2.7 -- Excitation Contraction Coupling in Skeletal Muscle

Question 1

What is the first step of connecting an action potential to muscle contraction?

Hint: Releases a neurotransmitter

Answer 1

Somatic motor neuron releases ACh at neuromuscular junction

Question 2

What is the second step of connecting an action potential to muscle contraction?

Hint: Entry of what through what initiates what?

Answer 2

Net entry of Na+ through ACh receptor-channel initiates a muscle action potential

Question 3

The DHP (Dihydropyridine L-type) receptor at the t-tubule is what sort of channel?

Answer 3

Voltage-gated calcium channel

Question 4

What is the third step of connecting an action potential to muscle contraction?

Hint: What in what alters confirmation of what receptor?

Answer 4

Action potential in t-tubule alters confirmation of DHP receptor

Question 5

When does the ryanodine receptor open? What does it do?

Answer 5

In response to action potential in t-tubule, which lets calcium into cytoplasm from sarcoplasmic reticulum

Question 6

What is the fourth step of connecting an action potential to muscle contraction?

Hint: DHP receptor opens what in where, which does what?

Answer 6

DHP receptor opens ryanodine calcium release channels in sarcoplasmic reticulum, which makes calcium enter the cytoplasm

Question 7

What is the fifth step of connecting an action potential to muscle contraction?

Answer 7

Ca2+ binds to troponin, allowing actin-myosin binding

Question 8

What is the sixth step of connecting an action potential to muscle contraction?

Answer 8

Myosin heads execute power stroke

Question 9

What is the seventh step of connecting an action potential to muscle contraction?

Answer 9

Actin filament slides toward center of sarcomere

Question 10

What pumps Ca2+ back into the sarcoplasmic reticulum via ATP hydrolysis in a relaxation state?

Answer 10

SERCA pump

Question 11

What is the eighth step of connecting an action potential to muscle contraction?

Answer 11

SERCA pump CA2+ back into sarcoplasmic reticulum, decreasing free Ca2+ in the sarcoplasm

Question 12

What is the ninth step of connecting an action potential to muscle contraction?

Answer 12

Ca2+ unbinds from troponin

Question 13

What is the tenth step of connecting an action potential to muscle contraction?

Answer 13

Tropomyosin recovers binding site and filaments go back to the relaxed position

Question 14

What activates thin filament for contraction?

Answer 14

Calcium

Question 15

When stimulated, calcium leaves the sarcoplasmic reticulum out of what calcium release channels?

Answer 15

Ryanodine receptors

Question 16

At the end of contraction, Ca2+ is what back into the sarcoplasmic reticulum via SERCA pumps?

Answer 16

Actively pumped

Question 17

Is ATP required for the initiation, termination, or both of contraction?

Answer 17

Both

Question 18

Is action potential or contraction faster?

Answer 18

Action potential is much faster

Question 19

The action potential refractory period is finished when the what is still high?

Answer 19

Force

Question 20

What is tetany?

Answer 20

The maximum force a muscle can reach

Question 21

Can multiple action potentials occur together in a close period of time?

Answer 21

Yes

Question 22

When is the maximum tension generated in muscle for its resting length?

Answer 22

100-120% of its resting muscle length

Question 23

What are the two things that varies force generation at a cellular level?

Answer 23

Frequency of action potentials and sarcomere length

Question 24

What varies force generation at an organ level?

Answer 24

Amount of motor units going and subbing them

Question 25

During tetany, individual muscle fibers respond in what sort of fashion?

Answer 25

All-or-none fashion

Question 26

What is a motor unit?

Answer 26

The motor neuron and all the muscle fibers it innervates

Question 27

Can a muscle can multiple motor units of different types?

Answer 27

Yes

Question 28

Recruitment of additional motor units by the nervous system increases what?

Answer 28

Contraction force

Question 29

What about motor units helps avoid fatigue?

Answer 29

Asynchronous recruitment

Question 30

While synchronous movement makes fatigue occur faster, what is the advantage?

Answer 30

Allows more force to be produced

Question 31

A single motor neuron makes what contact with a number of muscle fibers?

Answer 31

Synaptic

Question 32

A single muscle fibers typically receives synaptic input from how many motor neurons?

Answer 32

One

Question 33

When a motor neuron fires, all the muscle cells in the motor neuron's unit will do what?

Answer 33

Contract together

Question 34

Does the thickness of a fiber produced more force?

Answer 34

Yes, as it has more contractile units