Module One, Lecture Nine

Question 1

What is a Myofilament?

Answer 1

The thin and thick protein filaments within a muscle cell that are responsible for a concentration

Question 2

What are the two types of Myofilament?

Answer 2

1. Actin ( Thin Filaments )
2. Myosin ( Thick Filaments )

Question 3

What are some functions of Actin? ( 3 )

Answer 3

1. To form the structural framework of the cytoskeleton
2. Provides shape and stability
3. Ability to move

Question 4

What are some functions of Myosin? ( 2 )

Answer 4

1. Muscle Contraction
2. Cell mobility and transport

Question 5

What is the Cross-Bridging Cycle?

Answer 5

A repeating sequence of events that occur during muscle contraction, involving the interaction between myosin and actin filaments

Question 6

What are the steps of the Cross-Bridging Cycle? ( 4 )

Answer 6

1. Cross-Bridging formation
2. Power Stroke
3. Detachment
4. Resetting

Question 7

Describe the Cross-Bridging Formation Step…

Answer 7

Myosin heads bind to actin filaments

Question 8

Describe the Power Stroke Step…

Answer 8

The myosin head changes its conformation, pulling the actin filament along the myosin filament, which causes the muscle to shorten

Question 9

Describe the Detachment Step…

Answer 9

ATP binds to the myosin head, causing it to detach from the actin filament

Question 10

Describe the Resetting Step…

Answer 10

The myosin head hydrolyzes ATP, which returns it to a high-energy state, ready to bind to another actin molecule and start the cycle again

Question 11

Define Hydrolyzes…

Answer 11

Break down of a compound by a chemical reaction with water

Question 12

What are the two main determinants of skeletal muscle force generation? ( 2 )

Answer 12

1. Muscle Length
2. Contraction Velocity

Question 13

What is the Effect of Lengthening the Muscle?

Answer 13

The overlap between actin and myosin decreases, leading to fewer cross-bridges and reduced force generation

Question 14

What is the Effect of Shortening the Muscle?

Answer 14

The actin and myosin filaments become overly compressed, also reducing the number of cross-bridges and force

Question 15

What does Muscle Tension ( or force ) depend on? ( 2 )

Answer 15

1. The number of muscle fibres recruited
2. The rate at which the muscle is stimulated

Question 16

What is Muscle Tension Recruitment mean?

Answer 16

The process by which the nervous system controls the force generated by a muscle

Question 17

What is Muscle Tension Frequency of Stimulation mean?

Answer 17

A single AP will result in a pulse of Ca2+ into the cytoplasm, and a short period of tension is developed ( called a twitch )

Question 18

What does a rapid release of many AP result in?

Answer 18

Summation

Question 19

What does the Maximal Signalling Contraction result in?

Answer 19

Tetanus

Question 20

When are Cross-Bridges formed?

Answer 20

When actin and myosin bind together when calcium is present, allowing a contraction to occur

Question 21

What are Fast Muscle Fibres?

Answer 21

Muscles rich in fast fibres produce lots of force quickly thanks to their energy reserves, but they tire out quickly too

Question 22

What are Slow Muscle Fibres?

Answer 22

Slow fibres are able to generate a lot of energy even while working, so they are difficult to fatigue