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Support and Movement

2nd Year Biology Notes

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Support and Movement
Irritability

The ability of an living organism to produce response against any stimula are called Irritability it is also called Sensitivity.


Movement

Living organism shown the responses towards stimuli are called Movement.


Support in Plant

Plants require proper strength and support it is necessary to maintain their shape, increase in size and keep them straight and strong. The support maintains balance. In plant body support is provided by two ways.

* Turgidity in soft parts of plants

* Mechanical tissues


Support Through Turgor Pressure

The living cell of epidemics, cortex and pith take in water by osmosis. Thus an Internal hydrostatic pressure called "Turgor Pressure", which keeps them rigid and resistant to bending. If they loose turgidity stem wilts. The turgor pressure is extremely important to maintain the turgidity in plants.


Support Through Supporting Tissue

In plants there are certain tissue called Mechanical tissues. These tissue provide strength to the plant body.

1. Parenchyma

2. Collenchyma

3. Sclerenchyma


1. Parenchyma

Structure

* Parenchyma is a simple tissue. It is composed of thin walled spherical, oval or elongated cells.

* They are with or without Intercellular spaces.

* They are living cell.

Location

They are found in cortex, pith and epidemics, mesophyll region of leaves.

Functions

Their function is synthesis of food and storage of food. They may serve as a supporting tissue in soft plant due to internal turgor pressure.


2. Collenchyma

Structure

* Collencym is a simple permanent tissue. It is composed of rounded, oval or polygonal cells.

* They are living cells with protoplasm.

* Intra cellular spaces are absent and these cells thickened at the corners due to deposition of cellulose and protopectin.

Location

These tissues are found in the dicot stem below the epidermis.

Functions

Collenchyma cell provide support to young herbaceous part of the plant. It elongate with the grow stem and leaves.


3. Sclerenchyma

Structure

* Sclerenchyma is a simple permanent tissue. It is composed of long, narrow thick walled cell.

* They have no intracellular spaces.

* They are dead cell without protoplasm.

* A thick materials is deposit along the wall of cell called pectin and lignin.

Location

Sclerenchyma tissues are found in xylem which are vascular tissue.

Functions

They provide strength and Mechanical support to the plant parts.


Types of Sclerenchyma

There are two type of sclerenchyma

1. Fibers

2. Sclerides


1. Fibers

The sclerenchyma elongated cell with tapered ends. They are tough and strong but flexible Fibers.

2. Sclerides

The variable often irregular in shape sclerenchyma are called sclereids. Simple unbranched sclerids are generally called stone cell.


Secondary Growth

An increase in plant girth due to the activity of cambium ring is called secondary growth.


Secondary Tissue

Tissues which are formed by the activity of cambium ring are called secondary tissue.


Significance of Secondary Tissue

Cambium Ring

The ring of activity dividing cells responsible for lateral growth in plant are called cambium ring.

Secondary growth occurs due to cell division in cambium ring. There are two type

i. Vascular Cambium Ring

The cambium present between xylem and phloem is called Vascular Cambium Ring. The cell within the vascular bundles are called fusiform initials.

Vascular cambium gives rise to two new tissues.

* Secondary Xylem (Toward the inside)

* Secondary Phloem (Toward the outside)

Growth Rings

The secondary Xylem causes most of the increase in stem thickness. Over the year a woody stem get thicker and thicker as it vascular cambium produce layer upon payer of secondary Xylem. These layers are visible as rings.

Sap Wood and Heart Wood

The outer region of secondary wood is of lighter color and take part in the conduction of water from root to leaf are called Sap Wood.

The inner region of secondary wood is dark brown in color and do not take part in the conduction of water are called Heart Wood.

In most plant heart wood accumulate a variety of chemical such as resins, oil, gum and tannins. Which provide a resistant to decay and insect attack.


ii. Cork Cambium Ring

The cambium ring present in cortex region and increase the diameter of stem are called cork cambium ring.

Cork cambium cell divide and form new cells on both side.

* Cork / Phellem ------> Outerside

* Secondary Cortex ------> Inner Side

Cork / Phellum

Cork is formed on the outer side by the cork cambium. Which is an insulating layer prevent transpiration. Cork cell are dead and thick wall.

Secondary Cortex

It is formed on the inner side by cork cambium. It is consist of few layers of parenchymatous cells. They contain chloroplast.

