Movement (11.2)

Question 1

Describe the movement systems in the body.

Answer 1

• The skeletal system - consists of bones that act as levers and provides a structure for the muscles to pull.
• The muscular system - muscles deliver the force required to move one bone in relation to another.
• The nervous system - delivers signals to the muscles which cause them to constrict and create movement.

Question 2

Define a skeleton.

Answer 2

A rigid framework that functions to provide support and protection for body organs. They provide a surface for muscle attachment.

Question 3

Describe endoskeletons.

Answer 3

An internal skeleton. An example is humans.

Advantages of endoskeletons are that they allow for even growth/development and fast movement. Disadvantages are that they do not provide the same level of protection as exoskeletons.

Question 4

Describe exoskeletons.

Answer 4

An external skeleton. Sometimes known as ‘shells’. An example is lobsters.

Advantages of exoskeletons are that they provide protection against predators and protect the internal body. Disadvantages are that the exoskeleton cannot grow so must be shed if the organism wants to expand.

Question 5

Describe hydrostatic skeletons.

Answer 5

Flexible skeletons that are supported by fluid pressure. An example is jellyfish.

Advantages of hydrostatic skeletons is that they have a fluid shape, are well suited to their environment and have rapid healing. Disadvantages are that they have little protection.

Question 6

Define joints.

Answer 6

The part of the body where two or more bones meet to allow movement. They function to maintain structural stability by allowing certain movements but not others.

Question 7

Define synovial joints.

Answer 7

Capsules that surround the articulating surfaces of two bones. They allow certain movements but not others.

Question 8

Give the types of synovial joints in the body.

Answer 8

• Ball and socket joints eg. shoulder and hip. Allows for movement in three planes.
• Hinge joints eg. fingers, toes, elbows and knees. Allows for movement in one plane.
• Pivot joints eg. the neck. Allows limited rotating movements.
• Ellipsoidal joints eg. the wrists. Allows all types of movement apart from pivotal movements.

Question 9

What makes up a joint?

Answer 9

Cartilage - A connective tissue covering the bones which helps to reduce the friction of movement. Also helps to absorb shock.
Synovial fluid - A fluid secreted by the synovial membrane that provides oxygen and nutrition to the cartilage and also lubrication to reduce friction.
Joint capsule – Seals the joint space and provides stability by restricting the range of possible movements.

Question 10

What is the purpose of muscles?

Answer 10

Muscles connect to bones (via tendons) and contract to provide the force required to produce movement.

Question 11

Give the three types of muscle tissue.

Answer 11

1) Cardiac muscle cells: located in the walls of the heart, appear striated and are under involuntary control.
2) Smooth muscle cells: located in the walls of hollow visceral organs (except the heart), appear spindle shaped and are under involuntary control.
3) Skeletal muscle fibres: located in muscles attached to the skeleton, appear striated and are under voluntary control.

Question 12

What are antagonistic pairs?

Answer 12

Muscles that work in pairs. One muscle contracts (called the agonist) while the other relaxes (called the antagonist).

Question 13

Give examples of antagonistic muscles.

Answer 13

Abs and lower back.
Biceps and triceps.
Back and chest.
Quadriceps and hamstring.

Question 14

Describe the elbow joint.

Answer 14

The elbow joint is a hinge joint. It is capable of angular movement in one direction (flexion and extension). It may also be capable of a small amount of rotation.

The bicep and tricep muscles within the elbow are antagonistic.

Question 15

Give the function of the following components of the elbow:
Bicep (muscle)
Tricep (muscle)
Joint capsule (joint)
Synovial fluid (joint)
Cartilage (joint)
Humerus (bone)
Radius (bone)
Ulna (bone)

Answer 15

Bicep: Bends the forearm (flexion).
Tricep: Straightens the forearm (extension).
Joint capsule: Seals joint space and limits range of movement to promote stability.
Synovial fluid: Provides oxygen and nutrients to the cartilage and lubrication to reduce friction.
Cartilage: Absorbs shock and reduces the friction of movement.
Humerus: Anchors muscle (muscle origin).
Radius: Acts as a forearm lever for the biceps.
Ulna: Acts as a forearm lever for the triceps.

Question 16

Explain the action of antagonistic muscles in insects.

Answer 16

Many types of insects have hind legs that are specialised for jumping. The jointed exoskeleton of the hind leg is divided into three parts: femur, tibia and tarsus. The femur and tibia are connected by two antagonistic muscles: the flexor muscle and extensor muscle.

When the flexor muscle contracts, the extensor muscle relaxes and the tibia and femur are brought closer together. This retracts the hind quarters in preparation for pushing off the ground.

When the extensor muscle contracts, the flexor muscle relaxes and the tibia is pushed away from the femur. This extends the hind quarters and causes the insect to jump.

Question 17

Describe the organisation of muscle fibres.

Answer 17

A muscle consists of tightly packaged muscular bundles. Each bundle contains multiple muscle fibres. Within each muscle fibre are cylindrical structures called myofibrils. The myofibrils consist of repeating units called sarcomeres which have light and dark bands.

Question 18

Describe the specialised features in each muscle fibre.

Answer 18

Each individual muscle fibre has specialised features designed to facilitate muscle contraction.

• Multinucleate (as fibres are formed from the fusion of many individual muscle cells).
• Large number of mitochondria (for ATP hydrolysis).
• Specialised endoplasmic reticulum (stores calcium ions).
• Myofibrils made up of two different myofilaments (actin and myosin).

Question 19

What are the two protein myofilaments in sarcomeres?

Answer 19

Myosin - thick dark filaments.
Actin - thin light filaments.

Question 20

Describe muscle contraction in terms of sarcomeres.

Answer 20

An electrical impulse reaches the sarcomere and depolarisation causes the sarcoplasmic reticulum to release stores of calcium ions. At high concentrations of calcium, myosin cross bridges are formed with actin filaments. The cross bridges are broken by ATP. ATP hydrolysis causes the myosin heads to swivel and change orientation. The repositioning of the myosin heads move the actin filaments towards the centre of the sarcomere. The sliding of actin along myosin therefore shortens the sarcomere, causing muscle contraction.