BIOLOGY O LEVEL(FORM THREE) NOTES – MOVEMENT

MOVEMENT

Movement is the act of changing position or posture by the whole organism or part of the organism.

Types of movement

1. Movement of curvature (growth movement)
2. Movement of locomotion

1. MOVEMENT OF LOCOMOTION

This is the type of movement whereby the whole organism moves from one place to another.

Movement in locomotion is shown in all animals and some protoctists exhibit a variety of movements. These are:

1. Amoeboid
2. Ciliary
3. Muscular
4. Flagellar

I. AMOEBA MOVEMENT

This is the type of movement exhibited by some protozoans such as Amoeba and white blood cells (WBC). Amoeba movement is caused by streaming of the cytoplasm towards a peripheral region of the cell resulting in projections known as PSEUDOPODIUM.

The cytoplasm streaming into these projections is withdrawn from others and flows in one direction to bring about movement.

II. CILIARY MOVEMENT

This is the type of movement whereby some protozoan organisms use cilia for movement.

These protozoans include paramecium and larvae of some aquatic animals. The body of such organisms is covered by thousands of small hair-like structures called cilia. Movement is brought about by the coordinated backward and forward beating of cilia. The backward pushing of water propels the organism forward.

III. FLAGELLAR MOVEMENT

This is the type of movement exhibited by some organisms which possess flagella.

Such organisms include Euglena, Chlamydomonas, Trypanosome, and some bacteria.

Flagella are very similar in structure to cilia but are much longer. In Euglena, the whipping of the flagellum causes the swirling of the water around the organism. This swirling makes the organism rotate while moving forward.

IV. MUSCULAR MOVEMENT

This is the type of movement exhibited by the contraction and relaxation of muscles. Since muscles alone cannot bring about fast movement, most animals have a firm and hard base for support and attachment of muscles. This firm and hard base is called the skeleton.

Importance of movement in animals and plants

• Organisms move in search of food and shelter.
• Organisms move away from a negative stimulus, e.g., predator, chemicals, fires, to secure protection.
• Movement enables animals to come together for mating.
• Movement enables organisms to move towards positive stimuli such as light, gravity, and water.

MOVEMENT OF THE HUMAN BODY

Contraction and relaxation of muscles cause muscular movement in vertebrate animals such as humans.

Movement of the human body is made possible by supportive structures like the skeleton, which provides attachment for muscles and other body organs. The muscle fibers become shorter on contraction. Muscles are paired, producing movement in opposite directions.

One muscle contracts while the other relaxes; this is called antagonistic action.

THE HUMAN SKELETON

The skeleton is a framework of tissue supporting a human or animal’s body.

The human/mammalian skeleton consists of the following major parts:

1. Skull
2. Vertebral column
3. Limb
4. Girdles

The human skeleton is made up of separate units which are joined together; the points of junction where two units meet are called joints.

The skull, sternum, ribs, and vertebral column form the axial skeleton. The limbs and limb girdles form the appendicular skeleton.

TYPES OF SKELETON

There are 3 types of skeleton:

1. Hydrostatic skeleton
2. Exoskeleton
3. Endoskeleton

I. HYDROSTATIC SKELETON

This is a skeleton found in soft-bodied animals. The body tube is filled with fluid that produces pressure when muscles around it contract, bringing about movement. Example: Earthworm.

II. EXOSKELETON

These are skeletons found outside of the body, typical of arthropods, e.g., insects.

III. ENDOSKELETON

This is a rigid framework of bones and cartilages surrounded by muscles that contract and relax, bringing about movement.

Bone is one of the hardest tissues and is found only in vertebrates.

Cartilage is softer and more flexible tissue than bone. In animals, cartilage is found in the nose, part of the ear, and at the ends of bones.

FUNCTIONS OF SKELETON

1. Support: The skeleton provides a rigid framework which supports softer parts of the body and provides attachment for muscles and body organs.
2. Locomotion: The skeleton enables the organism to move from one place to another.
3. Protection: It protects delicate internal organs. For example, the skull protects the brain, the sternum protects the spinal cord, and the ribcage protects the lungs and heart.
4. Formation of blood cells: Red and white blood cells are made in the bone marrow.
5. Shape: The skeleton gives animals a definite shape.
6. Mineral storage: It stores minerals such as calcium and phosphorus.

The human skeleton system is divided into two major parts:

1. The Axial skeleton
2. The Appendicular skeleton

1. THE AXIAL SKELETON

The axial skeleton consists of four parts:

1. The skull
2. Ribcage
3. Vertebral column
4. Sternum

The skull

The skull is made up of small bones joined together to form the cranium. The bones are joined together by irregular edges called sutures, which are immovable joints.