Bark

Epidemics, lenticels and cork collectively called bark which is the outer part of stem.

Callus

Another important function of the cambium is to form callus or wood tissue on over the wound. The tissue are rapidly formed below the damage surface of stem and root.


Movement in Plant
Definition

Any action taken by living organs to reduce its irritability produce by stimuli are called Movement.


Type of Movement

There are two type of movement in plant.

1. Autonomic Movement

2. Paratonic Movement


1. Autonomic Movement

Movement which occurs due to internal stimuli factor inherent inside the plant body itself are called Autonomic or spontaneous movement.


Types of Autonomic Movement

There are three type of autonomic movement.

i. Locomotory Movement

ii. Growth Curvature Movement

iii. Turgor Movement


i. Locomotory Movement

Movement of whole plant body or an organ or material within plant cell from one place to another due to internal stimuli is called movement of locomotion.

Example

* The streaming movement of cytoplasm (Cyclosis).

* Movement of chromosome during cell division.


ii. Growth Curvature Movement

Change in the form and shape of plants or plant organs due to the differences in the ratio of growth of different parts are called growth and curvature movement.

Types of Growth Curvature

There are two type of growth movement.

* Nutation

* Nastic

Nutation

The growth tip of young stem moves in zigzag manner due to alternate changes in growth on opposite side of the apex. This type of growth is called nutation.

Example

Movement of climber around any rope as found in railway crupper.


Nastic

When the process of growth occurs in different manner in the parts of a plant and slow in other part it is called Nastic Movement.

There are two type of Nastic movement

* Epinastic

* Hyponastic


Epinastic

When faster growth occurs on the upper side of the organ is known as epinastic.

Hyponastic

When faster growth occurs on the lower side of the organ is known as hyponastic.


iii. Turgo Movement

Movement occur due to change in the turgidity and size of cells as a result of loose or gain of water called Turgo Movement.

Example

* Movement of leaves of touch me not.


2. Paratonic Movement

The movement occurs due to external stimuli are called paratonic or Induce Movement.

Type of Paratonic Movement

There are two type of paratonic movement.

i. Nastic Movement

ii. Tropic Movement


i. Nastic Movement

The non directional movement of parts of plant in response to external stimuli are called Nastic Movement.

Usually this movement occur in leaves or petals of flower.

Type of Nastic Movement

There are two of nastic

i. Photonastic

ii. Haptonastic


i. Photonastic

The nastic movement occurs due to light are called photonastic.

Example

The flower open and close due to light intensity.

ii. Haptonastic

The nastic movement occurs due to the touch of any living organism are called Haptonastic.


ii. Tropic Movement

Tropic ------> Tropos mean "to turn"

The movement in response of growth of whole organ toward and away from stimuli are called tropic movement. It is also known as directional movement.


Type of Nastic Movement

The main type of tropic movement are as follow

* Phototropism

* Geotropism

* Chemotropism

* Hydrotropism

* Thigmotropism


Phototropism

Photo ------> Light Tropos ------> turn

The movement of part of plant in response to stimulus of light are called phototropism.

Example

* Positive phototropism in stem

* Negative phototropism in root


Geotropism

Geo ------> earth Tropos ------ turn

The movement of part of plant in response to force of gravity are called Geotropism.

Example

Root display positive Geotropism and shoots negative geotropism.


Chemotropism

Chemo ------> Chemical Tropos ------> turn

The movement in response to some chemicals is called Chemotropism.

Example

The hyphase of fungi show chemotropism.


Hydrotropism

Hydro ------> Water Tropism ------> turn

The movement of plant parts in response to stimulus of water is called hydrotropism.

Example

The growth of root toward water is due to positive hydrotropism and shoots negative hydrotropism.


Thigmotropism

Thigmos ------> touch Tropos ------> turn

The movement of plant parts in response to stimulus of touch are called Thigmotropism.

Example

The movement in climber

Skeleton
Definition

The tough hard and rigid framework of the body which gives particular shape and support to animal body are called Skeleton.


Human Skeleton

Endoskeleton present inside the human body. It consist of 206 bones. In man endoskeleton divide into two parts.

