Differentiate between the following.

Voluntary muscles and Involuntary muscles. 

1. Movement and Locomotion:

(i) Movement is defined as the act of changing the place or position by one or more parts of the body. It helps to perform necessary functions in an organism.

(ii) Movement can be both voluntary and involuntary. 

(iii) The movement of an organism from one place to another is known as locomotion.

2. Movement in different animals:

(i) Earthworms move by alternate extension and contraction of the body using muscles. Tiny bristles on the underside of the body help in gripping the ground. 

(ii) In Cockroaches, the body and legs have hard coverings forming an outer skeleton. The muscles of the breast connected with three pairs of legs and two pairs of wings help the cockroach to walk and fly. 

(iii) In Birds, strong muscles and light bones work together to help them fly. They fly by flapping their wings. 

(iv) Snakes slither on the ground by looping sideways. A large number of bones and associated muscles push the body forward. 

(v) Fish swim by forming loops alternately on two sides of the body. 

3. Types of movements:

(i) Amoeboid motion helps in the ingestion of food and locomotion as well.

(ii) Ciliary movements of cells lining the trachea of humans helps to remove the invading microbes and dust particles.

(iii) Muscular movement is the basic mechanism used in the majority of vertebrates including humans.

4. Joints:

(i) The point at which two separate bones meet is called a joint.

(ii) Joints are essential for all types of movements involving the bony parts of the body. 

(iii) Force generated by the muscles is used to carry out movement through joints, where the joint acts as a fulcrum. 

5. Types of joints:

(i) In Fixed or Immovable joints, there will be no movement possible between the two bones. 

(ii) In Slightly movable joints, only very little (partial) movement occurs between the two bones. 

(iii) In Freely movable joints, varying degree of movement is possible between the two bones forming the joint.

(a) Ball and Socket joint is formed by two bones where a ball-shaped end of one bone fits into the hollow cup-shaped socket of the other bone.

(b) Hinge joint is formed by two bones and is similar to the hinge of a door.

(c) Gliding joint or plane joint is formed between the bones where they meet at the flat surface.

(d) Pivot joint is formed in such a way that one bone rotates around the other.

(e) Saddle joint is the imperfectly developed ball and socket joint. It helps in extending movement.

(f) Condyloid joint is the modified form of hinge joint which allows the movement in two planes.

(iv) A synovial joint is a joint which makes the connection between two bones consisting of a cartilage lined cavity filled with fluid, which is known as a diarthrosis joint.

6. Skeletal system:

(i) The skeletal system has four components: bones, cartilage, tendons and ligaments.

(ii) The average adult human skeleton has 206 bones.

(iii) The skeletal system is divisible into axial and appendicular.

(a) Skull, vertebral column, ribs and sternum constitute the axial skeleton.

(b) Limb bones and girdles form the appendicular skeleton.

(iv) Three types of joints are formed between bones or between bone and cartilage - fibrous, cartilaginous and synovial.

7. Muscles:

(i) Muscles work by contraction and relaxation. Muscles work in pairs - one contracts and the other relaxes.

(ii) Based on their location, in humans, muscles are broadly classified into three categories: skeletal muscles, smooth muscles and cardiac muscles.

(a) Skeletal muscles are attached to the bones by tendons and help in the movement of the parts of the skeleton. They are striated and voluntary in nature.

(b) Smooth muscles are involuntary and non-striated muscles. They are present in the inner walls of visceral organs.

(c) Cardiac muscles are the muscles of the heart. They are striated, but these muscles are branched and involuntary.