unit may contain a few muscle fibers

Question 33

In muscles designed for powerful, coarsely controlled movement,

Answer 33

a single motor unit may contain many muscle fibers

Question 34

Muscle fatigue

Answer 34

the inability to maintain muscle tension at a given level

Question 35

The body _______ to prevent or delay fatigue

Answer 35

alternates motor unit activity

Question 36

The body alternates motor unit activity to prevent or delay fatigue
How is this possible?

Answer 36

Muscles consist of a mixture of fiber types that differ metabolically, some being more resistant to fatigue than others.

Question 37

Various factors influence the extent to which tension can be developed, including the following:

Answer 37

1. Frequency of stimulation
2. Length of the fiber at the onset of contraction
3. Extent of fatigue
4. Thickness of the fiber

Question 38

Twitch Summation and Tetanus

Answer 38

Question 39

Muscle Length – Tension Relationship

Answer 39

Question 40

Muscle Metabolism

-Four steps in the excitation, contraction, and relaxation processes require ATP:

Answer 40

1. Myosin ATPase Splits ATP to provide energy for the power stroke of the cross bridge.
2. Binding of a fresh molecule of ATP to myosin lets the cross bridge detach from the actin filament at the end of a power stroke.
3. Active transport of Ca2+ back into the lateral sacs of the SR during relaxation
4. The ATP-dependent Na+–K1+ pump actively returns the ions that moved during the generation of an action potential in the muscle cell.

Question 41

Answer 41

Question 42

There are two types of fatigue:

Answer 42

Muscle fatigue

Central fatigue

Question 43

There are three major types of muscle fibers:

Answer 43

1. Slow-oxidative (type I) fibers
2. Fast-oxidative (type IIa) fibers
3. Fast-glycolytic (type IIx) fibers

Question 44

Question 45

https://www.youtube.com/watch?v=8x8H-GFtwyU&t=6s

Question 46

Two types of changes can be induced in muscle fibers:

Answer 46

Changes in their oxidative capacity
Changes in their diameter (hypertrophy)

• Influence of Testosterone
• Interconversion Between Fast Muscle Types

Question 47

Use memo 1, 2, 3 in summaries!!