1. Axial Skeleton

2. Appendicular


1. Axial Skeleton

The skeleton composed of skull, sternum, ribs and vertebral column are called Axial Skeleton.


i. Skull

The skull is made up of cranium and facial bones.

(Cranium)

The part of the skull consist of eight bones and form a box like structure which protect the brain are called Cranium.

(Facial Bones)

The other bones of skull form face are called facial bones. There are 14 facial bones such as check bones, upper jaws and lower jaws single bone called dentary.


ii. Ribs Cage

Ribs are semicircular bones attached on their dorsal side with the vertebrae and on their ventral side with sternum.

Rib Cage is composed of 12 pairs of ribs. The lower two pairs of ribs are called floating ribs because they do not attached with the sternum.

(Function)

The rib cage enclosed the chest cavity and protects heart and lungs.


iii. Sternum

The narrow rod shaped bones present in ventral wall of thorax are called sternum. It is also known as breast bone.


iv. Vertebral Column

A hollow spine in which spinal cord protected extend from skull to pelvis are called V column.

(Bones of Vertebral Column)

The vertebral column consists of 33 bones called vertebrate but due to fusion 26 bones are formed.


2. Appendicular

The skeleton system consist of pectoral girdle and hind limbs and easy to move are called Appendicular skeleton.

Pectoral Girdle and Fore Limb

(Pectoral Girdle)

The girdle present in shoulder region and attach the arm to the trunk are called Pectoral Girdle.

(Parts of Pectoral Girdle)

Pectoral girdle consist of two parts.

1. Scapula ------> board part

2. Clavicle ------> Collar bone which connects scapula with sternum.


For Limb consist of

* Humerus (1)

* Radius (1)

* Ulna (1)

* Carpals (8)

* Meta Carpals (5)

* Phalanges (14)


Arrangement of Bones in Fore Limb

Arm: Humerus forms ball and socker joint with scapular while at distal end humerus forms hinge joint with radius and ulna.

Wrist: The radius and ulna at their distal end from multistage with eight wrist bones called Carpals.

Hand: Five metacarpals from the frame work of palm of the hand.

Digits: Five rows of the phalonges in fingers are attached to the meta carpals. They support the finger.


Pelvic Girdle and Hind Limb

Pelvic Girdle

The girdle present in lower region (hip region) and attached the hind limbs (legs) to the vertebral column are called Pelvic gridle.

Structure of Pelvic Girdle

Each pelvic girdle consist of large bone called Innominate. It is formed by the fusion of three bones called Illium, Ischium and Pubis.


Hind Limbs

The hind limbs consist of

* Femur (1)

* Tibia (1)

* Fibula (1) + Patella (1)

* Tarsals (8)

* Meta tarsals (5)

* Phalanges (14)


Arrangement of Bones in Fore Limb

Thigh: Femur is the largest bones of the body which forms a ball and socket joint with the Pelvic girdle.

Knee and Calf: At the distal end the femur from knee joint with the proximal end of two parallel bones called tibia and fibula.

Ankle: The distal end of the tibia and fibula form a joint with eight tarsals, which are also attached with five meta tarsal bones of foot.

Digits: Five rows of the fourteen phalonges of the toes are attached with meta tarsals.

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Types of Skeleton

There are three main types of skeleton in animals.
1. Hydrostatic Skeleton
2. Exoskeleton
3. Endo Skeleton

1. Hydrostatic Skeleton
A fluid filled gastro vascular cavity or coelom act like a skeleton are called hydrostatic skeleton.

Functions
Hydrostatic skeleton provides support and resistance to the contraction of muscle so motility results.
Example
Hydrostatic skeleton found in annelids and other soft bodies invertebrate.
Mechanism of Working
The fluid filled body cavity of in these animals is surrounding by layer of two types of muscles.

• Circular Muscles

• Longitudinal Muscles

When circular muscles contract and pressure comes on body fluid by this process the body become elongated and hard.
When the longitudinal muscles contract the body becomes short and thick due to the lengthen and shorten body move easily in the soil.

2. Exoskeleton
The hard non living external covering that is secreted by the outer epidermal layer of animals are called exoskeleton.
OR
The skeleton present outside the body are called Exoskeleton.
Composition of Exoskeleton
Exoskeleton are made up of different materials.
1. Silica
The exoskeleton of single celled diatoms made up of silica.
2. Calcium Carbonate
The exoskeleton of mollusks made up of lime (Caco3)
3. Cuticle
The exoskeleton of arthropods made up of hard, non living substance called chitin. It is the complex of protein and carbohydrates. This exoskeleton is dividing by soft flexible joints.
Functions

• It provides a surface to which internal muscle can be attached.

