Maharashtra Board Class 11 Biology Chapter 16 Skeleton and Movements PDF Download

16. Skeleton and Movements

There are about 640 muscles in human body. Out of these 634 are paired and 6 muscles are unpaired.

Can You Recall?

1. Which are different types of muscular tissues?

2. Name the type of muscles which bring about running and speaking.

3. Name the muscles which do not contract as per of our will.

4. Which types of muscles show rhythmic contractions?

5. Which type of muscle is present in the diaphragm of the respiratory system?

6. Name the part of human skeleton situated along the vertical axis.

Always Remember

There are about 640 muscles in human body. Out of these 634 are paired and 6 muscles are unpaired.

Think About It

1. Why do we shiver during winter?

2. Why do muscles show spasm after rigorous contraction?

3. Did you ever feel tickling in muscles?

Teacher's Note

When you run or play, your muscles work hard. Your body gets warm because muscles produce heat when they contract. This is just like how a machine gets hot when it works.

Exam Trick

Remember: There are 640 muscles in your body. Most are paired (634). Think of it like your hands - you have two hands, two arms, two legs. Muscles work in pairs too!

Points to Remember

There are 640 muscles in human body.
Most muscles are paired (634 paired muscles).
Only 6 muscles are unpaired.
Muscles help us move and run.
Different muscles have different jobs.

16.1 Movements and Locomotion

Movements

Movements may be internal or external. Movements may be voluntary or involuntary. Three types of muscles bring about these movements in human beings.

a. Smooth muscles bring about involuntary movements like peristaltic movements in the alimentary canal, constriction and dilation of blood vessels, etc.

b. Contraction and relaxation of the heart is controlled by cardiac muscles.

c. Voluntary movements of limbs, head, trunk, eyes, etc. are controlled by striated muscles.

Locomotion

The change in locus of whole body of living organism from one place to another place is called locomotion. Locomotion is for search of food, shelter, mate, breeding ground and escape from enemy. There are four basic types of locomotory movements found throughout the animal kingdom.

1. Amoeboid movement: performed by pseudopodia e.g. leucocytes.

2. Ciliary movement: performed by cilia e.g. ciliated epithelium. In Paramecium, cilia help in passage of food through cytopharynx.

3. Whorling movement: performed by flagella e.g. Sperms.

4. Muscular movement: Performed by muscles, with the help of bones and joints.

Remember: All locomotions are movements but all movements are not locomotion. Skeletal muscles are attached to the bones by tendons and help in the movement of the parts of skeleton. Tendons are inelastic thick band of collagen fibers. Movement and locomotion is the combined action of bones, joints and skeletal muscles.

Teacher's Note

When you walk or run, you are using locomotion. When you just move your hand without moving from your place, that is movement only. Your legs help you move from one place to another - that is locomotion!

Exam Trick

Remember: Locomotion = change in position. Movement = change in body parts. If you move your hand, it is movement. If you run to school, it is locomotion. Think: Loco = place, so locomotion = change in place.

Points to Remember

Movement can be inside or outside the body.
Muscles help us move and walk.
Smooth muscles help our food move inside body.
Heart muscles always work without rest.
Locomotion means moving from one place to another.

16.2 Location and Structure of Skeletal Muscles

Major part of the muscle which moves a bone usually do not lie on the same bone but is located on the bone atop. e.g. Biceps and triceps that move forearm are located in the upper arm. At any joint, two types of bones are present i.e. stationary and movable.

On the basis of movement, striated muscles are of three types.

Agonists (Prime movers): Bring initial movement of part e.g. Biceps

Synergists: Assist prime movers e.g. Brachialis assist Biceps

Antagonists: Bring the action opposite to that of prime movers e.g. Triceps

The end of muscle attached to stationary bone is called origin while the opposite end attached to movable bone is called insertion. The middle thick part of muscle is called belly. All the fibres in a muscle do not extend from end to end and there is a maximum number in the middle. Thus, large muscles are most often fusiform in shape.

Teacher's Note

Your biceps and triceps work together like a team. When you bend your arm, biceps pulls. When you straighten your arm, triceps pulls. In India, when we play tug of war, one team pulls with their muscles like this!

Exam Trick

Remember: Biceps bends, Triceps straightens. Bi = two heads of biceps, Tri = three heads of triceps. Your forearm moves because of these two muscles working together like a see-saw!

Points to Remember

Muscles are attached to bones by tendons.
Biceps is the muscle that bends your arm.
Triceps is the muscle that straightens your arm.
Origin is where muscle starts (fixed bone).
Insertion is where muscle ends (moving bone).

This is a preview of the first 3 pages. To get the complete book, click below.