Muscle Contraction

Question 1

What is the primary role of calcium ions (Ca2+) in muscle contraction?

Answer 1

Calcium ions bind to troponin, causing a conformational change that allows myosin to bind to actin.

Question 2

True or False: ATP is required for muscle contraction.

Answer 2

True

Question 3

Fill in the blank: The stages of muscle contraction include __________, where the muscle fiber generates tension.

Answer 3

twitch

Question 4

What is the role of ATP in muscle contraction?

Answer 4

ATP provides energy for the myosin heads to perform the power stroke and is necessary for detaching myosin from actin.

Question 5

What happens during the relaxation phase of muscle contraction?

Answer 5

Calcium ions are pumped back into the sarcoplasmic reticulum, and the muscle fiber returns to its resting state.

Question 6

What is the first step in muscle contraction?

Answer 6

The release of acetylcholine at the neuromuscular junction.

Question 7

In what structure is calcium stored in muscle cells?

Answer 7

Sarcoplasmic reticulum

Question 8

True or False: Muscle relaxation occurs when calcium ions bind to troponin.

Answer 8

False

Question 9

What is a muscle twitch?

Answer 9

A brief contraction and relaxation cycle of a muscle fiber in response to a single stimulus.

Question 10

What initiates the cross-bridge cycle in muscle contraction?

Answer 10

The binding of calcium to troponin.

Question 11

During muscle contraction, what happens to the sarcomere?

Answer 11

The sarcomere shortens as actin filaments slide over myosin filaments.

Question 12

What is the term for the period of time between stimulus and the beginning of muscle contraction?

Answer 12

Latent period

Question 13

What is the role of myosin in muscle contraction?

Answer 13

Myosin heads bind to actin and pull the filaments during the power stroke.

Question 14

True or False: ATP is not required for muscle relaxation.

Answer 14

False

Question 15

What happens to myosin heads during the power stroke?

Answer 15

They pivot and pull the actin filaments toward the center of the sarcomere.

Question 16

What is the effect of a lack of ATP on muscle contraction?

Answer 16

Muscles cannot relax, leading to rigor mortis.

Question 17

Which ion is essential for the exposure of binding sites on actin?

Answer 17

Calcium ions (Ca2+)

Question 18

What are the three phases of a muscle twitch?

Answer 18

Latent period, contraction phase, and relaxation phase.

Question 19

What occurs during the contraction phase of a muscle twitch?

Answer 19

Muscle fibers actively shorten and generate force.

Question 20

Fill in the blank: The primary source of energy for muscle contraction is __________.

Answer 20

ATP

Question 21

What is the relationship between calcium and the sarcoplasmic reticulum during contraction?

Answer 21

Calcium is released from the sarcoplasmic reticulum into the cytoplasm.

Question 22

True or False: The relaxation phase is longer than the contraction phase in a muscle twitch.

Answer 22

True

Question 23

What effect does repeated stimulation have on muscle contraction?

Answer 23

It can lead to summation and tetanus, resulting in increased muscle tension.

Question 24

What is the function of troponin in muscle contraction?

Answer 24

Troponin binds calcium and regulates the interaction between actin and myosin.

Question 25

During the relaxation phase, which enzyme helps break down acetylcholine?

Answer 25

Acetylcholinesterase

Question 26

What is meant by ‘tetanus’ in muscle physiology?

Answer 26

A sustained muscle contraction due to rapid, repeated stimulation.