• It provides the protection and support to the body.

• It is not help in locomotion but in arthropod. It helps in movement due to joint.

Disadvantages of Exoskeleton
1. Due to exoskeleton the size of arthropods is short.
2. Growth is also limited because the exoskeleton is non living and non growing.
3. Moulting or ecdysis: When the size of animal increase the exoskeleton become short and it is separated from the body. It is replaced by a new skeleton this process are called moulting.

3. Endoskeleton
The skeleton present inside the body and made up of rigid living connecting tissue bones and cartilages are called endoskeleton.


Functions of Skeleton

1. Support and Shape
It provides supporting frame work of the body, it gives the body a particular shape.
2. Protection
Bones protect critical internal organs, such as brain spinal cord, heart, lungs and reproductive organs.
3. Movement
Skeletal muscles attached to the bones help move the body.
4. Mineral Homeostasis
Bones serve as depository for calcium, phosphorus, sodium and potassium. Bones can release or take up minerals through negative feed back mechanisms to maintain the homeostasis.
5. Blood Cell Production
Red and white blood cells are produced in bone narrow.


Bones and Cartilages

In vertebrate animals the endoskeleton contains two types of connective tissues.
1. Bones
2. Cartilage

1. Bones
Bones is the most rigid form of connective tissue.
Structure of Bones
Cell of bones are called Osteocytes. They secrete a gel like matrix around them. It contains a network of collagen fibres but unlike cartilages it is hardened by the deposition of Osteoblasts and crystals of calcium phosphate. This process called Ossification or Calcification, takes place in the presence of vitamin D.

2. Cartilage
Cartilage is the softer and flexible form of connective tissue.
Structure of Cartilage
The living cells of cartilage are called chondrocytes. These cells secrete flexible, elastic, non-living matrix. It consists of protein and polysaccharides. The main protein in the matrix is collagen whose fibres run in all directions and surrounds the chondrocytes. No blood vessels penetrate into this cartilage.
Function
It covers ends of the bone at the joint and also supports the flexible portion of nose, external ears and larynx.


Joint

The point at which two or more bones connect each other are called Joint. The help in motality of skeleton.


Types of Joint on the Basis of Movement

Joints are classified on the basis of the amount of movement allowed by them, into three categories.
i. Immovable Joints
ii. Slightly Moveable Joints
iii. Freely Moveable

i. Immovable Joints
The joints fit together tightly like the pieces to a puzzle. These joints are called immoveable joints or fixed joints because they don't allow the joining bones to move.
Example
Example of fixed joint are the joints of skull in the term of case to protect the brain.

ii. Partially Moveable Joints
The joints which allow a little government is called partially moveable joints or slightly moveable joints.
Example
Example of partially moveable joint is the attachment of ribs with vertebrate. These joints permit out ribs to moves ups and down while we breath.

iii. Freely Moveable Joints
The joints which allow the movement in several directions is called freely moveable joints.

Types of Freely Moveable Joint
Freely moveable joint that are present in human skeleton system are
i. Ball and Socket Joint
ii. Hing Joint
iii. Pivot Joint
iv. Sliding Joint
v. Gliding Joint

i. Ball and Socket Joint
The joint which allow the movement in all directions even in a circle is called ball and socket joint.
In this joint ball like head of the long bone of leg and upper are fit into a cup like socket of girdle.
Example
Joint of hibs and shoulder

ii. Hing Joint
The joints that allow the movement in two directions such as show the back and forth movement is called hing joint.
Example
Joint of fingers, elbow and knee.

iii. Pivot Joint
The joints which allow a twisting movement as well as side way movement is called pivot joint.
Example
Joints of elbow and skull connected to the spine are the examples of pivot joint.

iv. Sliding Joint
The joints which allow the bones to slides over one another and show the movement in many directions are called sliding joint.
Example
Joints of wrist and ankle.

v. Gliding Joints
The joints in which bones moves easily over one another in a back and forth manner is called gliding joints.
Example
Joints of vertebral column that makes the back bone flexible are the example of gliding joint.