• It acts like a box enclosing and protecting the brain, parts of the inner ear, nose, and eyes.
• It consists of the upper and lower jaw bones which hold teeth.
• Parts of the skull form hollows which protect the eyes (orbits) and ears.
• The main function of the skull is to protect the brain, olfactory organs, middle and inner ear, and the eyes.

Ribcage and sternum

The ribcage is composed of the sternum and ribs. These bones form a thoracic cage which encloses the thoracic cavity, protecting the heart, lungs, and major blood vessels.

It consists of 12 pairs of ribs joined to thoracic vertebrae at the back and sternum at the front.

The last 2 ribs that are not joined at the sternum are known as floating ribs.

This arrangement enables a protective cage of bones to be formed which encloses the heart and lungs. Between the ribs are intercostal muscles. The ribs are associated with the axial skeleton.

The sternum consists of small bones known as sternebrae. The sternum forms part of the ribcage and provides surface for attachment of ribs.

III. Vertebral column

This is the main axis of the body.

It is made up of 33 small bones known as vertebrae. Between two adjacent vertebrae is a cartilage known as the intervertebral disc which acts as a shock absorber and reduces friction.

The main function of the vertebral column is to support the body and protect the spinal cord. The backbones have five types of vertebrae:

• Cervical
• Thoracic
• Lumbar
• Sacral
• Caudal

a) Cervical vertebrae

There are 7 short cervical vertebrae found in the neck region. The first below the skull is the atlas, followed by the axis.

The atlas articulates with the skull to allow nodding movement of the head.

The axis allows rotational movement of the atlas which acts as a pivot. This allows turning or side-to-side movement of the head (e.g., shaking the head to say no). Cervical vertebrae support the head region and protect blood vessels that pass through their canals. They also provide surface for attachment of neck muscles.

b) Thoracic vertebrae

These are found in the chest region; there are 12 vertebrae. The thoracic vertebrae with the ribs and sternum form the thoracic cage.

The main role of the thoracic cage is to protect the heart, lungs, and major blood vessels. It also plays a major role in breathing movements.

c) Lumbar vertebrae

There are five lumbar vertebrae in humans, seven in rabbits, and six in rats.

They are short bones found in the abdominal region. Lumbar vertebrae have a number of projections that provide surface for attachment of abdominal muscles and muscles of the lower half of the back. The large thick centrum gives support to the upper half of the body.

Lumbar vertebrae permit bending, sideways movement, and rotation of the trunk. This is the region where large muscles of the abdomen are attached.

d) Sacral vertebrae

Sacral vertebrae are fused together to form the sacrum, found in the sacral region. The sacrum provides a large surface area for the attachment of muscles of the back.

e) Caudal vertebrae

These are found in the tail region. The number of caudal vertebrae varies from one animal to another depending on the size of the tail. In humans, there is no external tail; there are four caudal vertebrae which form the coccyx (with no significant function).

2. THE APPENDICULAR SKELETON

The appendicular skeleton is composed of the appendage limbs which are attached to the axial skeleton.

There are two types of limbs:

1. Forelimbs
2. Hind limbs

I. FORELIMBS

Forelimbs are attached to the axial skeleton at the anterior part of the body. Forelimbs comprise the following parts:

Pectoral girdle

b) Humerus

Is the long bone of the upper arm and provides surface for attachment of muscles.

c) Ulna and Radius

d) Carpals, metacarpals, and phalanges

Carpals are nine small bones which form the wrist. They articulate with the radius and ulna at the upper end and metacarpals at the lower end.

• They allow free movement of the hands and wrist.
• They provide surface for attachment of wrist muscles.

Metacarpals are five slightly elongated bones found in the palm.

• Each of them articulates with the phalanges of finger bones.
• They provide surface for attachment of palm muscles.
• They support and maintain the shape of the arm.

Phalanges

Phalanges form the skeleton of the fingers.

2. HIND LIMBS

Hind limbs are attached to the axial skeleton at the posterior part of the body. Hind limbs comprise the following:

a) Pelvic girdle

Is made up of several bones found around the hip region. It contains two halves, the left and right. Each half lies on either side of the vertebral column. In this way, it supports the hind limbs.

Pelvic girdles have two bones known as pubic bones. Each pubic bone comprises three bones known as ischium, ilium, and pubis. The ischium and ilium are fused together.

The size of the pubic cavity is very important in females during birth, causing the widening of the female girdle.

• The pelvic girdle forms a protective cage around vital organs such as female reproductive organs.
• It also supports legs, articulating with the head of the femur to form the hip joint.
• It articulates with the sacrum and provides for a tail where it is present.

b) Femur

Is a long bone on the upper part of the hind limb (thigh region).

