Muscles & Joints

Question 1

How do muscles move?

Answer 1

In antagonistic pairs which move bone to and fro; only can pull not push so need a pair

Question 2

What are extensors and flexors?

Answer 2

Extensors = muscles which contract to extend the joint
Flexors = muscles which contract to retract/reverse movement

Question 3

Describe structure of synovial joint

Answer 3

Where bones meet, separated by cavity filled with synovial fluid
- tipped with layer of cartilage
- synovial cavity encased in synovial membrane
- synovial membrane surrounded by fibrous capsule
- bones joined by thin ligaments
- surrounded by muscle —> tendon joins muscle to bone

Question 4

Describe role of cavity in synovial joint

Answer 4

Filled with synovial fluid which acts as a lubricant

Question 5

Describe role of cartilage

Answer 5

Absorbs synovial fluid, acting as a shock protector and protects bone from friction

Question 6

Describe role of synovial membrane

Answer 6

Surrounds synovial cavity, secreting synovial fluid

Question 7

Describe properties of ligaments

Answer 7

Strong yet flexible

Question 8

What are the types of muscle found in the body and how are these controlled?

Answer 8

Skeletal muscle (controlled by voluntary NS, sends messages from CNS to nervous tissue), cardiac muscle (myogenic, muscle fibres contract using impulses from the heart itself) and smooth muscle (displays rhythmic contractions, controlled by autonomic NS)

Question 9

What is a muscle fibre and what is it made up from?

Answer 9

Many individual muscle cells fused together
Made up of myofibrils which are made up of sarcomeres

Question 10

Describe structure of a sarcomere

Answer 10

~ Z line at end of each sarcomere repeating units, at centre of I zone
~ A band across centre containing both actin and myosin, appears dark under electron microscope
~ apart from H zone in middle of A zone, only contains myosin, appears lighter
~ I band at ends contains only actin, appears lighter

Question 11

How do actin and myosin appear under an electron microscope?

Answer 11

Actin appears lighter as it is thinner and myosin appears darker as it is thicker

Question 12

How do bands in the sarcomere change shape during contraction?

Answer 12

• Distance between Z lines becomes shorter
• I band becomes shorter
• H zone becomes shorter
• A band stays the same
  = actin is pulled over myosin

Question 13

What is the role of tropomyosin?

Answer 13

Forms a fibrous strand around actin filament, covering binding sites

Question 14

Describe process in sliding filament mechanism

Answer 14

1) Calcium ions bind to tropomyosin - released by sarcoplasmic reticulum (shared cytoplasm of myosin and actin)
2) Shape of tropomyosin altered, moving it along
3) Binding sites on action exposed and myosin heads move and bind to actin
4) Myosin head changes angle, tilts backwards and slides actin over myosin —> this is a power stroke, requires energy from hydrolysis of ATP on myosin head

Question 15

What are the two types of skeletal muscle fibres?

Answer 15

Slow twitch and fast twitch

Question 16

Describe adaptations of fast twitch muscle

Answer 16

Carry out anaerobic respiration
- thicker and more numerous myosin filaments
- store phosphocreatin which rapidly generates ATP in anaerobic conditions
- high concentration of glycogen

Question 17

Which forms of exercise are associated with fast twitch muscle fibres?

Answer 17

Short but intense (e.g. sprinting), build up of lactic acid from anaerobic respiration means it cannot occur for long periods

Question 18

Describe adaptations of slow twitch muscle fibres

Answer 18

Carry out aerobic respiration
- numerous mitochondria to produce ATP
- large store of myoglobin storing oxygen
- rich supply of blood vessels to deliver oxygen and glucose

Question 19

Which form of exercise is associated with slow twitch muscle fibres?

Answer 19

Endurance (e.g. marathon running)