Structure of Hing and Ball and Socket Joint

• At moveable joints the joining bones are held in place by strong straps of connective tissues called Ligaments. Ligaments connect the bones to each other and don't allow the bones to slip and dislocate at a joint. As ligaments stretch they allow the joints to move.

• Highly moveable joints also need lubrication and cushioning to prevent the adjoining bones crushing with each other. This is the function of Synovial Cavities prevent around fluid the reduces the friction and keeps the joint moving freely.

• In addition cartilage pads at the end of bones act as shock absorber and present bones from grinding together.

Deformities Skeleton

Human skeleton support and upright body. Sometimes in skeleton certain disorders are developed which weak a skeleton system are termed as Deformities of skeleton.


Causes of Deformities

The causes of deformities are
1. Genetic Disorder
2. Hormonal Disorder
3. Nutritional or Malnutrition
4. Physical Trauma

1. Genetic Disorder
i. Cleft Palate
It is a genetic disorder in which cleft present in the palate which interferes with sucking. It can lead to inhalation of food into the lungs causing aspiration pneumonia.
ii. Microcephaly
It is genetic disorder in which the skull becomes small sized.
iii. Arithritis
Arthritis is the inflammatory or degenerative disease that damage the joints. Osteo arthritis is the most chronic arthritis which is a degenerative joint disease also caused by genetic defect.

2. Hormonal Disorder
The skeleton deformities of the bones caused by hormonal deficiency.
i. Osteoporosis
Osteoporosis mostly occurs in aged women, which is related to decrease the level of estrogen hormone.
Symptoms
In osteoporosis, the bones become porous, thin and weak and consequently easily breakable.

3. Nutritional Or Malnutrition
The skeleton deformities occur in the bones due to nutritional deficiency.
Some of the nutritional disorders are
i. Osteomalacia
Osteomalacia is the softening of bones in which the bones receive in adequate minerals and patient feels pain when weight is put on affected bones. In this disease calcium salts are not deposited and hence bones soften and weaken weight bearing bones of legs and pelvis, bend and deform.
ii. Rickets
Rickets in children results in bowed legs and deformed pelvis. It is caused by deficiency of calcium in diet or vitamin D deficiency. It treated by vitamin D fortified milk and exposing sink to sunlight to cure disorder.

4. Physical Trauma
Certain diseases caused by physical trauma are as follows
i. Disc slip
ii. Spondylosis
iii. Arthritis
iv. Sciatica

i. Disc Slip
The backbone of body consists of many vertebrate. Between these vertebrate special cartilage pad are present called Disc.
Functions
The discs act as shock absorber during walking, jumping, running and lesser extend to the bend laterlly.
Disease
If due to physical trauma, the cartilaginous ring of disc ruptures and displaces it is called Disc Slip.
Symptoms

• Protrution presses spinal nerve and cause sever pain.

• Unability to move.

Treatment

• As a result of disc slip the person should use hard bed and should take rest for long time.

• Pain killer medicine should be used.

ii. Spondylosis
Spondylosis is deformity of joints of two vertebrate particularly of neck region when the space between two vertebrate becomes narrow.
Symptoms
Due to spondylosis the nerves of spinal cord are pressed. It causes pain in neck shoulder and upper parts of arm.
Treatment

• In this condition a hard collar is used around neck.

• Pain killer are used.

iii. Arthritis
Arthritis is inflammatory or degeneration disease that damage joints.
Causes
It may be due to

• Hereditary

• Viral Infection

• Injury

• Old age

Symptoms

• It results in pain, stiffness, swelling of the joint.

• Smooth and flexible cartilage between the bones of a joint is denatured by the deposits of calcium, which makes the cartilages hard.

Treatment

• Knee joint and hip joint can be replaced by artificial rubber or plastic joint.

• Sometimes it is treated by medicines and physiotherapy.

iv. Sciatica
Sciatica is a nerve pain of hind limbs which occur when nerve of sciatic plexus is being pressed.
Causes
It may be due to

• Injury

• Disc Slip

• Improper administration of injection in the iliac vein.

Symptoms

• It makes the leg highly painful and virtually immovable.

