Muscles

Question 1

What is the hierarchical structure of muscle

Answer 1

Sarcomeres –> Myofibril –> Fibres –> Fascicles –> Muscle

Question 2

What does the endomysium surround

Answer 2

Inidividual muscle fibres

Question 3

What does the perimysium surround

Answer 3

Fascicles

Question 4

What does the epimysium surround

Answer 4

Entire muscle - continuous with the tendon

Question 5

What does the z-line/disk demarcate in sarcomeres

Answer 5

The lateral borders of the sarcomeres

Question 6

Is actin the thin or thick filament

Answer 6

thin

Question 7

Structure of actin

Answer 7

Contains two twisted alpha helices

Question 8

Special feature of actin filaments?

Answer 8

They exhibit polarity

Question 9

What 2 proteins are associated with actin

Answer 9

Troponin & Tropomyosin

Question 10

What is the function of Titin in the sarcomere

Answer 10

Anchors the myosin filaments to the Z-line

Question 11

What is the function of CapZ in the sarcomere

Answer 11

Covers the positive end of actin filaments

Question 12

Shape and function of troponin

Answer 12

Globular protein

Binding site for Calcium

Question 13

Shape and function of tropomyosin

Answer 13

Rod-like filamentous protein
Spirals round actin to stabilise it
Seals myosin binding sites on actin

Question 14

What do we learn from looking at the length-tension curve on a sarcomere scale

Answer 14

At resting length, there is maximum contact between filaments so maximum tension can be generated
• Any shorter, there is excessive overlap between actin filaments which reduces the contact area and minimal forces can be generated
• Any longer (due to stretch), there is no overlap so there is NO contact area & minimal forces can be generated

Question 15

What are the 3 components to a length-tension curve on a whole muscle scale

Answer 15

Active tension
Passive tension
Total tension

Question 16

What is the active tension component of the length-tension curve on a whole muscle scale

Answer 16

Tension generated by muscle contraction

Question 17

What is the passive tension component of the length-tension curve on a whole muscle scale

Answer 17

Increase in tension due to stretching of connective tissues (e.g. tendons, epimysium) when contracting a muscle that has been stretched past the ideal/resting length

Question 18

What is active insufficiency

Answer 18

Failure to produce significant/sufficient force when the muscles are too short

Question 19

What is passive insufficiency

Answer 19

Failure to produce significant/sufficient force when the muscles are too stretched

Question 20

Describe the Hill Muscle model

Answer 20

A contractile element is in series with an elastic element and in parallel with another elastic element

Question 21

Describe the Hill Muscle model

Answer 21

A contractile element is in series with an elastic element and they are both in parallel with another elastic element

Question 22

What does the elastic element in series represent in the Hill Muscle model

Answer 22

This represents the tendons and cross-bridges

Question 23

What does the elastic element in parallel represent in the Hill Muscle model

Answer 23

Connective tissue in the muscle (epimysium, endomysium and perimysium)

Question 24

What factors affect force production in muscles? (3)

Answer 24

Length of muscle
Velocity of shortening
Amount of stimulation

Question 25

What is concentric contraction and examples

Answer 25

Where movement is caused by shortening of the muscle Extending the knee Lifting a dumbbell close to the chest

Question 26

What is an isometric contraction and examples

Answer 26

When there is no change in muscle length and thus no movement Holding a bicep at 90 degrees to the body

Question 27

What is the relationship between moment and joint angle in concentric contraction

Answer 27

The moment is in the same direction as joint angle change

Question 28

What is an eccentric contraction and examples

Answer 28

When a muscle increases in length to decelerate joint movement Extension phase of a bicep curl

Question 29

What is the relationship between moment and joint angle in eccentric contraction

Answer 29

The moment is in the opposite direction as joint angle change

Question 30

Place the 3 types of contractions in descending order of force they are able to produce

Answer 30

Eccentric > Isometric > Concentric

Question 31

Why is eccentric able to produce the most force ? (4)

Answer 31

Greater cross bridging due to greater length Contraction time (decreased rate of cross-bridge detachments) Passive tension in elastic components Elastic energy stored in the actin-myosin cross bridges

Question 32

How many times greater is the max eccentric tension than an isometric

Answer 32

1.25x greater

Question 33

How does velocity of ECCENTRIC contraction affect tension

Answer 33

Increasing velocity increases force up to a maximum

Question 34

How does velocity of CONCENTRIC contraction affect tension

Answer 34

Increases velocity decreases force to ZERO | a rapid concentric contraction will generate no/minimal force