11.2 Movement

Question 1

What are exoskeletons?

Answer 1

Exoskeletons are external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects.

Question 2

What is a bone’s role in movement?

Answer 2

Bones and exoskeletons facilitate movement by providing an anchorage for muscles and by acting as levers. Levers change the size and direction of forces. In a lever there is an effort force, a pivot point called the fulcrum and a resultant force. The relative positions of these determine the class of lever.

Question 3

What is the fulcrum?

Answer 3

Pivot point of a lever.

Question 4

What are the classes of lever?

Answer 4

First class - EFFORT FULCRUM RESULTANT
Second class - FULCRUM RESULTANT EFFORT
Third class - FULCRUM EFFORT RESULTANT

Question 5

Which is the bicep?

Answer 5

The front muscle of the arm, the one on top that shows muscle

Question 6

What is the tricep?

Answer 6

The back muscle of the arm

Question 7

What is the humerus?

Answer 7

The bone in the arm between the biceps and triceps.

Question 8

What is the radius?

Answer 8

The smaller bone on top in the lower half of the arm

Question 9

What is the ulna?

Answer 9

The larger bone below in the lower half of the arm

Question 10

What is a first class lever?

Answer 10

Effort fulcrum resultant

For example nodding your head backwards

Question 11

What is a second class lever?

Answer 11

Fulcrum resultant effort

For example lifting up on to your tip toes

Question 12

What is a third class lever?

Answer 12

Fulcrum effort resultant

For example moving your arm down.

Question 13

What are antagonistic muscles?

Answer 13

Skeletal muscles occur is pairs that are antagonistic. This means that when one muscle contracts, the other relaxes. Antagonistic muscles produce opposite movements at a joint. For example, in the elbow, the triceps extends the forearm while the biceps flex the forearm.

Question 14

How does the hind-leg of a grasshopper work?

Answer 14

The grasshopper has a jointed back leg. The flexor muscles are on the inside of the upper back leg, the extensor muscles are on the outside. When the grasshopper is preparing to jump the flexor (inside) muscle contracts and the extensor relaxes bringing the leg in. When he jumps the flexor muscles relax and the extensor muscles contract bringing the leg out.

The fulcrum is called the tibia.

LOOK AT DIAGRAM 478

Question 15

What is a joint?

Answer 15

A point where bones meet.

Question 16

What does cartilage do?

Answer 16

It is a touch smooth tissue that covers the regions of bone in the joint. It prevents contact between regions of bone that might otherwise rub together and so helps to prevent friction. It also absorbs shocks that might cause bones to fracture.

Question 17

What is synovial fluid?

Answer 17

Synovial fluid fills a cavity in the joint between the cartilages on the ends of the bones. It lubricates the joint and so helps to prevent the friction that would occur if the cartilages were dry and touching.

Question 18

What is a joint capsule?

Answer 18

The joint capsule is a tough ligamentous covering to the joint. It seals the joint and holds in the synovial fluid and it helps to prevent dislocation.

Question 19

What is a hinge joint?

Answer 19

Only allows 2 movements

Question 20

What is a pivot joint?

Answer 20

Allows side to side movement.

Question 21

What is the structure of muscle fibres?

Answer 21

Skeletal muscle fibres are multinucleate and contain specialised endoplasmic reticulum.
Striated muscle is composed of bundles of muscle cells known as muscle fibres. Although a single plasma membrane called the sarcolemma surrounds each muscle fibre, there are many nuclei present and muscle fibres are longer than typical cells. These features are due to the fact that embryonic muscle cells fuse together to form muscle fibres.
A modified version of the endoplasmic reticulum extends throughout the muscle fibre. It wraps around ever myofibril conveying the signal to contract to all parts of the muscle fibre at once. The sarcoplasmic reticulum stores calcium. Between the myofibrils are large numbers of mitochondria which provide ATP for contraction.

Question 22

What are skeletal muscles?

Answer 22

Muscles connected to bones

Question 23

What is the sarcoplasmic reticulum?

Answer 23

A modified version of the endoplasmic reticulum extends throughout the muscle fibre. It wraps around ever myofibril conveying the signal to contract to all parts of the muscle fibre at once. The sarcoplasmic reticulum stores calcium. Between the myofibrils are large numbers of mitochondria which provide ATP for contraction.

Question 24

What are myofibrils?

Answer 24

These are parallel elongated structures in muscle fibres. They have alternating light and dark bands which give striated muscle its stripes.

Question 25

What is the Z line?

Answer 25

A line in a myofibril which is dark in a section of light. The part of a myofibril between one Z line and the next is called a sarcomere?

Question 26

What is a sarcomere?

Answer 26

The area of a myofibril between one Z line and the next. It is the functional unit of the myofibril.
It is made up of thick myosin filaments and thin actin filaments.

Question 27

What are the light and dark bands of a sarcomere?

Answer 27

ANYTHING WITH ACTIN THERE IS DARK, ANYTHING WITHOUT ACTIN IS LIGHT.

Question 28

How do you draw a sarcomere?

Answer 28

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Question 29

How do muscles contract?

Answer 29

In a relaxed muscle, the regulatory protein called tropomyosin blocks the binding sites on actin.

Question 30

How do muscles contract?

Answer 30

In a relaxed muscle, the regulatory protein called tropomyosin blocks the binding sites on actin. When a motor neurone sends a signal to a muscle fibre to make it contract, the sarcoplasmic reticulum releases calcium ions. These calcium ions bind to a protein called troponin which causes tropomyosin to move, exposing actin’s binding sites. Myosin heads then bind and swivel towards the centre of the sarcomere, moving the actin filament a small distance.

For this to significantly contract the muscle it needs to happen repeatedly. And so the heads need to come apart in order to contract again.

ATP causes the breaking of the cross bridges by attaching to the myosin heads, this changes their shape and causes them to detach from the binding sites on actin. Hydrolysis of the ATP to ADP and phosphate, provides energy for the myosin heads to swivel outwards away from the centre of the sarcomere - this is sometimes called the cocking of the head. New cross bridges are formed by the binding of myosin heads to actin at binding sites adjacent to the ones previously occupied.
Energy stored in the myosin head when it was cocked causes it to swivel inwards towards the centre of the sarcomere, moving the actin filament a small distance. This sequence continues until the motor neurone stops sending signals to the muscle fibre.