Muscles and Movement

Question 1

Skeletal system

Answer 1

Consists of bones or exoskeleton which act as levers and provide a structure for the muscles to pull

Question 2

Muscular system

Answer 2

Muscles contract and deliver the force needed to move one bone in relation to another

Question 3

When do muscles exert a force?

Answer 3

When they contract

Question 4

Antagonistic muscles

Answer 4

Muscles that work in pairs and cause opposite movements. When one contracts, the other relaxes

Question 5

What do bones provide?

Answer 5

The anchorage and insertion for muscles and act as levers

Question 6

How are muscles attached to bones?

Answer 6

By tendons at both ends of the muscle

Question 7

Anchorage

Answer 7

A firm point of attachment that does not move when the muscle contracts

Question 8

Insertion

Answer 8

Muscle contraction causes the bone or section of exoskeleton forming the insertion to move

Question 9

How are bones connected to other bones?

Answer 9

Ligaments

Question 10

Joint

Answer 10

Junctions between bones

Question 11

Synovial joints

Answer 11

Allow certain movements but not others

Question 12

What are the three parts of a synovial joint?

Answer 12

Cartilage
Synovial fluid
Joint capsule

Question 13

Annotate the diagram of the human elbow joint

Question 14

Biceps

Answer 14

Flexor muscle- used to bend the arm at teh elbow

Question 15

Triceps

Answer 15

Extensor muscle- used to straighten the arm

Question 16

Radius

Answer 16

Bone that is the insertion for the biceps and acts as forearm lever for the biceps

Question 17

Ulna

Answer 17

Bone that is the insertion for the triceps and acts as forearm lever for the triceps

Question 18

Humerus

Answer 18

Bone that provides a firm anchorage for the biceps and triceps

Question 19

Tendon

Answer 19

Attaches muscle to bone

Question 20

Cartilage

Answer 20

Layer of smooth, tough tissue that covers the surface of the bones at the joint. It helps to prevent friction where the bones could rub against each other. It also absorbs shocks

Question 21

Synovial fluid

Answer 21

Fills the cavity between the cartilage-covered surfaces of the bones. It lubricates the joint and helps to prevent friction

Question 22

Joint capsule

Answer 22

Tough ligamentous covering to the joint. It seals the joint, holds the synovial fluid and helps to prevent dislocation

Question 23

Ligaments

Answer 23

Tough tissue connecting the humerus with the ulna and radius. Holds the bones in proper alignment, restrict movement and help to prevent dislocation

Question 24

Describe antagonistic muscles in an insect leg

Answer 24

Insects leg are divided in three parts: femur, tibia and tarsus. There is a pair of antagonistic muscles inside the femur which causes the tibia to flex and extend. The tendons at the distal ends of these muscles are attached to opposite sides of the exoskeleton of the tibia, so one of them is the flexor of the joint and the other the extensor

Question 25

What happens when a grasshopper prepares to jump?

Answer 25

The flexor muscle contracts bringing the femur and the tibia closer. This causes the tibia to bend. The extensor muscle then contracts extending the tibia and producing a propelling force.

Question 26

Describe the composition of skeletal muscle

Answer 26

It caused of muscle fibres which are multinucleated
The plasma membrane is called sarcolemma
Each muscle fibre has many myofibrils. Around each myofibrils there is sarcoplasmic reticulum.
Each myofibrils ahs many repeating units of sarcomeres.

Between the myofibrils are large numbers of mitochondria

Question 27

Describe the structure of a sarcomere

Answer 27

• Sarcomeres have light and dark bands giving it a striated appearance
• Consists of thin actin filaments and thick myosin filaments
• Through the centre of each light band is a Z-line
• One sarcomere is the part of a myofibril between one Z-line and the next
  -The part of the sarcomere containing myosin is the dark band and the part containing only actin filament is the light band.

Question 28

Draw a repeating unit of sarcomere

Question 29

Briefly describe muscle contraction

Answer 29

Skeletal muscle contracts when stimulated by a motor neuron. Contraction is achieved by the sliding of actin and myosin filaments over each other. The myosin filaments pull the actin filaments inwards towards the centre of the sarcomere. The sliding of the filaments requires energy from ATP.

Question 30

Describe the mechanism of muscle contraction

Answer 30

1. Myosin filaments have heads which form cross-bridges when bound to binding sites on actin filaments
2. ATP binds to the myosin heads causing them to detach from the actin binding sites, thus breaking the cross-bridges
3. ATP is hydrolysed to ADP and phosphate, causing the myosin heads to change their angle. The heads are said to be ‘cocked’ as they are storing potential energy from ATP
4. The myosin heads attach to adjacent binding sites on actin that are further from the centre of the sarcomere than the previous sites.
5. The ADP is released and the heads push the actin filament inwards towards the centre of the sarcomere. This is called the power stroke.
6. The Z lines are pulled closer together, shortening the sarcomere

Question 31

Describe the CONTROL of mechanism contraction

Answer 31

1. In the relaxed muscle, the regulatory tropomyosin blocks the binding sites on actin
2. Muscle fibres are stimulated to contract by motor neurons. When a nerve impulse arrives at motor end plates, the neurotransmitter acetylcholine is released into the synaptic cleft
3. Acetylcholine diffuses across the synaptic cleft and binds to receptors in the membranes of muscle fibres causing their depolarisation which is spread through the muscle fibres via T tubules
4. This causes the sarcoplasmic reticulum to release Ca2+
5. The calcium ions binds to troponin a protein associated with actin filaments causing the shape of troponin to change
6. This in turn causes tropomyosin to move, exposing the binding sites on actin
7. This allows myosin heads to form cross-bridges by binding to actin and cause the power stroke, as myosin filaments pull actin towards the centre of the sarcomere.

When the motor neuron stops sending signals, calcium ions are pumped back into the sarcoplasmic reticulum.

Question 32

How has radioactive calcium been used?

Answer 32

To investigate the control of muscle contraction and it was shown that radioactive calcium is concentrated in the region of overlap.

Question 33

How do you measure the length of one sarcomere?

Answer 33

Measure the distance in mm from the start of one dark band to the start of a dark bands away.
Divide by ten to find the length of one sarcomere in the micrograph.
Concert the length to micrometre by multiplying by 1000
Divide this length by the magnification of the micrograph

Question 34

How can you tell a contracted muscle fibre from a micrograph?

Answer 34

The light band decreases, but the dark band stays the same. Z lines are closer and sarcomere is shorter.