Treatment
The treatment of sciatica is very slow and prolonged. There is no permanent treatment of this disorder.
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Muscular System

Muscle made up to muscular tissue. A muscular tissue is a group of specialized cells contain numerous filament of protein and perform a unique functions to generates a pulling force.
There are more than 600 muscles in a human body and almost half of body weight is due muscles.


Types of Muscles

The vertebrate possess three kinds of muscles
1. Skeleton Muscles
2. Smooth Muscles
3. Cardiac Muscles

1. Skeleton Muscles
The muscles that are attached with the skeleton and associated with the movement of bones are called Skeleton Muscles.
Characteristics

• Skeleton muscles are voluntary in function.

• They can contract strongly and rapidly but fatigue quickly.

• Skeleton muscle are striated muscles because they show alternate dark and light band.

• They are under the control of somatic nervous system.

Muscles are attached to the bones by special structure called tendon.
Functions
With the help of skeleton muscles all the body parts can move.

2. Smooth Muscles
The simplest type of muscles which form all the internal hollow body's organs and it found in throughout animal kingdom, called smooth muscles.
Structure
Smooth muscles are structurally very simple muscles. They are spindle shapes uni-nucleated cells. They are arranged in a sheet around the hollow organs of the body.
Characteristics

• These are unstriated muscles.

• They are involuntary in function i.e. their movement is not in our control but they are controlled by hormones and autonomic nervous system.

• They contract more slowly than skeleton muscles but it can prolonged for a long period of time.

Location
These muscles are found in the blood vessels, digestive tract and many other organs.
Functions

• Smooth muscles push the food to the digestive track.

• They empty the urinary bladder.

• They control the diameter of the blood vessels.

• They also control the diameter of the pupit of eye.

3. Cardiac Muscles
The muscles which are present only inside the wall of heart are called Cardiac Muscles.
Characteristics

• These are striated muscles.

• They are involuntary in function and fatigueless.

• They contract and relax continuously in a rhythmic pattern. This rhythmic contraction called heart beat.

• Cardiac muscles have more mitochondria to continuous supply of energy to the tissues of heart.

• Cardiac muscles regulate by the sino atrial node (SAN) or pace maker.

Heart is quite independent of nervous system for its contraction and heart beat is generated by the cardiac muscles itself.
Structure
They are uninucleated or binucleated and branched to create a meshwork of contractile tissue hence their fibres can not be separated like that of a skeletal muscle.
Functions
The function of cardiac muscle is pump the blood.

__________________________________________________________________________________

Structure of Skeleton Muscles

Muscle Fibre
Each skeleton muscle is actually a bundle of long and parallel closely packed thread like multinucleated cells called the muscle fibres.
Size
Skeleton muscle fibres are huge cells. Their diameters is 10 to 100 mm.
Structure o Muscle Fibre
Each muscle fibre is bounded by thin elastic membrane called Sarcolemma. Similar to plasma membrane. Inside the sarcolemma, there is a semifluid called Sarcoplasm.
Myofibril
Each muscle fibre contain a large number of many individual, ultra microscopic contractile fine thread like structure called Myofibril.
The diameter of myofibril is 1-2 mm that run in parallel fashion and extend entire length of the cell.
Sarcomere
The myofibrils consist of smaller contractile units called Sarcomere.
Structure of Sarcomere
In each sarcomere a series of dark and light band are evident along the length of each myofibril.
Microfilaments
The myofibril contains myofilaments or mocrofilaments. Microfilament is made up of two types of filament.
i. Thick Filament
ii. Thin Filament

i. Thick Filament
The central thick filaments extend the entire length of the A-band. The thick filament which is about 16mm in diameter is composed of myosin.
Structure of Myosin
Each myosin molecule has tail terminating in two globular heads. Myosin tail consists of two long polypeptide chain coiled together. The heads are sometimes called cross bridge because they link the thick and thin myofilaments together during contraction.
ii. Thin Filament
The thin filaments extend across. The I-band and pathway into A-band. Thin filaments are 7-8 mm thick and composed of chiefly actin molecule.
Structure of Actin
The actin molecules are arranged in two chains which twist around each other like twisted double strand of pcarls. Twisting around the actin chains are two strands of another protein tropomyosin. The other major protein in thin filament is troponin. It is actually three polypeptide complex. One bind to actin, another binds to tropomyosin while third binds calcium ions.