• The head of the femur fits in the pelvic girdle to form the hip joint.
• It articulates with the tibia at the lower end to form the knee joint.
• It provides surface for the attachment of leg muscles and supports the thigh.

c) Tibia and fibula

These are long bones of the lower leg.

• Tibia is a very long bone, found on the side of the big toe. It may be free or partly fused to the smaller fibula which lies alongside it.
• Fibula is much smaller in size and fused to the tibia in the lower part of the leg.

A small round bone called the patella (knee cap) lies in front of the knee joint; it prevents the leg from bending upwards at the knee.

• The tibia and fibula support the front part of the leg below the knee.
• They provide surface for attachment of the knee (shin) muscles.
• They articulate with the femur to form the knee joint, and with metatarsals to form the ankle joint.
• Red blood cells are manufactured in the tibia and fibula bone marrow.

d) Tarsals, metatarsals, and phalanges

Tarsals are six small bones in the ankle. Two of them are elongated and one projects backwards to form the heel bone. The tarsals provide surface for attachment of ankle muscles. The heel bone prevents the foot from bending backwards.

Metatarsals are elongated bones in the foot. There are five in humans and most animals. Each one leads to a phalange. The metatarsals provide surface for attachment of foot muscles and support and maintain the shape of the foot.

Functions

• Tarsals articulate with fibula to form the ankle joint.
• Tarsals articulate with metatarsals to form the foot.
• Metatarsals articulate with phalanges to form toes.

DEFINITIONS OF TERMS

1. Bone: A hard, tough connective tissue composed of mineral salts such as calcium and phosphate.

2. Cartilage: A soft tissue found in the trachea, ear, nose, and at the ends of bones, especially at joints, to reduce friction.
3. Ligaments: Fibrous tissues which join one bone to another. Ligaments are elastic to allow movement at a joint.
4. Tendon: Tough connective tissue which attaches a muscle to bone. Tendons are inelastic to firmly attach muscles to bones.
5. Joints: Areas or regions where bones meet. Joints provide articulation between bones, making movement possible.

Types of joints

1. Movable joints
2. Immovable joints

1. Fixed/immovable joints

These joints do not allow movement of bones. Examples include pelvic girdles and sutures (bones found in the skull).

2. Movable joints

These joints allow movement of bones. Examples include the hip joint and shoulder joint.

Types of movable joints

These are classified according to the movement of bones at the joint in different shapes or structures. There are four types:

1. Ball and socket joints
2. Hinge joints
3. Gliding joints
4. Pivot joints (peg and socket joints)

a) Ball and Socket joint

This type of movable joint allows movement of bones in many directions.

These joints allow the greatest flexibility of all joints, e.g., hip joint and shoulder joint.

It is called a ball and socket joint because the round head, which looks like a ball of one bone, fits into the socket of another bone. At the shoulder, the rounded head of the humerus fits into the socket of the pectoral bone. Some joints have synovial fluid which reduces friction by lubricating the bones, e.g., hip, shoulder, and knee joints.

b) Gliding joints (sliding)

These joints occur between the vertebrae. This type of joint is found where two or more bone surfaces move over each other. It allows movement in two directions. It occurs at the wrist and ankle and allows the hand and foot to be moved up and down or rotated slightly.

They lack fluid between them and instead have a layer of cartilage that reduces friction.

c) Hinge joints

This joint allows movement of bones in one direction only. It is called a hinge joint because it operates like the hinge of a door, which allows movement in one direction only. Examples include the elbow, knee, finger knuckles, and joints between the phalanges of toes.

d) Pivot joint (on the neck)

The skull pivots at the first cervical vertebra (atlas). The joint allows the head to move sideways, e.g., when a person shakes their head to say no. It also allows nodding movement.

Adaptations of joints to movement

• Freely movable joints such as those of the limbs may cause dislocation; hence, movement joints involve more than one bone. Dislocation and friction are prevented by ligaments which hold the bones together.
• Knocking of bones against each other and strain due to compression are prevented by cushioning in the joints, such as the cartilage discs in the intervertebral column.

In freely movable joints such as those of limbs, dislocation is prevented by ligaments which hold bones together.

• Joints which support weight are provided with cushions. The cushion absorbs compression due to weight. Cushioning in the joint is provided by the disc (in the intervertebral column) of cartilage as in the case of vertebrae joints.

MUSCLES

Muscle is a tissue consisting of cells that have the capacity to contract and exert a pull.

Types of muscles

1. Skeletal muscle (voluntary)
2. Cardiac muscle (involuntary)
3. Smooth muscle (involuntary)

Muscles are tissues that cover the skeleton.

The skeleton alone can’t bring about locomotion and movement of the body. To bring about movement, there must be muscles. These muscles are attached to the bones. Muscles are composed of many elongated cells called muscle fibres which are able to contract and relax.

