16. Skeleton and Movements - part 01- Types of locomotory movements and Location and structure of skeletal muscles

 

16. Skeleton and Movements - part 01- Types of locomotory movements and Location and structure of skeletal muscles




 Movements and locomotion :
              Movements : 

  •  Movements may be internal or external. 
  •  Movements may be voluntary or involuntary. 
  • Three type 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.
Types of locomotory movements :

  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.There are about 640 muscles in human body. Out of these 634 are paired and 6 muscles are unpaired. 
  4. Muscular movement : Performed by muscles, with the help of bones and joints.

  • 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.


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 
  1. stationary 
  2. movable.
  • 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.

Working of Skeletal Muscles :

  • Generally muscles work in pairs and produce opposite action 
                         e.g. Biceps (flexors) bring flexion (folding) and
                                triceps (extensors) bring extension of elbow joint.

  • The muscles which bring opposite action are called antagonistic.  
  • If one member of a pair is capable of bending the joint by pulling of bones, the other member is capable of straightening the same joint also by pulling. 
e.g. Triceps and Biceps of upper arm are antagonistic to each other.


  • In antagonistic pair of muscles, one member is much stronger than the other. e.g.The biceps is stronger than the triceps.
  • The fundamental characteristic of muscle is contraction. 
  • Therefore, muscle can only pull and not push the bone.

Some important antagonistic muscles :

  1. Flexor and Extensor:  Flexor muscle on contraction results in bending or flexion of a joint            e.g. Biceps.                                                                                                                                                                                                                                                                                   Extensor on contraction results in straightening or extension of a joint                                    e.g. Triceps.
  2. Abductor and Adductor : Abductor muscle moves body part away from the body axis e.g. Deltoid muscle of shoulder moves the arm away from the body.                                              Adductor moves body part towards the body axis e.g. Latissimus dorsi of shoulder moves the arm near to the body.
  3. Pronator and Supinator : Pronator turns the palm downward. Supinator to turns the palm upward.
  4. Levator and Depressor : Levator raises a body part. Depressor lowers the body part
  5. Protractor and Retractor : Protractor move forward. Retractor move backward.
  6. Sphincters : Circular muscles present in inner wall of anus, stomach, etc. for closure and opening.



  • Both flexion and extension take place by contraction of skeletal muscles. 
  • Striated muscles are specifically designed to bring about vigorous contractions.
  • The contractile unit of muscles is called sarcomere which contains contractile proteins actin and myosin.

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