I-Band
The area which appear light and contain only thin filament is called I-Band.
H-Band
The area which appear bright and contain only thick filament is called H-Band.
A-Band
The area of sarcomere which appear dark and contain both thick and thin filament is called A-Band


Mechanism of Contraction of Skeleton Muscles

There are two theories which explain the mechanism of contraction of skeleton muscles.
1. Sliding Filament Theory
2. Cross Bridge Theory

1. Sliding Filament Theory
Introduction
H.Huxley and A.F. Huxley and their colleagues suggested a hypothesis in 1954 to explain all even in muscle contraction this is called Sliding Filament Theory.
Statement
According to this theory
The thin and thick filament of a muscle fibre move together by sliding over each other. This is like sliding the fingers of our hand between fingers of the other hand. The sliding of the filaments is the reason that the muscle gets shorter and thicker.

2. Cross Bridge Theory
Introduction
When the bulbous heads end of the myosin filament discovered so the another theory explain the mechanism of contraction of muscle which show physical contact are called Cross Bridge Theory.
Statement
According to this theory
The bulbarious head of thick filament myosin become attached to binding sites on the actin filament. The cross bridge are formed then contract to pull the actin filament towards center of sarcomere and the muscles become contract.


Motor Unit

A set of all the muscle fibres innervated by the branched of the single neuron and a single muscle fibre is made up of many motors units.


Controls of Muscle Contraction

The contraction of a muscle depends upon three factors.
1. Nerve Impulse
2. Energy
3. Calcium Ions

1. Nerve Impulses
Nerve impulse cause muscle contraction. The nerve impulses (nerve message) are recieved from brain and spinal cord through motor nerves. The muscles entirely depend upon these nerve impulses. When these impulses do not reach to the muscles, they become fatigue. They loss stimulation and contraction stops gradually.

2. Energy
Muscles also need energy for contraction. Energy required for muscle contraction comes from food. The energy from food is stored in muscles in the form of glycogen. It is transformed from glycogen to creative phosphate and finally to ATP where it is stored and is readily available for use of muscle.

3. Calcium Ions
Calcium ions play very important role in the initiation of muscle fibre contraction. It is stored in sarcoplasmic reticulum.

• When the nerve impulse reaches the acetyl choline is released.

• Due to acetyl choline great number of calcium ions released from Sarcoplasmic reticulum.

• The calcium ions bind to troponin molecule and exposed the active site of actin molecule.

• The cross bridge is formed between actin and myosin and the muscles become contracted.

• After contraction has occurred the impulse stops, calcium ions back into sarcoplasmic reticulum and the muscles fibres relaxed again.

Fatigue

Muscle fatigue is a state of physiological unability to contract.
OR
When the muscles become functionless it is called Fatigue.

Causes
ATP Deficit
Muscle fatigue results from relative deficit of ATP, not its total absence.
Lactic Acid Accumulation
Excess accumulation of lactic acid due to the breakdown of glucose in absence of O2 and ionic imbalances also causes muscle pH to drop and the muscle to ache hence causes extreme fatigue.
Recovery
When the heavy exercise stops and continues the supply the excess oxygen to the fatigued tissues, which now break lactic acid into water and carbon dioxide. Lactic acid is converted the fatigued condition of the muscle is over. The amount of oxygen needed to remove lactic from the tired muscle is called Oxygen Dept.


Abnormal Muscle Contraction

There are two common abnormal muscle contractions
1. Tetany
2. Cramps

1. Tetany
Tetany is a sudden involuntary contraction of striated muscle.
Causes
Tetany is caused by the low level of calcium in the blood.
Symptoms
It excites neurons which influence the muscles contract before gaining the normal position of actin and myosin filaments, therefore it is called abnormal function. In tetany there is continue contraction of muscle fibres. Due to this continue contraction the Ca++ ions cannot be separated from the sarcoplasm of muscles and continue contraction becomes very rapid, so it is known as Tetany. If tetany occurs in respiratory organs, they may become functionless.

2. Cramps
It is also known as titanic contraction of entire muscle. It lasts for just few seconds or several hours, causing the muscles to become taut and painful. It is most common in thigh and hip muscles, it usually occurs at night or after exercise.
Causes
The main causes for cramps are as follows

• Sugar level in blood is reduced

• Sometimes dehydration occurs in the body.