During relaxation, muscles can be stretched but they show elasticity which allows them to regain their original size and shape after being stretched.

Muscles are made up of specialized tissues known as contractile tissue. When these tissues contract, they become shorter and tighter, causing movement.

1. SKELETAL MUSCLE

These muscles are attached to bones of the skeleton. They are made up of long fibres and cover the skeleton. They are also known as striated or voluntary muscles because they are controlled by the will.

Skeletal muscles can contract and relax quickly but get fatigued quickly.

Functions

• Skeletal muscles are concerned with movement of the limbs and parts of the skeleton.

2. SMOOTH MUSCLE

These muscles are found on the walls of internal organs.

• Such internal organs include the alimentary canal, bladder, uterus, sperm ducts, and blood vessels.
• Smooth muscles are controlled by the involuntary nervous system, meaning they cannot contract at will. So they are involuntary muscles.
• Smooth muscles contract slowly and get fatigued relatively slowly.

Functions of smooth muscle

• They contract and relax to cause movement in different organs, e.g., peristalsis in the alimentary canal causes movement of materials through the canal with the help of smooth muscle.

3. CARDIAC MUSCLE

These muscles are found only in the heart. Their muscle fibres branch and connect to each other like a network (interconnecting network).

Cardiac muscle has the capacity to contract and relax throughout life without becoming fatigued.

The contractions of these muscles are not initiated or helped by the nervous system, so they are involuntary muscles.

MUSCLE AND MOVEMENT

The skeleton alone cannot bring about locomotion and movement of body parts such as arms, fingers, and jaws when the arm is straightened.

The muscles above the arm become thin while those below become thick. The bending and straightening of the arm is brought about by two sets of muscles located above and below the humerus.

The muscles above the humerus are called biceps and those at the back are called triceps.

Bending of the arm is brought about by contraction of muscles called flexors and relaxation of triceps muscles called extensors. For the arm to straighten, the triceps contract and the biceps relax.

Muscles which work as pairs in opposition to one another are called antagonistic pairs. Their antagonistic action is necessary to bring about continued movement. Therefore, biceps and triceps are known as antagonistic muscles. Muscles are attached to bones at both ends by strong, inelastic fibres called tendons.

Muscle contraction

• For muscle to contract, energy is required. This energy is derived from respiration and is found in the muscle cells in the form of ATP.
• During muscle contraction, ATP is broken down to ADP, thereby releasing energy. The released energy is used to cause the muscle tissue to contract.

MUSCLE CRAMPS

These are sudden, involuntary contractions of muscles or groups of muscles.

The tissue may become hard and knotted. Cramps in skeletal muscles may occur after prolonged exercise, e.g., swimming. They may also be caused by lack of salt in the body. Stretching and warming the affected muscles can help to relieve cramps.

Causes of muscle cramps

1. Dehydration
2. Lack of magnesium
3. Muscle fatigue
4. Excessive exercise

Prevention of muscle cramps

• Stretch muscles more often.
• Do regular physical exercise.
• Take salt through a solution of water.

GROWTH OF CURVATURE (MOVEMENT IN PLANTS)

Since most plants remain fixed to the ground, they are incapable of moving from one place to another.

However, their leaves, stems, and roots may show growth responses. These responses result in parts of the plants growing away from or toward a stimulus; this is called growth of curvature.

Growth movement enables plants to obtain their requirements despite being fixed in one place.

Growth curvature movements are the result of tropic responses.

Tropic movement is when a plant moves either towards or away from a stimulus. If the response is toward the stimulus, it is referred to as a positive (+) response.

If the response is away from the stimulus, it is referred to as a negative (-) response.

Movement or growth of curvature is categorized into two groups:

1. Tropic movement or tropism
2. Nastic movement

Tropism

Tropism is movement by plant organs in response to a unilateral stimulus in which the direction of the movement is related to the direction of the stimulus.

Tropic Movement includes:

1. Phototropism: Growth movement in response to the source of light.
2. Hydrotropism: Movement by which roots grow toward water.
3. Geotropism: Movement in response to the stimulus of gravity.
4. Chemotropism: Growth movement in response to a source of chemicals.
5. Haptotropism: Movement due to touch.

II. Nastic movement

Nastic movement is a non-directional response.

Examples of nastic responses include the opening and closing of flowers and leaves of certain plants in response to changes in light intensity and temperature, closing of flowers of carnivorous plants when touched, and the closing and opening of dandelion flowers in response to changes in humidity.

Tropic and nastic movements of plants are responses to external stimuli.

Importance of Tropic Movement

• Exposes the leaves of the plant to trap maximum sunlight for photosynthesis.
• Enables plants with weak stems to obtain mechanical support.