Muscular Physiology

Question 1

What happened to the A and I band, during muscle contraction

Answer 1

I band= narrows

A band = stays the same

Question 2

What happens when the calcium ions bind to troponin

Answer 2

moves tropomyosin, exposing actin = attachment of myosin head

Question 3

A protein that acts like a molecular motor that walks along actin like feet pulling the rope

Answer 3

Myosin

Question 4

During the power stroke, actin :

Answer 4

pulls inward towards the center of the sarcomere

Question 5

What happened to the Z discs during muscle contraction

Answer 5

sliding movement causes the Z discs drawn closer together towards the center of the sarcomere (sarcomere shortens)

Question 6

When the calcium is not released from the sarcoplasmic reticulum:

Answer 6

no muscle contraction
muscle remains in a relaxation state
tropomyosin remains in its blocking position

Question 7

One stroke is equivalent to how many microns to perform the shortening of muscles

Answer 7

1 micron

Question 8

This is a lighter region within the middle of the A band.

Answer 8

H zone

Question 9

Myosin molecule consist of:

Answer 9

1= tail
2 = globular head

Question 10

The entire length of the thick filaments, where the thin filaments overlap with the thick filaments.

Answer 10

A band

Question 11

What happens when the ACh binds to the receptor on the motor end plate

Answer 11

Triggers ion channel opening

Na+ enter the cell= muscle AP generated

Question 12

It brings the electrical signal deep into the core of the muscle cell

Answer 12

T-tubules

Question 13

A specialized endoplasmic reticulum that serve as calcium bank

Answer 13

Sarcoplasmic reticulum

Question 14

What happen when the DHP receptors opens?

Answer 14

Calcium influx and binds to RyR2, opening the Ca 2+ channels

Question 15

The greater the SR volume, the more

Answer 15

a. more Ca²⁺ release and reuptake
b. more efficient Ca²⁺ transients
faster contraction-relaxation cycles.

Question 16

What happen to the excess calcium ions after muscle contraction?

Answer 16

Actively pumped back into the SR via Ca2+ -AtPase

Question 17

What is the functional role of calsequestrin within the sarcoplasmic reticulum

Answer 17

Buffers and stores calcium within the SR

Question 18

Which event directly initiates skeletal muscle relaxation

Answer 18

Detachment of Ca²⁺ from troponin

Question 19

What causes rigor mortis in skeletal muscle after death

Answer 19

ATP depletion preventing detachment of myosin from actin

Question 20

What initiates the cross-bridge cycle in skeletal muscle contraction

Answer 20

Binding of Ca²⁺ to troponin

Question 21

During the power stroke of the cross-bridge cycle, which event occurs

Answer 21

ADP and inorganic phosphate are released from myosin

Question 22

What is the role of ATP hydrolysis in the cross-bridge cycle

Answer 22

It energizes the myosin head to return to its cocked position

Question 23

During rigor mortis, why can the muscle fibers not relax?

Answer 23

Myosin heads remain bound to actin due to lack of ATP

Question 24

What allows the myosin head to detach from actin after the power stroke

Answer 24

Binding of ATP to the myosin head

Question 25

How are muscles categorized based on microscopic appearance

Answer 25

Striated (skeletal and cardiac) and unstriated (smooth) based on presence of striations

Question 26

What is the function of tropomyosin in relaxed skeletal muscle fibers?

Answer 26

To cover actin binding sites, preventing cross-bridge formation

Question 27

What happens to tropomyosin when calcium binds to troponin

Answer 27

Tropomyosin moves to expose binding sites on actin

Question 28

What are myofibrils primarily composed of

Answer 28

Thick filaments (myosin) and thin filaments (actin)

Question 29

High glycogen content in some specialized muscles suggest about their function:

Answer 29

They are specialized for high-frequency contractions requiring rapid energy

Question 30

Muscle contractions that produce sound in some fish can reach frequencies up to:

Answer 30

350-650 Hz

Question 31

Approximately what percentage of human male body weight is skeletal muscle

Answer 31

40%

Question 32

Which muscle type contributes approximately 10% of the total body weight in humans

Answer 32

Cardiac and smooth muscle combined

Question 33

The significance of muscle isoforms in muscle function

Answer 33

Allowing the muscles to perform different functions by slight structural differences

Question 34

In hummingbirds, flight muscles account for approximately what percentage of body weight

Answer 34

25%

Question 35

Muscle that moves contents through hollow internal organs is primarily which muscle type

Answer 35

Smooth muscle