• Electrolytes (ions) are not in balance state.

• Extra exercise is also harmful and causes cramps.

Treatment
Simultaneous squeezing and stretching the cramped muscle may help.


Antagonisitic Muscles

The muscles work in pairs with one muscle working against the other are called Antagonisitic Muscles.
Types of Antagonisitic Muscles
On the basis of their function and affect they produce the muscles are of following type.
1. Protractor and Retractor
Protractor Muscle: These muscle pull the lower part of limb in forward direction.
Retractor Muscle: These muscle pull the limb in backward direction.
2. Abductor and Adductor
Abductor Muscle: These muscle pull the limb away from the body.
Adductor Muscle: These muscle pull the limb towards the body.
3. Flexor and Extensor
Flexor Muscle: They close the joint.
Extensor Muscle: These muscle open the joint.


Locomation in Protozoa

Protozoans are the unicellular animals. Then locomotion is carried out by single called structures. These are of three types Pseudopodia, cilia and flagella. These structures arise from the body surface and may also help to capture the food.

1. Locomotion in Amoeba
Organs of Locomotion
Locomotion in Amoeba is called amoeboid movement. Amoeboid movement takes place by means of Pseudopodia.
Method of Locomotion
The pseudopodia are finger like projections in the direction of movement. After the formation of pseudopodia the Amoeba attaches with the substratum and pull the body in the forward direction.
The exact mechanism of pseudopodia formation is still not known.

2. Locomotion in Euglena
Organs o Locomotion
Euglena moves with the help of flagellum.
Methods of Locomotion
As the flagellum is whipped backward the organism moves forward. However, when flagellum moves forward the Euglena does not move backward. Flagellum is at is anterior end of the body and pulls the organism forward. Wave of activity generated by itself and they pass in spiral fashion from its base in spiral fashion from its base to its tip.
Euglena increases amplitude and velocity. The activity of the flagellum caused the body of Euglena to rotate forward abouts its axis.
Euglenoid Movement
In this mode of locomotion, a wave of contraction and expansion passes from the anterior to posterior in entire body. The contraction and expansion is brought by the contraction of protoplasm. The body becomes shorter and wider first at the anterior, then in the middle and finally at posterior.

3. Locomotion in Paramecium
Organs of Locomotion
Paramecium moves with the help of Cilia. The movement by cilia is called Ciliary movement.
Structure of Cilia
Cilia are short fine thread-like extensions of the cell membrane.
Method of Locomotion
The locomotion in paramecium take place by the beating of these cilia. The beating action occurs in two strokes.
Effective Strokes
During effective stroke the cilia become rigid and bent backward but obliquely propel the animal forward.
Recovery Strokes
During recovery stroke the cilia become softer and returns to it original position.
As a result of effective and recovery stroke paramecium swims against water. The body move forwards.

4. Locomotion in Animals
1. Locomotion in Jelly Fish
Jelly fish has umbrella like body which floats on the surface of water at the mercy of waves. However it can swim slowly by muscular contraction.
Mechanism
In jelly fish the water enters in the umbrella like body (Bell). Then the muscle of the body contract and water is forced out in a jet, as a result animal movement is known as "Jet Propulsion". The jelly fish moves in jerks in the direction opposite to the expelled water.

2. Locomotion in Snail
Organs of Locomotion
Snail crawl or move very slowly by "foot".
Mechanism
The foot of snail produces a wave of muscular contraction on its under side. This wave is from front to rear and animal is pushed forward. The movement is lubricated by slime which is poured on land immediately from glands below the mouth.

3. Locomotion in Star Fish
Organs of Locomotion
Starfish moves with the help of tube feet. The tube feet are present on both sides of radial canal that extends up to the tip of arm.
Structure of Tube Feet
The tube feet are hollow muscular and are like rubber bulb of the medicine dropper. The tube feet consist of three parts.

• Ampula

• Podia

• Sucker

Mechanism
In starfish locomotion is controlled by a special water vascular system. Water is drawn into the body through a small opening and is passed through a ring canal to large number of hollow muscular tube feet. The tube feet extend when water is pumped into them then they fix themselves by suction cup (sucker) with some object. When sucker muscle contract the water is pushed back into the ampullae, making the tube feet flaccid losing the grip and the starfish is pulled forwards.